Report: Analyses of biochar properties

Demolition wood Cabbage

Leek Potato

Analyses of biochar properties

Report presented by

The Char Team

25th September 2015

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Correspondence: Suzanne Allaire 2480 Boulevard Hochelaga Pavillon Envirotron Université Laval Québec, QC, Canada G1V 0A6 email: [email protected] Photos: Agnès Lejeune © 2015 Reference: Allaire SE, Lange SF, Auclair IK, Quinche M, Greffard L (The Char Team) (2015) Report: Analyses of biochar properties. CRMR-2015-SA-5. Centre de Recherche sur les Matériaux Renouvelables, Université Laval, Québec, Canada, 59 p. DOI: 10.13140/RG.2.1.2789.4241

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Table of contents

1. INTRODUCTION 5

2. OBJECTIVES 7

3. MATERIALS AND METHODS 13 3.1. RESIDUAL ORGANIC MATTER (ROM) AND PYROLYSIS METHODS 13 3.1.1. HARDWOOD 13 3.1.2. CONIFEROUS SOFTWOOD 13 3.1.3. NON-CONIFEROUS SOFTWOOD 14 3.1.4. NON-WOODY MATERIALS 15 3.2. BIOCHAR ANALYSIS METHODS 19 3.2.1. GENERAL PROPERTIES 19 3.2.2. PHYSICAL PROPERTIES 20 3.2.3. CHEMICAL PROPERTIES 21 3.2.4. BIOLOGICAL PROPERTIES 22

4. RESULTS AND DISCUSSION 28 4.1. GENERAL PROPERTIES 28 4.2. PHYSICAL PROPERTIES 28 4.3. CHEMICAL PROPERTIES 38 4.4. BIOLOGICAL PROPERTIES 47

5. CONCLUSION AND FUTURE WORK 47

6. REFERENCES 56

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List of Tables Table 1. Team members 9 Table 2. Biochar producers or industries that provided access to their pyrolyzer 10 Table 3. Institutions that provided the feedstock to be pyrolyzed 11 Table 4. Institutions that contributed to the project through grants or supplemental student scholarships 12 Table 5. List of biochars with their feedstock and pyrolysis method 16 Table 6. Photos of some biochars 18 Table 7. Analysis methods for general properties of biochars 23 Table 8. Analysis methods for physical properties of biochars 24 Table 9. Analysis methods for chemical properties of biochars 25 Table 10. Analysis methods for biological properties of biochars 26 Table 11. Comparison between analyses in this report and those of IBI (2012) and EBC (2012) 27 Table 12. General properties of biochars 31 Table 13. General physical properties of biochars 33 Table 14. Physical properties related to water 34 Table 15. Physical properties related to particle-size distribution and abrasion resistance of biochars 36 Table 16. Chemical properties of biochars related to acidity 40 Table 17. Biochar contents in N, P, and S 41 Table 18. Biochar contents in exchangeable macro- and micronutrients (related to plants) 42 Table 19. Biochar contents in soluble macro- and micronutrients (related to transport of contaminants and plants) 43 Table 20. Biochar contents in other elements (related to the environment) (Part 1) 44 Table 21. Biochar content in other elements (related to the environment) (Part 2) 45 Table 22. Biochar contents in PAH (related to the environment) 46 Table 23. Percentage of earthworms that chose the mixture of garden soil with 10% biochar compared to garden soil alone,

or with 50% biochar compared to garden soil alone, and germination rate of lettuce after 3 and 6 days in the same

mixtures (related to biological toxicity) 48 Table 24. Summary of general and physical properties of biochars 53 Table 25. Summary of chemical properties of biochars 54 Table 26. Summary of biological properties of biochars 55

List of figures

Figure 1. Relative content of C types in biochars (green: Corg, red: Cinorg, blue: Cgraph) 32 Figure 2. Capillary rise of different biochars under tensions of -0.05 m (very wet) to -1.5 m (humid) 35 Figure 3. Cumulative particle-size distribution of biochars 37 Figure 4. Preference of earthworms for garden soil alone (0% biochar) or a mixture of garden soil with 10% v/v biochar 49 Figure 5. Preference of earthworms for garden soil alone (0% biochar) or a mixture of garden soil with 50% v/v biochar 50 Figure 6. Germination rate of lettuce in garden soil amended with 10% biochar 51 Figure 7. Germination rate of lettuce in garden soil amended with 50% biochar 52

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Analyses of biochar properties

1. Introduction

The province of Quebec produces millions of tonnes of residual organic matter (ROM) every year. This ROM comes from municipal sources and from forest, agricultural, food, and demolition industries. Cities alone produce 5.8 M tonnes of commercial and urban ROM. Although some ROM is recycled in fields either directly or following composting, millions of tonnes cannot be used because of biological risk, the possibility of recirculation of pathogens, or non-compostability. ROM from the food industry is often too humid for composting, and most parts of the food industry do not have suitable locations to spread their residues or would have to transport them to distant sites to do so, which is costly. In most cases, the food industry must send its ROM to municipal facilities for treatment; cities also lack sufficient land for spreading their ROM. Instead, they regularly send them to landfills.

Municipalities, particularly the large ones, also generate millions of tonnes of ROM on their own, much of which is contaminated. For example, green wastes such as those from lawn mowing and leaf collection can be composted, but these wastes are often contaminated with plastic bags and other impurities. Cities also produce large volumes of ROM from street, sewer, and septic tank cleaning. Recycling bins and eco-centres provide ways to recycle and reuse ROM, but these facilities also produce millions of tonnes of ROM.

To provide numbers, about 60% of the 5.8 M tons of urban ROM generated annually in Quebec is not reused, and only 21% of putrescible residues were recycled in 2012 (Recyc-Québec, 2014). In order to force the urban and industrial sectors to find solutions to this problem, the Quebec government has developed an action plan for ROM management. The Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec (MAPAQ) has mandated, by legislation, that 60% of ROM should be diverted from landfill by 2015 and 100% by 2020. In response, the industrial sector has greatly increased its efficiency in recycling materials. For example, the Quebec forest industry hopes to reuse the entire 6.4 M tons of biomass generated by its forest activities (CEF, 2015). It has developed a panoply of new products made from sawdust and wood chips, among other materials. Much work is still required, however, to utilize all of the ROM produced by the industry, especially bark and branches, which represent about 25% of the trees. Thus, millions of tonnes of ROM produced annually by this industry remain unexploited.

