Study on the Feasibility of a Harvesting, Transporting ... · establish a low-cost harvesting and...

AGri-Bioscience Monographs, Vol. 1, No. 1, pp. 1–60 (2011) www.terrapub.co.jp/onlinemonographs/agbm/

© 2011 TERRAPUB, Tokyo. All rights reserved.doi:10.5047/agbm.2011.00101.0001

Received on May 18, 2010Accepted on October 18, 2010Online published on

March 31, 2011

Keywords• forest biomass resources• harvesting, transporting, and

chipping cost• energy and carbon dioxide

(CO2) balance• life cycle inventory (LCI)

analysis• geographic information sys-

tem (GIS)

lized at a lower level and the need for bioenergy de-creased.

Now, many years later, the use of renewable energyis now being universally proposed as a countermeas-ure to global warming. Biomass as an alternative tofossil fuels is an environmentally friendly source ofenergy and is composed of organic materials, oftengenerated as waste by-products. It is attracting wide-spread attention for its potential as an ideal primaryenergy resource in a sustainable society. Japan is cur-rently promoting the use of bioenergy. In 2001, thegovernment officially defined biomass as one of thenew energy resources in the “Law Concerning SpecialMeasures for Promotion of the Use of New Energy.”The targets, based on the premise of maximum effortsfrom the government and the public in the fiscal year2010, are 340,000 m3 crude oil equivalent with biomasspower generation, corresponding to 330 MW capacityof electrical power generation, and 670,000 m3 crudeoil equivalent with thermal utilization of biomass(Yokoyama 2002). Thus, the utilization of bioenergyis once again becoming an important political and sci-

AbstractThe aim of this study was to assess and discuss various aspects related to the feasibilityof a harvesting, transporting, and chipping system for processing forest biomass resourcesin Japan. Within this framework, the author first comprehensively discussed the visionsfor introducing and diffusing woody bioenergy utilization in terms of the quantificationof available woody biomass resources for energy, the development of low-cost harvest-ing and transporting systems, and the conversion processes. Second, a harvesting, trans-porting, and chipping system for logging residues was constructed, and the feasibility ofthe system was examined from the points of view of cost, energy balance, and carbondioxide (CO2) emissions on the basis of field experiments at forestry operation sites.Third, the feasibility of the energy utilization of forest biomass resources in a mountain-ous region was assessed by analyzing the relationship between the mass and the procure-ment cost of forest biomass in the region with the aid of a geographic information system(GIS). The conclusions derived from this study will contribute to the practical implemen-tation of the harvesting, transporting, and chipping system for forest biomass resourcesand to the realization of utilizing forest biomass for energy production in Japan.

Study on the Feasibility of a Harvesting,Transporting, and Chipping System forForest Biomass Resources in Japan

Takuyuki Yoshioka

Laboratory of Sustainable Forest Utilization, Department of Forest Science and Resources,College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa 252-0880, Japane-mail: [email protected]

1. Introduction

1-1. Background of the study

The two oil crises that occurred in the 1970s spurredresearch on bioenergy worldwide. In Japan, the Min-istry of Agriculture, Forestry and Fisheries imple-mented the “Biomass Conversion Project” during thefiscal period covering 1980 to 1990 (Agriculture, For-estry and Fisheries Research Council Secretariat (ed.)1991). Various studies were carried out within theframework of this project, all focusing on the construc-tion of a system of efficient bioenergy utilization. Theseincluded studies on methods of harvesting and trans-porting logging residues, i.e., tree tops and branchesthat are generated during limbing and bucking, con-sidering logging residues to be a usable forestry prod-uct rather than a logging waste product (Forestry Sci-ence and Technology Promotion Center 1984 and1985). Although promising results were obtained fromsuch studies, the project was not implemented as a sys-tem at an actual site because the crude oil price stabi-

2 T. Yoshioka / AGri-Biosci. Monogr. 1: 1–60, 2011

doi:10.5047/agbm.2011.00101.0001 © 2011 TERRAPUB, Tokyo. All rights reserved.

entific issue.Among the various potential biomass resources that

can be used to achieve these targets, woody biomassin particular is attracting a great deal of interest in Ja-pan. A number of factors underlie this interest. First,woody biomass is abundant in Japan. Secondly, theenergy utilization of woody biomass is expected tocontribute to a revitalization of the forestry and forestproducts industries, which have long been depressedin Japan. Thirdly, woody biomass utilization will con-tribute towards maintaining the relevant ecological (in-cluding biological diversity), economic, and socialfunctions of man-made forests, which are currentlybeing neglected. However, in order to realize bioenergyutilization, programs for the introduction and imple-mentation of bioenergy utilization should be adoptedat a national level as soon as possible. These programsshould be comprehensive in considering how to ap-proach the quantification of available woody biomassresources for energy, the development of low-cost har-vesting and transporting systems, and the conversionprocesses, as well as how these should meet the needsof the social system. To date, only a few studies ondeveloping the necessary harvesting and transportingtechniques have been carried out. In contrast, a numberof energy-conversion technologies for woody biomasshave already been developed to the level of practicaluse. In order to promote the introduction and diffusionof bioenergy utilization, therefore, it is necessary toestablish a low-cost harvesting and transporting sys-tem for woody biomass as soon as possible.

The Japanese forestry industry has undergone majorchanges in the last years aimed at improving the pro-ductivity through mechanization, and the introductionof whole-tree logging systems has made rapid progress.However, due to the high productivity of the proces-sors, a number of new problems have appeared, suchas the large quantity of logging residues generated atlandings. The use of forwarders has also made rapidprogress, with the construction of low-grade strip ac-cess roads instead of expensive forest roads being pro-moted at the national level. Taken together, there is agolden opportunity for forwarders to haul slashes gen-erated by processors, and these slashes can be con-verted into usable energy, such as heat, electricity, andliquid fuel, after they are transported by trucks andcomminuted by chippers.

1-2. Review of the studies on harvesting, trans-porting, and chipping for forest biomass re-sources

In this section, previous studies on the harvesting,transporting, and chipping of forest biomass resourcesare reviewed. The aim of this review is to identify thetransitions that have occurred in the development anddiffusion of the various relevant technologies and de-

termine which of these may be appropriate for the de-velopment of a feasible and appropriate system in Ja-pan (Yoshioka and Inoue 2006). The review is dividedinto two sections, namely, studies carried out “In the1970s and 1980s” and those carried out “In and afterthe 1990s.”

1-2A. In the 1970s and 1980sIn the 1970s and 1980s, when mainly only whole

trees were harvested and utilized, many studies wereconducted in North America (the United States andCanada) and Nordic countries (mainly Sweden andFinland), where forests grow on flat terrain. Most ofthe studies carried out in the 1970s investigated log-ging systems that consisted of felling trees using fel-ler-bunchers, skidding the whole trees to forest roadsusing grapple skidders, limbing and bucking or chip-ping the whole trees at roadside landings, and thentransporting the logs and wood chips. In the 1980s,researchers began looking at other logging systems aswell.

Before the two oil crises in the 1970s, which stimu-lated studies on forest biomass harvesting, systems forchipping whole trees were researched and subsequentlyput into practice in the pulp and paper industries. In1975 and 1976, four reports on chipping whole treeswere published in the Technical Association of the Pulpand Paper Industry (TAPPI) Journal (Malac 1976,Morey 1975, Palenius 1976, Tufts 1976).

Morey in the United States reported that the processof whole-tree chipping had spread throughout NorthAmerica when feller-bunchers and grapple skidderswere introduced and technologies developed for sepa-rating clean wood chips for pulp production, with theresult that increasingly more pulp mills accepted thosewood chips (Morey 1975). The use of machines forfelling, limbing, and bucking doubled the productivityin comparison to that of the conventional system bychain saws. In the mechanized system, a team of sixoperators produced 280–300 tons of wood chips a day,and the material cost at upon arrival at the mills wasreduced from the conventional 20–30 US$ per ton to6.22 US$ per ton. Morey also mentioned that mecha-nization reduced the expenses associated with cuttingarea, labor, and reforestation and that the chipping sys-tems were effective for utilizing small-diameter thinnedtrees and low-quality logs of broad-leaved forests,which otherwise would be left unused.

Also in the United States, Tufts studied the produc-tivity of whole-tree chipping and reported that althoughthe system required a large initial investment, it washighly productive and could produce 800 tons of woodchips a week when applied to the thinning of a plantedpine forest and transporting of the chips to a mill (by ateam of 11 workers, a distance of 40–50 miles) and150 tons of wood chips a day when used to clearcut abroad-leaved forest (by a team of 8 workers) (Tufts

T. Yoshioka / AGri-Biosci. Monogr. 1: 1–60, 2011 3


1976). Malac reported that reforestation expenses werereduced by 33–65% in the United States when con-ventional shortwood logging was changed to mecha-nized whole-tree logging, although the expenses var-ied according to forest conditions (Malac 1976).

Palenius, however, reported that whole-tree chippingmachines were introduced into Nordic countries dueto insufficient manpower and the need both to producethe necessary amount of pulp wood and to appropri-ately thin forests (Palenius 1976). Therefore, accord-ing to this Finnish author, the background to the intro-duction of mechanized systems differed from that inNorth America. In Nordic countries, whole trees thatwere chipped were mainly thinned ones.

An FAO report that summarized the production andtransport of wood chips supported the results and con-clusions of these four studies (FAO 1976). This report,which also investigated the possibility of harvestingroots and logging residues left at cut-over areas inNordic countries, concluded that the combined use ofwhole-tree chippers and separators of clean wood chipsfor pulp production was the most economical methodfor harvesting forest biomass and described varioustypes of whole-tree chipping systems and mobile chip-pers. The chipping of small-diameter trees, such asthose from forest thinning programs, was particularlymentioned as the only means by which whole-tree chip-ping could be profitable.

The utilization of forest resources as an energy sourcehas also been studied. In Canada, Folkema comparedtwo whole-tree chipping methods that used feller-bunchers and grapple skidders and reported that skid-ding whole trees directly to the chipper using the grap-ple skidder was more productive than moving the chip-per along a forest road after skidding and accumulat-ing whole trees along the roadside using the grappleskidder (Folkema 1977). Folkema reported that such atotally mechanized system was feasible only in largeforests, in which the material cost, including expensesfor transporting the wood chips to a mill, was 22.55–26.00 Canadian dollars per ton (45% of water content(wet basis), a distance of 50 km). Folkema indicatedthat total mechanization was difficult in medium tosmall forests where the optimal system for producingwood chips consisted of either (1) felling trees usingchain saws, skidding the whole trees to forest roadsusing cable skidders, and chipping the trees at road-side landings using chippers or (2) felling trees usingchain saws, chipping the whole trees using chippersconnected to tractors, and hauling the chips to forestroads, and that the transportation distance by truckshould not exceed 30 km (Folkema 1989).

Methods other than chipping whole trees have beenstudied by Stuart et al. in the United States (Stuart etal. 1981). These authors compared two systems:(1) one that involved felling trees using feller-bunchers,skidding the whole trees using grapple skidders, in-

tensively limbing and bucking, and then chipping orbaling tree tops and branches, and (2) one that involvedfelling trees using chain saws, limbing and bucking,collecting the logs and logging residues separately us-ing forwarders, and then chipping or baling theresidues. They reported that whole-tree logging wasthe most economical approach and that collecting log-ging residues from forests required was expensive interms of time, labor, and financial cost. Baling wasreported to be more effective than chipping on a smallscale.

Watson et al. compared the costs of producing logsand wood chips among the following three differentsystems (Watson et al. 1986):1) Felling trees using feller-bunchers, limbing by chainsaws, and skidding the tree-length logs using skidders;2) Felling trees using feller-bunchers, skidding thewhole trees using skidders, and limbing and buckingas well as chipping while separating the materials forlogs and wood chips (one-pass system);3) First felling small-diameter trees for wood chipsusing feller-bunchers, skidding the whole trees usingskidders, and processing them into wood chips, andthen producing logs in the same manner (two-pass sys-tem).They reported that the one-pass system was the leastexpensive for producing logs and wood chips.

Typical studies in Nordic countries include the seven-year “Forestry Energy Project” by the Swedish Uni-versity of Agricultural Sciences (Andersson and Falk(eds.) 1984). In this project, diverse studies were car-ried out on using logging residues as an energy source,including the history of using wood for fuel and theproblem of removing nutrients from forests by harvest-ing tree tops and branches.

A “tree section” system was a main topic of theproject, although other large-scale harvesting systemswere also investigated, such as whole-tree logging thatinvolved felling trees using feller-bunchers and skid-ding the whole trees using skidders, a collecting andchipping system that involved clearcutting by harvest-ers and producing wood chips from scattered loggingresidues using chipper-forwarders, and a chipping sys-tem that involved harvesting logging residues usingforwarders and producing wood chips along forestroads or at terminals. The “tree section” system in-volved felling trees using feller-bunchers, cutting thetrees into sections using grapple saws installed on for-warders, and collecting the sections (with branches)using the forwarders. This method was more produc-tive than those systems that produced logs using har-vesters. In order to load and transport “tree sections”or logging residues onto a trailer, the loads had to becompressed using the attached grapple; otherwise only20–30% of the effective loading weight capacity of thetrailer could be loaded.

In terms of small-scale systems, the study group re-



ported that using materials from forest cleaning wasan effective approach to improving the efficiency ofsubsequent forest operations. They recommended ei-ther felling trees using chain saws and then producingwood chips using chippers installed on agriculturaltractors or collecting whole trees using cable skiddersand producing wood chips at landings (a disadvantageof this method is the need for large landings). The re-port mentions the risks of work-related accidentscaused by noise and striking of rebounded logs sincelogs must be put into chippers manually. Almqvist andLiss followed up this point and prepared a manual onchipping operations for small-scale forestry managers(Almqvist and Liss 1987).

Hakkila from Finland published a comprehensivereview of studies on the utilization of forest biomassas energy that had been conducted prior to the end ofthe 1980s, including the aforementioned studies, stud-ies by the U.S. Department of Energy (USDOE), andthe “ENFOR Project” of the Canadian Forest Service(Hakkila 1989). With respect to forest biomass harvest-ing, which is the topic of this study, case studies werepresented for diverse systems together with investiga-tions and projects on harvesting, chipping, and trans-porting of whole trees, “tree sections,” and loggingresidues.

1-2B. In and after the 1990sStudies carried out during and after the 1990s on

harvesting of forest biomass can be broadly classifiedinto IEA Bioenergy studies and others.(a) IEA Bioenergy studies

The International Energy Agency (IEA) was estab-lished in 1974 under the auspices of the Organizationfor Economic Co-operation and Development (OECD),with the aim of achieving international cooperation interms of all aspects related to energy. In 1978, the firstbiomass study project, “IEA Forestry Energy,” wasinitiated. In 1986, the project was renamed “IEABioenergy” to include non-forest biomass resources.Thereafter, the word “bioenergy” has been widely usedto refer to the utilization of biomass energy.

The first IEA Bioenergy study on forest biomass wasconducted from 1986 to 1988 under the title “Devel-opment of Improved Methods for Harvesting, Process-ing and Transport of Forest Biomass (IEA BioenergyTask III).” The main findings of this project were sum-marized in 1990. Research on harvesting forest biomasswas summarized in the section entitled “IntegratedHarvesting Systems to Incorporate the Recovery ofLogging Residues with the Harvesting of ConventionalForest Products” by Goulding and Twaddle from NewZealand (Goulding and Twaddle 1990). Research onharvesting early thinnings was summarized in “Har-vesting Early Thinnings of Energy” by Brenøe andKofman from Denmark (Brenøe and Kofman 1990).

Goulding and Twaddle reviewed trials of harvesting

whole trees that had been carried out in participatingcountries and presented a design for an “integratedharvesting” system that involved harvesting loggingresidues, such as previously wasted tree tops andbranches, and using these for energy as well as har-vesting conventional forestry products, such as logsand pulp wood (Goulding and Twaddle 1990). “Inte-grated harvesting” became a keyword of IEA Bioenergyprojects on harvesting forest biomass in the early1990s.

Brenøe and Kofman reviewed the eight tests on har-vesting early thinnings conducted within the frameworkof the project, which also included tests on “integratedharvesting” (Brenøe and Kofman 1990). They classi-fied the sites for processing whole trees into terminals,landings, and forests, and analyzed the feasibilities,advantages and disadvantages of each site. Their con-clusion was that the only economically feasible inte-grated method for harvesting early thinnings was the“tree section” method used in Sweden and Finland.

From 1992 to 1994, studies were carried out underthe theme “Harvesting and Supply of Woody Biomassfor Energy (IEA Bioenergy Task IX).” In Canada,Puttock investigated “integrated harvesting” of wholetrees by comparing the costs of collecting forestbiomass to landings and chipping for the systems usedin the participating countries and analyzing their ad-vantages and disadvantages (Puttock 1995). The ad-vantages of recovering logging residues included thereduced risk of pest insects and forest fire, improvedefficiency of planting seedlings, and the resultant in-creases in the survival rate of planted young trees, al-though the economic benefits were difficult to quan-tify. The disadvantages included soil erosion causedby compaction and disturbance of the soil due to theincreased work-associated activity in forests, removalof nutrients, and resultant adverse effects on treegrowth. Puttock suggested that compaction and ero-sion of the soil could be avoided by restricting theroutes of machines used in forests and that the fertilityof the soil could be recovered by returning incinera-tion ashes of forest biomass to prevent decreases innutrients.

The main results of IEA Bioenergy Task IX weresummarized in 1995. Culshaw and Stokes summarizedthe mechanization of short rotation forestry (SRF)(Culshaw and Stokes 1995), Hudson summarized thesection on “integrated harvesting” (Hudson 1995),Gingras summarized the harvest of small-diameter treesand recovery of logging residues (Gingras 1995), andAngus-Hankin et al. summarized the section on forestbiomass transportation (Angus-Hankin et al. 1995).

Hudson published a report on the efforts made byparticipating countries on “integrated harvesting”(Hudson 1995). Two different technologies, the chainflail method developed in North America and the“Massahake Method” developed in Finland, involve



separating clean wood chips for pulp production fromthose for fuel during the production of whole-tree chips.Hudson reported that these technologies made thinningoperations economically feasible. In comparison, the“tree section” system, which was developed in Nordiccountries and was once the most popular “integratedharvesting” system, was used less frequently due tothe increasing use of single-grip harvesters. Accord-ing to Gingras, the multi-tree felling heads that werebeing developed in Nordic countries would be able tocut two or more small-diameter trees simultaneously,representing an option for mechanizing early thinningand improving its cost effectiveness (Gingras 1995).Angus-Hankin et al. compared the costs of transport-ing wood chips produced from logging residues, in-tact logging residues, and “tree sections” over a dis-tance of 80 km on a trailer that could carry at least 100m3 (Angus-Hankin et al. 1995). They also discussedthe possibility of transporting baled logging residues.Comparative studies on the costs of the different har-vesting methods of forest biomass, such as wood chips,logging residues, and baled residues, started during thisperiod.

From 1998 to 2000, studies were conducted as partof the “Conventional Forestry Systems for Bioenergy(IEA Bioenergy Task 18)” project. It should be notedthat SRF and “integrated harvesting,” such as the chainflail technology (which are regarded as “one-pass sys-tems”), were discussed within the framework of “ShortRotation Crops for Bioenergy (IEA Bioenergy Task17)” mainly in the United States. Thus, Task 18 spe-cialized in the use of bioenergy in forestry. The statusand efforts of participating countries were reportedfrom Finland (Nurmi 1999), Denmark (Heding 1999),the Netherlands (Vis 1999), and New Zealand (Hall2000).

Nurmi reported that logging residues in Finland wereusually transported after they had been processed intochips using chipper-forwarders in forests or at road-side landings and that harvesting of the loggingresidues could reduce reforestation costs by 100 US$per hectare (Nurmi 1999). The transportation distanceof forest biomass that formed a break-even point was40–50 km when a cogeneration plant was assumed.

Heding reported that in Denmark wood chips weremainly a product of forest thinning, which involvedfelling trees in winter, leaving the trees in the forestduring the summer to reduce the water content to one-third and return the leaves to the soil, and chipping thewhole trees in the forest using chipper-forwarders(Heding 1999). The market price per gigajoule was 6US$. Although the production of wood chips on its ownwas only just profitable, this method had greatly im-proved the efficiency of the final cutting of the thinnedforests.

Vis reported that the mechanization of forestry in theNetherlands had reduced the production cost by 70%

during final felling and by 66% during thinning (Vis1999). Since there was no demand for low-qualitymaterials other than for timber and pulp, mechaniza-tion provided a good opportunity for utilizingbioenergy. A harvesting system similar to that of Den-mark was used, but logging residues after final cuttingwere also harvested.

Hall reported that forestry in New Zealand hadshifted from collecting “tree sections” to harvestingwhole trees and intensively limbing and bucking atlandings, resulting in vast amounts of logging residues;consequently, methods for dealing with the residueshad to be developed (Hall 2000). Four methods wereinvestigated: (1) disposed of as waste; (2) burned atthe site; (3) used as fuel in pulp mills; (4) used as ma-terial for producing fiberboard and pulp chips. Onlymethod (4) was profitable.

Studies on the development of test balers and multi-tree felling heads were also carried out within theframework of Task 18. Balers process logging residuesinto cylindrical bales by compression, thereby enablingthe bales to be handled as logs. A bale is also called a“bundle” or “composite residue log (CRL).” Multi-treefelling heads can cut two or more small-diameter treessimultaneously. The two harvesting systems that re-ceived the most attention were (1) a method that in-volved felling, limbing, and bucking trees in the forestusing harvesters, collecting the logs using forwarders,and then harvesting forest biomass, and (2) whole-treelogging that involved limbing and bucking at roadsidelandings and transporting the forest biomass. Thesesystems can be regarded as “two-pass systems” andare classified into several groups according to the lo-cation for producing wood chips.

This project was characterized by a number of com-parative studies on harvesting cost per unit weight (orunit energy), which were conducted by assuming twoor more systems for each type of forest biomass trans-portation. For example, the harvesting costs of non-chipped logging residues, wood chips, and bales oflogging residues were investigated (Andersson 1999,Andersson et al. 2000, Eriksson 2000, Hudson andHudson 1999, 2000, Hunter et al. 1999). In many stud-ies, transporting non-chipped logging residues to en-ergy-conversion plants on large-sized trailers and chip-ping intensively by large-sized chippers was found tobe the least expensive method. However, Hudson andHudson determined that baling would become rela-tively less expensive with increasing transportationdistance, even though balers were still being used onan experimental basis (Hudson and Hudson 2000).Asikainen and Kuitto from Finland compared the har-vesting costs between (1) collecting logging residuesto roadside landings and then chipping and (2) chip-ping logging residues in the forest using chipper-for-warders or chipper-trucks (Asikainen and Kuitto 2000).Andersson and Eriksson tested multi-tree felling heads



and reported that mechanization of early thinning,which was conventionally conducted using chain saws,would improve productivity, reduce costs, and enableutilization of early thinnings for energy (Andersson1999, Eriksson 2000).

A summary of the results of Task 18 was publishedin 2002 (Richardson et al. (eds.) 2002), but the projectcontinued for a further 6 years following 2001 underthe auspices of the “Conventional Forestry Systems forSustainable Production of Bioenergy (IEA BioenergyTask 31).” Although Task 18 stayed in the pilot phase,the new Task 31 holds the promise of both practicalityand business possibilities; for example, the bundler hasbeen diffused in Finland (Hakkila 2004) and exportedto other countries (Cuchet et al. 2004).(b) Other studies

Studies have also been carried out on the harvestingof forest biomass outside of the framework of IEABioenergy Tasks. The majority of these studies on for-est biomass focused on logging residues from finalfelling and small-diameter trees from early thinning.

Based on the findings of a Canadian study,Desrochers et al. reported that residues from shortwoodlogging, a type of logging widely performed in con-ventional forestry, were difficult to harvest due to tech-nological problems, low productivity, and high costs(Desrochers et al. 1993). However, an energy-utiliza-tion system that involved collecting logging residues,producing chips at roadside landings, and transportingthe chips would be feasible due to the spread of chip-pers for chipping residues and the advantages of re-moving residues from forest floors, including the re-duction in reforestation costs. These authors verified asystem of harvesting logging residues and collectingto roadside landings by chipping the residues using anewly developed chipper-forwarder and compared theresults with that of a system used in Canada that con-sisted of collecting logging residues using a skidderinstalled with a loader and chipping the residues usinga chipper mounted on a truck. A similar investigationon harvesting and chipping logging residues using chip-per-forwarders was conducted by Asikainen andPulkkinen in Finland (Asikainen and Pulkkinen 1998).Both studies showed that the use of chipper-forward-ers was lower in terms of productivity and more ex-pensive than producing chips at roadside landings.

In New Zealand, Hall et al. compared the costs ofharvesting logging residues in forests and at landingsfor each chipping location (including the introductionof chipper-forwarders) (Hall et al. 2001). Since thescale of chipping had a large effect on the costs, theleast expensive method was to transport residues toenergy-conversion plants and chip the residues inten-sively using large-sized chippers for residues both inforests and at landings.

In Finland, Malinen et al. conducted an analysis onthe use of logging residues in forests generated during

thinning and final felling based on calculations of theamount of forest biomass that could be utilized whenit had to be hauled a distance of 250 m in the forestand transported a distance of 40 km on truck to an en-ergy-conversion plant, with a focus on various upperlimits in cost (Malinen et al. 2001). In Finland, log-ging residue is widely utilized as an energy source, andmanuals for harvesting residues have been prepared(Alakangas et al. 1999).

In Spain, Delgado and Giraldo investigated the uti-lization of small-diameter trees from early thinning asboiler fuel by limbing and bucking in forest, collect-ing by tractors, producing chips at roadside landings,and transporting (Delgado and Giraldo 1995). For amaximum transportation distance of 30 km, the costsfor harvesting and chipping were 1.45 and 2.45 pese-tas per kg (water content was 15% (wet basis)), re-spectively.

In Sweden, Sennblad estimated the cost of produc-ing wood chips for a regional heating plant by harvest-ing logging residues during thinning and final fellingand small-diameter trees during early thinning forsmall- and large-scale systems (Sennblad 1994). For ahauling distance of 300 m in the forest and a transpor-tation distance of 30 km on truck, a large-scale systemwas more profitable than a small-scale system.Sennblad proposed schedules of harvesting forestbiomass for small-scale forestry managers, includingthe processes from early thinning to final felling, tohelp them overcome this disadvantage (Sennblad1995).

A point worth noting is that since tree tops andbranches on forest floors are decomposed and serve asnutrients for trees, harvesting logging residues mayremove nutrients from the forest and adversely affectthe growth of trees. This topic has been widely studiedin Nordic countries, and Lundborg from Sweden hassummarized the study results into a review (Lundborg1997). Lundborg investigated the effects of harvestinglogging residues and whole trees on organic matter andmineral nutrients in the soil and concluded that theharvesting of forest biomass had almost no effect onorganic matter. In contrast, mineral nutrients are re-duced by harvesting, although returning the incinera-tion ash of forest biomass to the forest can prevent thesoil acidification (Lundborg 1998). Börjesson fromSweden assessed the return of incineration ash in termsof cost (Börjesson 2000). In Sweden, the cost of har-vesting logging residues was 3.8–4.2 US$ pergigajoule, but the cost of returning incineration ash wasonly 0.18–0.48 US$ per gigajoule. Moreover, when theenvironmental benefits of returning the ashes wereconverted into monetary value, the procurement costof logging residues was estimated to be 1.1–4.6 US$per gigajoule.

