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Energy Policy 36 (2008) 1247–1250

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Viewpoint

Virtual biofuels—A cheaper, better, faster alternative?

Harry D. Saunders�

Decision Processes Incorporated, 2308 Saddleback Drive, Danville, CA 94506, USA

Received 12 December 2007; accepted 17 December 2007

Available online 8 February 2008

Abstract

This viewpoint article offers the proposition that purpose-grown biomass buried in landfills constitutes a ‘‘virtual’’ biofuel that is more

practical, economic, and immediate than the use of actual biofuels from cellulosics. While not a permanent solution, it may be a useful

bridge to the hoped-for era of actual biofuels prior to the time technology for economically converting cellulosics to actual liquid biofuels

is realized.

r 2008 Elsevier Ltd. All rights reserved.

Keywords: Biofuels; Landfill; Cellulosic

1. Introduction

Biofuels generate carbon emissions, just as do petro-leum-based fuels.

But the promise of biofuels lies in the notion that whilethey are indeed emitters of greenhouse gases when burnedto fuel economic activity, they also, in the course of theirgrowth and development, sequester carbon from theatmosphere.

The full promise of biofuels can be appreciated byconsidering the following idealized end-state:

Picture a situation in which all transportation fuels arederived from biofuels. The carbon emitted from burningthese biofuels enters the atmosphere, adding to greenhousegases. But since the growing of these biofuels hassequestered from the atmosphere the identical amount ofcarbon as is released by their burning, the net contributionto atmospheric carbon of this burning is zero. In plainerlanguage, if the annual quantity of biofuels grown andharvested equals its annual quantity of use in transporta-tion, biofuels-based transportation is ‘‘carbon-neutral’’ inits impact on climate.

Now a key difficulty, as of this writing, is such biofuelsare often derived from biomass that has alternative use inthe form of food for human and livestock consumption,

e front matter r 2008 Elsevier Ltd. All rights reserved.

pol.2007.12.024

743 8400; fax: +1 925 743 8406.

ess: hsaunders@decisionprocessesinc.com

such as corn, vegetable oils, and sugar. This createsobvious problems. Perhaps more worrisome, the carboncost of their production for use as fuels is not zero owing tothe energy needed for their cultivation, processing, anddistribution—and in the case of corn this is evidentlysubstantial.The commonly perceived ‘‘holy grail’’ of biofuels

production is technology that could economically extractbiofuels from biomass not used for food. For instance, ifbiofuels could be extracted from corn plant biomass leftover when the corn ears themselves are harvested, theimpact on food markets would be de minimus. Suchbiomass is commonly referred to as ‘‘high-cellulose’’ or‘‘cellulosic’’ material and the ‘‘holy grail’’ is technologythat uses ‘‘cellulosics’’ for the production of liquid biofuels.However, creating the technology to do this is extremelychallenging and is currently not developed to the point ofbeing economic.At present most such material is left unharvested.

Cellulosic material left in the field will eventually decom-pose and thereby return to the atmosphere whatevercarbon it has sequestered in the course of its growing.

2. ‘‘Virtual’’ biofuels

If instead this material could be prevented fromreturning its carbon to the atmosphere, there would becreated a ‘‘carbon sink’’ that continually removes carbon

ARTICLE IN PRESSH.D. Saunders / Energy Policy 36 (2008) 1247–12501248

from the atmosphere. One could picture a carbon-neutralscenario, different from the one above, wherein petroleumcontinues to be used for transportation but a sufficientamount of cellulosic material is removed from thedecomposition and atmospheric re-injection cycle toentirely offset what carbon is added to the atmosphere bythe burning of petroleum products for transportation.

Such an idea was presaged in somewhat narrowerfashion by Metzger et al. (2002). These researchersconcluded on the basis of a straightforward carbon-to-useful-energy-output analysis that it was ‘‘carbon-better’’(our term), rather than burning leftover cellulosic cornmaterial in power plants, to instead burn natural gas inthese plants and dispose of the cellulosic materials bydumping them in the ocean, injecting them below thethermocline to prevent unwanted ecological impacts.

We suggest a somewhat more comprehensive approach.The idea is to take waste cellulosics, and perhaps moreimportantly, purpose-grown biomass and at each harvestbury this biomass in landfills designed for this purpose.Such buried biomass would be what one might call ‘‘virtualbiofuel.’’ Virtual biofuel’s ‘‘energy content’’ continues tocome from conventional petroleum, but conventionalpetroleum’s carbon signature is erased by burial of thebiomass.

An important recent development comes in the form ofresearch by Tilman et al. (2006), who demonstrated thathigh-quality biofuels material can be productively grown inthe form of mixtures of native grassland perennials onagriculturally degraded lands. These biofuels accordinglyneither displace food production nor cause loss ofbiodiversity via habitat destruction. This strongly suggestspurpose-grown biomass could exploit these advantages.