All ROM could potentially be used to produce energy. However, existing subsidies render hydro-electricity very inexpensive in Quebec; energy from ROM is unable to compete with this low price. Composting offers an alternative means of recycling such materials, but it is not suitable for many types of ROM, and there is insufficient market demand for the quantities of compost that could be produced. Composting also emits large quantities of greenhouse gases (GHG) that are usually not captured, because doing so requires large installations. The majority of this ROM must therefore be processed using another way.

Methanization of ROM can produce large quantities of biogases, but it also generates 50 to 90% of its initial volume in ROM (Agrinova, 2013). The resulting digestates are subject to legislation from the Ministère du Développement Durable, de l’Environnement, et de la lutte contre les changements

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Climatiques (MDDELCC) regarding their use in the environment (Agrinova, 2013). Their use depends upon the quality, innocuity, and nutrient content of the digestate, while their quality depends upon their storage, the original type of ROM, and the transformation process (Agrinova, 2013). Because the ROM that remain contain more than 70% of water, solids have to be separated from the liquid components. Composting, dehydration, or pyrolysis can then treat these solid residues.

Incineration often offers the ultimate alternative for ROM treatment. However, while incineration decreases the volume of ROM considerably, it is also costly. The energy produced by the process could be used to heat industrial plants, but the low cost of energy in Quebec and the large variability in demand between seasons renders this alternative complex and uneconomical. Also, the ash that remains after incineration is not easily valorized.

Pyrolysis provides an interesting alternative to direct soil application, composting, methanization, and incineration since the gases produced are usually captured and recycled within the pyrolysis system, thus reducing GHG emissions; and the resulting material, known as biochar, is stabilized, making it easy to handle, transport, and distribute. Biochar offers the possibility of reducing the cost of transformation and storage of ROM, plastics, and other contaminants. In addition, biochar is sterile.

Pyrolysis carbonizes organic matter in the absence or in quasi absence of oxygen at temperatures between 275°C and 1000°C. The organic matter is thermo-chemically transformed, producing gases, oils, and solid residues, the solid is name biochar. The oils can be used to produce energy or new products such as biopesticides. In Quebec, the gases produced are often recycled to dry the source material before pyrolysis. Since biochar can be produced using a variety of feedstock and pyrolysis technologies, the properties of the resulting products vary.

Also called "biocarbon" or "vegetal charcoal", biochar differs from standard coal and charcoal because its source material is mostly fresh residual matter rather than fossilized or good quality hard wood. The final result consists of black, carbon-rich, initially sterile fragments that are lightweight, highly porous, and easy to transport.

The potential uses of biochar have excited growing interest among producers, processors, and managers of ROM, retailers of agro-environmental products, farmers, environmental consulting firms, and others - potentially everyone involved in agricultural production, environmental protection, or the disposition of organic residues. Possible applications in agriculture and environmental protection include carbon sequestration, interception of contaminants, and improvement of plant growth (Verheijen et al., 2010; Montanarella, 2013). For example, biochar can be used to improve soil fertility, water retention, and microbial activities, thus improving plant productivity (Allaire and Lange, 2013).

Therefore, the young biochar industry in Quebec has the potential to grow into a multi-million-dollar sector, but a number of steps are needed to clear the way for its development in Quebec. However, the listed advantages vary, depending on the type of biochar used, the oil type, the climate conditions, and the plant species involved. Although pyrolysis has existed for millennia, the methods for manufacturing biochar with specific characteristics for specific applications have yet to be fully mastered.

In order to make the best use of biochar, we must improve our understanding of its properties in relation to both the feedstock and the pyrolysis method used to manufacture it. In addition, to ensure that obstacles such as unnecessary regulation, subsidies for other methods of ROM transformation, and lack of knowledge about biochar no longer limit the development of this sector, greater knowledge is needed concerning the properties of biochar in relation to manufacturing processes and source materials, including new feedstocks.

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The main part of the report describes the analysis methods used, the properties of the biochars examined, most of which were made in Quebec, and their manufacturing technologies. Several analyses remained underway. Consequently, statistical analyses are not presented or discussed, nor are correlations between manufacturing procedures and specific biochar properties. Values are simply given without interpretation. Comparisons, relationships, correlations, and further discussion will come in subsequent papers.

In this report, we also present our work team (Table 1), the institutions that manufactured them or gave accesses to their pyrolyzer (Table 2), those that provided feedstock (Table 3), and financially supported the project (Table 4). The team thanks all the individuals and institutions that have contributed to this project. 2. Objectives

Our purpose in conducting a comparative analysis of the bio-physico-chemical properties of biochar was to create a reference database that will be of use to generators and managers of ROM, manufacturers of pyrolyzers and biochars, and biochar users. This information will help the industry better understand how to obtain desired products with desired characteristics and predictable properties for specific uses. The goal is to reduce the amount of trials and errors required, facilitating the development and marketing of biochar for agricultural and environmental applications in Quebec. Characterisation of the biochars is the first step towards this goal.

The team also set itself a sub-goal of defining a set of biochar analysis methods for Quebec conditions. Biochar specifically designed to amend agricultural soils, rehabilitate contaminated or degraded sites, or as supplement to potting soils began appearing on the market only recently, and thus methods of biochar analysis have not yet been formalized in Quebec or Canada as a whole. Some of the methods used in the literature are derived from standard analyses in the coal and energy industries, while others come from fertilizer and agricultural amendment applications. Other analyses derived from mandatory reporting requirements related to environmental protection, as in the case of heavy metals. The International Biochar Initiative (IBI) has suggested a set of biochar analysis methods (IBI, 2012), but the list is incomplete for some uses, including those related to plant growth. The European Biochar Foundation has suggested another set of methods for use with its European Biochar Certificate (EBC, 2012) that are similar but not identical to those recommended by the IBI. Some of the methods are applicable primarily to the coal and energy industries and have little relevance to agricultural and environmental applications.

In Quebec, the Bureau de Normalisation du Québec (BNQ) is accredited by the Standards Council of Canada (SCC) to develop norms and certifications using procedures and methods in accordance with the rules of the International Organization for Standardization (ISO) and the World Trade Organization (WTO). The use of ROM in agricultural fields, for food production, or for application on environmentally degraded sites is subject to Canadian federal government and Quebec provincial government legislation, but those rules differ from the standards of the IBI and EBC. For now, Quebec and Canada do not have standards specific to biochar.