Studies on harvesting forest biomass in SRF havebeen conducted on separating clean chips for pulp pro-



duction from chips for fuel using the chain flail tech-nology (Hartsough et al. 2000, Stokes and Watson1991), methods for chipping small-diameter trees andthe development of baling machines (Felker et al.1999), the performance of skidders and front-end load-ers used in whole-tree logging (in Italy) and actualchipping operations (Spinelli and Hartsough 2001a, b).Spinelli and Hartsough (2001c) reviewed the Italianchipping operations in detail.

In summary, Fig. 1 illustrates the overview of thedevelopment and diffusion of harvesting technologiesaccording to the kinds of forest biomass resources.

1-3. Objective and framework of the study

The objective of this study is to discuss the feasibil-ity of a harvesting, transporting, and chipping systemfor forest biomass resources in Japan. The subject isfirst approached by presenting a comprehensive dis-cussion of the various visions on the introduction anddiffusion of woody bioenergy utilization in terms ofthe quantification of available woody biomass re-sources for energy, the development of low-cost har-vesting and transporting systems, and the conversionprocesses. Second, a harvesting, transporting, and chip-ping system for logging residues is constructed, andthe feasibility of the system is examined from the pointsof view of cost, energy balance, and carbon dioxide(CO2) emissions on the basis of field experiments at

forestry operation sites. Third, the feasibility of theenergy utilization of forest biomass resources in amountainous region is discussed by analyzing the re-lationship between the mass and the procurement costof forest biomass in the region with the aid of a geo-graphic information system (GIS). The following sub-jects are examined and discussed in six chapters andthe conclusions derived from the chapters are summa-rized in the last chapter:• Chapter 2: The feasibility of utilizing woody biomassas an energy resource in Japan is discussed based onamount and availability of woody biomass, and energy-conversion technologies;• Chapter 3: The concept of a “harvesting system forlogging residues by a processor and a forwarder” isexamined for the purpose of constructing a system toharvest logging residues as a new resource for energy;• Chapter 4: A “harvesting and transporting system forlogging residues” is constructed with reference to threeEuropean countries where the utilization of bioenergyis making steady progress and examined on the basisof field experiments in Japanese forestry;• Chapter 5: An experiment on the comminution oflogging residues with a tub grinder is carried out inorder to calculate the productivity and procurement costof wood chips;• Chapter 6: Using the method of a life cycle inven-tory (LCI) analysis, the energy balance and the CO2emission of logging residues from Japanese conven-

Fig. 1. Overview of the development and diffusion of harvesting technologies according to the kinds of forest biomass re-sources.



tional forestry as alternative energy resources isanalyzed over the entire life cycle of the residues;• Chapter 7: The feasibility of the energy utilizationof forest biomass in a mountainous region in Japan isdiscussed with the aid of the GIS.

2. Woody biomass resources and conversion inJapan: The current situation and projectionsto 2010 and 2050

In this chapter, the feasibility of utilizing woodybiomass as an energy resource in Japan is discussedbased on the amount and availability of this resourceand energy-conversion technologies (Yoshioka et al.2002b, 2005b). First, an overview of the present stateof woody biomass is given, with an estimation of theamount of resources available for energy as well as adiscussion of the future prospects of the resources.Secondly, the systems for logging residues are exam-ined with respect to the development of low-cost har-vesting and transporting systems, which is a key issuein the discussion on the introduction and diffusion ofwoody bioenergy utilization. Thirdly, the visions onthe bioenergy utilization are presented in terms of 2010,which is the time frame for achieving the goals of theKyoto Protocol on the reduction of greenhouse gasemissions, and 2050, when the problems on the deple-tion of fossil fuel resources are expected to worsen, asthese years represent the targets for realization of theshort-term and long-term visions, respectively. Finally,

the utilization patterns, conversion processes, problemsof technical development, and policy actions that thegovernment should adopt are discussed on the condi-tion that a small-scale and decentralized system and alarge-scale and centralized system can coexist.

The following items are considered to be woodybiomass (waste paper and black liquor are excluded):• Logging residues, i.e., tree tops and branches thatare generated during limbing and bucking operations;• Thinned trees that are left in forests because the log-ging costs are higher than the timber price;• Trees to be thinned from coniferous forests whichare behind in tending;• Coppice forests, i.e., broad-leaved forests that wereformerly managed, mainly for fuelwood use, but arenow left unutilized;• Bamboo and bamboo grass (Sasa spp.);• Mill residues, i.e., wood shavings and barks gener-ated in the sawmill and plywood industries;• Wood-based waste material;• Trimmings of park trees, roadside trees, and gardentrees.

2-1. The present situation of woody biomass inJapan

2-1A. The amount of woody biomassVarious studies (New Energy Foundation 2000, Re-

search Institute of Innovative Technology for the Earth1999, Saka (ed.) 2001, Yamaji et al. 2000) have been

Item Amount (Tg/y)

Logging residues2 3.0Trees to be thinned from coniferous forests which are behind in tending3 5.0Coppice forests, i.e. , broad-leaved forests4 9.0Bamboo5 0.3Bamboo grass6 3.0Mill residues7 0.4Wood-based waste material8 8.0Trimmings of park trees, roadside trees, and garden trees9 3.0

Total 31.7

Table 1. Annual potential amount of woody biomass in Japan on a dry-weight basis.1 Reprinted from Biomass and Bioenergy,29(5), Yoshioka et al., Woody biomass resources and conversion in Japan: The current situation and projections to 2010 and2050, 336–346, Copyright (2005), with permission from Elsevier.

1The annual potential amount here is based on studies by Harada (2000) and Honda (1986).2Including thinned trees that are left in forests because the logging costs are higher than the timber price.3Cutting forests which should have been thinned at the thinning rate of 20%.4Cutting broad-leaved forests (excluding the forests for logs and bed-logs for shiitake mushroom production) less than 500 mfrom forest roads with the cutting cycle of 30 years.5Harvesting 30% of the annual amount of 1.0 Tg/y on a dry-weight basis.6Harvesting the grass less than a certain distance from forest roads.7Covering all of the wood industries.8Consisting of demolition woods, wastes from new construction, and old materials of pallets and packages.9Net primary production of the park, roadside, and garden trees.



conducted to estimate the amount of woody biomassin Japan. The annual potential amount here is basedon the studies made by Harada (2000) and Honda(1986) as shown in Table 1. The value of 31.7 Tg/ygiven in Table 1 is in accordance with the estimationsreported in the studies mentioned above. This amountof woody biomass has a calorific value of 634 PJ (176TWh), corresponding to 2.8% of the national primaryenergy supply in the fiscal year 1999, 23.0 EJ (6.39PWh) (Energy Data and Modelling Center (ed.) 2001).

The amount of logging residues (3.0 Tg/y, Table 1)was estimated based on the annual cut volume of 29Mm3/y. Even subtracting this cut volume, the growingstock continues to increase by 69 Mm3 annually in Ja-pan, mainly in the 10 million ha of the man-made for-ests which were afforested after the war. Therefore,the future available amounts of logging residues andthinned trees for energy are expected to increase con-siderably from a current total of 8.0 Tg/y, provided thatpolicy-makers focus on bioenergy and the cutting offorests is promoted. In terms of the utilization ofthinned trees, it is assumed that all of the cut materialfrom thinning can be used for energy at the actual Japa-nese market value. However, this assumption may beunrealistic based on the “cascade use” or multistageuse of wood (which means that wood fiber should beused for higher valued products as much as possiblebefore it is recycled as an energy resource), so thatfurther discussion is necessary.

Broad-leaved forests are potential sources of largeamounts of biomass annually (9.0 Tg/y). The rich eco-systems of coppice forests were traditionally main-tained by periodic cutting (coppice forests were cut forcharcoal for iron and steel as well as cooking). At the

present time, however, broad-leaved forests are leftunutilized, and degradation is progressing. Therefore,a new type of hardwood forest management that in-volves cyclic logging for the purpose of energy use isproposed so that the rich ecosystems of the broad-leaved forests can be restored.

The growth characteristics of bamboo and bamboograss make it a valuable biofuel resource. A bamboograss harvesting machine was developed in the oil cri-ses of the 1970s, but never put into practical use. Infield trials using this machine, the harvesting cost wascalculated to be 17.5–20.8 US$/Mg on a dry-weightbasis when the haulage distance was 200 m to forestroads (Agriculture, Forestry and Fisheries ResearchCouncil Secretariat (ed.) 1991); this cost is quitefavorable compared to those of other existing technolo-gies. Therefore, it should not be too difficult to intro-duce the machine into forests with gently undulatingterrain on a trial basis and estimate the actual avail-able amount of bamboo grass.

In addition to the total of 8.4 Tg/y of mill residuesand wood-based waste material noted in Table 1, 1.90Tg/y, 3.84–3.86 Tg/y, and 3.83–4.15 Tg/y of thesematerials are already used for compost and litter, in-dustrial materials, and fuels, respectively (Harada2000). However, it is supposed that there should bethe following patterns of disagreeable waste recyclingor disposal to no small extent:1) Accepted free of charge by wood chip merchandis-ers as industrial materials and by stock farmers forcompost and litter;2) Disposed of by industrial waste disposal contrac-tors with compensation;3) Burned in private garbage incinerators unavoidably.

Process Machine Harvesting and transportation cost (US$/Mg)Case 1 Case 2 Case 3

Compression Bundler1 26.7Comminution Mobile chipper2 58.3 58.3Haulage Forwarder3 35.0 35.0 25.8Transportation Truck4 130

Trailer5 18.3 16.7Comminution Large-sized chipper6 11.7

Total 223 112 80.8

Table 2. Harvesting and transporting costs of logging residues per Mg on a dry-weight basis. Reprinted from Biomass andBioenergy, 29(5), Yoshioka et al., Woody biomass resources and conversion in Japan: The current situation and projections to2010 and 2050, 336–346, Copyright (2005), with permission from Elsevier.

1From Hudson and Hudson (2000).2Power output of the engine is 79.4 kW/2,200 rpm.3A wheel-type forwarder with 3,000 kg of load capacity is assumed.4A truck of 4 tons by a transport contractor.5Purchasing a 18-ton trailer with a cubic capacity of 60 m3 and employing a driver is considered.6A tub grinder is assumed, and power output of the engine is 295 kW/2,100 rpm.



The items listed above can be switched over to energyutilization by purchasing item 1) for a small amountof money and by collecting items 2) and 3) withoutcharge.

Gardening companies are obliged to dispose of theirtrimmings as industrial wastes. Such wastes can alsobe used for energy by collecting them without charge.

The introduction of energy utilization of woodybiomass is viewed as the next logical step in the se-quence of recycling waste. As such, it is necessary toassess the actual amounts of mill residues, wood-basedwaste material, and trimmings that are available forenergy purposes. However, there is also a need for es-tablishing a collection system within a region prior totheir use.

2-1B. A harvesting and transporting system forwoody biomass

In order to utilize logging residues and thinned treesfor energy, it is necessary to harvest them from forestsand transport them to energy-conversion plants. Threecase studies on the costs of a harvesting and transport-ing system for logging residues are presented in thischapter as examples of a lowest cost system and itsrefinement:• Case 1: The lowest cost system is constructed byusing state-of-the-art machines that are currently com-ing into widespread use in Japanese forestry processes.This system, in which a mobile chipper is operated atthe landing of a logging site (in a forest), is based onthe field experiments carried out within the frameworkof ongoing studies (Yoshioka et al. 2000, 2002a);• Case 2: In the transportation process, the shift froma transport contractor with a truck of 4 tons to the pur-chase an 18-ton trailer with 60 m3 of cubic capacityand an employed driver would be of interest becausethe transporting cost in Case 1 is too high (Yoshioka etal. 2002b). In Japan, trailers of this class are ownedmainly by paper companies;• Case 3: A bundler, which compresses loggingresidues into cylindrical bundles, has been recentlydeveloped in the Nordic countries. Bundles can be col-lected and transported in the same way as logs. Japa-nese forest engineers have shown a great interest inbundlers because they may improve the operationalefficiencies of harvesting and transporting residues.Thus, in Case 3, the bundling process is incorporatedinto the system of Case 2 and examined with referenceto the findings of Hudson and Hudson (2000).

The harvesting and transporting costs of the threecases listed above are shown in Table 2. The cost inCase 2 is almost half of that in Case 1. However, inorder to realize a system similar to that of Case 2 inJapan, it is necessary to construct networks of high-grade forest roads so that large-sized trailers can traveldirectly to the landings of the logging sites. Addition-ally, for the purpose of enhancing the operational

efficiencies of comminution and haulage, the introduc-tion of bundlers or chipper-forwarders that have bothchipping and forwarding functions needs to be consid-ered.

The cost in Case 3 is lower than that in Case 2, sug-gesting the feasibility of incorporating bundlers intothe low-cost harvesting and transporting system. A bun-dling system, however, is applicable only for gentleterrain like that found in Nordic countries; conse-quently, it will be necessary to develop a machine suit-able for Japan where the topography is very steep.

The average transportation distance of the systemsexamined in this chapter is 40 km. Hudson andHudson (2000) calculated the harvesting and transport-ing cost of logging residues in the U.K. to be 45.0US$/Mg when the transportation distance was 100 km.This is a more favorable result than Case 3, which isthe cheapest case of the three presented above. Thecalculation for Japanese conditions is based on fieldexperiments complemented with data from studies per-formed outside of Japan. Therefore, it is still possibleto reduce the harvesting and transporting cost in Japanif the introduction and diffusion of bioenergy utiliza-tion are promoted. The improvement of the systemshould include an accumulation of experience from thefield experiments such as, for example, improvementsin operating techniques.

Consequently, for the purpose of establishing a low-cost harvesting and transporting system for loggingresidues, it will be necessary that the infrastructureshould be improved; however, the development of tech-nology as well as the promotion of testing in field ex-periments should be considered as short-term tasks.

2-2. Prospects for woody bioenergy utilization inJapan

The regulation of dioxin emissions by the alreadystrengthened “Waste Management and Public Cleans-ing Law” and Japan’s obligations under the Kyoto Pro-tocol, with the first commitment period starting in2008, are expected to be the driving forces for woodybioenergy utilization in both the waste recycling andenergy production sectors. The Kyoto Protocol stipu-lates that Japan must reduce its greenhouse gas emis-sions by 6% from 1990. Therefore, 2010 is the targetyear for the short-term time frame. The long-term timeframe extends to 2050, when the problems associatedwith the depletion of fossil fuel resources are expectedto worsen. Thus, possible technological and infrastruc-ture developments need to be put in the perspective ofthese time frames.

2-2A. Short-term vision (around the year 2010)(a) A small-scale and decentralized system

In the year 2010, the following pattern of woodybiomass utilization will be diffused: All of mill



residues, wood-based waste material, and trimmingsthat formerly needed to be disposed of as waste prod-ucts in addition to some of logging residues and thinnedtrees will be utilized as energy resources. There willbe two aspects to the energy utilization of woodybiomass, namely, waste recycling and energy produc-tion.

Unlike energy forest products that are cultivated andharvested systematically, many types of biomass gen-erated as wastes are dispersed in low-density centers,necessitating collection and transportation for use atan energy-conversion plant. Converting biomass toenergy directly at the location where waste biomass isactually generated is one option for reducing the costsof collection and transportation. Two possibilities,namely, “on-site” and “regional” types of energy-con-version processes feasible in Japan, are discussed here.

The present situation of energy-conversion processesof woody biomass in Japan is briefly outlined in Fig.2. Bio-oil production by the process of fast pyrolysisis becoming of interest internationally, especially inEurope, but it has attracted less attention in Japan. Bio-oil as liquid fuel, for example, may be less availabledirectly to vehicles and still needs technical develop-ment. Consequently, direct combustion or gasificationis considered to be easier for the case of the small-scale energy-conversion technology of woody biomass.On the other hand, upgraded wood fuels, such as pel-lets and briquettes, are becoming popular in Japan, andmore than ten pellet-production plants using millresidues, wood-based waste material, and trimmingsare already in operation.(a-1) “On-site” type of energy-conversion process

This is the case where woody biomass is convertedto energy and utilized at the site of waste biomass gen-eration. In such a case, a company which experiencesdifficulty in disposing of wastes but which has a de-

mand for heat and electrical power is expected to in-troduce this process into its own facility for waste re-cycling and energy production. According to the sur-vey by the Japan Institute of Energy, the averageamount of woody biomass generated per company in aJapanese sawmill, plywood, and gardening industry is2–10 Mg/d on a dry-weight basis.

The following three processes are considered to bepromising energy-conversion processes with the capa-bility to cope with such amounts of biomass:1) Thermal utilization by the direct combustion ofwoody biomass;2) Power generation and thermal utilization, i.e., com-bined heat and power (CHP), by the direct combustionof woody biomass and a steam turbine;3) CHP by a fixed bed gasifier and a gas engine.Among the processes listed above, processes 1) and 2)are already at the level of introduction and diffusion.Process 3) is considered to be at the level of demon-stration, since various types of technical developmentshave been promoted nationally and globally and/or indeveloped and developing countries. With regard to thesmall-scale gasification with a gas engine, however, alow-cost technology that treats tarry waste water fromscrubbing has still to be developed.

In terms of the operational management and energydemand of a small-scale system, it is difficult for an“on-site” type of energy-conversion facility to operatearound the clock; therefore, a system that starts andstops daily is desirable. In this case, the utility aspectsof the energy-conversion facility are important; forexample, such systems require a device for rapidly fir-ing up and turning off the gasifier.

With respect to the scale of a plant, when the through-put of woody biomass, hours of operation, and ther-mal efficiency are 5 Mg/d on a dry-weight basis, 8hours a day, and 8%, respectively, the net generation

Methanol/DME synthesis by gasification

Slurry fuel

CHP by direct conbustion and a steamturbine

(Pellet)

Co-firing of biomass with coal

Power generation by gasification and agas engine/a gas turbine

R&D level Demonstration level Practical level

Thermal utilization by direct conbustion

Direct thermochemical liquefaction

Fuel oil production using methanol fromsupercritical water gasification

Ethanol fermentation by acid hydrolysis

Power generation by a Stirling engine

Fig. 2. Present R&D development and stages for energy-conversion processes of woody biomass in Japan. Reprinted fromBiomass and Bioenergy, 29(5), Yoshioka et al., Woody biomass resources and conversion in Japan: The current situation andprojections to 2010 and 2050, 336–346, Copyright (2005), with permission from Elsevier.



of power is calculated to be 420 kW. This output mayprovide all of the electricity needed to run the facility;moreover, there may be surplus. At the present time,Japanese electric power companies seldom buy elec-tricity from small-scale biomass-based power genera-tion plants. In order to diffuse the “on-site” type ofenergy-conversion process, it is essential to improvethe system of trading surplus electricity.(a-2) “Regional” type of energy-conversion process

This is the case where biomass generated within aregion is collected and converted to energy. In this sce-nario, the larger the collection area is, the greater theamount of biomass resources for energy can be col-lected, leading to some reduction in the investment andoperation costs of a plant. On the other hand, the trans-portation cost increases with expansion of the collec-tion area. Thus, in the case of the “regional” type ofenergy, there will always be a trade-off between thesetwo factors in terms of the appropriate utilization ofwoody biomass and the technical development.

The relationship between the collection area and theamount of woody biomass cannot be defined com-pletely. The net power output, however, is calculatedas 4.2 MW when the throughput of woody biomass,hours of operation, and thermal efficiency are 50Mg/d on a dry-weight basis, 8 hours a day, and 8%,respectively, by the process of direct combustion anda steam turbine, which is the available energy-conver-sion technology at the present moment. A grate-firedfurnace is usually adopted to the process of direct com-bustion and a steam turbine. When a grate-fired fur-nace is used, the volume of steam is relatively stableto any variation in the components of the fuel. There-fore, power generation by direct combustion of woodybiomass and a steam turbine is suitable for using vari-ous types of biomass within a region as fuel.

In this process, it is possible to utilize loggingresidues and thinned trees generated within a regionas fuel, in addition to the mill residues, wood-basedwaste material, and trimmings that are the targets forthe “on-site” utilization mentioned above. Moreover,it is realistic to deal with unutilized agriculturalresidues, such as rice straw and rice hull, generatedwithin the same region together. Many kinds of agri-cultural residues are generated intensively in one spe-cific period of the year, so it is not effective to estab-lish an energy-conversion facility dedicated solely toprocessing these residues. Consequently, as the aim ofthe facility should be to convert all the biomass re-sources available within a region to energy, a powergeneration plant financially sponsored by joint publicand private sector investment is desirable.

In order to realize the “regional” utilization, improve-ment of the energy-conversion technologies is neces-sary to obtain higher efficiency. Construction of low-cost harvesting and transporting systems for biomassis also necessary.

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(b) A large-scale and centralized systemCo-firing of woody biomass with coal is expected to

be the most feasible in the year 2010. Table 3 lists theadvantages and disadvantages of the co-firing of woodybiomass at an existing coal-fired power plant.

It is very important to adopt a vision that maximizesthe advantages and minimizes the disadvantages to-ward energy utilization of woody biomass. Whenwoody biomass is co-fired with coal at the 5–10% ra-tio of biomass, for example, a simple arithmetic calcu-lation demonstrates that the carbon dioxide emissionswill also be reduced by 5–10%. Although the harvest-ing and transporting cost of woody biomass is ratherhigh as mentioned above, the effectiveness of the re-duction is still substantially advantageous. Japan is sopoor in fossil fuel resources that the self-sufficiencyrate in the energy supply is around the 10% level.Therefore, the introduction of such an approach tobioenergy utilization will have a great effect not onlyon the self-sufficiency rate in the energy supply butalso on the utilization of national forest resources andthe conservation of the global environment.

In order to promote the diffusion of a large-scale andcentralized system, it is essential that Japan establisha national consensus as well as a strategic scenariobased on the international situation and to develop theenergy-conversion process. These must be aimed atlong-term development and should not remain in theshort-term vision. Based on the forecast for future en-ergy demand in Japan and the target for the conserva-tion of global environment (including the measuresagainst global warming), it is necessary to establish aprogram for the effective use of biomass that will guar-antee a stable supply of energy resources of hydrocar-bon origin, as well as to prioritize the direction of fu-ture research and development. It is also necessary toconsider a scenario in which both the long-term visionis realized in the target year 2050 and bioenergy utili-zation is promoted. In this scenario, for example, acomprehensive system that includes the import ofbiomass from foreign countries will be proposed. Interms of a large-scale and centralized system, promo-tion of the design and development of the IntegratedGasification Combined Cycle (IGCC) and the cleanliquid fuel production process, which substitute for coaland oil, respectively, is desirable from the point of viewof a smooth transition to bioenergy utilization follow-ing the depletion of fossil fuel resources.

2-2B. Long-term vision (around the year 2050)(a) A small-scale and decentralized system

Around the year 2050, almost all the woody biomasswaste resources will be utilized for energy productionin one way or another, so that the “on-site” type ofenergy-conversion process combining waste recyclingand energy production will already have been diffused.Therefore, the “regional” utilization system targeted

for unutilized resources is considered to be the maintype of energy-conversion process at this time. Theterm “region” here is assumed to be an area smallerthan the administrative unit (a city, town, or village).In this case, the comprehensive energy-conversionplant that accepts all of the biomass resources within aregion and produces electrical power, heat, and liquidfuel according to the energy demand in the region willbe realized.

In 2050, the depletion of oil will have become a re-ality, so the demand for liquid fuel which substitutesfor oil is assumed to increase considerably. In townsand cities, building the infrastructure of natural gas andhydrogen will be promoted (but not in mountainousareas), and the shift to hydrogen and the like in theenergy supply is expected to start.

In such a situation, it will be necessary to utilizebiomass generated within a region as effectively aspossible and to fulfill the energy demand in the region.Not only logging residues, thinned trees, and unutilizedagricultural residues but also mill residues, wood-basedwaste material, and trimmings will be targeted for en-ergy use. Moreover, the sustainable use of unutilizedbroad-leaved forests, bamboo, and bamboo grass, i.e.,without damage to these ecosystems, will have started.With the aid of the global land use and energy (GLUE)model (Yamaji et al. 2000), the annual potential amountof biomass indicated above is estimated to be 1.44EJ/y (400 TWh/y), corresponding to 6.3% of the na-tional primary energy supply in the fiscal year 1999.

The scale of an energy-conversion plant is largelydependent on the amount of generated biomass. How-ever, given the realization of a plant with throughputof biomass, hours of operation, and thermal efficiencyof 200 Mg/d on a dry-weight basis, 8 hours a day, and20%, respectively, the net power output is calculatedas 33 MW, which is sufficient to fulfill the regionalenergy demand. Various types of combinations of en-ergy-conversion technologies, such as a combinationthat supplies heat and power by gasification as well asliquid fuel by alcohol fermentation, should be devel-oped. In order to realize such a combination, improve-ments in energy-conversion technologies and efficiencyas well as reductions in the construction costs of a plantare necessary.

The management pattern of such an energy-conver-sion facility cannot be predicted at this time. However,a power generation plant financed by the joint invest-ment of local residents, a municipality, and companiesis regarded as one of the possibilities.(b) A large-scale and centralized system

The population of Japan will decrease to about 105million around the year 2050 (Energy Data and Mod-elling Center (ed.) 2001); however, energy consump-tion per capita may increase as the standard of livingcontinues to rise. A reduction in the amount of carbondioxide emissions will also be required, but this re-



duction will be difficult to achieve through the effec-tive utilization of fossil fuel resources only, thus ne-cessitating the changeover to renewable energies. Spe-cifically, bioenergy as well as solar and wind energiesmust become the main sources of the primary energysupply. At the same time, given possible developmentsin utilizing existing solar and wind energies, hydrogenenergy systems could be introduced and diffused. Insuch a situation, woody biomass and unutilized agri-cultural residues can contribute to the national primaryenergy supply only at the single-figure-% level at most,as mentioned above, so the utilization of foreignbiomass resources must be considered.

The import of foreign biomass resources has beenstudied (Dote and Ogi 2001). In terms of carbon diox-ide emissions related to the shipping of biomass, theamount of the emissions can be reduced by convertingbiomass to liquid fuel in foreign countries. In this case,however, potential environmental degradation in thosecountries supplying the biomass should be a point ofgreat concern. It will therefore be necessary for Japanto make an import and export contract with eachbiomass supply country in which there is an explicitagreement that the forest cultivation program based onperiodic biomass plantation is carried out in a sustain-able way in that country. Japan will also be required toimplement a policy that takes into account the curbingof global carbon dioxide emissions, such as throughprojects of revegetation in the desert, and others. More-over, it will be important to work at the internationallevel for approval of these activities, which are ex-

pected to reduce the amount of carbon dioxide emis-sions both nationally and globally as well as to protectthe forests in developing countries from destruction,as part of the clean development mechanism (CDM).According to the GLUE model, North America, LatinAmerica, the former USSR, and Eastern Europe arepossible countries for biomass plantation use when thefuture increase in demand for food production is takeninto consideration (Yamaji et al. 2000). The conflictbetween biomass plantation and food production mustbe prevented.