So the idea is to grow such biofuels materials in anamount equivalent to a quantity of biofuels that wouldentirely displace petroleum-based transportation fuels, butto then bury these materials in landfills—instead ofattempting to convert them to biofuels. If sufficientbiomass can be grown and disposed of in otherwise

Table 1

Qualitative side-by-side comparison of virtual to real biofuels

Grow and convert: actu

biofuels–cellulosics

Use of arable land Identical

Use of water resources Identical

Conversion infrastructure Yes

Transportation/distribution infrastructure Nation-wide

Technology availability Future

Use of land for disposal None

Cultivation costs Comparable

Transportation costs to Processing/landfill Comparable

Feedstock costs None

Conversion costs Yes

Conventional fuels Production costs Small

Distribution costs to end use Yes

Landfill costs None

unutilized land, ecologic and economic impacts will beminimized and the transportation sector would therebybecome carbon-neutral. An important caveat: such asolution is only a temporary one, and beyond this doesnot reduce dependence on fossil fuels, imported orotherwise. Fossil fuels are exhaustible and subject to non-competitive and political forces. To the extent transporta-tion is fossil fuel-based, ‘‘virtual’’ biofuels cannot extendthe lifetime of these non-renewable fuels nor increaseenergy security in the way actual biofuels would. Butvirtual biofuels could buy the world precious time climate-wise.We offer the proposition that virtual biofuels may

provide a useful bridge to the hoped-for era of actualcellulosic biofuels prior to the time technology foreconomically converting cellulosics to actual liquid biofuelsis realized.

3. Comparison of ‘‘virtual’’ biofuels to real biofuels

Table 1 provides a qualitative side-by-side comparison ofvirtual to real biofuels.Let us take each comparison dimension in turn:An objection might arise that purpose-grown virtual

biofuels may have large impacts on arable land use.However, purpose-grown actual biofuels would have anidentical impact. Whether the biomass is grown forconversion or burial is immaterial to the amount of landused. And this is true whether the biomass is purpose-grown or not—the cellulosic waste material from growingcorn does not care whether it goes to a landfill or a gas tankwith respect to the amount of land it requires for itscultivation. In fact, it might be argued biomass grown forthe purpose of sequestering carbon might have a land useadvantage if such biomass can sequester more carbon perhectare than biomass grown for its energy content.Similarly, the same water to grow virtual biofuels would

be needed to grow actual biofuels.

al Grow and convert: actual

biofuels–non-cellulosics

Grow and bury: ‘‘virtual’’

biofuels

Identical Identical

Identical Identical

Yes None

Nation-wide Local/regional

Now Now

None Yes

Comparable Comparable

Comparable Comparable

Competes with food Crude oil

Yes None

Yes Yes

Yes None

None Yes

ARTICLE IN PRESSH.D. Saunders / Energy Policy 36 (2008) 1247–1250 1249

Actual biofuels require facilities where biomass can betemporarily stored, processed, and converted to biofuels.Conversion is an expense (and a use of land) totallyavoided by virtual biofuels.

Transportation and distribution infrastructure wouldlikely be much less for virtual biofuels. Actual biofuelsultimately require distribution to gas tanks in a broadgeography. Virtual biofuels require transportation to adump site. Landfill sites would be regional and are likely tobe located near where the biomass is grown. Further, it isconceivable some landfills could be on-site, with topsoilremoved and replaced each growing season, thus eliminat-ing transportation costs altogether.

Virtual biofuels are available today. The technology fortransport and burial in landfills is hardly somethingneeding to be developed. In contrast, the technology forproducing actual liquid biofuels from high-cellulosematerials economically is not available today. Virtualbiofuels also have the technology advantage that they canbe grown for their carbon affinity, not their extractableenergy content. An associated technology benefit is thereneed be no specific conversion processes tailored to anyspecific plant species for maximizing energy recovery.

Virtual biofuels require land for landfills. This is the onlydimension on which virtual biofuels are plainly inferior toactual biofuels. This disadvantage will be smaller to theextent landfills can be located in uninhabited areas whereecological impacts of landfills are smaller, perhaps in aridor semi-arid regions. By way of perspective, it should benoted most countries make extensive use of landfills forgarbage disposal with strong attention paid to minimizingenvironmental impact. And again, if landfills could belocated on-site, impacts on land use will be reduced.

From the above, one would incline toward the strongpresumption that virtual biofuels are also less costly thanactual ones—no conversion processing needed, no dis-tribution needed to gas tanks in broad geographies, thesame land and water required for growing. However, tomake a fair comparison to actual biofuels, we have toaccount for the fact that actual biofuels deliver usableenergy directly to transportation while virtual biofuels donot. So the cost comparison has to account for the cost ofcontinuing to produce the conventional fuels that will notbe displaced by biofuels, if they are virtual. A wrinkle isthat actual biofuels also require conventional fuels for theirproduction.

The dimensions of the cost comparison are shown in thelower part of the table above. Two of these dimensions canbe set aside for comparison purposes. That is, let us assumethe cultivation costs are identical for actual and virtualbiofuels. Let us also assume the cost of transporting thematerial to actual biofuel-processing sites is the same asthat to transport virtual biofuels to landfills. This isgenerous to actual biofuels to the extent landfills can belocated on-site.