To fill this gap, the team has sought to compile a list of the most appropriate methods for the analysis of biochar for agricultural contexts (effects on soil properties and plant growth, and environmental factors), taking into consideration the norms and regulations of the Quebec government for protecting the environment. We also wanted to assess a wide range of biochars using the standards of the IBI, the EBC, and the Quebec government in order to better understand their potential for use in Quebec and abroad. This classification will be discussed in another document.

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The present report is only preliminary since it only provides data on a selection of available biochars. Additional biochars have recently arrived at the laboratory, while others are in production in order to expand the range of pyrolysis conditions and raw materials examined. Following analysis of these biochars and application of multivariate statistical methods, we will map the properties of all of these and new biochars according to method of pyrolysis and type of feedstock. Classification of the biochars will be the subject of another paper, while their effects on plant growth (across various plants and conditions) will be addressed in a number of different thesis and articles.

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Table 1. Team members

Photo Name E-mail Title and institution

Degree Responsibility in this project

Speciality

Suzanne E. Allaire

[email protected]

Full professor, Université Laval

Ph.D. Director of soil physics lab

Soil physics and porous media

Sébastien F. Lange

[email protected]

Researcher, Université Laval

Ph.D. Lab management Soil physics

Melissa Quinche Gonzalez

[email protected]

Ph.D. student, Université Laval

M.Sc. Some analyses Agro-environment

Isabelle K. Auclair

[email protected]

Ph.D. student, Université du Québec à Trois-Rivières

M.Sc. Pyrolysis method, recycled wood and vegetables

Agroforestry

Laurence Greffard

[email protected]

M.Sc. student, Université Laval

Biologist Some analyses Biology

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Table 2. Biochar producers or industries that provided access to their pyrolyzer

Company Logo Contact person E-mail Internet site

Abri-Tech

Peter Fransham, Vice-President

[email protected]

http://www.advbiorefineryinc.ca/

Airex Energy

Sylvain Bertrand, CEO

[email protected]

http://www.airex-energy.com/fr/abr

Award Rubber

Michel Kaine, President

[email protected] http://www.awardrubber.com/

Biopterre

Benoît Cayer, CEO

[email protected]

http://www.biopterre.com/

Basques Hardwood Charcoal

David Huard, Director

[email protected]

http://charbonbasques.com/

IRDA

Stéphane Godbout, Researcher

[email protected]

http://www.irda.qc.ca/fr/

Maple Leaf

Simon Langlois, Director

[email protected]

http://mapleleafcharcoal.com/fr/

Pyrovac

Christian Roy, Owner

[email protected] http://www.canbio.ca/events/quebec/presentations/roy_f.pdf

Wood Ash Industries Inc.

Brian Coghlan, Owner

[email protected] http://www.woodash.net

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Table 3. Institutions that provided the feedstock to be pyrolyzed

Institution Logo Contact Internet site Feedstock

Biopterre

[email protected] http://www.biopterre.com/ Forest residues, phragmites

BRQ Fibre et broyure

[email protected] http://www.brq.ca/ Recycled wood

Centre de Tri Co-Éco

[email protected] http://co-eco.org/ Branches, bark

Ferme Norvie None [email protected] None Potato residues

Ferme Massibec

[email protected] http://www.massibec.com/ Cabbage residues

Ferme du Domaine 2000

[email protected]

http://www.fermedudomaine.com/

Leek residues

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Table 4. Institutions that contributed to the project through grants or supplemental student scholarships

Acronym Name Internet site Contribution

Airex Airex Energy http://www.airex-energy.com/fr/abr

1. MITACS scholarship, 2. Participation in a CRIBIQ project

Biopterre Biopterre http://www.biopterre.com/ 1. BMP scholarship, internship in industry

CJLP Centre Jardin Lac Pelletier http://www.cjlp.ca/ 1. MITACS scholarship, 2. Participation in a CRSNG-RDC project operated by the CTRI

CRIBIQ Consortium de Recherche et d’Innovations en Bioprocédés Industriels au Québec

http://www.cribiq.qc.ca/fr/ Grant program

CRIEB Industrial UQTR-foundation research chair on environment & biotechnology

http://www.uqtr.ca/CRIEB They paid the cost of some analyses

CRSNG Conseil de Recherche en Sciences Naturelles et Génie du Canada

http://www.nserc-crsng.gc.ca/index_fra.asp

1. BMP scholarship, internship in the industry, 2. Two Grant programs

CTRI Centre de Traitement des Résidus Industriels

http://www.ctri.qc.ca/ MITACS scholarship

FOGRN BC Programme de formation en gestion des ressources naturelles du Bassin du Congo

http://www.projetfogrn-bc.ulaval.ca/pefogrn_bc_ulaval/

Ph.D. scholarship

FQRNT Fonds Québécois de Recherche Nature et Technologie

http://www.frqnt.gouv.qc.ca/

MITACS and BMP scholarships

Innofibre Centre d’innovation de produits cellulosiques

http://innofibre.ca/ MITACS scholarship

MAPAQ Ministère des pêcheries et de l’alimentation du Québec

http://www.mapaq.gouv.qc.ca/fr

Grant through Innov’Action program

MITACS MITACS https://www.mitacs.ca/fr Scholarships

U. Laval Soil physics lab http://www.fsaa.ulaval.ca Scholarships to undergrad students

Biochars were obtained from a number of different research projects, funded or not. Only parts of certain grants were used for biochar analysis in each of these projects, all of which concerned agricultural, horticultural, or environmental issues related to the use of biochar. Most biochars were donated by the industrial partners.

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3. Materials and methods

3.1. Residual organic matter (ROM) and pyrolysis methods

This report examines the physical, chemical, and biological properties of a selection of biochars. The biochars were grouped into five categories by feedstock: hardwood, coniferous softwood, non-coniferous softwood, non-woody ROM, and other carbon-containing residues (e.g., pig manure) (Table 5).