These foreign biomass resources and converted liq-uid fuel will be unloaded at sea ports in the same wayas coal. Therefore, those energy-conversion plants lo-cated along the sea coast that are currently used to storeand refine coal and oil can be converted into the large-scale and centralized type of biomass utilization fa-cilities by increasing the biomass co-firing rate or byimproving the device for biomass processing. Liquidfuels, such as ethanol, for transportation use will besupplied by utilizing the existing infrastructure.

In summary, Fig. 3 shows the prospects for woodybioenergy utilization in Japan in terms of time and theuse of technologies and resources.

2-3. Further considerations

In the future, the government, municipalities, andprivate sector are expected to become promoters of andstake-holders in the woody bioenergy utilization. It istherefore important not only to assess the available

"On-site" type of energy-conversion process[Technology] Thermal utilization by direct combustion CHP by direct combustion and a steam turbine ("On-site" utilization will have been already diffused.) CHP by a fixed bed gasifier and a gas engine[Resource] Mill residues, wood-based waste material, and trimmings

"Regional" type of energy-conversion process[Technology] [Technology] Power generation by direct conbustion and a steam Comprehensive energy-conversion that produces turbine (using a grate-fired furnace) electrical power, heat, and liquid fuel (e.g., supplying[Resource] heat and power by gasification as well as liquid fuel by Mill residues, wood-based waste material, and trimmings alcohol fermentation)(+ Logging residues and thinned trees [Resource](+ Unutilized agricultural residues) Mill residues, wood-based waste material, and trimmings

Logging residues and thinned trees(Unutilized agricultural residues)(+ Unutilized broad-leaved forests, bamboo, and bamboo(+ grass

[Technology] [Technology] Co-firing of biomass with coal Changing the energy-conversion plants on the seashore[Resource] that are treating coal and oil now to the biomass Mill residues, wood-based waste material, and trimmings utilization facilities

Supplying the liquid fuel for transportation use by utilizing the existing infrastructure[Resource] Import of foreign biomass resources that are chipped or converted to liquid fuel in foreign countries

2050

Large-scale and

centralized system

Small-scale and

decentralized system

2010

Fig. 3. Prospects for woody bioenergy utilization in Japan from the aspects of the time and the use of the technologies and theresources. Reprinted from Biomass and Bioenergy, 29(5), Yoshioka et al., Woody biomass resources and conversion in Japan:The current situation and projections to 2010 and 2050, 336–346, Copyright (2005), with permission from Elsevier.



woody biomass resources according to their harvest-ing and transporting costs but also to establish energy-conversion systems that can use various types of wastebiomass together. Moreover, the construction of low-cost harvesting and transporting systems suitable forJapan is essential.

3. Feasibility of a harvesting system for loggingresidues by a processor and a forwarder

In this chapter, a “harvesting system for loggingresidues by a processor and a forwarder” is examinedwith the aim of constructing a system to harvest slashesmainly for energy use (Yoshioka et al. 2000). In thissystem, which was designed with reference to the pro-posal by Sundberg and Silversides (1989), a forwarderhauls slashes generated by a processor from the land-ing of a logging site (in the forest) to another landingalongside a forest road.

3-1. The harvesting system for logging residuesby a processor and a forwarder

This system consists of whole-tree yarding/skidding,processor limbing and bucking at a landing of a log-ging site, and forwarder hauling of logs and slashesseparately on a strip road (Fig. 4). In the proposal bySundberg and Silversides, which is suitable for coun-tries, such as Sweden, with a gentle terrain, forward-ers are used to recover slashes for energy use, and asystem consisting of harvesters and forwarders is sug-gested for collecting logging residues. However, Ja-pan is characterized by a steep topography and the needfor a high density of forest roads; as such, the “har-

vesting system for logging residues by a processor anda forwarder” is more suitable for Japan. Harvesterscannot be used on such steep terrain. Basic theoreticalequations for several operations have been constructedhere with reference to existing studies (Sakai 1987,Sakai et al. 1995) in order to analyze the feasibility ofthis type of system for harvesting slashes. The param-eters of the equations (from (3.1) to (3.15)) are sum-marized in Table 4.

3-1A. Processor limbing and buckingThe volume of logs (EP, m3/d) and the weight of

slashes (EPS, kgDM/d; DM: dry mass) processed perday are expressed as:

EP = 3600·cP·DP·VP/CTP (3.1)

EPS = 3600·cP·DP·WP/CTP (3.2)

3-1B. Forwarder hauling of logs and slashesThe volume of logs (EF, m3/d) and the weight of

slashes (EFS, kgDM/d) hauled by a forwarder per dayfrom a landing of a logging site to another landingalongside a forest road per day are expressed as:

EF = 3600·cF·DF·VF/CTF (3.3)

EFS = 3600·cFS·DFS·WFS/CTFS (3.4)

One cycle consists of loading in the forest, runningdownward fully-loaded on a strip road, unloadingalongside a forest road, and running upward with noload; the cycle times for hauling logs (CTF, s/cycle)and slashes (CTFS, s/cycle) are then expressed as:

Whole-tree yarding/skidding

Transport by truck

Forwarder hauling of logs and slashes (Running downward fully-loaded) (Forwarder

)gnidaolnU gnibmil rossecorP and bucking (Forwarder loading) Strip road (gravelled or only soil compacted)

(Running upward with no load)

Landing alongside a forest road

Hauling distance L (m)

Forest road)dellevarg ro devap( tseroF

Landing in a forest

Fig. 4. Harvesting system for logging residues by a processor and a forwarder. Reprinted with kind permission from SpringerScience + Business Media: Journal of Forest Research, Feasibility of a harvesting system for logging residues as unutilizedforest biomass. 5(2), 2000, 59–65. Yoshioka, T, Iwaoka, M, Sakai, H, Kobayashi, H, Fig. 1. 2000, Springer Japan.



Item Parameter

Volume of logs processed per day (m3/d) EP

Modification coefficient* cP

Effective working time per day (h/d) DP

Volume of logs processed from a whole tree (m3/tree) VP

Cycle time (s/tree) CTP

Weight of slashes processed per day (kgDM/d) EPS

Weight of slashes processed from a whole tree (kgDM/tree) WP

Volume of logs hauled per day (m3/d) EF

Modification coefficient* cF

Effective working time per day (h/d) DF

Volume of logs hauled per cycle (m3/cycle) VF

Cycle time (s/cycle) CTF

Hauling distance (m) LSpeed (m/s)

of running downward fully-loaded v1

of running upward with no load v2

Operation time (s)of loading TL

of unloading TU

Weight of slashes hauled per day (kgDM/d) EFS

Modification coefficient* cFS

Effective working time per day (h/d) DFS

Weight of slashes hauled per cycle (kgDM/cycle) WFS

Cycle time (s/cycle) CTFS

Operation time (s)of loading TLS

of unloading TUS

Input energy for harvesting slashes (MJ/d) HFS

Calorific value of fuel per unit volume (MJ/dm3) uFS

Fuel consumption of hauling slashes per day (cm3/d) FFS

Fuel consumption per cycle (cm3/cycle) CFFS

Fuel consumption per second (cm3/s)of running downward fully-loaded a1

of running upward with no load a2

of loading aLS

of unloading aUS

Output energy of slash biomass (MJ/d) HS

Calorific value of slashes per unit weight (MJ/kgDM) uS

Cost of hauling slashes per unit weight (US$/kgDM) CWFS

Cost of hauling slashes per day (US$/d) CFS

Cost per hour (US$/h)of labor Pof machine Mof fuel F

Weight of slashes per unit volume of logs processed (kgDM/m3) kWeight of logs per unit volume (kgDM/m3) mkProportion of the whole-tree weight (%)

weight of tops r1

weight of branches r2

weight of others r3

Table 4. Parameters of the basic theoretical equations (from (3.1) to (3.15)). Reprinted with kind permission from SpringerScience + Business Media: Journal of Forest Research, Feasibility of a harvesting system for logging residues as unutilizedforest biomass. 5(2), 2000, 59–65. Yoshioka, T, Iwaoka, M, Sakai, H, Kobayashi, H, Table 1. 2000, Springer Japan.

*The modification coefficients, cP, c

F and c

FS, modify the performance of the processor, E

P and E

PS, and forwarder, E

F and E

FS,

according to elements such as the rate of operation and the load of the forwarder.



CTF = L·(1/v1 + 1/v2) + TL + TU (3.5)

CTFS = L·(1/v1 + 1/v2) + TLS + TUS (3.6)

3-1C. Energy consumptionIt is clearly not efficient to harvest the slashes if the

energy input for harvesting slashes is more than theenergy output of the slash biomass. In light of the con-clusions from existing studies, such as the work editedby Shibata and Kitani (1981), which showed that en-ergy input was several times more than the output inthe case of alcoholizing wood, the energy consump-tion for collecting logging residues and the proportionof energy input to output must be evaluated carefully.

The energy input for harvesting slashes (HFS, MJ/d)is defined as the fuel consumption per day for haulingslashes (FFS, cm3/d) converted into the calorific value,so HFS is expressed as:

HFS = uFS ·(FFS/1000) (3.7)

and FFS is expressed as:

FFS = 3600·cFS·DFS·CFFS/CTFS (3.8)

When the fuel consumption of each element operationis regarded as being proportional to the operating time,then the fuel consumption per cycle for hauling slashes(CFFS, cm3/cycle) is expressed as:

CFFS = a1·L/v1 + a2·L/v2 + aLS·TLS + aUS·TUS (3.9)

In terms of the calorific value of wood per unitweight, the more moisture the wood contains, the lowerits calorific value (Forestry Experiment Station (ed.)1982). However, the potential energy of slashes is ex-amined by converting dry weight of slashes into calo-rific value.

The potential energy output of the slash biomass (HS,MJ/d) is defined as EFS converted into the calorificvalue, so HS is expressed as:

HS = uS·EFS (3.10)

The ratio of the energy input for harvesting slashesto the potential energy output of the slash biomass (p,%) is expressed as:

p = (HFS/HS)·100 (3.11)

p is defined as the “energy input rate” of haulingslashes. When p is greater than 100%, that is, energyinput is in excess of output, then it is no longer effi-cient to harvest slashes as a source of energy.

3-1D. Cost estimationThe cost of hauling slashes per unit weight (CWFS,

US$/kgDM) is expressed as:

CWFS = CFS/EFS (3.12)

and the cost of hauling slashes per day (CFS, US$/d) isexpressed as:

CFS = (P + M + F)·DFS (3.13)

The longer the whole-tree yarding/skidding distance,the more likely it is that transportation energy and thecost of harvesting slashes will increase. However, it isassumed that the energy and cost of carrying slashesto the nearest landing of a logging site does not needto be considered since slashes are carried along withstems during whole-tree yarding/skidding.

3-1E. Weight of slashesWhen the weight of slashes per whole tree (WP,

kgDM/tree) is considered proportional to the volumeof logs per whole tree (VP, m3/tree), WP is expressedas:

WP = k·VP (3.14)

where k is a proportional coefficient (kgDM/m3). Sincek is interpreted as the weight of slashes per unit vol-ume of logs processed, it can be regarded as a valuespecific to the type of tree. In the estimation of quan-tity of logging residues per annum in Japan performedby the Forestry Agency, residues are classified into“tops,” “branches,” and “others” (Forestry Science andTechnology Promotion Center 1985). However, in thisstudy, only “tops” and “branches” are considered asslashes generated during processor limbing and buck-ing, so k is expressed as:

k = mk·(r1 + r2)/{100 – (r1 + r2 + r3)} (3.15)

3-2. Materials and methods

To test the theoretical equations (from (3.1) to (3.15))at an actual logging site, a field experiment was car-ried out at the site of a thinning operation conductedby the Toyoma-cho Forest Owner’s Association inMiyagi Prefecture on July 23–24, 1997 (Table 5). Al-though the expected period of the thinning operationin Table 5 was from July 22 to August 12, trees to bethinned were felled in the previous spring to reducethe weight of the logs by allowing them to dry in thesun. The logging system at the site consisted of whole-tree skidding by one skidder, limbing and bucking byone processor (NIAB, Sweden), and hauling on a striproad by one forwarder (RMF-CH, Oikawa Motors Co.,Ltd., Japan). There was one operator per machine, andtwo chain saws were used supplementally.

The operation times for processor limbing, bucking,



and forwarder hauling of logs, respectively, and thevolume of logs were measured. Tests were conductedusing a forwarder to haul slashes (Fig. 5), and the op-eration times, weight of slashes, and fuel consumptionof each operation were measured.

3-3. Results

Table 6 shows the data collected from the field ex-periment.

Item Investigated site

Site Toyoma-cho town owned forest, No. 29 compartment and I-2,3 sub-compartment, Miyagi Prefecture

Area 1.30 haForest management type Planted forestSpecies Cryptomeria japonica D. Don (“sugi,” or Japanese cedar)Age 55 yearsMethod of treatment ThinningExpected period of operation July 22 to August 12, 1997Number of operators 3 peopleNumber of standing trees

(total) 772 trees(per hectare) 594 trees/ha

Volume of standing trees(total) 520.493 m3

(per hectare) 400.379 m3/ha(per tree) 0.876 m3/tree

Thinned trees(number) 390 trees(volume) 273.259 m3

Rate of thinning(by number of trees) 50.5%(by volume) 52.5%

Fig. 5. Experimenting with a forwarder hauling of slashes. Reprinted with kind permission from Springer Science + BusinessMedia: Journal of Forest Research, Feasibility of a harvesting system for logging residues as unutilized forest biomass. 5(2),2000, 59–65. Yoshioka, T, Iwaoka, M, Sakai, H, Kobayashi, H, Fig. 2. 2000, Springer Japan.

Table 5. Outline of the investigated site. Reprinted with kind permission from Springer Science + Business Media: Journal ofForest Research, Feasibility of a harvesting system for logging residues as unutilized forest biomass. 5(2), 2000, 59–65.Yoshioka, T, Iwaoka, M, Sakai, H, Kobayashi, H, Table 2. 2000, Springer Japan.



3-3A. Processor limbing and buckingFourteen trees were limbed and bucked during the

total observation time of 12,445 seconds. From theprocessor limbing and bucking data in Table 6 andgiven cP = 1 and DP = 6, the EP of Eq. (3.1) and EPS ofEq. (3.2) were calculated as 31.23 m3/d and 1,189kgDM/d, respectively. Setting the modification coef-ficient, cP, equal to 1 indicates “standard” operations.In other words, when “standard” operations were con-ducted for 6 hours a day, the processing productivitywas 31.23 m3/d and the weight of slashes generatedsimultaneously was 1,189 kg/d on a dry weight basis.

3-3B. Forwarder hauling of logsThree cycles of hauling were observed during 8,590

seconds. Using the data in Table 6 for forwarder haul-ing of logs, the cycle time, CTF (s/cycle) of Eq. (3.5),was calculated as:

CTF = 2.28·L + 1821 (3.16)

Using Eq. (3.16) and Table 6, the volume of logs hauled

per day, EF (m3/d) of Eq. (3.3), was calculated as:

EF = 3600·cF·DF·5.53/(2.28·L + 1821) (3.17)

3-3C. Experiment on forwarder hauling of slashes(a) Operating time

One cycle of forwarder hauling of slashes was ob-served during 3,651 seconds. From the data in Table6, the cycle time, CTFS (s/cycle) of Eq. (3.6), was cal-culated as:

CTFS = 2.28·L + 2874 (3.18)

Using Eq. (3.18) and Table 6, the weight of slasheshauled per day, EFS (kgDM/d) of Eq. (3.4), was calcu-lated as:

EFS = 3600·cFS·DFS·425.3/(2.28·L + 2874) (3.19)

(b) Fuel consumptionFuel (light oil) consumption of each operation was

measured and divided by the time for each operation

1On an average basis.2Excluding rest time.3The forwarder hauling distance of the site was measured with a compass.4Excluding the time for experimental arrangement.

Item Result

Processor limbing and buckingCycle time, CTP (s/tree)1,2 830Volume of logs processed from a whole tree, VP (m

3/tree)1 1.20Weight of slashes processed from a whole tree, WP (kgDM/tree)1 45.7

Forwarder hauling of logsOperation time (s)1

of loading, TL 1080of unloading, TU 741

Hauling distance, L (m)3 191.4Speed (m/s)1

of running downward fully-loaded, v1 0.67of running upward with no load, v2 1.27

Volume of logs hauled per cycle, VF (m3/cycle)1 5.53

Forwarder hauling of slashesOperation time (s)4

of loading, TLS 2238of unloading, TUS 636

Weight of slashes hauled per cycle, WFS (kgDM/cycle) 425.3Fuel consumption (cm3/s)

of loading, aLS 0.47of unloading, aUS 0.47of running downward fully-loaded, a1 0.94of running upward with no load, a2 1.50

Table 6. Data collected from the field experiment. Reprinted with kind permission from Springer Science + Business Media:Journal of Forest Research, Feasibility of a harvesting system for logging residues as unutilized forest biomass. 5(2), 2000,59–65. Yoshioka, T, Iwaoka, M, Sakai, H, Kobayashi, H, Table 3. 2000, Springer Japan.



to calculate the fuel consumption per unit time (seeTable 6). Based on this fuel consumption data, the fuelconsumption per cycle for hauling slashes, CFFS(cm3/cycle) of Eq. (3.9), was calculated as:

CFFS = 2.58·L + 1351 (3.20)

Using Eqs. (3.18) and (3.20), the fuel consumption perday for hauling slashes, FFS (cm3/d) of Eq. (3.8), wascalculated as:

FFS = 3600·cFS·DFS·(2.58·L + 1351)/(2.28·L + 2874)(3.21)

(c) Cost calculationGiven that the price of light oil per liter was 0.70

US$ and the relative prices of other oils, such as a ra-tio of machine oil cost to fuel cost of 0.2 (Sakai 1987),the fuel cost per hour, F (US$/h), was calculated as:

F = 8.4 × 10–4·FFS/DFS (3.22)

Labor cost per hour, P, was 25.77 US$/h (from per-sonal communication) and machine cost per hour, M,was 34.43 US$/h from the machine price (ForestryMechanization Society (ed.) 1996) and the standardproductivity list (Umeda et al. 1982). Therefore, usingEq. (3.22), P = 25.77 US$/h, and M = 34.43 US$/h,the cost of hauling slashes per day, CFS (US$/d) ofEq. (3.13), was calculated as:

CFS = (60.20 + 8.4 × 10–4·FFS/DFS)·DFS (3.23)

(d) Weight of slashesIn this chapter, the weight of slashes is considered

on a dry weight basis. However, during the field ex-periment, the green weight of slashes (dried in the sunfor a few months after felling) was measured and con-verted into dry weight by estimating the water con-tent. Based on five samples of logs, the green weightof logs per cubic meter was calculated to be 485.7kg/m3. Therefore, assuming that the water content was50% (Forestry Experiment Station (ed.) 1982), the dryweight of logs of the Cryptomeria japonica D. Don(“sugi,” or Japanese cedar) at the site per cubic meter,mk, was calculated to be 323.8 kg/m3.

In the field, some limbing had been done at fellingduring the previous spring and the trees left to dry inthe sun; consequently, the exact ratio of the weight oftops and branches to the whole-tree weight could notbe obtained. The ratios of the weight of tops, r1,branches, r2, and others, r3, to the weight of a wholetree of the Cryptomeria japonica D. Don are consid-ered to be 2, 8, and 5%, respectively, on the basis ofdata used by the Forestry Agency to calculate the quan-tity of logging residues (Forestry Science and Tech-nology Promotion Center 1985). From mk = 323.8

kgDM/m3, r1 = 2%, r2 = 8%, and r3 = 5%, the weightof slashes per unit volume of logs processed, k of Eq.(3.15), was calculated to be 38.1 kgDM/m3. Using k =38.1 kgDM/m3 and data from Table 6, the weight ofslashes per whole tree, WP of Eq. (3.14), was calcu-lated to be 45.7 kgDM/tree.

In this experiment, the green weight of slashes hauledduring one cycle was measured as 638.0 kg. There-fore, taking the water content of both slashes and logsinto account, the dry weight of slashes hauled per cy-cle, WFS, was calculated as 425.3 kgDM/cycle.

3-4. Discussion

3-4A. The harvesting system for logging residues bya processor and a forwarder

Given that one operator is in charge of the processorfor limbing and bucking and a second operator is incharge of the forwarder hauling of logs and slashes,the relation between DP (effective working time ofprocessor per day), DF (effective working time of for-warder hauling of logs per day), and DFS (effectiveworking time of forwarder hauling of slashes per day)is expressed as:

DP = DF + DFS (3.24)

The volume of logs hauled by the forwarder per daynever exceeds the volume of logs limbed and buckedby the processor per day. If the efficiency of the for-warder is higher than that of the processor, the for-warder still has time to spare after hauling all the logsprocessed and can haul slashes during this spare time.Given that the forwarder hauls all the logs processedduring the day, the relation between EP (volume of logsprocessed per day) and EF (volume of logs hauled perday) is expressed as:

EP = EF (3.25)

The weight of slashes generated during limbing andbucking is considered to be proportional to the vol-ume of logs processed and a proportionality coefficient,k (weight of slashes per unit volume of logs processed),is used to express the relation between EP and EPS(weight of slashes processed per day):

EPS = k·EP (3.26)

The relation between EPS and EFS (weight of slasheshauled per day) is expressed as:

EFS = α·EPS (3.27)

where α is defined as the “rate of slash harvesting,”and equals 1 when the forwarder hauls all of the slashesgenerated by the processor.



If the value of α is known, the ratio of the weight ofslashes hauled to that of slashes processed can be esti-mated (hauling of slashes by the forwarder is carriedout during spare time, as mentioned above). Therefore,α is regarded as an index of the capability to haulslashes by utilizing the spare time of the forwarder.

From Eqs. (3.17), (3.19), (3.24), (3.25), (3.26), and(3.27), the volume of logs hauled per day, EF (m3/d),is calculated as:

EF = cF·cFS·DP/{(1.15 × 10–4·cFS + 1.49 × 10–6·α·k·cF)·L+ (9.15 × 10–3·cFS + 1.88 × 10–3·α·k·cF)} (3.28)

Therefore, EF can be expressed as a function of L (haul-ing distance).

Using k = 38.1 kgDM/m3 and given cF = cFS = 1 andDP = 6, which means that the “standard” (as modifica-tion coefficients cF = cFS = 1) operation of the forwarderis carried out for 6 hours a day, the relation between Land EF is shown in Fig. 6 for rates of slash harvestingof α = 0, 0.5, and 1. The value of k is specific to thekind of tree, and k in Eq. (3.28) can be adjusted forvarious types of trees, such as for pines and broad-leaved trees. The modification coefficients cF and cFSshould be adjusted for type of tree, volume of logs,and weight of slashes hauled by the forwarder.

α = 0 means that the forwarder hauls only logs andno slashes at all. At a site where a highly productivemachine, such as a single-grip processor, is used, it ispossible that the operating point in Fig. 6 would havean EP coordinate above the curved line for α = 0. Insuch a case, the performance of the processor is higherthan that of the forwarder, so some logs remain at the

landing of the logging site when both machines areoperated for the same amount of time. Therefore, theforwarder must be operated longer than the processor.Examples of possible measures for resolving this prob-lem are listed as follows:1) Shorten the hauling distance until the coordinate ofthe operating point (L, EP) shown in Fig. 6 is belowthe curved line for α = 0;2) Introduce a large-sized forwarder capable of copingwith the high productivity of the processor;3) Add another forwarder.

α = 1 means that the forwarder hauls all of logs andall slashes. Therefore, the curved line for α = 1 in Fig.6 indicates the relation between the hauling distanceand the volume of logs hauled per day when the for-warder is expected to haul all of the slashes as well asall of the logs. When the productivity of the processoris plotted below the curved line for α = 1, the perform-ance of the forwarder is higher than that of the proces-sor. So, even if the forwarder hauls all logs and allslashes, there is still spare time.

EF in Fig. 6 can be replaced with EP under the condi-tion that the forwarder hauls all of the logs limbed andbucked by the processor during the day. In the casewhere L and EP are given, the point (L, EP) can be plot-ted on this graph. If the point (L, EP) is below the curvedline for α = 1, then all of the slashes processed in thesite can be hauled by the forwarder. If the point (L, EP)is between the curved lines for α = 0 and α = 1, theratio of the weight of slashes harvested to the weightof slashes generated can be found by estimating thevalue of α from the graph. For example, at a site whereL = 500 m and EP = 30 m3/d, α is approximately 0.5; itcan therefore be estimated that about 50% of slashesprocessed can be hauled to a landing alongside a for-est road. At the investigated site, α was found to beabout 0.95 when L = 191.4 m and EP = 31.23 m3/d wereused in Fig. 6, thereby ascertaining that almost all theslashes could be hauled.

3-4B. Energy analysisFrom Eqs. (3.7), (3.10), (3.19), and (3.21), the “en-

ergy input rate” of hauling slashes, p (%) of Eq. (3.11),is calculated as:

p = (uFS/uS)·(6.07 × 10–4·L + 3.18 × 10–1) (3.29)

Therefore, p can be expressed as a function of L. Sincethe value of uS is specific to the type of tree, Eq. (3.29)can be applied for various kinds of trees.

The hauling distance at the investigated site was191.4 m. When the calorific value of light oil (fuel ofthe forwarder) per unit volume and the higher calo-rific value of the Cryptomeria japonica D. Don (driedthoroughly) per unit weight are considered to be 38.49MJ/dm3 and 19.54 MJ/kgDM, respectively (Honda1986), using L = 191.4 m, uFS = 38.49 MJ/dm3, and

Investigated site(L =191.4,E P=31.23)

Example ofα=0.5

(L =500,E P=30)

020

4060

8

0

0 200 400 600 800 1000

L : Hauling distance of forwarder (m)

EF :

Vol

ume

of lo

gs h

aule

d pe

r day

(m3 /d

)

(EP :

Pro

duct

ivity

of p

roce

ssor

)α=0α=0.5α=1α=0.95

Fig. 6. Relationship between hauling distance of forwarder,L, and volume of logs hauled per day, E

F. Reprinted with

kind permission from Springer Science + Business Media:Journal of Forest Research, Feasibility of a harvesting sys-tem for logging residues as unutilized forest biomass. 5(2),2000, 59–65. Yoshioka, T, Iwaoka, M, Sakai, H, Kobayashi,H, Fig. 3. 2000, Springer Japan.



uS = 19.54 MJ/kgDM, the p of Eq. (3.29) is calculatedas 0.85%. Consequently, it was confirmed that there isa potential for the efficient energy utilization of slashes.By fixing the desired “energy input rate” of haulingslashes by a hauling distance beforehand, the optimumhauling distance can be decided, enabling effectiveplanning of a forest road system.