But assuming these costs are identical, the cost analysisfundamentally becomes one of comparing feedstock,

conversion and distribution costs on the actual biofuelsside to feedstock, continued conventional fuels productioncosts and landfill costs on the virtual biofuels side.Feedstock costs for actual cellulosics biofuels will be

solely the costs of cultivation and transportation to theconversion site. In contrast, feedstock costs for non-cellulosics need to account for the ‘‘opportunity cost’’ oftheir use as food. To the extent their cultivation displacesagriculture aimed at food markets, this cost could besignificant. Feedstock costs for virtual biofuels are the costof crude delivered to refineries for processing intoreplacement transportation fuels. To the degree crudeprices are high and alternative-use food prices low, actualbiofuels are advantaged; to the degree the opposite is true,virtual biofuels are advantaged. On this dimension, theeconomics appear to favor actual cellulosics biofuels overvirtual ones, but this assumes actual cellulosics biofuels’overall economics makes them practical. For non-cellulo-sics, the economics can go either way, but in currentconditions in the United States, these costs appearcomparable or slightly in favor of virtual biofuels.Currently, conversion costs for cellulosics are much

higher than conventional fuels production costs. In fact,these costs are difficult to even define given the early stateof technology for cellulosics conversion. Realistic conver-sion costs need to await the development of such practicaltechnology. Even then, the economics may favor virtualbiofuels for some time.Virtual fuels, because they require ongoing production

of conventional fuels, carry a ‘‘replacement’’ productioncost. However, actual non-cellulosic biofuels carry ananalogous penalty because conventional fuels are requiredfor their production. Currently, the US Department ofEnergy (2007) finds that for every unit of energy puttowards ethanol production, 1.3 units are returned; most ofthis energy goes for conversion. Actual cellulosic biofuelswould carry corresponding costs for cultivation, transpor-tation, and conversion. Virtual biofuels would likewisecarry such costs for cultivation, transportation, andburial—but not conversion, substantially lowering net fuel(and crude) replacement needs. Net replacement produc-tion costs for virtual fuels would reflect prevailing refiningcosts. So on balance, the conventional fuels productioncosts/biofuels conversion cost comparison would certainlyfavor virtual biofuels over actual cellulosic biofuels, andthe comparison to actual non-cellulosics at present isperhaps slightly in favor of actual non-cellulosics—but itmay be close excluding government incentives.The cost of distributing fuels to end users is non-existent

for virtual biofuels but may be significant for actualbiofuels. These fuels must make their way to refineries orpetroleum product distribution depots.What about landfill costs? Landfill costs should be much

lower than those seen for typical municipal landfills.Typical municipal landfills require expensive handlingequipment to sort and separate materials. For virtualbiofuels, there is no need to do this. Further, the landfills

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we envision would likely be large and able to takeadvantage of economies of scale not available to individualmunicipalities. Moreover, these landfills would not face thecostly challenges associated with handling hazardous andtoxic materials.

All this strongly suggests a cost advantage for virtualbiofuels by comparison to actual cellulosic-based biofuelsin the near term: high conversion costs plus distributioncosts on the actual biofuels side compared with (net added)conventional fuels production costs and landfill costs onthe virtual biofuels side. And virtual biofuels may well havea cost advantage even over non-cellulosic-based biofuels, atleast in the near term.

In summary, while it clearly awaits detailed cost analysisto validate the economics, on the basis of this high-levelqualitative analysis virtual biofuels look like a highlyattractive alternative to actual cellulosics-based biofuelsalong nearly all dimensions, and perhaps an attractivenear-term alternative to non-cellulosics-based ones.

4. General caveat

There is no fundamental reason to attach virtual biofuelsto the quantity of petroleum fuels used in transportation.The case is easily made that high-carbon-affinity biomassshould be purpose-grown and buried to capture carbonindependently of whatever petroleum may be used intransportation—or in any other sector, for that matter.The only real connection comes if governments requiretransportation fuels producers to supply a certain percen-tage of biofuels in their mix. In such a case, conventionalfuels producers may find such a virtual regime more

economic than producing biofuels directly, especially ifbiofuels requirements outstrip what can be realized fromnon-cellulosic feedstocks.Linkages aside, the economy broadly considered may

find virtual biofuels an attractive possibility solely due totheir appeal as a direct near-term means of sequesteringcarbon.

5. Conclusions

It is possible to disagree on the urgency of introducingbiofuels in a significant way to the world energy economy.But if one views it as urgent virtual biofuels hold out atleast the possibility of making this happen practically andquickly. And it is entirely possible it could be donerelatively cheaply. Whether this is really true, the promiseappears significant enough to call for energy economists,and ecologists, to sharpen their pencils and either validatethis proposition or demonstrate it can be safely dismissedwithout further consideration.

References

Metzger, R.A., Benford, G., Hoffert, M.I., 2002. To bury or burn:

optimum use of crop residues to reduce atmospheric CO2. Climatic

Change 54, 369–374.

Tilman, D., Hill, J., Lehman, C., 2006. Carbon-negative biofuels from

low-input–high-diversity grassland biomass. Science 314 (5805),

1598–1600.

US Department of Energy, 2007. Net Energy Balance for Bioethanol

Production and Use /http://www1.eere.energy.gov/biomass/net_energy_

balance.htmlS.