3.1.1. Hardwood The hardwood biochars included residues from charcoal manufacturers such as Maple Leaf and

Basques Hardwood Charcoal (Table 5). These manufacturers burn large logs, principally maple (Acer sp.) and birch (Betula alleghaniensis, also called yellow birch), for about two days (Table 5) without oxygen in a batch furnace (Missouri-type kiln). The wood that enters the Maple Leaf pyrolyzer contains between 30 and 52% moisture, depending on season and wood inventory. The Maple Leaf pyrolyzer operates at about 350ºC at a set pressure and recycles its gases. The company's ovens can produce about 15 tonnes of charcoal per day (Leaf-Maple-350). The Basques Hardwood Charcoal pyrolyzer operates at a slightly higher temperature (500ºC) for two to three days (Table 5). Both companies produce biochar as a by-product of their charcoal manufacturing. The residues are sieved after pyrolysis. The three biochars from Basques Hardwood Charcoal examined in this report (BQ-Maple-500-1, 2, and 3) differ primarily in particle size and date of manufacture. The technology used by these manufacturers produces mainly biochars rather than oils, although the ratio depends on the speed of pyrolysis and the extent of desorption of water before carbonization. Bark is an integral part of the biochars. We also examined two other biochars (Award-Maple-700 and Nuchar-1000) made from hardwood residues from the forest industry. The Award-Maple-700 biochar is made from maple bark, rather than logs, burned at 700ºC for just 20 minutes. The Nuchar-1000 (MeadWestVaco, MWV SN-20) was purchased from Buyactivatedcharcoal.com. This biochar is activated at 1000°C after production. No further information was given about the manufacturing process. Nuchar-1000 is the only activated biochar made from hardwood discussed in this report. By examining a range of biochars, we were able to compare the effects of different production temperatures on the properties of biochars made from the same plant species (Table 5).

We also examined eucalyptus bark (B-Eu-300) processed in Cameroon in a small-batch vertical pyrolyzer with a gas recycling system. The operating temperature of this pyrolyzer varies around 300ºC, and pyrolysis lasts from 4 to 6 hours. A small amount of air is allowed to enter the system. The bark was collected at the soil surface, which resulted in the addition of soil impurities.

3.1.2. Coniferous softwood Other biochars were made from softwood residues such as branches, bark, and sawdust from

spruce (Picea sp.), fir (Abies sp.), or other species. These biochars were made by three companies: Biopterre, Airex Energy, and Pyrovac. Biopterre uses Abri-Tech technology, while Airex Energy and Pyrovac use their own technology.

The Abri-Tech system processes batches of about 2000 kg per hour. It was designed primarily to produce pyrolytic oils, with an output of about 65% oil and 20% biochar. The biochar is a by-product and not the final goal, and may contain volatiles. The source biomass is converted thermally in contact with steel balls heated to increase the gasification of the material. The size of the biomass

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particles has to be very small (usually less than 2 mm; maximum 20 mm), so there is no need for sieving after pyrolysis. Pyrolysis takes only a few minutes, at temperatures ranging between 425 and 550ºC depending on the product requested, without oxygen, at a pressure of about 1 cm. The two softwood biochars produced using Abti-Tech technology discussed in this report (BP-Res-400 and BP-Res-500) differed in terms of pyrolysis temperature (400 or 500ºC).

Airex Energy, the developer of the Carbon FX technology, is a spin-off from the company Airex Industries, which specializes in industrial dust. The Airex Energy pyrolyzer is a cyclonic bed reactor developed for fine particles such as sawdust. Biomass is pyrolyzed at about 427ºC over the course of several seconds, at atmospheric pressure, using a fine air inlet and heat transfer via high turbulence. The system can continuously produce about 250 kg of biochar per hour. Very little oil is produced. The main differences between the Airex biochars discussed in this report relate to production temperature in the case of the first two biochars (Airex-Res-427 and 454) and the type of ROM used (recycled wood from BRQ) in the case of the second two (Airex-RW-315 and 426).

Pyrovac's pyrolyzer processes softwood with 10 to 15% moisture content. It can accommodate a variety of products, accepting heterogeneous particles between 0.4 and 40 mm in size. Pyrolysis is performed at a pressure of 20 kPa and a temperature of 475ºC in a slightly oxygenated environment for 15 minutes. The pyrolyzer can produce 3000 kg of biochar per hour. The two Pyrovac biochars discussed in this report differed in terms of storage and sieving. The first (Pyr-Res-475) was stored for about 2 years in a warehouse and a waterproof container. The second (Pyr-Res-475-aged) was sieved to 2 mm and stored outside in leaky super sacks (polypropylene bags).

We also tested recycled wood residues. These residues represent a large, unexploited resource, but one that often contains toxic agents. For this report, we tested two biochars made from demolition wood and/or construction residues composed roughly 90% of spruce and 10% of assorted hardwoods (I-RW-300-24 and 48). The large volume of residues produced by the forest industry are stored relatively homogeneously by species. It is therefore possible to obtain biochars made from specific wood species from this source. By contrast, the residues of the construction–demolition industry offer mostly mixtures of wood species, which are therefore less homogeneous. However, since the frames and walls of Quebec buildings are mainly made from spruce, a large proportion of Quebec demolition wood is composed of this species. The recycled-wood biochars that we examined were made in a batch furnace with a small amount of air. As the wood was old, its initial water content was low (less than 10%). The wood was ground and screened to a particle size of 0-2 mm. Atmospheric pressure was maintained in the furnace. The biomass remained in the oven for 24 to 48 hours at 300ºC. Neither gas nor oil was recycled. Two recycled-wood biochars made with the Airex technology were also tested (Airex-RW-315 or 426).

3.1.3. Non-coniferous softwood Other biochars are made from non-coniferous softwood (Table 6) such as white birch (Betula

papyrifera) and willow (Salix sp.), using branches, bark, or the entire tree. Biopterre has produced a variety of such biochars (BP-Willow-x, BP-Birch-x, x being the temperature) with the Abri-Tech technology, using a range of raw materials (bark vs. branches vs. whole trees) and production temperatures. We also examined activated charcoal made from coconut shell residues (Coco-1000) sold by Buyactivatedcharcoal.com. The only activated biochar in the softwood category discussed in this report, Coco-1000 is produced by slow pyrolysis at about 300ºC, with the temperature increasing by 5° per minute for about 1 hr. It is then activated at 1000°C. Other manufacturing conditions were not disclosed.

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3.1.4. Non-woody materials Phragmites (Phragmites australis sp.) is a highly invasive plant that causes many problems in

Quebec. To control it, we tend to mow it. Hay residues were used to test the potential of this material for the manufacture of biochar. Mowing was carried out in spring on stems from the previous year that had dried during winter. The residues were shredded to 8 mm but not dried, and then pyrolyzed with the Abri-Tech technology at 400 or 500ºC to form two biochars (BP-Phragmite-400 and 500).