In this chapter, only the simplest case, where thor-oughly dried slashes are converted directly into energy,is considered. With respect to energy input, the energyconsumption of the forwarder operator must also betaken into account. Energy conversion efficiency mustbe strictly examined for the practical realization of asystem to harvest logging residues for energy use.

3-4C. Cost analysisFrom Eqs. (3.19), (3.21), and (3.23), the cost of haul-

ing slashes per unit weight, CWFS (US$/kgDM) of Eq.(3.12), is calculated as:

CWFS = {(8.96 × 10–5 + 5.06 × 10–6·cFS)·L+ (1.13 × 10–1 + 2.65 × 10–3·cFS)}/cFS (3.30)

Therefore, CWFS can be expressed as a function of L.Using L = 191.4 m and given cFS = 1, which means

that the “standard” operation of the forwarder is car-ried out, CWFS of Eq. (3.30) is calculated as 0.134US$/kgDM. By considering the value of cFS with re-gard to the load of slashes, Eq. (3.30) can be applied

for various kinds of trees.It has been reported that in Japan, slashes as fuel are

worth several yen per kg on a green weight basis(Honda 1986; the exchange rate was roughly 115 yento the U.S. dollar as of July 1997), so the cost per unitweight for hauling slashes must be reduced. To increasethe hauling efficiency, it may be effective to enhancethe load capacity of the forwarder. In the field experi-ment, the average volume of logs hauled in one cycle,5.53 m3, was converted into 1,791 kg on a dry weightbasis, which was 4.21-fold greater than the weight oflogging residues hauled per cycle, 425.3 kg; therefore,the efficiency of hauling the residues was less than 25%of that for hauling logs. One proposed solution to thisproblem is that the volume of slashes be decreased byintroducing a chipper. In the future, another forwarderwhich has chipping capability and is dedicated to har-vesting only slashes needs to be developed and exam-ined in terms of energy and cost.


Steady progress in the utilization of forest biomassis being made in Nordic countries in general and inSweden in particular where woody biomass accountsfor more than 20% of the primary energy supply. Withinthe framework of a project for the expansion of biomassutilization, several studies on a chipper (Asikainen andPulkkinen 1998) are ongoing as basic research on the

Energy-conversion plant

Transporting distance of a truck

Truck transporting of slashes/chips Public road

Whole-tree yarding/skidding

(Forwarder unloading)

Landing alongside a forest road

Forest road)dellevarg ro devap(tseroF

Forwarder hauling of logs and slashes/chips(Running downward fully-loaded)

Strip road (gravelled or only soil compacted)

(Running upward with no load)

Hauling distance of a forwarder

Processor limbingand bucking

(Forwarder loading)

Landing in forest

Fig. 7. Harvesting and transporting system for logging residues. Reprinted with kind permission from Springer Science +Business Media: Journal of Forest Research, Cost, energy and carbon dioxide (CO

2) effectiveness of a harvesting and trans-

porting system for residual forest biomass. 7(3), 2002, 157–163. Yoshioka, T, Aruga, K, Sakai, H, Kobayashi, H, Nitami, T,Fig. 1. 2002, Springer Japan.



energy utilization of slashes. However, these systemsare for countries with a gentle terrain; a system suit-able for countries with a steep terrain, such as Japan,needs to be developed.

It is also desirable that a method for the efficient useof slashes is developed and used in practical applica-tions. It is effective to harvest slashes in and aroundan operating site as a source of local energy, althoughthis approach is associated with concern that nutrientswould be removed from the forest. Possible solutionsto this problem, such as, returning slashes to forest ar-eas to conserve the nutrients and control weeds, needto be examined.

4. A case study on the costs and fuel consump-tion of harvesting, transporting, and chippingchains for logging residues in Japan

As a follow-up to the analysis in Chapter 3, the fo-cus of Chapter 4 is an examination of a “harvestingand transporting system for logging residues” basedon data collected from field experiments and existingstudies (Yoshioka et al. 2002a, 2006a). This system,in which the process of chipper comminuting is newlyintroduced and a truck transports biomass to an en-ergy-conversion plant, was constructed with referenceto three European countries, i.e., the U.K. (Hunter etal. 1999), Sweden (Andersson 1999), and Finland(Korpilahti 1998). Utilization of bioenergy is makingsteady progress in these countries. The feasibility of

the system in Japan is discussed from the standpointsof cost and energy, and the system is compared withthose of these European countries. A preliminary sen-sitivity analysis to the system is also carried out, fol-lowed by a discussion of the problems for realization.


4-1A. A harvesting and transporting system for log-ging residues

This system, which was designed taking due consid-eration of the present situation of Japanese forestry,includes the following processes (Fig. 7):1) Whole-tree yarding/skidding: The machine used inthis process is not particularly limited here, while theoperation is usually conducted by yarders, tower-yarders, or tractors in Japan. Compared with conven-tional machines like yarders and tractors, the use oftower-yarders has been increasing in Japanese forestry,especially for the purpose of thinning;2) Processor limbing and bucking: This operation isconducted at the landing of a logging site (in a forest);3) Forwarder hauling: A forwarder hauls logs andslashes/chips on a strip road from the landing of a log-ging site to another landing alongside a forest road. InJapan, low-grade strip roads complement the low den-sity of forest road networks because the constructioncost of forest roads is too high. However, trucks can-not travel on such low-grade strip roads, so two land-ings are inevitably essential for this system;

[Operating site]

Landing in forest

Strip road

Landing alongsidea forest road

Forest road andpublic road

Energy-conversionplant

Energy conversion

Comminuting by a

of chipsForwarder hauling of slashes

Comminuting by alarge-sized chipper

mobile chipper

Truck transporting of chips Truck transportingof slashes

Comminuting by amobile chipper

Forwarder hauling

"Plant" type

Whole-tree yarding/skiddingProcessor limbing and bucking

"In-forest" type "Landing" type

Fig. 8. Three types of the systems classified according to the operating sites of chipper comminuting. Reprinted with kindpermission from Springer Science + Business Media: Journal of Forest Research, Cost, energy and carbon dioxide (CO

2)

effectiveness of a harvesting and transporting system for residual forest biomass. 7(3), 2002, 157–163. Yoshioka, T, Aruga, K,Sakai, H, Kobayashi, H, Nitami, T, Fig. 2. 2002, Springer Japan. Reprinted from Biomass and Bioenergy, 30(4), Proceed-ings of the third annual workshop of Task 31 ‘Systainable production systems for bioenergy: Impacts on forest resources andutilization of wood for energy’ October 2003, Flagstaff, Arizona, USA, Yoshioka et al., A case study on the costs and the fuelconsumption of harvesting, transporting, and chipping chains for logging residues in Japan, 342–348, Copyright (2006), withpermission from Elsevier.



4) Truck transporting: A 4-ton truck transports slashes/chips on a forest road and a public road;5) Energy-conversion: There is no energy-conversionplant in Japan that is suitable for receiving loggingresidues as fuel; this process is therefore only provi-sional here.

In terms of the distances of hauling and transport-ing, these are assumed to range from 100 to 1,000 mand from 20 to 80 km for the case discussed in thischapter, respectively, on the basis of the actual situa-tion of Japanese forestry and the results of a past ques-tionnaire sent to logging enterprises (Nitami andKamiizaka 1982).

In addition to the five processes listed above, chip-per comminuting is incorporated into the system withthe dual purpose of enhancing the hauling and trans-porting efficiency of logging residues and carrying theresidues in the form of chips to an energy-conversionplant. Chipper comminuting, however, increases thecost and energy of the system. Therefore, the systemis classified into three types, namely, “In-forest,”“Landing,” and “Plant,” according to the operating sitesof chipper comminuting, i.e., a landing in a forest, alanding alongside a forest road, and an energy-conver-sion plant, respectively (Fig. 8). Mobile chippers areused in the “In-forest” and “Landing” systems, whilea large-sized chipper is used in the “Plant” system. Theeffect of the difference between the operating sites ofchipper comminuting on the system’s cost and fuelconsumption per unit mass of biomass on a dry basisis also examined.

Fig. 9. Experimenting with a forwarder hauling of slashes. Reprinted with kind permission from Springer Science + BusinessMedia: Journal of Forest Research, Cost, energy and carbon dioxide (CO

2) effectiveness of a harvesting and transporting

system for residual forest biomass. 7(3), 2002, 157–163. Yoshioka, T, Aruga, K, Sakai, H, Kobayashi, H, Nitami, T, Fig. 3. 2002, Springer Japan. Reprinted from Biomass and Bioenergy, 30(4), Proceedings of the third annual workshop of Task 31‘Systainable production systems for bioenergy: Impacts on forest resources and utilization of wood for energy’ October 2003,Flagstaff, Arizona, USA, Yoshioka et al., A case study on the costs and the fuel consumption of harvesting, transporting, andchipping chains for logging residues in Japan, 342–348, Copyright (2006), with permission from Elsevier.

4-1B. Description of machinesWith regard to forwarder hauling, the experiment on

hauling logging residues by a wheel-type forwarderwith a 2,000 kg load capacity (RM8WDB-6HG,Oikawa Motors Co., Ltd., Japan) was carried out inthe Takizawa Experimental Forest of Iwate University,Iwate Prefecture (Fig. 9). The logging residues werefresh tops and branches of a 26-year-old Cryptomeriajaponica D. Don (“sugi,” or Japanese cedar). The massof logging residues at the experimental site was about50 Mg/ha on a dry basis. The operation time, mass ofslashes, and fuel (light oil) consumption of each op-eration were measured, and the water content of slasheswas estimated by drying several samples thoroughly.

An experiment on comminuting slashes by a mobilechipper was also carried out. The chipper used in thisexperiment was a test model manufactured by theOikawa Motors that was equipped with an Isuzu 6BD1diesel engine (displacement and power output are 5,785cm3 and 79.4 kW/2,200 rpm, respectively). As in theexperiment on forwarder hauling, the operation time,mass of chips, and fuel (light oil) consumption weremeasured, and the water content of chips was estimated.An additional parameter, the “volume reduction rate”(see Table 9), was also measured for the purpose ofdetermining how the efficiency of hauling and trans-porting logging residues was enhanced by chipper com-minuting.

This is the first time that such a large-sized chipperas the one described here has ever been put into opera-tion in Japanese forestry. Therefore, the process of



Item Result

Cost per h (US$/h)of labor 28.093

of machine 23.994

Fuel (light oil) price per dm3 (US$/dm3) 0.76Ratio of the total price of other oils, such as machine oil, to the fuel price 0.25

Dry weight hauled per cycle (kgDM/cycle)1,2

of slashes 113.96

of chips 415.7Speed (m/s)

of running downward fully-loaded 1.41of running upward with no load 1.42

Hauling distance (m) 100–1000Operating time (s)

of loading 552of unloading 545

Fuel consumption per s (cm3/s)of running downward fully-loaded 0.32of running upward with no load 1.13of loading 0.28of unloading 0.35

Table 7. Data collected from the field experiments and existing studies: (a) Forwarder hauling. Reprinted with kind permis-sion from Springer Science + Business Media: Journal of Forest Research, Cost, energy and carbon dioxide (CO

2) effective-

ness of a harvesting and transporting system for residual forest biomass. 7(3), 2002, 157–163. Yoshioka, T, Aruga, K, Sakai,H, Kobayashi, H, Nitami, T, Table 1(a). 2002, Springer Japan. Reprinted from Biomass and Bioenergy, 30(4), Proceedingsof the third annual workshop of Task 31 ‘Systainable production systems for bioenergy: Impacts on forest resources andutilization of wood for energy’ October 2003, Flagstaff, Arizona, USA, Yoshioka et al., A case study on the costs and the fuelconsumption of harvesting, transporting, and chipping chains for logging residues in Japan, 342–348, Copyright (2006), withpermission from Elsevier.

1In Chapter 4, thoroughly dried biomass is considered in order to discuss the potential energy of logging residues.2One cycle consists of the four element operations, i.e., loading in the forest, running downward fully-loaded on a strip road,unloading alongside a forest road, and running upward with no load.3From a previous personal communication (see Chapter 3).4From the machine price (Forest Mechanization Society (ed.) 1996) and the standard productivity list (Umeda et al. 1982).5From Sakai (1987).6The weight of slashes hauled in the experiment was 249.80 kg on a green-weight basis, and the average water content ofseven samples of slashes was 119.3% (dry basis, and the standard deviation = 10.9%). Therefore, the dry weight of slasheshauled per cycle was calculated as 113.9 kgDM/cycle.

comminuting by a large-sized chipper is discussed tak-ing the results of an existing study into account inwhich the performance of a tub grinder (TG 400A,Vermeer Manufacturing Company, USA) was investi-gated at a grading site. The tub grinder was introducedin order to recycle logged trees effectively at the site.

4-2. Results

Tables 7, 8, 9 present the data collected from thefield experiments and existing studies. The total costof each process, namely, hauling, transporting, andcomminuting, was calculated separately by aggregat-ing the labor, machine, and fuel costs in these tables.

Table 10 presents the cost and fuel consumption ineach of the three systems (the distances of forwarderhauling and truck transporting are 100–1,000 m and

20–80 km, respectively) as well as the “energy inputrate” (see footnote of the table), the cost per MWh ofbioenergy, and the results of a preliminary sensitivityanalysis. In Table 11, data on the cost and CO2 emis-sion, which are obtained from the fuel consumption,per MWh of bioenergy are compared to data for threeEuropean countries, i.e., the U.K., Sweden, and Fin-land.

4-3. Discussion

4-3A. CostOf the three systems proposed in the chapter, the “In-

forest” type has the lowest cost per unit weight of log-ging residues and the “Plant” type has the highest (Ta-ble 11). In other words, the earlier chipper comminut-ing can be incorporated into the system, the lower the



costs per MWh for fossil fuels and for logging residuesfrom final felling were 5.33–18.7 US$/MWh and 16.0US$/MWh, respectively. The energy generation costsconsisted of the capital, R&M (repair and mainte-nance), and operating costs, with all these costs beingalmost at the same level and very small compared withthe costs for logging residues listed in Table 10. Thiscomparison indicates that the procurement cost greatlyinfluences the total cost with regard to logging residuesfor energy and that in order to realize the energy utili-zation of logging residues in Japan, it is essential todevelop low-cost harvesting, transporting, and chip-ping techniques. The introduction of multifunctionalmachines is one possibility. For example, a chipper-forwarder has both chipping and forwarding functions,while a chipper-truck carries out both chipping andtransporting operations. Implementation of such ma-chines will increase productivity.

Table 11 shows that there is a large difference be-tween Japan and the three European countries in termsof the cost per MWh of bioenergy, with almost all thecosts given for the European countries being around10 US$/MWh regardless of the operation site of chip-per comminuting and the type of machine. Accordingto Hunter et al. (1999), the procurement cost per unitenergy of biomass to an energy-conversion plant is thesame level as those of fossil fuels, i.e., coal, oil, andgas. This can be interpreted to mean that biomass asan energy resource is rather competitive against fossilfuels in these European countries. Accordingly, the costof 10 US$/MWh level is a target for the system de-scribed in this chapter.

Table 8. Data collected from the field experiments and existing studies: (b) Truck transporting.1 Reprinted with kind permis-sion from Springer Science + Business Media: Journal of Forest Research, Cost, energy and carbon dioxide (CO

2) effective-

ness of a harvesting and transporting system for residual forest biomass. 7(3), 2002, 157–163. Yoshioka, T, Aruga, K, Sakai,H, Kobayashi, H, Nitami, T, Table 1(b). 2002, Springer Japan. Reprinted from Biomass and Bioenergy, 30(4), Proceedingsof the third annual workshop of Task 31 ‘Systainable production systems for bioenergy: Impacts on forest resources andutilization of wood for energy’ October 2003, Flagstaff, Arizona, USA, Yoshioka et al., A case study on the costs and the fuelconsumption of harvesting, transporting, and chipping chains for logging residues in Japan, 342–348, Copyright (2006), withpermission from Elsevier.

1Considering the present-day situation of Japanese forestry; a truck with 4 tons of load capacity whose average volume oftransported logs was 5 m3 (Nitami and Kamiizaka 1982) was used in Chapter 4.2Truck transporting is assumed to be conducted on contract by a transport company, in accordance with Umeda et al. (1982).Therefore, from 4 tons of the tonnage and 20–80 km of the transporting distance defined in this chapter, the transporting costper cycle was 141.04–279.24 US$/cycle on the basis of the price list provided by the Kanto District Land Transport Bureau.3345.0 kgDM of slashes was to 5 m3 of logs what 381.6 kgDM of slashes was to 5.53 m3 of logs (see Chapter 3).

Item Result

Cost per cycle (US$/cycle) 141.04–279.242

Dry weight transported per cycle (kgDM/cycle)of slashes 345.03

of chips 1259.1Transporting distance (km) 20–80Mileage per dm3 of light oil (km/dm3) 5.5

total cost of the system. Consequently, the margin ofchips to slashes in forwarder hauling and truck trans-porting is larger than that of large-sized to mobile inchipper comminuting.

In Japan, the unit price of electricity was 148US$/MWh as of 2000. A considerably high proportionof the costs per MWh of bioenergy in the three sys-tems can be accounted for by the price of electricity.This factor is especially relevant in the “Plant” typewhere it is possible that the cost exceeds the price ofelectricity depending on the hauling conditions andtransporting distances of the system. The underlyingreasons for this development are:• The very small load capacities and chipper poweron studied machines compared to European machines;• Machinery that is not fully adapted to the work;• Operators with little experience with forest fuel re-covery.Therefore, at the moment, the outlook for realizationof a harvesting and transporting system for loggingresidues in Japan is not favorable from the standpointof cost. This is relevant to forestry conditions in Japanand shows that the studied system has low productiv-ity and is not financially sound. However, implemen-tation of better machines and well-trained operatorsmight change the results substantially. The conclusionto be drawn is, therefore, that improvement of the sys-tem, including the accumulation of field experience,such as increased skills in operating the machines andtechnological improvements in machinery, is essential.Nationwide field trials are currently ongoing.

Hektor (1998) reported that the energy generation



Table 9. Data collected from the field experiments and existing studies: (c) Chipper comminuting. Reprinted with kind per-mission from Springer Science + Business Media: Journal of Forest Research, Cost, energy and carbon dioxide (CO

2) effec-

tiveness of a harvesting and transporting system for residual forest biomass. 7(3), 2002, 157–163. Yoshioka, T, Aruga, K,Sakai, H, Kobayashi, H, Nitami, T, Table 1(c). 2002, Springer Japan. Reprinted from Biomass and Bioenergy, 30(4), Pro-ceedings of the third annual workshop of Task 31 ‘Systainable production systems for bioenergy: Impacts on forest resourcesand utilization of wood for energy’ October 2003, Flagstaff, Arizona, USA, Yoshioka et al., A case study on the costs and thefuel consumption of harvesting, transporting, and chipping chains for logging residues in Japan, 342–348, Copyright (2006),with permission from Elsevier.

1In Chapter 4, the “volume reduction rate” by chipper comminuting indicates the extent to which a chipper can reduce thevolume of slashes by comminuting them. In other words, it is the ratio of the volume of chips (after comminuting) to that ofslashes (before comminuting).2From the machine price of 75,829 US$ (personal communication) and assuming that the yearly operation hours, the life ofthe machine, and the annual interest were 1,000 h per year, 5 years, and 3%, respectively, the machine cost per h was 22.48US$/h on the basis of the simplified FAO cost calculation method (1974).3The fuel cost was based on the same cost calculation factors as that used for the forwarder hauling.4The volume of slashes before comminuting and that of chips after comminuting were 4.386 m3 and 1.20 m3, respectively (theformer was determined by measuring the volume of a container of a 2-ton truck, and the latter was determined by measuringthe volume of a chip bin). Therefore, the “volume reduction rate” was calculated as 0.274.5From the machine price of 473,934 US$ (Forest Mechanization Society (ed.) 1996), the total cost was based on the same costcalculation factors as for the comminuting by a mobile chipper.

In the European countries, for example, bundlers forcompressing logging residues (see Table 11) and trail-ers of the 30-ton class for transporting are used so thatthe hauling and transporting efficiency is fairly high.Therefore, it is still possible to reduce the differentialof the cost between Japan and the European countriesby introducing the process of compressing into thesystem. The bundler will reduce the total cost. How-ever, the bundler is applicable only for gentle terrain,such as that found in Nordic countries, so the develop-ment of a machine and a system suitable for the steeptopography of Japan is necessary.

4-3B. Fuel consumption and CO2 emissionThe “Plant” type has the highest fuel consumption

per unit weight of logging residues, with the “In-for-est” and “Landing” types being lower and almost atthe same level (Table 10). This indicates that the mar-gin of the landing alongside a forest road to the land-

ing in a forest at the site of chipper comminuting ispractically equal to the margin of chips to slashes inforwarder hauling.

In terms of “energy input rate,” all three systems aregenerally at single-figure-% levels. Consequently, therealization of the harvesting and transporting systemfor logging residues in Japan presents no specific prob-lem from the point of view of the “energy input rate,”i.e., the input and output of energy in the system

In terms of the CO2 emission per MWh of bioenergy(Table 11), Japan is almost on the same level as Fin-land. According to Korpilahti (1998), if the target ofsubstituting 1.5 million toe (tons of oil equivalent) offossil fuels in Finland by 2010 is fulfilled by increas-ing the use of bioenergy, the reduction in CO2 emis-sions will be 6.9% of the total emissions in 1996.Korpilahti also shows that CO2 emissions are 341kgCO2/MWh for coal and 304 kgCO2/MWh for oil.Therefore, it is possible for Japan to reduce domestic

Item Result

Mobile chipperCost per h (US$/h)

of labor 28.09of machine 22.482

of fuel 8.233

Dry weight of chips comminuted per h (kgDM/h)at a landing in a forest 618.30at a landing alongside a forest road 883.30

Fuel (light oil) consumption (dm3/h) 9.04Volume reduction rate1 0.2744

Large-sized chipperTotal cost per h (US$/h) 194.125

Dry weight of chips comminuted per h (kgDM/h) 4267.44–8534.88Fuel (light oil) consumption (dm3/h) 28.04



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The

U.K

.220

−80

11.3

−14

.010

.2−1

4.1

8.35

−11

.2

(10.

1−11

.9)6

Swed

en3

60

14.1

−15

.512

.4−1

3.8

(11.

9−13

.4)6

Fin

land

42

50

60

9.8

69

.67

5.7

85

.61

(8.0

5)7

(7.8

3)8

Tab

le 1

1.

Com

pari

son

wit

h th

ree

Eur

opea

n co

untr

ies

in t

erm

s of

har

vest

ing

cost

and

CO

2 em

issi

on p

er M

Wh

of b

ioen

ergy

.R

epri

nted

wit

h ki

nd p

erm

issi

on f

rom

Spr

inge

r S

cien

ce +

Bus

ines

s M

edia

: Jo

urna

l of

For

est

Res

earc

h, C

ost,

ene

rgy

and

carb

on d

ioxi

de (

CO

2) e

ffec

tive

ness

of

a ha

rves

ting

and

tra

nspo

rtin

g sy

stem

for

res

idua

l fo

rest

bio

mas

s. 7

(3),

200

2, 1

57–1

63.

Yos

hiok

a, T

, Aru

ga, K

, Sak

ai, H

, Kob

ayas

hi, H

, Nit

ami,

T, T

able

3.

2

002,

Spr

inge

r Ja

pan.

1 The

ma s

s of

CO

2 em

itte

d fr

om 1

dm

3 of

lig

ht o

il =

0.8

4 kg

CO

2 (K

orpi

laht

i 19

98)

(CO

2 em

issi

on p

e r M

Wh

of b

ioe n

e rgy

is

c alc

ula t

e d f

rom

thi

s va

lue

a nd

Tab

le 1

0).

2 Fro

m H

unte

r e t

al.

(19

99),

and

the

ha u

ling

dis

tanc

e w

a s n

ot r

e fe r

red

to.

3 Fro

m A

nde r

sson

(19

99),

and

the

ha u

ling

dis

tanc

e w

a s n

ot r

e fe r

red

to.

4 Fro

m K

orpi

laht

i (1

998)

.5 T

hese

va l

ues

a re

the

resu

lts

of t

he p

reli

min

a ry

sens

itiv

ity

a na l

ysis

(se

e Ta

ble

10

).6 T

hese

are

the

c ase

s in

whi

c h b

a le r

s w

e re

intr

oduc

e d. T

he b

a le r

com

pre s

ses

sla s

hes

into

cyl

indr

ica l

ba l

e s (

And

e rss

on 1

999)

. “B

a le”

is a

lso

c all

e d “

bund

le”

or “

c om

posi

te r

e sid

ue lo

g(C

RL

).”

7 The

se a

re t

he c

a se s

in

whi

c h c

hipp

e r-t

ruc k

s th

a t c

ombi

ne c

omm

inut

ing

a nd

tra n

spor

ting

we r

e in

trod

uce d

. The

chi

ppe r

-tru

c k c

omm

inut

e s s

lash

e s d

urin

g tr

a nsp

orta

tion

.



CO2 emissions by utilizing logging residues as alter-native energy resources.

However, in all of the European countries discussedin this chapter, biomass provides a share of the do-mestic energy supply, and the governmental target topromote the use of bioenergy is consistently held up.These facts suggest that realization of bioenergy utili-zation in Japan necessitate government support in vari-ous forms such as, for example, taxing CO2 emissionsfrom fossil fuels. Development of the machines andsystems as a government-subsidized project focusedon global warming countermeasures is also a possibil-ity.

4-3C. Preliminary sensitivity analysisIncreasing the efficiency in the process of transport-

ing is examined (see Table 10 and footnotes), espe-cially because the transporting cost is too high. As aresult, the total costs are reduced almost to half (Table10) and the differential between Japan and the Euro-pean countries is also reduced (Table 11), which inturn indicates the importance of the load size of haul-ing and transporting vehicles. Therefore, the introduc-tion of large-sized trailers, as shown in Table 10, andthe construction of a network of high-grade forest roadsso that large-sized trailers can travel directly to thelandings of logging sites are necessary. In addition, theintroduction of bundlers or chipper-forwarders shouldbe considered as a measure to reduce the total harvest-ing cost by increasing the efficiency of the comminut-ing and hauling process.


The harvesting cost must be reduced by variousmeasures, such as introducing the process of compress-ing slashes into the system. The bundler, for example,will reduce the total cost. However, the current bun-dling system is applicable only for gentle terrain, suchas that found in Nordic countries, necessitating thedevelopment of a machine and a system suitable forthe steep topography of Japan. On the other hand, interms of the input and output of energy, a more de-tailed analysis, such as an LCI analysis that considersthe life cycle assessment (LCA) method, is necessaryto provide a scientific basis for the premise that biomassas an energy resource has a much lower environmen-tal impact over its entire life cycle than fossil fuels.