We also examined the potential to use residues from vegetable production that cannot easily be recycled by composting or incorporation directly into the field. Downgraded potatoes, cabbage leaves, and leeks are too wet to be easily composted, while direct field recycling can lead, in some cases, to proliferation of diseases. We pyrolyzed these materials to study their potential as biochars (I-Potato-300-24, I-Cabbage-300-48, I-Leek-300-48). The potatoes were manually julienned, while the cabbage and leek residues were cut up with a forage harvester. Pyrolysis was performed at Innofibre and Lignocellulosic Materials Research Centre (CRML) of the UQTR using ovens operating at atmospheric pressure, with little air entry. The biomass remained in the oven for either 24 or 48 hours at 300ºC. Neither gas nor oil was recycled. The potato biochars remained in the oven for just 24 hrs because experiments showed they were consumed before 48 hours.

We also looked at corncobs (B-Corn-300) that had been pyrolyzed in Cameroon using the same system as used for eucalyptus (a vertical pyrolyzer oven with gas recycling). The temperature of the oven varied around 300ºC, and pyrolysis lasted from 4 to 6 hours.

3.1.5. Other materials This category includes the use of non-standard biomass for biochar manufacturing.

Cogeneration activities by Kirkland Lake Power Corp. produce biochar that is sold by Ash Wood Industries (Wood-Ash-1500). The materials used in the cogeneration come in a wide range of sizes from a variety of wood wastes (softwood such as pine, birch, fir, and spruce) and often contain sand and other impurities. They are burned using flame at temperatures between 1500 and 1800ºC for less than one hour. Some residues are completely burnt, some are pyrolyzed into biochar, and others are less transformed. The process generates a highly variable product that is mostly ash (less than 50% biochar). Because of this variability, the features of the sample described in this report do not represent the full range of its potential properties. Even though this product contains less than 50% biochar, we included it in this report since the results could be of interest for other such industries.

Manure produced by the pork industry offers another potential source of biomass for biochar. The Quebec pork industry, which produces 7.5 million pigs annually (Gariepy and Lacroix, 2013), generates such a large amount of manure that the Quebec government has controlled pig production to limit its environmental and social consequences. The industry and various research bodies have sought improved technologies for processing pig manure slurry for many years. Recently, these efforts have included some small biochar trials. For this report, manure was collected from a pig growing–finishing farm where the liquid and solid fractions were separated under the slats of the barn. The collected solid was subsequently dried using the SHOC™ process (details of the process can be found in Léveillée et al., 2011) (http://www.irda.qc.ca/fr/publications/le-procede-shoc-une-solution-novatrice-pour-le-traitement-et-la-valorisation-des-residus-organiques/). The dry solid fraction of the pig slurry was converted into biochar (IRDA-Manure-500) using slow-batch pyrolysis at 500°C for 1.5 hours. A flow rate of 2 L min-1 of nitrogen was established in the reactor at atmospheric pressure to maintain an inert atmosphere and promote the evacuation of gases from the reactor. The material must enter with a moisture content below 85%.

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Table 5. List of biochars with their feedstock and pyrolysis method

Name Feedstock Conditioning Pyrolysis

Temp

(ºC)

Time (hrs)

Pressure (KPa)

Technology

Hardwood Leaf-Maple-350 Charcoal plant residues,

maple and cherry Sieved to ≤ 1.9 mm after pyrolysis + binding matter

350 40 Yes Missouri oven type

BQ-Maple-500-1 Charcoal plant residues, >75% maple

Sieved to medium-coarse after pyrolysis

500 48-72

Yes Missouri oven type


Sieved to fine after pyrolysis

500 48-72



Sieved after pyrolysis 500 48-72


Award-Maple-700 Maple bark None 700±100 0.4 Yes

Award Rubber

B-Eu-300 Eucalyptus bark Ground 300 6 0 Custom oven

Nuchar-1000 Hardwood from undeclared species

Activated at 1000ºC 300-1000 NA NA NA

Coniferous softwood BP-Res-400 50% fir branches, 50% spruce

branches Ground + dried before pyrolysis

400 0.08 0.1 Abri-Tech

BP-Res-500 50% fir branches, 50% spruce branches

Ground + dried before pyrolysis

500 0.08 0.1 Abri-Tech

Airex-Res-427 Resinous softwood sawdust Ground and sieved to ≤ 2 mm before pyrolysis

427 <0.01 0 Airex

Airex-Res-454 Spruce trunk sawdust Ground and sieved to ≤ 2 mm before pyrolysis

454 <0.01 0 Airex

Pyr-Res-475 Resinous softwood bark Sieved to ≥ 0.5 mm before pyrolysis

475 0.25 20 Pyrovac

Pyr-Res-475-aged Resinous softwood bark, aged in super bags and sieved

Sieved to ≥ 0.5 mm, dried to 8-15% moisture

475 0.25 20 Pyrovac

Airex-RW-315 Recycled demolition wood Sieved to < 6.4 mm before pyrolysis

315 0.01 0 Airex

Airex-RW-426 Recycled demolition wood Sieved to < 6,4 mm before pyrolysis

426 0.01 0 Airex

I-RW-300-24 100% demolition wood, 90% spruce, 10% hardwood

Ground and sieved to 0-3/4 inches before pyrolysis

300 24 0 Exp. oven

I-RW-300-48 100% demolition wood, 90% spruce, 10% hardwood

Ground and sieved to 0-3/4 before pyrolysis

300 48 0 Exp. oven

Non-coniferous softwood

BP-Willow-400 Whole willow Ground and sieved before pyrolysis

400 0.08 0.1 Abri-Tech

BP-Willow-450-2013 Whole willow Ground and sieved before pyrolysis

450 0.08 0.1 Abri-Tech

BP-Willow-450-2014 Whole willow Ground and sieved before pyrolysis

450 0.08 0.1 Abri-Tech


500 0.08 0.1 Abri-Tech


550 0.08 0.1 Abri-Tech

BP-Birch-400 >75% white birch branches Ground and sieved before pyrolysis

400 0.08 0.1 Abri-Tech

17

BP-Birch-500 >75% white birch branches Ground and sieved before pyrolysis

500 0.08 0.1 Abri-Tech

Coco-1000 Coconut shell Activated at 1000ºC 300 1 NA NA

Non-woody material BP-Phragmite-400 Phragmites Ground and sieved before

pyrolysis 400 0.08 0.1 Abri-Tech

BP-Phragmite-500 Phragmites Ground and sieved before pyrolysis

500 0.08 0.1 Abri-Tech

I-Potato-300-24 Non-marketable potatoes Cut into julienne potatoes

300 24 0 Exp. oven

I-Cabbage-300-48 Cabbage residues Ground with fodder 300 48 0 Exp. oven

I-Leek-300-48 Leek residues Ground with fodder 300 48 0 Exp. oven

B-Corn-300 Corn cobs Ground with fodder 300 6 0 Custom

Others IRDA-Manure-500 Dehydrated pig manure Sieved to 1-3 mm, dried

to 15% moisture 500±25 90 -27 to -

55 IRDA

Wood-Ash-1500 Mixed softwood (pine, spruce, birch, fir)

None 1500-1800

<1 Atm Kirkland Lake Power Corp.