5. Comminution of logging residues with a tubgrinder: Calculation of the productivity andprocurement cost of wood chips

For logging residues to be utilized as sources of en-ergy, it is necessary to comminute them so that theirforwarding and transporting efficiency can be en-hanced. In addition, residues should be pretreated, i.e.,

chipped or crushed, in an energy-conversion plant be-fore being converted into usable energy in the form of,for example, heat, electricity, and liquid fuel.

Logging residues can be comminuted in a forest, ata roadside landing, or at an energy-conversion plant.Various kinds of chippers and crushers for loggingresidues have been developed and examined worldwideunder field conditions (Asikainen and Pulkkinen 1998,Delgado and Giraldo 1995, Desrochers et al. 1993, Hallet al. 2001). In several countries, the technique hasalready taken final form, and operating manuals havebeen published (Alakangas et al. 1999, FAO 1976,Folkema 1989). In recent years, chippers and crushersfor comminuting logging residues and non-marketablethinned trees have been being diffused in Japanese for-estry. Increasing nationwide interest in bioenergy uti-lization is one reason for this development, and somesmall-sized and medium-sized chippers have beentested at the local government level in order to definethe productivity of these machines and the quality ofthe chips obtained.

When a large-sized chipper or crusher is introduced,economies of scale will be achieved, i.e., the commi-nuting cost of a large-sized chipper or crusher is ex-pected to be lower than that of a small-sized one. How-ever, few trials on comminuting logging residues by alarge-sized chipper or crusher with an engine outputhigher than approximately 150 kW have been carriedout in Japan. Data presented in Chapter 4, in which theappropriate site for comminuting logging residues fromthe viewpoint of the total procurement cost of woodchips was discussed, showed that the comminuting costof a large-sized crusher was lower than that of a small-sized chipper. In the discussion of comminution by alarge-sized crusher, reference was made to a study inwhich the performance of a tub grinder (TG400A,Vermeer Manufacturing Company, USA) was investi-gated at a grading site. In the cost calculation of thetub grinder, however, only the labor cost, the machinecost (expenses for depreciation and supplies), and thefuel cost incurred by the operation of the tub grinderitself were considered. Moriguchi et al. reported, basedon their study of comminution by a medium-sized chip-per with an engine output of 60.3 kW, that the sum ofthe cost of a grapple loader to feed logging residuesinto the chipper, that of carrying in, installing, and car-rying out the chipper and the loader, and that of con-structing a landing for the operation accounted for aconsiderably high proportion of the total chipping cost(Moriguchi et al. 2004). The results of this study sug-gest that those additional costs should be considered,particularly when calculating the cost of comminutinglogging residues with a large-sized crusher, such as atub grinder.

Therefore, the objective of this chapter is to investi-gate the following items by testing the comminutionof logging residues with a tub grinder (Yoshioka et al.



Fig. 10. Tub grinder. Reprinted with permission from Croatian Journal of Forest Engineering, 27(2), Yoshioka, T et al.,Comminution of logging residues with a tub grinder: Calculation of productivity and procurement cost of wood chips, 103–114, Fig. 1, 2006, Forestry Faculty of Zagreb University.

2006b):• Productivity of a large-sized crusher;• Proportion of the total costs accounted by the costof auxiliary machines, for example, a grapple loader,the cost of carrying in, installing, and carrying out thecrusher and auxiliary machines, and the cost of con-structing a landing;• Calculation of the cost of comminuting loggingresidues collected at a landing and transporting woodchips;• Balance of the processing capacity between the large-sized crusher and other machines, such as a yardingmachine and auxiliary ones.


5-1A. Experimental siteThe experiment was conducted at the Fukashiro Dam

construction site, Yamanashi Prefecture, which is situ-ated to the west of Tokyo. The site is located at theupper reaches of the Kazuno River, which forms partof the Sagami River system. Pulpwood was extractedfrom scrap trees generated during the course of build-ing the dam, and residual material was comminutedby a tub grinder. In other words, the residual materialwas regarded to be logging residues. The scrap trees,which had to be disposed of in accordance with localgovernment regulations, were collected from 18 haJapanese cedar (Cryptomeria japonica D. Don) andbroad-leaved tree stands that were to be submerged.

5-1B. Description of systemsThe operation was divided into two systems, that is,

a “COLLECT and SORT” system and a “COMMI-NUTE and TRANSPORT” one. After a certain amountof logging residues had been collected, the comminut-ing operation was carried out.

The “COLLECT and SORT” system consisted of fell-ing with chain saws, collecting with a yarder (cableyarding system: endless Tyler system; maximumyarding distance: 460 m), bucking with chain saws,and sorting with a grapple loader. Pulpwood and log-ging residues were sorted and piled into separated heapsof pulpwood and residues, respectively. Here, loggingresidues were considered to be by-products of pulp-wood production. In this sense, all of the costs associ-ated with this system are attributed to the pulpwoodproduced. A time study of a yarder was carried out,and the balance of the processing capacity between thissystem and the “COMMINUTE and TRANSPORT”one is discussed.

In the “COMMINUTE and TRANSPORT” system,a grapple loader fed logging residues into a tub grinder,a tub grinder comminuted the logging residues (thescreen size opening of a tub grinder was set at 5.0 cm),a bucket loader (a digging bucket of an excavator wasreplaced with a larger-sized bucket for the purpose ofloading wood chips) loaded wood chips onto a truck,and a truck transported the wood chips. Therefore, thesetwo loaders were regarded as auxiliary machines forthe tub grinder in this system. The tub grinder wasequipped with a conveyor to take wood chips directlyinto a truck. However, a bucket loader for loading chipswas introduced because the mobility of the truck wasconsidered to have priority. Time studies of the tubgrinder and the two loaders were conducted, and the



Fig. 11. Grapple loader. Reprinted with permission from Croatian Journal of Forest Engineering, 27(2), Yoshioka, T et al.,Comminution of logging residues with a tub grinder: Calculation of productivity and procurement cost of wood chips, 103–114, Fig. 2, 2006, Forestry Faculty of Zagreb University.

respectively. The maximum load volume of the truckwas 40 m3. The operators of the respective machineshad a significant amount of relevant work experience,and the landing was large enough for the operators tomaneuver the machines at will.

5-1D. Cost calculationThe total comminuting cost per m3 of the processed

wood chips, TC (US$/m3), is expressed as:

TCLA M F

P

CA

W

CO

Wi i i

i

i

i

= + + +

+ ( )∑ 5 1.

where LAi (US$/h), Mi (US$/h), and Fi (US$/h) are thelabor, machine, and fuel costs per hour, respectively,of each machine (i represents each machine, i.e., a tubgrinder, a grapple loader, and a bucket loader); Pi(m3/h) is the productivity of each machine; CAi (US$)is the cost of carrying in, installing, and carrying outeach machine; W (m3) is the whole amount of woodchips processed at the investigated site; CO (US$) isthe cost of constructing a landing. The machine cost(expenses for depreciation and supplies), Mi, and thefuel cost, Fi, are calculated on the basis of the follow-ing two equations:

MMP

H D LISi

i

i i ii= ×

× ×+ ( )0 9

5 2.

.

F FCi i= × ( )0 76 5 3. .

volume of the processed chips and fuel (light oil) con-sumption of each machine was measured. A bin (0.60m long, 0.50 m wide, 0.60 m high, with a weight of3.6 kg) was filled with chips, and the weight of the binwas also measured (scales: MODEL DS-261,Teraokaseiko Co., Ltd., Japan). Consequently, the greenweight of the chips per unit volume could be calcu-lated. Ten chip samples were taken to determine themoisture content of the chips. The green mass of eachsample was measured, and the samples were then driedat 103 degrees Celsius for more than 24 h. The mois-ture content was determined by dividing the mass ofwater contained within the sample by the dry mass ofthe sample.

5-1C. Description of machinesThe tub grinder (HD-9 Industrial Tub Grinder,

DuraTech Industries International, Inc., USA, Fig. 10)is 7.72 m long, 2.49 m wide, and 2.62 m high andweighs 8,760 kg. Its engine (275 HP John Deere) hasan output of 205.1 kW. The tub is 1.02 m deep, with adiameter at the top and bottom of 2.91 m and 2.29 m,respectively. A hammer mill crusher is positioned atthe bottom of the tub. The grapple loader (base ma-chine: EX120-5, Hitachi Construction Machinery Co.,Ltd., Japan; grapple: GS90LHV, Iwafuji Industrial Co.,Ltd., Japan, Fig. 11) is 7.58 m long, 2.50 m wide, and2.72 m high and weighs 11,800 kg. Its engine output is67.1 kW. The bucket loader (312B, Shin CaterpillarMitsubishi Ltd., Japan, Fig. 12) is 7.57 m long, 2.89 mwide, and 2.83 m high and weighs 12,300 kg. Its bucketcapacity and its engine output are 0.5 m3 and 66.9 kW,



Fig. 12. Bucket loader. Reprinted with permission from Croatian Journal of Forest Engineering, 27(2), Yoshioka, T et al.,Comminution of logging residues with a tub grinder: Calculation of productivity and procurement cost of wood chips, 103–114, Fig. 3, 2006, Forestry Faculty of Zagreb University.

where MPi (US$), Hi (h/d), Di (d/y), and LIi (y) are themachine price, hours of operation per day, days of op-eration per year, and life of each machine, respectively;Si (US$/h) is the expense for supplies; FCi (dm3/h) isthe fuel (light oil) consumption; 0.76 (US$/dm3) is theunit fuel price. Pi and FCi are calculated based on theresults of the field experiment. LAi, CAi, W, CO, Hi,and Si were gathered by means of a questionnaire (note:the expense associated with the supplies of a tub grindershould have been investigated in detail (such as, whatis the frequency of replacing old worn-out hammerswith new ones?); this aspect needs further discussion).

5-2. Results

This time study was considered to be finished whenthe tub grinder had comminuted almost all of the log-ging residues collected at the landing and the truck hadtransported three full loads of wood chips. Therefore,each quantity processed by the tub grinder and the twoloaders during the time study was considered to be 120m3 in terms of the loose volume of chips (the volumeof chips is expressed in loose measures).

During the time study, the effective working time ofthe tub grinder was 7,196 seconds; thus, the produc-tivity of the grinder was calculated to be 60.0 m3/h(the effective time does not include any delays). Incomparison, the effective working time of the grappleloader and that of the bucket loader were 6,779 s and7,127 s, respectively. Consequently, the performanceswere calculated to be 63.7 m3/h for the grapple loaderand 60.6 m3/h for the bucket loader. Table 12 provides

detailed information on the calculations of the totalcomminuting cost. The cost of constructing the land-ing per m3 of chips in Table 12, 0.732 US$/m3, wascalculated by dividing the cost of constructing the land-ing, 2,857 US$, by the whole amount of wood chipsprocessed at the investigated site, namely, 3,903 m3.However, as 361.8 m3 of pulpwood was also producedat the site, the cost of constructing the landing shouldhave been distributed between the amounts of pulp-wood and wood chips according to their economic val-ues. During the collection of materials for the timestudy of the tub grinder and the two loaders, the yarderwas in operation for 39,424 s, and the amount of thecollected materials was equivalent to 40 m3 of pulp-wood and 120 m3 of wood chips.

The bin filled with the processed wood chips (Fig.13) weighed 61.4 kg at the experimental site. The binweighed 3.6 kg and had a volume of 0.18 m3; there-fore, the green weight of the chips per unit volume wascalculated to be 321 kg/m3. Finally, the average mois-ture content of the chips measured 120.4% (on a dry-mass basis, with a standard deviation of 12.6%), andthe dry weight of the chips per unit volume was esti-mated to be 146 kgDM/m3.

Although the moisture content of logging residuesto be comminuted and the screen size opening of a tubgrinder would influence the productivity of the tubgrinder, only one instance (moisture content: 120.4%;screen size opening: 5.0 cm) was examined here. Thus,there is no further discussion on the quality of woodchips in terms of whether the processed wood chipsshown in Fig. 13 are suitable as a bioenergy source.



Item

Tub

gri

nder

Gra

pple

Buc

ket

Not

e

Pro

duct

ivit

y (m

3 /h)

[1]

60

.06

3.7

60

.6R

esul

ts o

f th

e fi

eld

expe

rim

ent

Lab

or c

ost

(US

$/h)

[2]

23

.82

3.8

23

.8F

rom

per

sona

l co

mm

unic

atio

nM

achi

ne c

ost

(US

$/h)

[3]

81

.62

2.3

19

.3[3

] =

[4]

+ [

9]E

xpen

se f

or d

epre

ciat

ion

(US

$/h)

[4]

61

.22

1.6

18

.6[4

] =

([5

] ×

0.9)

/([6

] ×

[7]

× [8

])M

achi

ne p

rice

(U

S$)

[5]

47

61

90

19

23

81

16

57

14

Fro

m F

ores

t M

echa

niza

tion

Soc

iety

(ed

.) (

1999

)H

ours

of

oper

atio

n pe

r da

y (h

/d)

[6]

78

8F

rom

per

sona

l co

mm

unic

atio

nD

ays

of o

pera

tion

per

yea

r (d

/y)

[7]

20

02

00

20

0L

ife

(y)

[8]

55

5E

xpen

se f

or s

uppl

ies

(US

$/h)

[9]

20

.40

.70

.7F

rom

per

sona

l co

mm

unic

a tio

nF

uel

cost

(U

S$/

h)[1

0]5

4.4

7.6

7.6

[10]

= [

11]

× 0.

76,

0.76

: un

it f

uel

pric

e (U

S$/

dm3 )

Fue

l (l

ight

oil

) co

nsum

ptio

n (d

m3 /h

)[1

1]7

1.4

10

.01

0.0

Res

ults

of

the

fiel

d e x

peri

men

tS

ubto

tal

of t

he c

osts

of

labo

r, m

achi

ne,

and

fuel

(U

S$/

h)[1

2]1

59

.85

3.7

50

.7[1

2] =

[2]

+ [

3] +

[10

]pe

r m

3 of

the

chip

s (U

S$/

m3 )

[13]

2.6

63

0.8

43

0.8

37

[13]

= [

12]/

[1]

Who

le a

mou

nt o

f th

e ch

ips

proc

esse

d at

the

sit

e (m

3 )[1

4]3

90

33

90

33

90

3F

rom

per

sona

l c o

mm

unic

a tio

nC

ost

of c

arry

ing

in,

inst

alli

ng,

and

carr

ying

out

(U

S$)

[15]

95

26

19

61

9F

rom

per

sona

l co

mm

unic

a tio

npe

r m

3 of

the

chip

s (U

S$/

m3 )

[16]

0.2

44

0.1

59

0.1

59

[16]

= [

15]/

[14]

Item

Va l

ueN

ote

Cos

t of

con

stru

ctin

g a

land

ing

(US

$)[1

7]2

85

7F

rom

per

sona

l c o

mm

unic

a tio

npe

r m

3 of

the

chip

s (U

S$/

m3 )

[18]

0.7

32

[18]

= [

17]/

[14]

Tot

al c

omm

inut

ing

cost

(U

S$/

m3 )

[19]

5.6

37

[19]

= [

13]

+ [

16]

+ [

18]

Tab

le 1

2.

Det

ails

on

the

calc

ulat

ions

use

d fo

r th

e to

tal c

omm

inut

ing

cost

. Rep

rint

ed w

ith

perm

issi

on f

rom

Cro

atia

n Jo

urna

l of

For

est

Eng

inee

ring

, 27(

2), Y

oshi

oka,

T e

t al

., C

omm

inut

ion

of lo

ggin

g re

sidu

es w

ith

a tu

b gr

inde

r: C

alcu

lati

on o

f pr

oduc

tiv-

ity

and

proc

urem

ent

cost

of

woo

d ch

ips,

103

–114

, Tab

le 1

, 2

006,

For

estr

y F

acul

ty o

f Z

agre

b U

nive

rsit

y .



Fig. 13. Processed wood chips. Reprinted with permission from Croatian Journal of Forest Engineering, 27(2), Yoshioka, Tet al., Comminution of logging residues with a tub grinder: Calculation of productivity and procurement cost of wood chips,103–114, Fig. 4, 2006, Forestry Faculty of Zagreb University.

the breakdown of the total comminuting cost is shownin Fig. 14. The percentage of the sum of the cost of theloaders, that of carrying in, installing, and carrying outthe machines, and that of constructing the landing is53% of the total comminuting cost. These costs haveto be reduced in order to improve the total cost. Thecost of the two loaders represents 30% of the total cost(Fig. 14). However, instead of the operational systemused in this chapter, other operation patterns, such asdifferent combinations of machines, could have beenadopted at the experimental site. Given this possibil-ity, a comparison between the calculated total cost andthe cost of the cases described below is necessary:• Case 1: Instead of a grapple loader, the operator of atub grinder manipulates a grapple by installing it inthe tub grinder or introducing another chipper orcrusher equipped with a grapple;• Case 2: Instead of a bucket loader, a tub grinderdumps wood chips directly into a truck with its con-veyor;• Case 3: Instead of two loaders (and a truck), a chip-per truck, which can comminute logging residues andtransport chips, is introduced. When only one machineworks at a landing, there is no interaction betweenmachines. Therefore, the operator of the chipper truckcan control the entire “COMMINUTE and TRANS-PORT” system. Although the operation rates of boththe chipping and transporting functions of the chippertruck will be lower than those of a tub grinder and atruck, it is easier to plan and carry out the operation ofone machine than the operations of two or three ma-chines from the point of view of management.The cost of carrying in, installing, and carrying out

5-3. Discussion

5-3A. Total comminuting costWhen only the labor cost, the machine cost, and the

fuel cost of the tub grinder were considered on the ba-sis of data presented in Chapter 4, the comminutingcost per m3 of the processed wood chips was calcu-lated to be 2.663 US$/m3 (Table 12). This value cor-responds to 18.2 US$/MgDM (=2.663 [US$/m3] × 1000[kg/Mg]/146 [kgDM/m3]; with 1,000 kg/Mg being theconversion coefficient) in terms of the cost per dry massof chips and is lower than the comminuting cost ex-amined in Chapter 4, i.e., 22.7–45.5 US$/MgDM. Themoisture content observed in the system analyzed inthis chapter, 120.4%, was quite similar to that in Chap-ter 4, 119.3%, and typical of green logging residues(Asikainen and Pulkkinen 1998). On the other hand,the bulk density, 146 kgDM/m3, was higher than thatin Chapter 4, 113.9 kgDM/m3. The reason for this dif-ference is the composition of the processed wood chips,which in the system described in this chapter includedconiferous and broad-leaved species, while in that de-scribed in Chapter 4 included only chips from Japa-nese cedar. In general, a broad-leaved tree is heavierthan a coniferous one from the viewpoint of weightper unit volume. Consequently, the higher bulk den-sity can be considered to be one of the reasons that thecomminuting cost in this chapter was lower than thatreported in Chapter 4 in terms of cost per dry mass ofchips.

The cost of the two loaders, that of carrying in, in-stalling, and carrying out the machines, and that of con-structing the landing, are also given in Table 12, and



small-sized chipper, which would be suitable for treetops and branches with a maximum diameter of 15 cm,was calculated to be 66.5 US$/MgDM in Chapter 4.Therefore, the comminuting cost of a large-sizedcrusher is lower than that of a small-sized chipper.

Based on personal communication, the cost of a truckwas shown to be 571 US$ per day at the investigatedsite. Figure 15 shows the relationship between thenumber of truck transportation events per day and thecosts of comminution and transportation per dry massof chips. The sums of the costs of comminution andtransportation were 136.4 US$/MgDM, 87.5US$/MgDM, and 71.2 US$/MgDM when the trucktransported wood chips once per day, twice per day,and three times per day, respectively (a truck will trans-port three times per day when its running speed, hoursof operation per day, operation time of loading andunloading per cycle, and one-way running distance are30 km/h, 6 h/d, 40 minutes per cycle, and 20 km, re-spectively). The cost of 71.2 US$/MgDM, for exam-ple, corresponds to 3.56 US$/GJ or 12.8 US$/MWh interms of the cost per calorific value of chips, and it isalmost on a par with those of European countries inwhich the energy utilization of logging residues ismaking steady progress (see Chapter 4). In terms ofthe energy utilization of logging residues, Fig. 15 maybe of use in designing the arrangement of landingsaround an energy-conversion plant and the order oftruck transportation, while the cost of a truck must beinvestigated and analyzed in detail.

the machines (10%) and that of constructing the land-ing (13%) shown in Fig. 14 are calculated by dividingtheir original cost by the whole amount of the woodchips processed at the investigated site. In order to re-duce these two costs, therefore, it is necessary to pro-duce as many wood chips as possible at one landing—in other words, as many logging residues as possibleshould be collected at one landing. For example, if a10% greater amount of wood chips were to be producedat the landing, the percentage of the two costs to thetotal cost would decrease to 21.3% and the total costwould decrease by 2.1%. Moreover, if 10,000 m3 ofwood chips were to be produced, the percentage of thetwo costs would decrease to 11.2% and the total costwould decrease by 13.3%.

The total comminuting cost is calculated as 5.637US$/m3 (Table 12). In a Finnish case study, the costof comminution with a tub grinder was 1.7 US$/m3

despite the productivity being similar to that reportedin this chapter (Asikainen and Pulkkinen 1998). Thereason for this difference would appear to be the useof only one machine in the Finnish system as the tubgrinder was equipped with both a grapple and a con-veyor. The grapple put logging residues into the tub,and the conveyor took wood chips directly into a truck;in other words, the tub grinder required no auxiliarymachines. On the other hand, the mobility of a truckfor transportation was probably restricted. This studyand the Finnish one should have been compared fromthe standpoint of the sum of the costs of comminutionand transportation. It should be noted that the total com-minuting cost of the system described in this chapter,5.637 US$/m3, corresponds to 38.6 US$/MgDM interms of the cost per dry mass of chips. The cost of a

0

50

100

150

1 2 3

Number of daily instances

Cos

t (U

S$/

tDM

)

Transportation

Comminution

0

2

4

6

Cos

t (U

S$/

m3 )

Constructing a landing

Carrying in, installing, andcarrying out a bucket loader

Carrying in, installing, andcarrying out a grapple loader

Carrying in, installing, andcarrying out a tub grinder

Bucket loader

Grapple loader

Tub grinder

Fig. 14. Breakdown of the total comminuting cost. Reprintedwith permission from Croatian Journal of Forest Engineer-ing, 27(2), Yoshioka, T et al., Comminution of loggingresidues with a tub grinder: Calculation of productivity andprocurement cost of wood chips, 103–114, Fig. 5, 2006,Forestry Faculty of Zagreb University.

Fig. 15. Relationship between the number of daily instancesof truck transportation and the costs of comminution andtransportation per dry mass of chips. Reprinted with per-mission from Croatian Journal of Forest Engineering, 27(2),Yoshioka, T et al., Comminution of logging residues with atub grinder: Calculation of productivity and procurement costof wood chips, 103–114, Fig. 6, 2006, Forestry Faculty ofZagreb University.



5-3B. Balance of the processing capacity betweena tub grinder and other machines

The productivity of a tub grinder ranges from 14–24to 100–150 m3/h in published studies (Asikainen andPulkkinen 1998). The difference in the results is saidto be due to difficulties in feeding logging residues intothe tub grinder. The productivity of the tub grinderduring the time study, 60.0 m3/h, is quite similar tothat of the Finnish case study, 60–70 m3/h (Asikainenand Pulkkinen 1998), demonstrating the high perform-ance of the tub grinder investigated.

In order to collect materials for the experiment, theyarder was in operation for about 11 h (39,424 s), whilethe tub grinder comminuted the sorted logging residuesfor almost 2 h (7,196 s). During the whole period (361.8m3 of pulpwood and 3,903 m3 of wood chips were proc-essed), the yarder and the tub grinder operated 105 daysand 21 days, respectively. Not all of the operation hoursof the yarder were for collecting wood chips becausethe yarder collected pulpwood material at the same timeby whole-tree yarding. However, the yarder had to workfor a much longer time than the tub grinder to copewith the relatively higher productivity of the grinder.

The percentage of time the grapple loader and bucketloader spent for idling was 6.2% and 4.6% of the totalobserved time, respectively. There was little time forboth machines to idle, so it is supposed that the twoloaders were running almost non-stop to cope with thehigh performance of the tub grinder.

Based on personal communication, the net produc-tivity of the tub grinder during the whole period was26.6 m3/h, which is 44% of the productivity based onthe time study, namely, 60.0 m3/h. This leads to theinterpretation that the rate of operation of the tubgrinder was less than 50% even when the grinderworked at the site and is likely due to the relativelyhigher productivity of the tub grinder than that of theyarder. As a result, the rate of operation of the tubgrinder will not be enhanced unless large amounts oflogging residues are collected for comminution. Thisaspect is further examined in a comparison of the costsof comminution and transportation between the twocases, as described below:• Case 1: A large amount of logging residues is col-lected to counterbalance the high productivity of thetub grinder. The total comminuting cost will be reducedbecause a larger amount of wood chips will be pro-duced at one landing and the cost of carrying in, in-stalling, and carrying out the machines and that of con-structing a landing will be reduced. However, a land-ing that is large enough to operate the auxiliary ma-chines for the tub grinder and accommodate the largeamounts of collected logging residues and processedwood chips must be constructed. Moreover, it wouldbe necessary to build a network of high-grade forestroads on which large-sized trucks that can carry loadsof as much as 40 m3 of wood chips can travel directly

to the landing;• Case 2: Another smaller-sized tub grinder is intro-duced. In order to keep the rate of operation of the tubgrinder high, the size of the grinder should be deter-mined in accordance with the amount of loggingresidues that can be collected at one landing, theprocessing capacity of a yarding (or skidding) machineand auxiliary ones, and the degree of preparation ofthe network of high-grade forest roads.In both of these cases, the productivity of a tub grinderis expected to be still higher, so it would be realisticfor Japanese forestry to consider the sharing of onetub grinder among several logging sites. If this wereto be the case, i.e., machines were to be transferredfrom one site to another, the planning and managementof an operational system at each site will need to takethe total comminuting cost into account, since the pro-portion of the sum of the cost of carrying in, install-ing, and carrying out machines and that of construct-ing a landing to the total cost is not negligible.

6. Energy and carbon dioxide (CO2) balance of

logging residues as alternative energy re-sources: System analysis based on the methodof a life cycle inventory (LCI) analysis

Biomass is carbon-neutral. For example, forestbiomass is neutral in terms of the balance of carbondioxide (CO2), which has been implicated in the ongo-ing changes in global climate. This neutrality can bemaintained if the management of naturally regeneratedand planted forests is carried out on a truly sustainablebasis. However, the veracity of this statement shouldbe challenged. In forest management programs, vari-ous operations are carried out that involve the use offorestry machines, and these forestry machines, whenin operation, usually consume liquid fossil fuel andexhaust CO2. Therefore, in any evaluation of the en-ergy and CO2 balance of forest biomass, not only thesequestration and consumption of biomass itself butalso the consumed fuel and the exhausted CO2 gas needto be discussed. The study on fuel consumption forchipping, forwarding, and transporting logging residues(see Chapter 4) indicated that there was no specificproblem from the point of view of the input and outputof energy, and the results suggested that Japan couldreduce its domestic CO2 emission by using biomass asan alternative energy resource. To conduct a fair evalu-ation of the balance of energy and CO2, however, itwill be necessary to examine not only the fuel con-sumption by forestry machines but also the energy bal-ance of the entire system, which would include mate-rials, construction, and the repair and maintenance ofmachines used in forestry as well as the costs associ-ated with an energy-conversion plant.