18

Table 6. Photos of some biochars

Leaf-Maple-350 (10 x)

Award-Maple-700 (67 x)

BQ-Maple-500-2 (67 x)

Airex-Res-427 (6.7 x)

I-RW-300-24 (10 x)

I-RW-300-48 (10 x)

Pyr-Res-475 (4.7 x)

BP-Willow-550 (67 x)

BP-Willow-450-2013 (6.7 x)

Wood-Ash (13 x) I-Cabbage-300-48 (10 x)

I-Leek-300-48 (6.7 x)

I-Potato-300-24 (6.7 x)

19

3.2. Biochar analysis methods

The methods for analysing biochars recommended by the IBI and the EBC are primarily related to energy industry requirements due to the resemblance between biochar and coal. Some analyses are required to assess environmental risk or to respond to environmental regulations. The methods are significantly less affected by the forest industry, which is the source of the materials most commonly used to make biochars. There is also very little influenced by agriculture, although biochars are often used as soil amendment or in potting soils. We attribute the current focus on energy industry requirements mainly to the history of biochar.

Our team sought to meet the main IBI, EBC, and Quebec government requirements in terms of analytical methods in order to (1) meet current standards, (2) enable later comparison with other studies, and (3) assist industry to obtain environmental recognition. We used ASTM methods or certified Quebec methods as often as possible. Since our goal was to study the potential of biochars for agricultural, forest, or environmental applications, we did not focus on properties related to energy (BTU, flash point, flammability, etc.). We focused instead on those properties, whether mandatory or not, that can help predict the behaviour of biochars in porous media such as soil, potting soils, mine tailings, and soil rehabilitation.

Biochar properties were divided into the following classes: general properties (Table 7), physical properties (Table 8), chemical properties relevant to plant growth or environmental protection (Table 9), and biological properties indicative of environmental risk (Table 10). For simplification, all methods are briefly described in tables with their reference with little explanations in the text.

The general properties analyzed were those normally considered of relevance to energy industry requirements. These properties affect the behaviour of biochar in soil and potting soil only slightly, and provide little help in identifying risks to the environment. However, determining the type of carbon does help to establish the potential for long-term C sequestration; graphitic carbon is probably the most stable form. The physical properties of biochars (Table 8), e.g., bulk density, solid density, surface area, water-related characteristics, and particle size distribution, greatly influence their behaviour in porous media, in storage, and in transport. Chemical properties (Table 9) were considered because they influence the effect of biochars on plant growth (solubility, exchangeability, total nutrients) or their exchange capacity with the environment (pH), or because environmental regulations require identification of their contents (heavy metals, PAHs). Dioxin and furan levels are not presented in this report because of the high analysis cost (~800 $ CAN ea.). Finally, we examined the effect of biochars on earthworms and lettuce (Table 10), two species sensitive to pollution and other environmental factors, in order to identify potentially negative effects on biology.

3.2.1. General properties

Data was collected on the total ash, C, H, N, and S contents of the biochars (Table 7). In addition to total carbon (Ctot) content, data is given on organic carbon (Corg), inorganic carbon (Cinorg), and graphite (Cgraph) content to provide an indication of the likely transformation modes of the various biochars in soil. Cinorg corresponds mainly to CaCO3 content. We expect that Cgraph would show the highest stability in soil. The ratios H/Corg and O/C are simple calculations from the previous measurements.

20

3.2.2. Physical properties Hydraulic properties

The physical properties examined for this report include a number of properties related to water (Table 8). The EBC and IBI both require declaration of the gravimetric water content (WC) of the materials. The EBC differentiates between easy-to-extract water and hygroscopic water that is strongly sorbed onto particles, whereas the IBI requires only the easy to extract be reported. For simplicity and ease, we measured only easily extractable water for this report. WC has little effect on the behaviour of biochars in porous media. It is used primarily for determining the heating value of the material and to indicate to buyers the amount of water they are paying for. WC is, however, important in the case of activated charcoal. WC was measured at temperatures of 70 or 105°C for 24 hrs, a method adapted from the IBI and soil analysis.

Another parameter suggested, but not required, by the two organizations concerns the water retention capability of the material. This property determines the behaviour of the biochar in porous media and during storage when exposed to water. The method suggested by the EBC indicates only if the biochar is capable of sorbing water when completely submerged. We did not use this method. Instead, we measured the amount of water that can be extracted by the biochar both from the atmosphere and from a porous medium by capillary rise. For the first, we exposed the biochar to a relative humidity (RH) of 80% and measured how much water it could sorb from the air in 72 hrs. For capillary rise (CR), the biochar was subjected to water retention forces (CRx) simulating both a very wet (matric potential, or tension, near zero) and a somewhat drier but still very moist (more negative matric potential) soil. We selected these properties because they best represent the behaviour of biochars in the environment. Such data are likely to be especially useful because, although it is frequently asserted in the literature that biochars increase soil water retention, such assertions are often made without actual measurements in porous media.

Properties related to size and shape of particles, porosity, and electrical conductivity

These physical properties strongly affect the behaviour of biochar in soils and porous media. Bulk density (BD) is the mass/volume of the material including intra- and inter-particle pores (Table 8). This property is relevant to storage and transport, and it indicates the potential change in soil or potting soil density when biochar is added. Information on this property is required by the EBC, but not the IBI. Solid density (SD) is the mass/volume of the material excluding inter-particle voids. SD indicates the behaviour of a particle in another medium, such as buoyancy in water. Total porosity, P, is calculated according to P=1-BD/SD. External surface area (SSext) provides information on the exchange and sorption capacity, and reactivity, of the biochar. SSext includes exchange sites at the particle surface only. Electrical conductivity (EC) indicates the capacity to transport electricity. The IBI and EBC both require this information, but they recommend different methods. EC depends on the salt content of the biochar and thus could be used to calculate the salinity of the material. The ability of plants to extract water from their environment depends not only on matric potential, but also on osmotic potential, which is created by salinity.