Therefore, a more detailed analysis of the system willbe required to provide scientific evidence that logging



scale system suitable for Japanese conventional for-estry.

In this chapter, the input and output of energy andCO2 emission of the forest biomass are analyzed overthe entire life cycle of the biomass within the contextof an LCI analysis, with the aim of determining whethera small-scale energy-conversion system that uses for-est biomass from Japanese conventional forestry as fuelis feasible from the point of view of energy and CO2balance (Yoshioka et al. 2005a).


Logging residues, i.e., tree tops and branches, areproduced during limbing and bucking; these materialsare considered here to be the sources of energy.Residues are supposed to be chipped, forwarded, andtransported by forestry machines, and then convertedto electricity in a biomass-fired power generation plant;the entire system is analyzed in this chapter. Basic dataon a harvesting and transporting system for loggingresidues and an energy-conversion plant are collectedfrom the field experiments (see Chapters 3, 4, and 5)and from published studies on biomass-fired and coal-fired power generation plants (Ogi et al. 2002,Uchiyama and Yamamoto 1991, 1992), respectively.Calculations of the energy input required by each proc-ess of the system and the output from an energy-con-

System boundary

EquipmentOperation

EquipmentOperation

EquipmentOperation

tuptuo ygrenEtupni ygrenE

Manual felling (chain saw)

Processor limbing and bucking

Whole-tree skidding/yarding

Biomass-fired power generation plant

Power generation

Chipper comminuting

Forwarder hauling

Drying in a forest(Water content is reduced to 50%.)

Equipment

Operation

CO2

CO2

CO2

CO2

Electricity

Truck transporting

Drying in a stockyard(Water content is reduced to 15%.)

Fig. 16. Process tree of a biomass procurement and bioenergysupply system. Reprinted with kind permission from SpringerScience + Business Media: Journal of Forest Research, En-ergy and carbon dioxide (CO

2) balance of logging residues

as alternative energy resources: System analysis based onthe method of a life cycle inventory (LCI) analysis. 10(2),2005, 125–134. Yoshioka, T, Aruga, K, Nitami, T, Kobayashi,H, Sakai, H, Fig. 1. 2005, Springer Japan.

residues could serve as an efficient alternative energysource and one that would have a lower environmentalimpact than fossil fuels. Such an analysis method iscalled a life cycle inventory (LCI) analysis and is basedon a method called a life cycle assessment (LCA). Thistype of analysis is essential when the aim is to obtainthe necessary scientific evidence. LCI has been usedto compare different options. Methodologies on howto perform the LCI are defined in the ISO 14000 stand-ard, which also applies to LCA (ISO 14040/JIS Q14040 1999, ISO 14041/JIS Q 14041 and ISO TR14049/JIS Q TR 14049 2001). LCI is an intrinsic partof the complete LCA.

With regard to the analysis of a bioenergy produc-tion system that considers all of the processes, manystudies based on the LCI analysis method have beenconducted in Europe (Boman and Turnbull 1997,Börjesson 1996a, b, Börjesson and Gustavsson 1996,Faaji et al. 1997, Forsberg 2000, Gustavsson et al.1995, Hektor 1998, Jungmeier et al. 1998). Hektor(1998) analyzed the difference in the amount of CO2emitted by a combined heat and power (CHP) systemfueled by fossil fuels and one fueled by various forestbiomass resources, e.g., logging residues and thinnedtrees from conventional forestry and whole-tree chipsfrom short rotation forestry (SRF). Boman and Turnbull(1997) calculated the reduction in the amount of CO2emission by replacing coal-fired power generation sys-tems with biomass-fired power generation systems. Anumber of Japanese research groups have analyzed abioenergy system based on LCI analysis or LCA (Doteand Yokoyama 1994, Dowaki et al. 2000, 2001, Taharaet al. 1998). All of these, however, regarded forestbiomass from SRF in foreign countries as an energyresource for the purpose of trading greenhouse gasemissions, taking the clean development mechanism(CDM) into account. Moreover, all the studies on theenergy conversion of biomass mentioned above tar-geted large-scale plants whose net power output weretens to hundreds MW.

In Japan, the energy utilization of forest biomass isexpected to improve the health of domestic man-madeforests. However, a large-scale energy-conversion plantusing forest biomass as the fuel source is not feasibledue to the small working unit of forest management aswell as the expensive harvesting and transporting costof the biomass. Forest biomass from Japanese conven-tional forestry will therefore have to be converted toenergy in a small-scale plant. The results from exist-ing studies on the evaluation of a large-scale systemcannot be applied to a small-scale system where thenet power output of an energy-conversion plant is atmost several MW for two primary reasons: (1) differ-ences in the type and size of forestry machines betweenforeign countries and Japan; (2) the difference in ther-mal efficiency between a large-scale plant and a small-scale one. Therefore, it is essential to evaluate a small-



(1)The scale of the plant discussed in Chapter 6 is based on a survey by Ogi et al. (2002) of nine biomass-fired power genera-tion plants, which were in operation in Japan as of 2002. The average values of the net power output and thermal efficiency ofthe nine plants surveyed were 3 MW and 12%, respectively. The plant is supposed to be in operation 24 h per day and 256 daysper year (the annual rate of operation is 70%), and the life of the plant is 30 years.(2)The generated electricity per year corresponds to the annual energy output from the system.(3)The generated electricity is calculated from the net power output, hours of operation per day, and days of operation per yearas: 3 [MW] × 24 [h/d] × 256 [d/y] = 18,432 [MWh

e/y].

(4)The necessary amount of logging residues per hour is calculated from the net power output and thermal efficiency as: 3[MW] × 3.6 [GJ/MWh]/0.12/18.2 [GJ/MgDM] = 4.9 [MgDM/h]; where 3.6 GJ/MWh is the conversion coefficient, and 18.2GJ/MgDM is the calorific value of logging residues considering 15% of the water content (dry basis) (Klass 1998). Theannual required amount is then calculated as: 4.9 [MgDM/h] × 24 [h/d] × 256 [d/y] = 30,106 [MgDM/y].(5)The number of the plants is calculated from 3.0 Tg/y of the annual potential of logging residues in Japan (Yoshioka et al.2006a) and 30,106 MgDM/y of the annual required amount per plant.(6)The area that one plant covers is assumed to form a circle. When the plant is in the center of a circle, the theoretical averagetransportation distance is two-thirds of the radius of the circle (Sundberg and Silversides 1988). The practical average trans-portation distance is supposed to be 20% greater than the theoretical one (Börjesson and Gustavsson 1996).

Item Value

Net power output (MW) 3Thermal efficiency (%) 12Hours of operation per day (h/d) 24Days of operation per year (d/y) 256Life (y) 30Generated electricity per year(2) (MWhe/y) (e: electricity) 18432(3)

Annual required amount of logging residues (MgDM/y) 30106(4)

Number of plants of the same scale that could be constructed in Japan 100(5)

Average transporting distance of a 4-ton truck (km) 27.8(6)

Table 13. Basic data on a biomass-fired power generation plant.(1) Reprinted with kind permission from Springer Science +Business Media: Journal of Forest Research, Energy and carbon dioxide (CO

2) balance of logging residues as alternative

energy resources: System analysis based on the method of a life cycle inventory (LCI) analysis. 10(2), 2005, 125–134. Yoshioka,T, Aruga, K, Nitami, T, Kobayashi, H, Sakai, H, Table 1. 2005, Springer Japan.

version plant were made to determine the energy bal-ance. In addition, the ratio of energy output to inputwas analyzed based on the LCI analysis. The CO2 emis-sion from each process was calculated by multiplyingthe energy input into each process and the CO2 emis-sion per unit energy. Finally, the CO2 emission per unitof bioenergy was estimated from the total CO2 emis-sions and the energy output was measured in the formof electricity.

6-1A. System componentsThe chipping, harvesting, and transporting chain for

logging residues (see Chapter 4) and the operations toreduce the water content of residues are combined inthis analysis. In terms of the energy-conversion sys-tem, the state-of-the-art power generation technologyavailable in Japan is supposed to be introduced; there-fore, a power generation system that supplies electric-ity by utilizing logging residues from domestic con-ventional forestry as fuel is assumed in this chapter.Figure 16 illustrates the process tree of a biomass pro-curement and bioenergy supply system.

Trees are felled by chain saws and left in forests fora few months to dry in the sun; this is called “sour”

felling, and it reduces the water content to 50% (drybasis). The operation of whole-tree yarding/skiddingis then conducted by tractors, yarders, or mobileyarders. Trees are limbed and bucked by a processorat a landing of a logging site in a forest. A large quan-tity of tops and branches are generated because of thehigh performance of the processor. These loggingresidues are the sources of energy.

With regard to the harvesting and transporting sys-tem for logging residues, the least costly system (seeChapter 4) was adopted. Biomass is comminuted at thelanding of the logging site by a mobile chipper, hauledon a strip road to another landing alongside a forestroad by a forwarder (haulage distance is 191.4 m), andtransported on a forest road and a public road to a powergeneration plant in a 4-ton truck. The comminutedbiomass is then dried in a plant stockyard, and the watercontent is reduced to 15% (dry basis).

The scale of the plant discussed in this chapter isbased on a survey by Ogi et al. (2002) of nine biomass-fired power generation plants that were in operation inJapan as of 2002. These plants mainly used millresidues as fuel. The average values of the net poweroutput and thermal efficiency of the nine plants sur-



Mac

hine

Wei

ght2,

3

(Mg)

Dur

able

hou

rs4

(h)

Pro

duct

ivit

y5

(MgD

M/h

)F

uel

cons

umpt

ion5

(dm

3 /h)

Num

ber

ofre

quir

ed m

achi

nes6

Wei

ght o

f re

quir

edm

ater

ial

(ste

el)7

(Mg/

y)

Qua

ntit

y of

req

uire

dfu

el (

ligh

t oi

l)8

(dm

3 /y)

Mob

ile

chip

per

2.4

55

00

00

.45

04

.53

55

.75

32

.83

03

05

7Fo

rwa r

der

5.6

05

40

01

.68

82

.01

14

.86

18

.53

58

18

Tru

ck7

.96

55

00

0.6

79

5.4

53

6.9

56

4.2

24

18

00

Tab

le 1

4.

Bas

ic d

ata

on t

he f

ores

try

mac

hine

s.1

Rep

rint

ed w

ith

kind

per

mis

sion

fro

m S

prin

ger

Sci

ence

+ B

usin

ess

Med

ia:

Jour

nal

of F

ores

t R

esea

rch ,

Ene

rgy

and

carb

on d

ioxi

de (

CO

2) b

alan

ce o

f lo

ggin

g re

sidu

es a

s al

tern

ativ

e en

ergy

res

ourc

es:

Sys

tem

ana

lysi

s ba

sed

on t

he m

etho

d of

a l

ife

cycl

e in

vent

ory

(LC

I) a

naly

sis.

10(

2), 2

005,

125

–134

. Yos

hiok

a, T

, Aru

ga, K

,N

itam

i, T

, Kob

ayas

hi, H

, Sak

ai, H

, Tab

le 2

.

200

5, S

prin

ger

Japa

n.

1 Hou

rs o

f op

e ra t

ion

per

yea r

of

e ac h

ma c

hine

is

supp

ose d

to

be 1

,200

h/y

(6

h/d

a nd

200

d/y)

he r

e .2 O

n th

e ba

sis

of t

he a

naly

sis

by H

ondo

et

al. (

2000

), a

ll t

he p

a rts

of

e ac h

for

e str

y m

a chi

ne a

re a

ssum

ed t

o be

mad

e of

ste

e l i

n C

hapt

e r 6

.3 F

rom

For

e str

y M

e cha

niz a

tion

Soc

iety

(e d

.) (

1999

).4 F

rom

Na t

iona

l F

ore s

try

Ext

e nsi

on A

ssoc

iati

on i

n Ja

pan

(ed.

) (2

001)

.5 T

he p

rodu

c tiv

ity

a nd

fue l

con

sum

ptio

n of

ea c

h m

a chi

ne a

re b

a se d

on

fie l

d e x

peri

men

ts o

n c o

mm

inut

ing,

ha u

ling

, and

tra n

spor

ting

logg

ing

resi

due s

(se

e C

hapt

e rs

3, 4

, and

5).

The

kind

of

fue l

in

the

e xpe

rim

enta

l si

tes

wa s

lig

ht o

il. 1

91.4

m o

f ha

ulin

g di

sta n

c e i

s re

fle c

ted

in t

he p

rodu

c tiv

ity

a nd

fue l

con

sum

ptio

n of

the

for

wa r

der ,

and

27.

8 km

of

tra n

spor

ting

dist

a nc e

is

refl

e cte

d in

the

pro

duc t

ivit

y a n

d fu

e l c

onsu

mpt

ion

of t

he t

ruc k

.6 T

he n

umbe

r of

re q

uire

d m

a chi

nes

is c

a lc u

late

d fr

om t

he h

ours

of

ope r

a tio

n pe

r ye

a r,

1,20

0 h/

y, t

he p

rodu

c tiv

ity

of e

a ch

ma c

hine

, a n

d 30

,106

MgD

M/y

of

the

a nnu

a l r

e qui

red

amou

nt o

f lo

ggin

g re

sidu

e s f

or t

he p

lant

. For

exa

mpl

e , t

he n

umbe

r of

re q

uire

d tr

ucks

is

c alc

ula t

e d a

s: 3

0106

[M

gDM

/y]/

1200

[h/

y]/0

.679

[M

gDM

/h]

= 3

6.95

.7 T

he w

e igh

t of

the

re q

uire

d m

a te r

ial

is c

a lc u

late

d fr

om t

he h

ours

of

ope r

a tio

n pe

r ye

a r,

1,20

0 h/

y, t

he w

e igh

t a n

d th

e du

rabl

e ho

urs

of e

a ch

ma c

hine

, a n

d th

e nu

mbe

r of

re q

uire

dm

a chi

nes.

For

exa

mpl

e , t

he w

e igh

t of

the

re q

uire

d m

a te r

ial

for

the

forw

a rde

rs i

s c a

lcul

a te d

as:

5.6

0 [M

g] ×

120

0 [h

/y]/

5400

[h]

× 1

4.86

= 1

8.5

[Mg/

y].

8 The

qua

ntit

y of

re q

uire

d fu

e l i

s c a

lcul

a te d

fro

m t

he h

ours

of

ope r

a tio

n pe

r ye

a r,

1,20

0 h/

y, t

he f

uel

c ons

umpt

ion

of e

a ch

ma c

hine

, a n

d th

e nu

mbe

r of

re q

uire

d m

a chi

nes.

For

e xam

ple ,

the

qua

ntit

y of

re q

uire

d fu

e l f

or t

he m

obil

e c h

ippe

rs i

s c a

lcul

a te d

as:

4.5

3 [d

m3 /

h] ×

120

0 [h

/y]

× 55

.75

= 3

0305

7 [d

m3 /

y].



Table 15. Required materials for a biomass-fired power generation plant.* Reprinted with kind permission from SpringerScience + Business Media: Journal of Forest Research, Energy and carbon dioxide (CO

2) balance of logging residues as

alternative energy resources: System analysis based on the method of a life cycle inventory (LCI) analysis. 10(2), 2005, 125–134. Yoshioka, T, Aruga, K, Nitami, T, Kobayashi, H, Sakai, H, Table 3. 2005, Springer Japan.

*The quantity of required materials for a power generation plant is reported to be proportional to the 0.7 power of the netpower output of the plant (Tahara et al. 1998). In Chapter 6, the required materials for the 3 MW biomass-fired power genera-tion plant are calculated with reference to a 1,000 MW coal-fired power generation plant (Uchiyama and Yamamoto 1991),given the multiplier 0.0171 (=(3/1000)0.7).**The subtotal weight of the steel rod, concrete, cable, plumbing, cable tray, conduit, turbine, and boiler corresponds to 70%of the total of the plant. The other 30% is taken up by miscellaneous parts.

veyed were 3 MW and 12%, respectively. The plantused as an example in this chapter is supposed to be inoperation 24 hours per day and 256 days per year (theannual rate of operation is 70%), and the life of theplant is 30 years. Table 13 shows the basic data on thebiomass-fired power generation plant.

6-1B. System boundaryThe system boundary defined in this chapter is also

shown in Fig. 16. Bioenergy is considered as a by-product to conventional forestry practices. In this sense,forestry activities are not influenced by the existenceof a downstream bioenergy system. Therefore, thebioenergy system boundary starts with the comminu-tion of logging residues at the landing of the loggingsite by a mobile chipper. All environmental impactsup to this point are accredited to forestry.

Basic data on the forestry machines and requiredmaterials for the biomass-fired power generation plantthat are used to calculate the energy input into the sys-tem are listed in Tables 14, 15, respectively. The datacontained in these tables have been obtained from fieldexperiments and published studies (see footnotes ofrespective tables). Table 16 shows the energy densityof the required materials and fuel.

6-1C. Calculation methodsThe goal of this chapter is to investigate three envi-

ronmental load profiles of the defined biomass pro-curement and bioenergy supply chain. The first is theenergy balance factor (EBF), which is the ratio of en-ergy output to input and used to confirm whether or

not the system is feasible as an energy production sys-tem. The second is the energy payback time (EPT),which is the index that accounts, by energy produc-tion, for the number of years required to recover thetotal energy input into the system over an entire lifecycle. Logging residues are compared with fossil andrenewable resources from the perspectives of EBF andEPT, respectively. The third is the CO2 emission fac-tor (CEF), which is the CO2 emission per unit of elec-tricity generated. The CEF of the biomass-fired powergeneration plant is compared with that of a coal-firedpower generation plant, which has been reported tohave the highest environmental impact among variouspower generation technologies. The reduction in theamount of CO2 emission in Japan that will result fromreplacing coal-fired generation systems with biomass-fired generation systems is calculated to evaluate towhich extent logging residues as alternative energyresources can contribute to achieving the goals of theKyoto Protocol in the first period of commitment start-ing in the year 2008, when Japan must reduce its green-house gas emissions by 6% of the amount recorded in1990.

After the goal and scope of this section have beendefined, an inventory analysis is carried out based onthe collected and processed data. The parameter thathas the most impact on the LCI results, i.e., EBF, EPT,and CEF, is evaluated with a sensitivity analysis so thatproblems and improvements of the system can be re-vealed.

Basic theoretical equations of three environmentalload profiles defined here (EBF, EPT, and CEF) are

Item Unit Steel Aluminum Concrete

Steel rod Mg 124.6 — —Concrete Mg (m3) — (—) — (—) 3006.9 (1307.3)Cable Mg (km) 3.9 (19.1) 10.7 (19.1) — (—)Plumbing Mg (km) 138.4 (1.9) — (—) 42.4 (1.9)Cable tray Mg (km) 42.4 (3.7) — (—) — (—)Conduit Mg 43.6 — —Turbine Mg 654.9 — —Boiler Mg 55.9 — —

Subtotal (70%)** Mg 1063.7 10.7 3049.3Total Mg 1519.6 15.3 4356.1



Material Unit Electricity** Oil Coal Light oil Total

Steel MJ/Mg 4709 0 20930 — 25640(kWhe/Mg) (500)

Aluminum MJ/Mg 164826 46047 0 — 210872(kWhe/Mg) (17500)

Concrete MJ/Mg 184 435 255 — 875(kWhe/Mg) (20)

Light oil kJ/dm3 — — — 38512 38512

Table 16. Energy density of the required materials and fuel.* Reprinted with kind permission from Springer Science + Busi-ness Media: Journal of Forest Research, Energy and carbon dioxide (CO

2) balance of logging residues as alternative energy

resources: System analysis based on the method of a life cycle inventory (LCI) analysis. 10(2), 2005, 125–134. Yoshioka, T,Aruga, K, Nitami, T, Kobayashi, H, Sakai, H, Table 4. 2005, Springer Japan.

*This table is prepared with reference to Uchiyama and Yamamoto (1991), given the conversion coefficient 4.18605 J/cal.**In terms of electricity, the value of 9.419 MJ/kWh

e, which was calculated based on the composition of power resources in

Japan as of 1988 (14% for coal, 24% for oil, and 22% for natural gas), was adopted in Chapter 6.

based on the rule made by Uchiyama and Yamamoto(1991) and expressed as:

EBFLCEO

LCEE LCOEi ii

=+( ) ( )

∑6 1.

EPT

LCEE

AEO AOE

ii

ii

=−

( )∑

∑6 2.

CEF

LCEEE LCOEE CEE

LCEO

ij ij jji=

+( ) ⋅{ }( )

∑∑ .6 3

where LCEO is the energy output from an energy-con-version plant over its entire life cycle; LCEEi andLCOEi are the “equipment” and “operation” energiesover the life cycle of each process of the system, re-spectively (i: each process, i.e., comminuting, haul-ing, transporting, and power generation); AEO is theannual energy output; AOEi is the annual “operation”energy of each process; LCEEEij and LCOEEij are the“equipment” and “operation” energies, respectively, ofeach kind of energy resources, e.g., electricity, coal,and oil, over the life cycle of each process (j: each kindof energy resources); CEEj is the CO2 emission perunit energy of each energy resource.

In this chapter, the energy input consists of the“equipment” and “operation” energies. Consequently,the denominator of the right-hand side of Eq. (6.1) rep-resents the energy input into the system over its entirelife cycle.

“Equipment” energy is defined as the energy neces-sary for manufacturing equipment, which constitutes

a system, i.e., forestry machines and a biomass-firedpower generation plant, and is composed of the “ma-terial,” “production,” “transportation,” and “construc-tion” energies. “Material” energy is the energy neces-sary for refining raw materials, e.g., steel, aluminum,and concrete. “Production” energy is the energy nec-essary for producing the parts of equipment, e.g., ma-chine engines and a plant generator. “Transportation”energy is the energy necessary for transporting theparts. “Construction” energy is the energy necessaryfor constructing equipment from the parts transported.On the other hand, “operation” energy is defined asthe energy necessary for operating a system and con-sists of the fuel consumption of forestry machines andthe “repair and maintenance” energy of a power gen-eration plant. Fuel consumption was measured in thefield experiments on chipping, forwarding, and trans-porting logging residues at forestry operating sites inJapan (see Chapters 3, 4, and 5). “Repair and mainte-nance” energy is the energy necessary for the repair ofparts and the maintenance of a plant.

With regard to the calculation of the energy input,this chapter adopts a process analysis in which theobject is divided into its component elements and theenergies required for the formation of each elementare integrated. The following three equations are usedto calculate the “equipment” energy over the entire lifecycle of the system:

LCEE ME PE TE CEii

i i i ii

∑ ∑= + + +( ) ( ) .6 4

ME MW EDMi k kjjk

= ⋅( ) ( )∑∑ 6 5.

PE TE CE MEi i i i+ + = ⋅ ( )0 2 6 6. .



where MEi, PEi, TEi, and CEi are the “material,” “pro-duction,” “transportation,” and “construction” energiesof each process, respectively; MWk is the weight ofeach kind of necessary materials (k: each kind of nec-essary materials); EDMkj is the energy density of eachnecessary material (the calorific value of each energyresource per unit weight of each material). Equation(6.6) shows an assumption that the sum of the “pro-duction,” “transportation,” and “construction” energiesis equivalent to 20% of the total “material” energy ac-cording to Uchiyama and Yamamoto (1991). The “op-eration” energy over the entire life cycle of the system(LCOEsystem) is calculated on the basis of the follow-ing three equations:

LCOE FC RME LCOEii

system machine plant= + =

( )∑ 6 7.

Process Energy** Unit Electricity Coal Oil Light oil Total

Comminuting Material GJ/y (MWhe/y) 154 (16.4) 687 841

P., T., and C. GJ/y (MWhe/y) 31 (3.3) 137 168

Hauling Material GJ/y (MWhe/y) 87 (9.3) 387 474

P., T., and C. GJ/y (MWhe/y) 18 (1.9) 77 95

Transporting Material GJ/y (MWhe/y) 302 (32.1) 1344 1646

P., T., and C. GJ/y (MWhe/y) 60 (6.4) 269 329

Subtotal GJ/y (MWhe/y) 653 (69.4) 2901 [2]

Power generation Material GJ (MWhe) 10478 (1114.6) 32917 2600 45996

P., T., and C. GJ (MWhe) 2096 (222.9) 6583 520 9199

Subtotal GJ (MWhe) 12574 (1337.5) 39501 3120 [3]

Process Unit Electricity Coal Oil Light oil Total

Comminuting GJ/y 11671 11671

Hauling GJ/y 1379 1379

Transporting GJ/y 9312 9312

Power generation GJ/y (MWhe/y) 629 (66.9) 1975 156 2760

Subtotal GJ/y (MWhe/y) 629 (66.9) 1975 156 22363 [4]

LCI result Value Calculation method

Energy balance factor (EBF) 5.69 [1] × 30/([2] × 30 + [3] + [4] × 30) (from Eq. (6.1))Energy payback time (EPT) 1.09 years ([2] × 30 + [3])/([1] − [4]) (from Eq. (6.2))

Table 17. Life cycle inventory of logging residues: (I) Energy balance.* Reprinted with kind permission from Springer Sci-ence + Business Media: Journal of Forest Research, Energy and carbon dioxide (CO

2) balance of logging residues as alterna-

tive energy resources: System analysis based on the method of a life cycle inventory (LCI) analysis. 10(2), 2005, 125–134.Yoshioka, T, Aruga, K, Nitami, T, Kobayashi, H, Sakai, H, Table 5. 2005, Springer Japan.

*Energy output: 173,604 GJ/y (18,432 MWhe/y from Table 13) ... [1].

**P., T., and C. refer to the “production,” “transportation,” and “construction” energies.

Energy input: “Equipment” energy

Energy input: “Operation” energy

FC FC EDFii

machine = ⋅( ) ( )∑ 6 8.

RME LCEEplant plant= ⋅ ( )0 05 6 9. .

where FCmachine is the total fuel consumption of for-estry machines; RMEplant is the “repair and mainte-nance” energy of a power generation plant; FCi is thefuel consumption of each machine; EDF is the energydensity of fuel consumed; LCEEplant is the “equipment”energy over the life cycle of the plant. Equation (6.9)indicates that RMEplant is equivalent to 5% of LCEEplanton the condition that the repair and maintenance of theplant is performed every year so that all parts of theplant may be updated in 20 years (Uchiyama andYamamoto 1991).



Comminuting38.2%Hauling

4.5%

Transporting30.5%

Powergeneration

9.0% Hauling1.9%

Comminuting3.3%

Transporting6.5%

Powergeneration

6.0%

("Equipment" energy)

("Operation" energy)

Energy input30516 GJ/y

Fig. 17. Breakdown of the annual energy input into the sys-tem. Reprinted with kind permission from Springer Science+ Business Media: Journal of Forest Research, Energy andcarbon dioxide (CO

2) balance of logging residues as alter-

native energy resources: System analysis based on themethod of a life cycle inventory (LCI) analysis. 10(2), 2005,125–134. Yoshioka, T, Aruga, K, Nitami, T, Kobayashi, H,Sakai, H, Fig. 2. 2005, Springer Japan.

6-2. Results and discussion

6-2A. Inventory analysis(a) Energy balance

From the data in Tables 14, 15, 16, it is possible tocalculate the “equipment” and “operation” energiesusing Eqs. (6.4), (6.5), and (6.6) and Eqs. (6.7), (6.8),and (6.9), respectively, thereby clarifying the energyinputs into all the processes of the system. The lifecycle inventory of the logging residues in terms of theenergy balance can then be completed, the results ofwhich are given in Table 17 (the life cycle inventoryexplains the details of a specific item inside the sys-tem boundary).

The energy input into the system can be analyzed byaggregating the “equipment” and “operation” energiesof each process in Table 17. Figure 17 illustrates thebreakdown of the annual energy input into the system.In this figure, 82.2% of the total energy input is the“operation” energy, with the “equipment” energy cor-responding to the other 17.8%; that is, the amount ofenergy required for operating the system is much largerthan the amount of energy required by the equipmentthat makes up the system. With respect to the “opera-tion” energy, the fuel consumption of the forestry ma-chines accounts for 73.2% of the total energy input,with the processes of comminuting and transportingbeing primarily responsible for these especially highrates of consumption. The essential first step towardsreducing the total energy input is to reduce the fuelconsumption of the mobile chipper and the truck perunit weight of logging residues by taking such meas-ures as developing efficient techniques and improving

the operational efficiency of both processes (in thischapter, 0.450 MgDM/h for a mobile chipper and 0.679MgDM/h for a truck; see Table 14). For example, ifthe efficiency of a mobile chipper increases by 25%and the fuel consumption per unit weight of residuesdecreases by 20%, the total energy input will be re-duced by 7.6%.

Table 17 also shows the EBF and the EPT calcu-lated from Eqs. (6.1) and (6.2), respectively. The EPTin Table 17 is 1.09 years, which represents the totalenergy input into the system consisting of a plant withan operating life of 30 years that can be recovered fora short period of 1.09 years with power generation;this results suggests that residual forest biomass is rela-tively superior to other renewable energy resources,such as wind (1.99 years) or solar energy (10.00 years)(Uchiyama and Yamamoto 1991). On the other hand,the EBF in Table 17 is 5.69, which means that 5.69-fold more energy than that required for the total en-ergy input can be produced during the entire life cycleof the system. This result indicates that the system inthis chapter is feasible as an energy production sys-tem. From the perspective of EBF, however, residualforest biomass is inferior to fossil energy resources suchas coal (17.15) or oil (20.75) (Uchiyama and Yamamoto1991). The average net power output of power genera-tion plants of those fossil resources is 1,000 MW; alarge-scale power generation system can supply a hugeamount of electricity steadily, while a small-scale sys-tem enables on-site or regional energy utilization. Bothsystems have advantages (and disadvantages), so asmall-scale 3 MW biomass-fired plant should not becompared with a large-scale one in the 1,000-MW classfrom the aspect of energy balance alone.(b) CO2 emission

The CO2 emissions from all of the processes of thesystem are calculated from Table 17 and the CO2 emis-sion per unit energy of each energy resource is deter-mined (see footnote of Table 18). The life cycle in-ventory of logging residues in terms of CO2 emissionis then completed and is listed in Table 18. The CO2emissions from the “equipment” energy and the “op-eration” energy account for 38% and 62%, respectively,of the total CO2 emission from the system, resulting ina smaller difference between both energies than thatin the case of the energy input into the system discussedabove.

Table 18 also shows CEF calculated from Eq. (6.3).The CEF of the biomass-fired power generation sys-tem is 61.8 kgCO2/MWhe (e: electricity), while that ofthe coal-fired power generation system in Japan is 960kgCO2/MWhe (the net power output is 1,000 MW, theannual rate of operation is 75%, and the life of a plantis 30 years (Uchiyama and Yamamoto 1992)). There-fore, through the system analysis based on LCI, it canbe determined that residual forest biomass from Japa-nese conventional forestry has a much lower environ-



mental impact than coal from the viewpoint of theamount of CO2 emitted in power generation. Moreover,the reduction in the amount of CO2 emission in Japanthat will result from replacing coal-fired power gen-eration plants with biomass-fired ones is calculatedfrom the CEFs of biomass and coal shown above, thegenerated electricity per biomass-fired plant per year,18,432 MWhe/y, and the number of the plants that canbe constructed in Japan, 100, as follows:

{(960 – 61.8) [kgCO2/MWhe]/1000 [kg/Mg]}× 18432 [MWhe/y] × 100 = 1655562 [MgCO2/y]

where 1,000 kg/Mg is the conversion coefficient. This

amount corresponds to 0.142% of the national CO2emission estimated for 2000, i.e., 1.162 PgCO2/y (En-ergy Data and Modelling Center (ed.) 2002).

Boman and Turnbull (1997) analyzed the CEFs offorest biomass and coal. In their analysis, the CEF ofcoal was calculated to be over 100 kgC/GJe (equiva-lent to 1,319 kgCO2/MWhe), while that of forestbiomass was less than 10 kgC/GJe (131.9kgCO2/MWhe); the results of the calculations per-formed in this chapter are roughly in accordance withthose of that analysis. Moreover, were all of the fuel tobe replaced with biomass in a 108 MW coal-fired powergeneration plant, the reduction in the amount of CO2emission per GJe would be eight-fold greater than when

Process Energy Unit Electricity Coal Oil Light oil Total

Comminuting Material MgCO2/y 6.4 62.2 68.6

P., T., and C. MgCO2/y 1.3 12.4 13.7

Hauling Material MgCO2/y 3.6 35.1 38.7

P., T., and C. MgCO2/y 0.7 7.0 7.7

Transporting Material MgCO2/y 12.6 121.7 134.3

P., T., and C. MgCO2/y 2.5 24.3 26.8

Subtotal MgCO2/y 27.2 262.8 [2]

Power generation Material MgCO2 437.3 2982.5 182.7 3602.5

P., T., and C. MgCO2 87.5 596.5 36.5 720.5

Subtotal MgCO2 524.7 3579.7 219.3 [3]

Table 18. Life cycle inventory of logging residues: (II) CO2 emission.* Reprinted with kind permission from Springer Science

+ Business Media: Journal of Forest Research, Energy and carbon dioxide (CO2) balance of logging residues as alternative

energy resources: System analysis based on the method of a life cycle inventory (LCI) analysis. 10(2), 2005, 125–134. Yoshioka,T, Aruga, K, Nitami, T, Kobayashi, H, Sakai, H, Table 6. 2005, Springer Japan.

CO2 emission from the energy input: “Equipment” energy**

CO2 emission from the energy input: “Operation” energy**

*Energy output: 18,432 MWhe/y (from Table 13) ... [1].

**The CO2 emissions from electricity, coal, oil, and light oil per unit energy are 392.33 kgCO

2/MWh

e, 90.61 kgCO

2/GJ, 70.28

kgCO2/GJ, and 21.81 kgCO

2/GJ, respectively (Uchiyama and Yamamoto 1992, Korpilahti 1998). The CO

2 emission from the

energy input in this table is calculated using these values and the energy input into each process in Table 17.

Process Unit Electricity Coal Oil Light oil Total

Comminuting MgCO2/y 254.6 254.6

Hauling MgCO2/y 30.1 30.1

Transporting MgCO2/y 203.1 203.1

Power generation MgCO2/y 26.2 178.9 11.0 216.1

Subtotal MgCO2/y 26.2 178.9 11.0 487.7 [4]

LCI result: CO2 emission factor (CEF) Value Calculation method

From the energy 23.6 kgCO2/MWhe ([2] + [3]/30)/[1] 5]From the energy 38.2 kgCO2/MWhe [6]Total 61.8 kgCO2/MWhe [5] + [6] (from Eq. (6.3))



only 10% of the fuel would be replaced (in terms ofthe co-firing of forest biomass with coal, there is stillan advantage that biomass can be converted to elec-tricity with high efficiency, so further discussion of thisaspect will be necessary). Their analysis can be re-garded as a practical one because they took the utiliza-tion of the existing coal-fired plant into consideration.On the other hand, in this chapter, it is assumed thatthe large-scale 1,000-MW class coal-fired system isreplaced with the small-scale 3-MW class biomass-

fired system. However, these systems differ not onlyin scale but also in suitable location (along the sea coastfor coal and mountainous regions for forest biomass).Just how the system is to be replaced within the presentsocial framework needs to be well discussed.

6-2B. Sensitivity analysisIn this section, the degree to which the LCI results

in this study, i.e., EPT, EBF, and CEF, will be influ-enced by changes in values of the parameters is evalu-

100

78.0

0

20

40

60

80

100

120

140

30 years 20 years

Life

Per

cent

age

to th

e ba

se c

ase

(%)

100107.3

120.2

0

20

40

60

80

100

120

140

3 MW 5 MW 8 MW

Net power output

Per

cent

age

to th

e ba

se c

ase

(%)

100

53.244.0

0

20

40

60

80

100

120

140

12% 27% 40%

Thermal efficiency

Per

cent

age

to th

e ba

se c

ase

(%)

100 97.0

0

20

40

60

80

100

120

140

30 years 20 years

Life

Per

cent

age

to th

e ba

se c

ase

(%)

(a) Energy payback time

10091.7

82.6

0

20

40

60

80

100

120

140

3 MW 5 MW 8 MW

Net power output

Per

cent

age

to th

e ba

se c

ase

(%)

100

209.7

277.7

0

50

100

150

200

250

300

350

12% 27% 40%

Thermal efficiencyP

erce

ntag

e to

the

base

cas

e (%

)

(b) Energy balance factor

100106.3

0

20

40

60

80

100

120

140

30 years 20 years

Life

Per

cent

age

to th

e ba

se c

ase

(%)

100105.0

113.3

0

20

40

60

80

100

120

140

3 MW 5 MW 8 MW

Net power output

Per

cent

age

to th

e ba

se c

ase

(%)

(c) CO2 emission factor

100

57.648.1

0

20

40

60

80

100

120

140

12% 27% 40%

Themal efficiency

Per

cent

age

to th

e ba

se c

ase

(%)

Fig. 18. Sensitivity analysis to the LCI results. Reprinted with kind permission from Springer Science + Business Media:Journal of Forest Research, Energy and carbon dioxide (CO

2) balance of logging residues as alternative energy resources:

System analysis based on the method of a life cycle inventory (LCI) analysis. 10(2), 2005, 125–134. Yoshioka, T, Aruga, K,Nitami, T, Kobayashi, H, Sakai, H, Fig. 3. 2005, Springer Japan.



ated by a sensitivity analysis. Figure 18 illustrates theresults of this analysis, in which the life span, net poweroutput, and thermal efficiency of the biomass-firedpower generation plant are chosen the primary deter-minants.

The shorter the life of the plant, the lower the EPT—which is a favorable tendency. However, the EBF de-creases and the CEF increases if the life of the plant isshortened, both of which are unfavorable tendencies.From the viewpoint of the input and output of energy,which is one of the main subjects of this study, EBF isthe most important parameter. Therefore, these find-ings suggest that the plant should be operated for aslong a period as possible. The more the net power out-put increases, the more EPT and CEF will increase andEBF will decrease, which are unfavorable tendencies.The chipping, forwarding, and transporting costs oflogging residues will increase when the scale of anenergy-conversion plant is expanded. For example, theaverage transporting distance of a 4-ton truck is calcu-lated to be 45.6 km when an 8 MW biomass-fired powergeneration plant is constructed. Therefore, from theaspects of energy and CO2 balance as well as the pro-curement cost, a larger-scale plant is unrealistic forlogging residues. The thermal efficiency of the planthas the greatest influence on the LCI results. The EPTand CEF will decrease and the EBF will increase whenthe thermal efficiency increases, which are favorabletendencies. If the energy-conversion technology ofbiomass whose thermal efficiency is 40% is realized,the reduction in the amount of CO2 emission in Japanis expected to be equivalent to 0.481% of the nationalCO2 emission. Consequently, with the aim of makingresidual forest biomass more advantageous to fossil re-sources, it is proposed that a small-scale and efficientenergy-conversion technology of biomass should be de-veloped.


There are additional problems that will require moredetailed study in the future. In terms of the method-ologies, for example, the allocation of the energy in-puts and the CO2 emissions of the felling, yarding/skid-ding, limbing and bucking processes to logs and log-ging residues will be necessary when logging residuesas energy resources are regarded not as by-products toconventional forestry but as forestry products equal invalue to logs. From the perspective of the standardsset by the Kyoto Protocol, the results of this study, inwhich only logging residues are taken into account,are not necessarily satisfactory; therefore, the amountof CO2 emissions of the other woody biomass re-sources, such as thinned trees, broad-leaved forests,mill residues, wood-based waste material, and trim-mings, over their entire life cycles should also be evalu-ated.

7. A GIS-based analysis of the relationship be-tween the annual available amount and theprocurement cost of forest biomass in a moun-tainous region in Japan

Detailed data on the annual available amounts offorest biomass, including spatial data, as well as thoseon harvesting and transportation costs (procurementcosts) are necessary prerequisites for the optimal andsustainable utilization of forest biomass for energy. vanBelle et al. (2003) conducted such analyses using ageographic information system (GIS). The GIS hasbeen used in a number of studies on forestry opera-tions and forest road planning (Dean 1997, Erikssonand Rönnqvist 2003, Forsberg and Rönnqvist 2003,Kluender et al. 2000, Martin et al. 2001, Pentek et al.2004, 2005) and for estimating the amount of domes-tic forest biomass resources in sufficient detail (Nord-Larsen and Talbot 2004, Ranta 2003, 2004, Talbot andNord-Larsen 2003).

In this chapter, the feasibility of the energy utiliza-tion of forest biomass in a mountainous region in Ja-pan is discussed based on an analysis of the relation-ship between the mass and the procurement cost ofbiomass in the region using a GIS (Yoshioka and Sakai2005). A model region was selected, and loggingresidues, thinned trees, and trees from broad-leavedforests were defined as forest biomass for energy.Mechanization in forestry for the energy utilization offorest biomass was assumed to be available. The ob-jective was to determine the actual situation of the re-gion in terms of possible utilization of forest biomassfor bioenergy production by investigating the distri-bution of forest resources, the topography, and thealignment of forest and public roads as exactly as pos-sible.


The model region selected is a county located in themiddle of Japan. It has a gross surface area of 493.28km2, with a population of 72,862 distributed in 21,769households. It is subject to an inland and basin-typeclimate; the annual average temperature is 13–14 de-grees Celsius, and the annual precipitation is 1,500–1,600 mm/y. The forests belong to the lucidphyllousforest zone, covering an area of 37,202 ha (75% of thegross area of the county). Coniferous plantation for-ests cover 58% of the forested area. The 43 sawmillsin the region annually consume 78,992 m3 of sawlogs.The county leads the prefecture in terms of forestryand timber business, but annual fellings have droppedby almost 50% in the past 5 years. The amount of for-est stands left tending is increasing. The slow progressof mechanized forestry in this region is assumed to beone of the major reasons for this decline in productiv-ity.



For

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fro

m C

roat

ian

Jour

nal

of F

ores

tE

ngin

eeri

ng, 2

6(2)

, Yos

hiok

a, T

, Sak

ai H

, Am

ount

and

ava

ilab

ilit

y of

for

est

biom

ass

as a

n en

ergy

res

ourc

e in

a m

ount

aino

usre

gion

in

Japa

n: a

GIS

-bas

ed a

naly

sis,

59–

70, T

able

1,

200

5, F

ores

try

Fac

ulty

of

Zag

reb

Uni

vers

ity.

*The

rep

rese

ntat

ive

tree

spe

cies

in

the

regi

on a

re “

hino

ki”

or a

cyp

ress

(C

ham

aecy

pari

s ob

tusa

) in

con

ifer

ous

fore

sts

and

“key

aki ”

or

a ze

lkov

a ( Z

elko

va s

erra

ta)

in b

road

-lea

ved

fore

sts.

**It

wa s

sup

pose

d in

Cha

pte r

7 t

hat

a ll

of t

he c

ut m

a te r

ial

a t t

hinn

ings

cou

ld b

e us

e d a

s a n

ene

rgy

sour

c e, t

a kin

g a c

tua l

Ja p

a ne s

e m

a rke

t va

lue

into

con

side

rati

on.

Bio

mas

s re

sou r

c es

Equ

atio

n (s

.v.:

Ste

m v

olum

e)N

ote

Log

ging

re s

idue

s**

Am

ount

(M

gDM

)=

s.v

.⋅15

/92

⋅0.4

0•1

5/92

: R

atio

of

the

volu

me

of t

he t

ops

and

bran

ches

to

that

of

the

stem

•0.4

0: D

ensi

ty o

f a

coni

fero

us t

ree

Thi

nned

tre

esA

mou

nt (

MgD

M)

= s

.v.⋅2

0/1

00

⋅10

0/9

2⋅0

.40

•20/

100:

Thi

nnin

g ra

te

•100

/92:

Rat

io o

f th

e vo

lum

e of

the

who

le t

ree

to t

hat

of t

he s

tem

•0.4

0: D

ensi

ty o

f a

coni

fero

us t

ree

Tre

es f

rom

bro

ad-l

eave

d fo

rest

sA

mou

nt (

MgD

M)

= s

.v.⋅1

00

/80

⋅0.5

6•1

00/8

0: R

atio

of

the

volu

me

of t

he w

hole

tre

e to

tha

t of

the

ste

m

•0.5

6: D

ensi

ty o

f a

broa

d-le

aved

tre

e

Tab

le 2

0.

Me t

hods

for

ca l

c ula

ting

the

am

ount

of

biom

a ss

reso

urc e

s.*

Re p

rint

e d w

ith

perm

issi

on f

rom

Cro

atia

n J o

urna

l of

For

e st

Eng

ine e

ring

, 26(

2), Y

oshi

oka ,

T, S

a ka i

H, A

mou

nt a

nd a

vail

a bil

ity

of f

ore s

t bio

ma s

s a s

an

e ne r

gy r

e sou

rce

in a

mou

n-ta

inou

s re

gion

in

Japa

n: a

GIS

-ba s

e d a

naly

sis,

59–

70, T

a ble

2,

200

5, F

ore s

try

Fa c

ulty

of

Za g

reb

Uni

vers

ity.

*The

coe

ffic

ient

s sh

own

in t

his

tabl

e ha

ve b

e en

basi

c all

y st

a nda

rdiz

e d b

y th

e Ja

pane

se g

ove r

nmen

t (A

gric

ultu

re, F

ore s

try

a nd

Fis

heri

e s R

e se a

rch

Cou

ncil

Se c

reta

ria t

(e d

.) 1

991)

.**

The

me t

hod

for

c alc

ula t

ing

the

c ut

volu

me

of l

ogs

in c

lea r

c utt

ing

is a

s fo

llow

s: V

olum

e of

log

s (m

3 ) =

s.v

.·85/

92 (

85/9

2: R

a tio

of

the

volu

me

of t

he l

ogs

to t

hat

of t

he s

tem

).



The forest survey data, statistics on the forest indus-tries, and guides to forestry practice were offered fromthe prefectural office. Using these data and the GIS(software: TNTmips®; MicroImages, Inc., USA), theannual available amount of biomass resources was cal-culated, and a distribution map was made. The shapesand the locations of sub-compartments are the vectordata, which are managed by the prefecture. The digitalelevation model (DEM) was utilized to calculate theheights above sea level and the angles of inclination.Forest and public roads were traced on the digital topo-graphic map of the region and converted to vector data.These data were integrated on the software and proc-essed. Harvesting and transportation systems for for-est biomass were classified depending on the fractionof the tree for energy and the topographical conditions,and the equations for calculating costs were made.

This section includes the methodology used to as-sess the forest biomass resources, to prepare topo-graphic information, and to select an optimal harvest-ing and transportation systems, with reference to themethodology of three European studies, i.e., Belgium(van Belle et al. 2003), Denmark (Nord-Larsen andTalbot 2004), and Finland (Ranta 2004).

7-1A. Calculation of the annual available amount offorest biomass

There were 2,168 sub-compartments in the regionand 7,841,851 m3 of total growing stock. This highaverage value of growing stock, i.e., 211 m3/ha, is dueto the fact that many of the forests in the region werejust maturing. Among the sub-compartments, therewere 1,113 coniferous plantation stands and 398 natu-rally regenerated broad-leaved stands; these standswere targeted for harvesting logs and energy fractions.Protection forest stands for the purpose of sedimentdisaster prevention and water conservation were ex-cluded. Thinning and clearcutting were supposed to be

Fig. 19. Conversion of forest and public roads into vector data. Reprinted with permission from Croatian Journal of ForestEngineering, 26(2), Yoshioka, T, Sakai H, Amount and availability of forest biomass as an energy resource in a mountainousregion in Japan: a GIS-based analysis, 59–70, Fig. 1, 2005, Forestry Faculty of Zagreb University.

carried out in the coniferous forests, and selection fell-ing in the broad-leaved forests. The representative treespecies in the region are “hinoki” or a cypress(Chamaecyparis obtusa) in coniferous stands and“keyaki” or a zelkova (Zelkova serrata) in broad-leavedstands. Table 19 lists the operation patterns of the sub-compartments to be felled. In the coniferous planta-tion forest, the annual cut volume was supposed toequal the annual increment. Thus, the cutting cycle wascalculated as 9.2016 years by dividing the total allow-able volume, 1,158,796 m3, according to the regionalforest survey records (see Table 19) by the annual in-crement, 125,934 m3/y.

The total stem volume of each sub-compartment isrecorded in the forest register. Thus, if a coefficientfor converting stem volume to dry mass is known, theamount of biomass resources can be calculated. Coef-ficients for the calculation of total tree biomass re-sources are listed in Table 20. The coefficients shownin Table 20 have been basically standardized by theJapanese government (Agriculture, Forestry andFisheries Research Council Secretariat (ed.) 1991). Byapplying the data shown in Tables 19, 20 to the forestregister and considering the cutting cycles of conifer-ous and broad-leaved forests, the annual availableamount of forest biomass in the region can be calcu-lated.

The amount of biomass in each sub-compartment wasalso calculated using the GIS in order to describe thespatial distribution of the resources.

7-1B. Preparation for topographic informationFirst, the vector data on the shapes and the locations

of the sub-compartments were entered into the GISsoftware together with the corresponding forest regis-ter data. Second, the digital topographic map of theregion (1:25,000 scale; the Geographical Survey In-stitute, Japan) was entered into the software, and all



roads exceeding 3 m width were traced and convertedto vector data (Fig. 19). Third, the DEM of the region(50 m mesh; the Geographical Survey Institute, Japan)was entered into the software to calculate the slope ofeach sub-compartment and to judge the skidding/yarding direction (uphill or downhill) (Fig. 20). Fourth,all of the vector data were converted to raster data,and the mesh of the raster data was based on the meshof the DEM, i.e., 50 m mesh. These layers were inte-grated according to the International Terrestrial Refer-ence Frame (ITRF). Figure 21 shows the vector dataprojected on a digital topographic map (Fig. 21(a)),the converted raster data on the shapes and the loca-tions of sub-compartments (Fig. 21(b)), and the con-

verted raster data on forest and public roads (Fig.21(c)).

The GIS software was used to generate transportsolutions from the forest to the energy plant. The skid-ding/yarding distance of each sub-compartment wasdetermined by calculating the distance from the “centerof gravity” mesh of a sub-compartment to the nearestroad mesh. A landing was to be arranged in the respec-tive road mesh. Road transportation distance was de-termined by calculating the distance from the “land-ing” road mesh to the energy-conversion plant, locatedin the center of the region, using the Dijkstra’s Algo-rithm. Finally, the average angle of inclination of eachsub-compartment was calculated, and skidding/yarding

422 428 426 436 457 500 544 562 552 529 503 479

440 450 454 455 458 494 537 575 575 551 525 508

450 477 483 498 499 501 538 583 584 542 514 493

475 502 513 524 523 534 553 600 578 529 492 465

510 526 546 559 553 570 591 607 565 522 478 451

541 548 578 593 593 610 625 619 583 539 498 476

566 576 605 620 626 629 645 640 602 562 524 498

565 567 579 590 586 589 620 631 625 581 547 518

541 540 550 551 550 561 599 599 597 601 566 526

517 510 522 516 515 546 582 565 560 585 576 542

496 478 498 488 488 530 559 530 528 555 579 556

475 451 477 463 468 512 529 505 497 526 551 555

(a) Projection of vector data on a digital

topographic map

(b) Converted raster data on the shapes and

locations of sub-compartments (mesh size: 50 m)

(c) Converted raster data on forest and public roads

(mesh size: 50 m)

608302 608302 608302 608302 608302 608302 608302 608403 608403 608403 608403 608403 608403 608403 608403 608403 608403 608501 608501 608502 608502 608502 608502 608502 608602

608302 608302 608302 608302 608302 608302 608403 608403 608403 608403 608403 608403 608403 608403 608403 608403 608501 608501 608501 608502 608502 608502 608502 608502 608502

608302 608302 608302 608302 608302 608302 608403 608403 608403 608403 608403 608403 608403 608402 608402 608501 608501 608501 608501 608502 608502 608502 608502 608502 608502

608302 608302 608302 608302 608302 608302 608403 608403 608403 608403 608403 608403 608403 608402 608402 608501 608501 608501 608501 608502 608502 608502 608502 608502 608502

608301 608301 608302 608302 608302 608403 608403 608403 608402 608403 608403 608403 608403 608402 608402 608501 608501 608501 608501 608502 608502 608502 608502 608502 608502

608301 608301 608301 608403 608403 608403 608403 608403 608403 608402 608402 608402 608402 608402 608501 608501 608501 608501 608501 608502 608502 608502 608502 608502 608502

608301 608301 608403 608403 608403 608403 608403 608403 608403 608402 608402 608402 608402 608402 608501 608501 608501 608501 608501 608502 608502 608502 608502 608502 608503

608301 608301 608403 608403 608403 608403 608403 608403 608402 608402 608402 608402 608402 0 608501 608501 608501 608501 608501 608502 608502 608502 608502 608503 608503

608301 608301 608403 608403 608403 608403 608401 608402 608402 608402 608402 608402 608402 0 608402 0 608501 608501 608501 608502 608502 608502 608503 608503 608503

608301 608403 608401 608403 608401 608401 608401 608401 608402 608402 608402 608402 608402 0 0 0 0 0 0 0 608503 608503 608503 608503 608503

608403 608403 608401 608401 608401 608401 608401 608401 608402 608402 0 0 608402 0 0 0 0 0 0 0 0 608503 608503 608503 608503

608403 608403 608401 608401 608401 608401 608401 608401 608401 608401 0 0 0 0 0 0 0 0 0 0 0 0 0 608503 608503

608401 608401 608401 608401 608401 608401 608401 608401 0 0 0 0 0 0 0 0 0 0 0 0 0 0 608503 608503 608503

608401 608401 608401 608401 608401 608401 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 608503

608401 608401 608401 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

608301 608401 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 608401 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 601902 601901 601901 601901 601901 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 601902 601902 601902 601902 601901 601901 601901 601901 601901 0 0 0 0 0

0 0 0 0 0 0 0 601902 601902 601902 601902 601902 601902 601902 601902 601901 601901 601901 601901 601901 601901 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 3984 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 3984 0 0 0 0 0 4027 4027 4027 4027 0 0 0 0

0 0 0 0 0 0 0 0 0 0 3984 3984 0 0 0 4027 4027 4027 0 0 4027 0 0 0 0

0 0 0 0 0 0 0 0 0 0 3984 0 0 4027 4027 4027 0 0 0 0 4027 0 5716 0 0

0 0 0 0 0 0 0 0 0 613 3984 3984 4027 4027 4027 4014 4014 4014 4014 1366 4027 5716 5716 5716 5716

0 0 0 0 0 0 613 613 613 613 0 0 0 0 0 0 0 0 4014 4014 0 0 0 0 5716

0 0 0 0 613 613 613 0 0 0 0 0 0 0 0 0 0 0 0 602 0 0 0 0 0

613 613 613 613 613 0 0 0 0 0 0 0 0 0 0 0 1367 1367 1367 5234 5234 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 1367 1367 1367 1367 0 0 0 5234 5234 5234 0 0

0 0 0 0 0 0 0 0 0 0 0 0 1367 1367 0 0 0 0 0 0 0 2392 2392 1365 0

7026 7026 7026 7026 7026 7026 1367 1367 1367 1367 1367 1367 1367 0 0 0 0 0 0 0 0 2392 0 1365 1365

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2392 0 2392 2392

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2392 2392 2392 0

Fig. 20. Digital elevation model (DEM, right) corresponding to a contour map (left). The vertical interval of the contour mapis 10 m. The mesh size of the DEM is 50 m, and the numerical value in each mesh indicates the height above sea level at thetop-left grid point of the mesh (unit: m). Reprinted with permission from Croatian Journal of Forest Engineering, 26(2),Yoshioka, T, Sakai H, Amount and availability of forest biomass as an energy resource in a mountainous region in Japan: aGIS-based analysis, 59–70, Fig. 2, 2005, Forestry Faculty of Zagreb University.