A particle-size analysis was performed using two successive sieving procedures for each sample: (1) the first with a column of sieves being 8-, 4-, 2-, 1-, 0.50-, 0.25-, and 0.125-mm mesh size, and (2) the second with an ultrasonic sieve to separate particles smaller than 0.250 mm. The stack included the following sieves: 0.250, 0.106, 0.053, and 0.025 mm. The IBI requires a particle-size

21

analysis, although not as complete, while the EBC does not require one. From these sieving procedures, several parameters were calculated. Mean weight diameter (MWD) indicates the average particle size. This information is important to determine the type of machinery necessary to apply the biochar in the environment and to predict its behaviour once applied. The MWD influences, for example, water retention and potential mixture with other ingredients such as fertilizers.

From the particle-size distribution curve, we can calculate parameters such as the diameter representing the finest 10% of particles (D10). These parameters are used to calculate the particle-size uniformity index (UI) of the material. A low uniformity index (D95/D10) value means that the particles are uniform in size. A highly heterogeneous distribution of particle sizes may provide some benefit over the homogeneous mixes often obtained by screening, since different particle sizes may play different roles in water retention, protection against soil erosion, and soil decompaction. In some cases, however, one might select a biochar with a very homogeneous particle-size distribution for a specific behaviour such as often found in horticultural potting soils. When working with mixtures of amendments, the UI of the material will indicate whether or not it might separate from the other components of the mixture during transportation, handling, spreading, or plant growth.

The biochars were also subjected to abrasion tests using steel balls. Abrasion-resistance measurements (AR) show the resistance offered by a material to the action of different forces during its movement. This information can help determine the effects of transport, storage, spreading, and handling of the biochar on the integrity of its particles. Particle size after the abrasion was measured using the sieving method described above. The variation in mean weight diameter (DMWD), uniformity index (DUI), and specific particle size (DDx) following the abrasion were also calculated. This information is not required by any of the standards, but it is inexpensive to produce and useful for determining bagging, transportation, and handling needs.

3.2.3. Chemical properties Properties related to acidity

Measured chemical properties included pH value and buffer capacity (BC) (Table 9). The IBI and EBC both require provision of the pH value, but each specifies a different method. These methods yield slightly different results, but considering the large variation in pH between biochars, the results are close enough for comparative purposes, as in the case of this report. We used a method similar to the IBI's, measurement in water, in this report. BC is required by IBI, but is also useful for determining biochar behaviour in a medium with a different pH. This information is valuable in agriculture. Biochars, which are often basic, can be incorporated into much more acidic environments, such as peat, podzols, or mine tailings, for example. The pH value of the material alone does not indicate whether the biochar has sufficient buffer capacity to maintain its pH. BC was measured until either pH 7 (BCpH7) or pH 4 (BCpH4) was reached.

Exchangeable elements

Measurements of the content of exchangeable elements (Table 9) are used to check the availability of elements to plants and their nutritional balance relative to plant needs. The sum of the exchangeable elements N, P, K, Ca, and Mg is normally used to calculate the cation exchange capacity (CEC) of the soil. Since soils are subject to rain year after year, it is their ability to retain these elements over time that indicates their CEC. Fresh biochar has not been subjected to such leaching, and thus the exchangeable element data only indicate total content of these elements on exit from the

22

factory, regardless of whether they can be exchanged or not. In this report, we therefore use the term "sum of exchangeable elements" rather than CEC.

Soluble element content indicates not only the availability of nutrients when water is present, but also the risk of their movement into and potential contamination of the environment. Soluble elements (K, Ca, Mg, Na, Mn, Fe, Al, Cu, Zn) were extracted with water.

Properties related to environmental protection

The IBI and EBC both require declaration of heavy metal content (Tables 9 and 11). These values are used to determine approved and prohibited uses for environmental protection purposes. The list of metals covered, methods of analysis, and maximum permitted values vary between the organizations. The accepted maxima of the EBC and IBI generally correspond to European or US government regulations. We measured most of the metals and several other elements (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mo, Ni, Pb, Se, and Zn) using the methods prescribed by the IBI. The results will be compared to Quebec regulations, and those listed by the IBI and EBC, in another paper. We also measured the presence of polycyclic aromatic hydrocarbons (PAHs) (Table 9) using the standard methods of the Centre d’Expertise en Analyse Environnementale du Québec (CEAEQ). PAH measurements are required by both the IBI and the EBC. The range of properties analyzed was greater than that requested by these organisations.

3.2.4. Biological properties The final group of properties corresponding to IBI information requirements was related to

biological toxicity (Table 10), which we investigated by examining the preferences of earthworms and the germination of lettuce in mixtures of garden soil and biochar. For these tests, the biochar content in the soil mixtures, the earthworm species and the variety of lettuce were not dictated by the IBI, but simply suggested.

Eisenia fetida sp., an earthworm species often used in vermicompost, was used to measure the reaction of earthworms to the biochar. The worms were deposited on the soil surface in the middle of containers vertically separated into two equal parts, after which they were able to move freely from one side to the other for 48 hrs. On one side we put garden soil and on the other we put a mixture of this soil containing either 10% or 50% biochar. The subsequent distribution of the earthworms indicated their preference for either the mixture or the soil alone. This preference depends on factors such as toxicity, pH, abrasion on their skin, etc.

The lettuce (Lactuca sativa var. Buttercrunch) germination experiments suggested by the IBI were also performed. Seeds were sown in dishes containing the same concentrations of biochar as in the earthworm avoidance tests (0, 10, and 50%) in the same soil for 10 days. The germination rate of 20 seeds was monitored over time and reported as a percentage of the number of sown seeds. This information indicates whether the mixture can support plant growth, as lettuce is sensitive to environmental factors such as pH, nutritional imbalances, and the presence of contaminants. Under these conditions, the test only examines the effects of chemical properties of the medium, not its physical properties (e.g., humidity, density, gas movement, abrasion).

Briefly, the methods selected were those that we believe are the most appropriate for agricultural and environmental uses as well as for meeting the requirements of the Quebec government and international organizations.