Fig. 21. Conversion of vector data into raster data. Reprinted with permission from Croatian Journal of Forest Engineering,26(2), Yoshioka, T, Sakai H, Amount and availability of forest biomass as an energy resource in a mountainous region inJapan: a GIS-based analysis, 59–70, Fig. 3, Fig. 4, 2005, Forestry Faculty of Zagreb University.



direction (uphill or downhill) was assessed by com-paring the altitudes of the “center of gravity” mesh withthose of the “landing” road mesh.

7-1C. Classification of harvesting and transportingsystems for forest biomass

The engine for the chipper used for comminutingwhole trees (see Table 19) must be larger than thatused for comminuting logging residues. A small-sizedchipper (engine power: 23 PS/17.2 kW) was supposedto be used for comminuting logging residues, and amiddle-sized chipper (200 PS/149 kW) for comminut-ing whole trees from thinnings and broad-leaved for-ests. Harvesting and transportation systems for forestbiomass were classified into two types depending onthe parts of a tree used for energy (logging residues orthe whole tree) (Fig. 22). The type of machine usedfor skidding/yarding is usually decided upon follow-ing consideration of the topographical conditions, i.e.,slope, distance, and direction (uphill or downhill).Here, tractors (skidders), tower yarders (mobileyarders), and yarders are to be used for the skidding/yarding process. Figure 23 shows how skidding/yarding machines were classified according to the topo-graphical conditions of sub-compartments.

Table 21 presents the cost functions for harvestingand transporting forest biomass taking the variablesslope, skidding/yarding distance, and transportationdistance into account. The performance of forestryoperations in Japan have been partly standardized bySakai (1987) and Sawaguchi (1996), and their studieswere referred to in order to formulate biomass harvestand transport operations. The costs of labor, machin-ery, and fuel were considered to be basically the sameas those used in the previous study by the author(Yoshioka et al. 2006a). The procurement costs of for-est biomass were calculated by applying the cost func-tions to the spatial data for each sub-compartment inthe region.

7-2. Results

7-2A. Annual available amount of forest biomassThe annual available amount of biomass resources

in the region was calculated by the method describedin Section 7-1A (Table 22). About half of the sub-com-partments in the region were targeted for harvestinglogs and energy sources, and the total annual availableamount was calculated to be 52.206 GgDM/y. Bothconiferous plantation forests and naturally regeneratedbroad-leaved forests will be felled in a sustainable way,i.e., by considering the cutting cycles of the forests.Therefore, the health of the forests is expected to beimproved by utilization of biomass resources for en-ergy. At least 143 MgDM (=52,206 [MgDM/y]/365[d/y]) of biomass can be supplied to an energy-con-version plant every day (the mass varies with the daysof operation). On the other hand, 57,162 m3/y of thecut volume of logs corresponds to 72% of the annual

Forest

Forest and

Whole-tree skidding/yarding

Comminuting by amiddle-sized chipper

Comminuting by asmall-sized chipper

Landing

public roads

Processes inside the bold lineare considered when harvestingand transporting costs arecalculated in this chapter.

Logging residues Thinned trees andbroad-leaved forests

Limbing and buckingby a processor

Transporting by a 8-ton truck

Felling by a chain saw

[Uphill]

)eerged()eerged(

[Downhill]

Tractor

(m)

Tower yarder

Yarder

300

[X axis: Slope; Y axis: Skidding/yarding distance]

Yarder

Tower yarder

Tractor

9111 0

Fig. 22. Classification of systems according to the parts of a tree for energy. Reprinted with permission from Croatian Journalof Forest Engineering, 26(2), Yoshioka, T, Sakai H, Amount and availability of forest biomass as an energy resource in amountainous region in Japan: a GIS-based analysis, 59–70, Fig. 5, 2005, Forestry Faculty of Zagreb University.

Fig. 23. Classification of machines according to the topo-graphical conditions. Reprinted with permission fromCroatian Journal of Forest Engineering, 26(2), Yoshioka,T, Sakai H, Amount and availability of forest biomass as anenergy resource in a mountainous region in Japan: a GIS-based analysis, 59–70, Fig. 6, 2005, Forestry Faculty ofZagreb University.



consumption of logs for timber in the region, and thetotal amount of logs and energy sources to be harvestedis sufficient enough to sustain the introduction of largeefficient forestry machines.

7-2B. Relationship between the mass and the pro-curement cost of forest biomass

The masses and the procurement costs of all sub-compartments were obtained using the data on the to-pography prepared in Section 7-1B and the cost func-tions described in Section 7-1C. Figure 24 shows thedistribution map of the procurement cost of forestbiomass from each sub-compartment, and Fig. 25shows the relationship between the annual availableamount and the cost of harvesting and transportingforest biomass in the region.

Logging residues were the cheapest, followed bytrees from broad-leaved forests; thinned trees were themost costly. Logging residues, i.e., tree tops and

branches generated during limbing and bucking, areregarded as by-products of logging operations (see Fig.22). Therefore, the procurement costs of the residues,which were calculated by considering only the chip-ping and transportation processes, were the cheapest.Although the procurement cost of thinned trees wasroughly the same as that of broad-leaved forests percubic meter, broad-leaved forests can be seen to becheaper than thinned trees in Fig. 25 because of thehigher bulk density of a broad-leaved tree comparedto a coniferous tree. (As such, broad-leaved trees areexpensive due to the selective cutting regime, leadingto low volume per machine position, and performanceis decreased by having to consider the remaining trees;the same is true for thinnings since the small size ofthe harvested trees may lead to high costs. In the fu-ture, however, once the choice is made to harvest log-ging residues, a portion of the logging cost for the mainoperation could be allocated to the residues based on

Table 22. Annual available amount of forest biomass in the region. Reprinted with permission from Croatian Journal ofForest Engineering, 26(2), Yoshioka, T, Sakai H, Amount and availability of forest biomass as an energy resource in a moun-tainous region in Japan: a GIS-based analysis, 59–70, Table 4, 2005, Forestry Faculty of Zagreb University.

Machine Equation (US$/MgDM)**

Tractor [Logging residues] 0.567·LT + 40.73

[Thinned trees] 1.76 × 10–2·LSY + 0.567·LT + 1.91·e0.117 ·d + 95.07

[Trees from broad-leaved forests] 1.26 × 10–2·LSY + 0.400·LT + 1.37·e0.117 ·d + 69.76

Tower yarder [Logging residues] 0.567·LT + 40.73[Thinned trees] 0.115·LSY + 299.23/LSY + 0.567·LT + 72.08

[Trees from broad-leaved forests] 8.24 × 10–2·LSY + 213.73/LSY + 0.400·LT + 53.35

Yarder [Logging residues] 0.567·LT + 40.73[Thinned trees] 15.87/LSY

–0.2142 + 258.53/LSY + 0.567·LT + 70.98[Trees from broad-leaved forests] 11.33/LSY

–0.2142 + 184.66/LSY + 0.400·LT + 52.56

Biomass resources Number ofsub-compartments

Amount(GgDM/y)

Cut volume of logs(m3/y)

Logging residues 120 4.035 57162Thinned trees 637 27.854 —Trees from broad-leaved forests 266 20.317 —

Total 1023 52.206 57162

Table 21. Cost functions for harvesting and transportation of forest biomass.* Reprinted with permission from CroatianJournal of Forest Engineering, 26(2), Yoshioka, T, Sakai H, Amount and availability of forest biomass as an energy resourcein a mountainous region in Japan: a GIS-based analysis, 59–70, Table 3, 2005, Forestry Faculty of Zagreb University.

*The performance of forestry operations in Japan have been partly standardized by Sakai (1987) and Sawaguchi (1996), andtheir studies were referred to in order to formulate biomass harvest and transport operations. The costs of labor, machine, andfuel, the values of which are basically the same as those used in an earlier study by the author (Yoshioka et al. 2006a), areconsidered here.**L

SY: Skidding/yarding distance (m), L

T: Transportation distance (km), d: Slope (degree).



net value or, possibly, volume. This will marginallyimprove the profitability of the main logging opera-tion.).

In terms of realizing the energy utilization of forestbiomass in the region, there are three advantages tothe relationship mentioned above:1) A set maximum purchase price of forest biomasscan be used to determine the annual available amount;2) In analogy to 1), the price needed to procure a cer-tain necessary annual amount of forest biomass canalso be determined;3) The procurement costs from all sub-compartmentsin the region are calculated. Therefore, in both 1) and2) above, the relationship can be used for prioritizingstands for harvesting in operational planning.

7-3. Discussion

7-3A. Assessment of the relationship between themass and the procurement cost

The construction of a power-generation plant thatuses forest biomass as fuel and supplies electricity tothe region is discussed here. In terms of the scale ofthe plant, the net power output, the thermal efficiency,and the operating rate are supposed to be 3 MW, 12%,and 70%, respectively (see Chapter 6), and the power-generation cost of the plant (costs for investment and

Fig. 24. Distribution map of the procurement cost of forest biomass (unit: US$/MgDM). Reprinted with permission fromCroatian Journal of Forest Engineering, 26(2), Yoshioka, T, Sakai H, Amount and availability of forest biomass as an energyresource in a mountainous region in Japan: a GIS-based analysis, 59–70, Fig. 7, 2005, Forestry Faculty of Zagreb Univer-sity.

108.6

86.5

(52.206,155.6)

(0,41.9)

(52.206,106.5)

(15.053,73.1)

30.1060

50

100

150

0 10 20 30 40 50

Annual available amount (GgDM/y)

Har

vest

ing

and

tran

spor

tatio

n co

st(U

S$/

MgD

M)

Solid line: Calculated costBroken line: Average cost

Fig. 25. Relationship between the mass and the procurementcost of forest biomass. Reprinted with permission fromCroatian Journal of Forest Engineering, 26(2), Yoshioka,T, Sakai H, Amount and availability of forest biomass as anenergy resource in a mountainous region in Japan: a GIS-based analysis, 59–70, Fig. 8, 2005, Forestry Faculty ofZagreb University.



operation at the plant) is 66.7 US$/MWhe (e: electric-ity). In terms of scale, this plant will provide electric-ity to 5,400 households, i.e., 24.8% of the householdsin the region, and consume 30.106 GgDM/y of forestbiomass. Therefore, the ceiling on a purchase price ofbiomass can be read as 108.6 US$/MgDM from Fig.25, and plans to harvest and transport biomass fromthe sub-compartments at a cost of less than 108.6US$/MgDM can be developed.

Figure 25 also shows the average cost, which is cal-culated by dividing the sum total of the purchase priceof forest biomass by the amount of biomass to be pur-chased. The average cost for the supposed plant canbe read as 86.5 US$/MgDM from the figure, which isequivalent to 141.3 US$/MWhe. From the viewpointof cost, it would appear that the utilization of forestbiomass as an energy resource in this region is diffi-cult because the unit price of electricity per MWh inJapan is 151.4 US$/MWhe while the power-generationcost is 66.7 US$/MWhe. However, the feasibility ofutilizing forest biomass for energy should not be dis-cussed only from the viewpoint of cost. A comprehen-sive analysis must also include the effects on the re-duction in the amount of CO2 emission and job crea-tion in the region. Furthermore, learning curves of mostcomplex operations, such as forest fuel procurement,indicate that there will be a considerable potential forcost reductions through performance improvements andeveryday rationalization once the system is imple-mented on a full scale.

In a case study in Denmark in which the technicaland economical availability of forest fuel resources wasestimated based on a GIS analysis, the mean deliverycost of wood chips ranged from 672 €/TJ to 716 €/TJfor the three “Average” consumption scenarios (Nord-Larsen and Talbot 2004), corresponding to 18.1–19.3US$/MgDM when 1 € = 1.35 US$ and 1 MgDM = 20GJ. The average cost in this section, 86.5 US$/MgDM,is over fourfold more expensive than in the Danishstudy. This difference has the same tendency as thatreported in a previous study by the author (Yoshiokaet al. 2006a), which examined the feasibility of a har-vesting and transporting system for logging residuesin Japan by comparing the calculated harvesting andtransportation costs with those of Nordic countries. Inthe earlier study, the authors emphasized the impor-tance of not only introducing technical developmentsinto the harvesting process, e.g., introducing a bundler,but also of improving the logistics. When 30.106GgDM/y of forest biomass is harvested for the opera-tion of the above-mentioned plant, the average skid-ding/yarding and transportation distances are 262 mand 14.5 km, respectively (362 m and 13.2 km for log-ging residues, 146 m and 13.1 km for thinned trees,275 m and 15.1 km for trees from broad-leaved for-ests). For example, the procurement cost of wood chipsfrom broad-leaved trees in the case of average yarding

(by a tower yarder, 275 m) and transportation (15.1km) distance is calculated 82.0 US$/MgDM, whichconsists of 15.5 US$/MgDM for fell ing, 33.2US$/MgDM for yarding, 16.7 US$/MgDM for com-minution, and 16.6 US$/MgDM for transportation.These costs are so high that the total procurement costcannot be economically competitive. The authors ofthe earlier study therefore suggest (reiterated in thischapter) that technical development, especially for theskidding/yarding process, as well as the improvementof logistics should receive high priority in terms ofoptimizing forest fuel utilization in Japan.

In addition to the forest biomass discussed here, itwould be realistic and valuable to utilize mill residues(wood shavings and barks generated in sawmills andplywood plants), wood-based waste material, and trim-mings of park trees, roadside trees, and garden treestogether. If half the amount of biomass necessary forthe supposed plant (15.053 GgDM/y) is covered by millresidues, wood-based waste material, and trimmingsgenerated in the region, the average cost of forestbiomass will be reduced to 73.1 US$/MgDM (Fig. 25).Moreover, at the present time in Japan, many of themill residues, wood-based waste material, and trim-mings can be obtained free of charge, so the effective-ness of the reduction in the procurement cost ofbiomass will be greater on the whole; for example,(15.053·73.1 + 15.053·0)/30.106 = 36.5 [US$/MgDM].However, as this will not be the case once a markethas been established and there is a clear demand forbiomass for fuel, further discussion on this aspect willbe necessary.

7-3B. Assessment of the resolution of the geospatialdata

With respect to the analytical method using the GIS,one of the main obstacles for integrating multiple lay-ers of geospatial information is to bring all data tomanageable spatial resolution and data format, i.e.,vector or raster. In the analysis described in this chap-ter, all of the vector data (shapes and locations of sub-compartment, forest and public roads) were convertedto the raster based on the mesh of DEM, i.e., a 50-m-cell grid; in other words, a 3-m-wide road in vectorformat was rasterized to a 50-m grid. GIS is scale de-pendent, and it is necessary to consider the appropri-ate spatial scale for addressing the problem at hand(Graham et al. 2000). From this point of view, theremay be a lack of locational accuracy in any analysisinvolving the road system, necessitating a more de-tailed analysis.


The relationship between the mass and the procure-ment cost of forest biomass analyzed in this chaptertargeted only the situation at the present time. Further



study and discussion of the long-term feasibility ofutilizing forest biomass in a sustainable way are es-sential.

8. Conclusions

The feasibility of a harvesting, transporting, and chip-ping system for forest biomass resources in Japan hasbeen discussed in this study. First, the visions for in-troducing and diffusing woody bioenergy utilizationin Japan were comprehensively discussed in terms ofthe quantification of available woody biomass re-sources for energy, the development of low-cost har-vesting and transporting systems, and the conversionprocesses. Second, a harvesting, transporting, and chip-ping system for logging residues was constructed andthe feasibility of the system was examined from thepoints of view of cost, energy balance, and carbon di-oxide (CO2) emissions based on the results of fieldexperiments in forestry operation sites. Third, the fea-sibility of the energy utilization of forest biomass re-sources in a mountainous region was discussed basedon an analysis of the relationship between the massand the procurement cost of forest biomass in the re-gion with the aid of a geographic information system(GIS). The following conclusions were derived fromthe results of this study:• Chapter 2: The feasibility of the utilization of woodybiomass as an energy resource in Japan was discussedbased on the amount and availability of woody biomassand energy-conversion technologies. The amount cur-rently available was estimated to be 31.7 Tg/y on adry-weight basis, corresponding to 2.8% of the nationalprimary energy supply. An analysis of the current sys-tems for the harvest and transport of logging residuesshowed that improvement were needed for such sys-tems to be sustainable/economic. The prospects forwoody bioenergy utilization around the years 2010 and2050 were also discussed based on the present state-of-the-art energy-conversion technologies. Around2010, both “on-site” utilization and “regional” utiliza-tion are expected to be feasible as a small-scale anddecentralized system. The co-firing of woody biomasswith coal at an existing coal-fired power plant is ex-pected to be feasible as a large-scale and centralizedsystem. Around 2050, “regional” utilization is expectedto be the main energy utilization for the small-scaleand decentralized system. Biomass plantations in for-eign countries would be needed for a large-scale andcentralized system in Japan;• Chapter 3: The concept of a “harvesting system forlogging residues by a processor and a forwarder” wasexamined with the aim of constructing a system to har-vest logging residues (or slashes) as a new resourcefor energy. The rate of slash harvesting, α, and the “en-ergy input rate” of hauling slashes, p (%), were de-fined as indices of the possibility of harvesting slashes

and the utilization of slashes for energy, respectively.From an analysis of the field experiment, both the vol-ume of logs hauled by the forwarder per day, EF(m3/d), and p are expressed as functions of the haulingdistance, L (m). The productivity of the processor, EP(m3/d), and L were used to calculate α. The resultsshowed that α was approximately 0.95 for the experi-ment site, indicating that almost all the slashes couldbe hauled. It was recognized that the energy utiliza-tion of slashes was feasible for this site because p wasless than 1%. The hauling cost per unit weight ofslashes was calculated to be 0.134 US$/kgDM (DM:dry mass). This high cost demonstrates that the costmust be reduced by taking measures such as enhanc-ing the hauling efficiency of the forwarder;• Chapter 4: A “harvesting and transporting system forlogging residues” was constructed with reference tothree European countries where the utilization ofbioenergy is making steady progress and examined onthe basis of field experiments in a Japanese forestrysituation. The feasibility of the system was discussedfrom the standpoints of cost and energy, and the sys-tem was compared with those of the three Europeancountries. In terms of costs, the incorporation of chip-per comminuting into the system as early as possiblewas desirable given the trends of harvesting cost andfuel consumption per unit weight of logging residues.Such a system is not particularly feasible from thestandpoint of the harvesting cost per MWh ofbioenergy. However, no specific problems were foundfrom the point of view of the “energy input rate,” andit was demonstrated that it is possible for Japan to re-duce domestic carbon dioxide emissions by utilizingbiomass as an energy resource. A comparison with thethree European countries and a preliminary sensitivityanalysis of the system demonstrated that technical de-velopments aimed at reducing the harvesting cost (e.g.,improving the forwarding and transporting efficiency)and wide-scale governmental support are essential forrealizing bioenergy utilization in Japan;• Chapter 5: An experiment on the comminution oflogging residues with a tub grinder was carried out inorder to calculate the productivity and procurement costof wood chips. At the investigation site, there was atub grinder equipped with a hammer mill crusher atthe bottom of the tub, and a grapple loader and a bucketloader were used as auxiliary machines for the grinder.The productivity of the tub grinder was 60.0 m3 pereffective hour, and the total comminuting cost was cal-culated as 5.637 US$/m3, indicating that the commi-nuting cost of a large-sized crusher was lower than thatof a small-sized chipper. The sum (in percentage) ofthe cost of the loaders, the cost of carrying in, install-ing, and carrying out the machines, and the cost ofconstructing a landing was 53% of the total commi-nuting cost. When a truck with a cubic capacity of 40m3 transported wood chips three times per day, the sum



of the costs of comminution and transportation was71.2 US$/MgDM, which was almost on a par with thoseof European countries in which the energy utilizationof logging residues was making steady progress. Basedon the discussion weighing the advantages and dis-advantages of the processing capacity of the tub grinderand that of other machines, a realistic option for Japa-nese forestry would be to consider the sharing of onetub grinder among several logging sites;• Chapter 6: Using the method of a life cycle inven-tory (LCI) analysis, the energy balance and the carbondioxide (CO2) emission of logging residues from Japa-nese conventional forestry as alternative energy re-sources were analyzed over the entire life cycle of theresidues. The fuel consumption of forestry machineswas measured in field experiments on harvesting andtransporting logging residues at forestry operating sites.In addition, a total audit of energy consumption wasundertaken that involved an assessment of materials,construction, and the repair and maintenance of for-estry machines as well as the costs associated with anenergy-conversion plant. As a result, the ratio of en-ergy output to input was calculated to be 5.69, indicat-ing that the system could be feasible as an energy pro-duction system. The CO2 emission per MWhe (e: elec-tricity) of the biomass-fired power generation plant wascalculated to be 61.8 kgCO2/MWhe, while that of coal-fired power generation plants in Japan was 960kgCO2/MWhe. Therefore, the reduction in the amountof CO2 emission that would result from replacing coalwith biomass by the power generation of as much as3.0 Tg/y of logging residues in Japan was estimated tobe 1.656 TgCO2/y, corresponding to 0.142% of the na-tional CO2 emission. The analysis in Chapter 6 pro-vides evidence that Japan could reduce its domesticCO2 emission by using logging residues as alternativeenergy resources;• Chapter 7: The feasibility of utilization of forestbiomass for energy in a mountainous region was dis-cussed based on analyses with the GIS. In Chapter 7,“forest biomass” denotes logging residues, thinnedtrees, and trees from broad-leaved forests. First, usingthe GIS, a complete distribution map of biomass re-sources was compiled and the topographical informa-tion of each sub-compartment was prepared for analy-sis. Second, harvesting and transportation systems wereclassified into six types based on the fraction of thetree for energy used (two types) and by topographicalconditions (three types). Equations for cost calcula-tions were developed and included the variables slope,skidding/yarding distance, and transportation distance.Finally, the relationship between the mass and the pro-curement cost of forest biomass in the region wasanalyzed. The results show that logging residues (theavailable amount was 4.035 GgDM/y) were the leastcostly followed by broad-leaved forests (20.317GgDM/y), while thinned trees (27.854 GgDM/y) were

the most costly. The analysis may support operationalplanning, especially the decision of selecting sub-com-partments to be felled. For example, the amount ofbiomass needed to supply a power-plant that couldsupply 24.8% of the electrical needs of the region wascalculated to 30.106 GgDM/y. This amount of forestbiomass could optimally be harvested from sub-com-partments where procurement costs were lower than108.6 US$/MgDM.

The conclusions drawn in this study will contributeto the practical implementation of the harvesting, trans-porting, and chipping system for forest biomass re-sources and to the realization of utilizing forest biomassfor energy production in Japan.

AcknowledgmentsThis study is based on the author’s doctoral dissertation

submitted to the University of Tokyo in 2003. The authorfirst of all would like to express his deep-felt gratitude tohis dissertation supervisor Professor Emeritus Dr. HiroshiKobayashi of the University of Tokyo for inspiring and en-couraging him to pursue a career in the field of Forest Engi-neering. His gratitude is also extended to four co-supervi-sors, Professor Dr. Hideo Sakai, Associate Professor Dr.Toshio Nitami, and Professor Emeritus Dr. MitsuhiroMinowa of the University of Tokyo, and Professor Dr.Katsumi Toyokawa of Tokyo University of Agriculture, fortheir guidance and criticism during the review of the disser-tation.

Many people have been involved in the practical aspectsthat have contributed to the completion of this study and,unfortunately, space requirements do not allow the authorto mention them all by name. He sincerely thanks ProfessorDr. Koki Inoue, who is his current supervisor at Nihon Uni-versity, Associate Professor Dr. Masahiro Iwaoka of TokyoUniversity of Agriculture and Technology, and AssociateProfessor Dr. Kazuhiro Aruga of Utsunomiya University fortheir excellent understanding, great cooperation, and valu-able advice. His sincere thanks are also extended to the mem-bers of the Laboratory of Forest Utilization of the Univer-sity of Tokyo, the technical officers of the University Forestin Chichibu of the University of Tokyo, the technical offic-ers of the Takizawa Experimental Forest of Iwate Univer-sity, the technical officers of the Toyoma-cho Forest Own-er’s Association, and the members of the Biomass Divisionof the Japan Institute of Energy for their cooperation in theexperimental work, fruitful discussions, and helpful advice.

This study was financially supported by the Grants-in-Aidfor Scientific Research from the Ministry of Education, Cul-ture, Sports, Science and Technology, Japan (Nos. 10460061,14-07654, 16-10303, and 18780121), the National Fund forForest Greenery and Waters from the National Land Affor-estation Promotion Organization of Japan, and Nihon Uni-versity.

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