23

Table 7. Analysis methods for general properties of biochars

Symb. Name Units Method Apparatus Reference

Ash Ash content % Loss to ignition Oven Adapted from l’ASTM-D1762-84 and from CAEAQ MA.1010-PAF 1.0

Ctot Total carbon content % Total dry combustion, elementary analysis

LECO Truspect Adapted from Meng et al. (2014) and Brewer (2012), LECO (2009)

Cinorg Inorganic carbon content % Quick determination of carbonate in soil

Several analysis methods

ASTM D4373-14 and CEAEQ (2009, 2013) and ISO 9686 (2006)

Corg Organic carbon content % Corg=Ctot-Cinorg --- ASTM D4373-14 and CEAEQ (2009, 2013) and ISO 9686 (2006)

Cgraph Graphitic carbon content % Combustion IR spectroscopy ASTM D4373-14 and CEAEQ (2009, 2013) and ISO 9686 (2006)

H H content % Total dry combustion, elementary analysis

LECO Truspect Adapted from Meng et al. (2014) and Brewer (2012)

O Oxygen content % Total dry combustion, elementary analysis


H/Corg Molar ratio of H/Corg --- H/Corg=H/Corg --- ---

O/C Molar ratio of O/C --- --- --- ---

N Nitrogen content % Total dry combustion, elementary analysis


S Sulfur content % Total dry combustion, elementary analysis


% = percent on a mass basis (g g-1 x 100).

24

Table 8. Analysis methods for physical properties of biochars

% = g g-1 x 100. For CRx, capillary rise curves were calculated using three replicates and the equation y = m ln(x) + b, where y = water sorption g g-1 h-1, x = tension (-m), and b = asymptote g g-1 h-1.


Density and porosity BD Bulk density g cm-3 Tapped density after

3 drops of 0.15 m Cylinder Adapted from ISO 5311

(1992) SD Solid density g cm-3 Gas pycnometer AccuPyc 1330

Micromeritics ASTM B923-10 TP Total porosity m3 m-3 TP=1-BD/SD --- Flint and Flint (2002)

SSext External specific surface area

m2 g-1 BET multi-points Surface area analyzer

ASTM D6556-10

Hydraulic properties EC Electrical

conductivity dS m-1 In water Radiometer,

Copenhagen Rajkovich et al. (2011), TMECC 4.11 (2001), IBI (2012)

WC Gravimetric water content

% Dried in oven at 105ºC (24h) or 70ºC (72h)

Oven Adapted from ASTM D1762-84

CRx Regression parameters of the water sorption rate by capillary rise at a tension of x

g g-1 h-1 -0.05, -0.25, -0.50, -0.75, -1.00, and -1.40 m tension

Tension table, non-linear regression

Adapted from Allaire and Parent (2004b)

CR72 Total water sorption over 72 hrs under different tensions

% -0.05, -0.25, -0.50, -0.75, -1.00, and -1.40 m tension

Tension table, non-linear regression

Adapted from Allaire and Parent (2004b)

Particle size and resistance MWD Mean weighted

diameter um Particle-size

distribution with standard sieve series

RX-29 Ro-Tap sieve shaker (W.S. Tyler) and ultrasonic sieve

Adapted from Gee and Or (2002) for sieving, Nimmo and Perkins (2002) for MWD

Dx Diameter of the x% of finer particles

um Particle-size distribution

--- Adapted from Gee and Or (2002), and Nimmo and Perkins (2002) for sieving, adapted from ASTM D2862-10 and from

UI Uniformity index --- D95/D10 --- Allaire and Parent (2003, 2004a), for Dx CFI (2001)

AR Abrasion resistance

um Abrasion with rotating steel balls

RX-29 Ro-Tap (W.S. Tyler, Mentor, Ohio, USA)

Paré et al. (2009), adapted from Kiekens et al. (1999), Kemper and Roseneau (1986)

DDx Change in Dx after abrasion

um DDx=Dxbefore-Dxafter abrasion

--- ---

DUI, DMWD

Changes after abrasion

---, and m

25

Table 9. Analysis methods for chemical properties of biochars

Symb. Name Units Method Apparatus Reference Related to acidity

pHH2O pH in water --- pH in water pH-meter (VWR SB20)

Rajkovich et al. (2011), AGDEX (1989)

PTpH4 Buffer capacity at pH 4

meq HCl Extraction HCl 1 N

Potentiometric electrode with pH-meter (VWR SB20)


PTpH7 Buffer capacity at pH 7

meq HCl Extraction HCl 1 N

Potentiometric electrode with pH-meter (VWR SB20)


Nutrients and Elements Pex Exchangeable

phosphorus cmol (+) kg-1

Formic acid 2% Spectrophotometer Wang et al. (2012), Rajan et al. (1992), AOAC (2005)

Kex, Caex, Mgex, Naex

Exchangeable elements

cmol (+) kg-1

Extraction CaBl2-NH4Cl

ICP Optima 4300DV Perkin-Elmer

Amacher et al. (1990)

Extot Sum of exchangeable elements

cmol (+) kg-1

Equation --- ---

Psol Content in soluble phosphorus

mg L-1 Water extraction ICP-AES Enders and Lehmann (2012), IBI (2012)

Ksol, Casol, Mgsol, Nasol, Mnsol, Fesol, Alsol, Cusol, Znsol

Soluble elements mg L-1 Water extraction ICP Optima 4300DV Perkin-Elmer

AGDEX 533 (1989)

Related to the environment

P, Cu, Zn, As, Cd, Co, Cr, Hg, Mo, Ni, Pb, Se

Total content in elements

mg kg-1 Modified ash methods

ICP-AES Enders and Lehmann (2012), IBI (2012)

PAH content: Acenaphtene, acenaphtylene, anthracène, benzo(a)anthacene, benzo(a)pyrene, benzo(b)pyrene, benzo(b+j+k)fluoranthene, benzo(c)phenanthrene, benzo(g,h,i)perylene, chrysene, dibenzo(a,h)anthracene, dibenzo(a,i)pyrene, dibenzo(a,h)pyrene, dibenzo(a,l)pyrene, diméthyl-7,12benzo(a) anthacene, fluoranthene, fluorene, indenol(1,2,3-cd)pyrene, methyl-3 cholanthrene, naphtalene, phenanthrene, pyrene, methyl-1naphtalene, methyl-2 napthalene, dimethyl-1,3 naphtalene, trimethyl-2,3,5 naphtalene

mg kg-1 Extraction with dichloromethane

GC/MS-SIM CAEAQ MA.400-HAP.1.1., ISO 17025 and G34

% = percent g g-1 x 100.

26

Table 10. Analysis methods for biological properties of biochars


Wormsx Percent of earthworms (Eisenia fetida sp.) that chose the mixture with x% of biochar

% Trays with garden soil on one side and garden soil+biochar at x% on the other side at 20°C

Small containers IBI (2012), ISO 17512-1 (2008), Major (2009)

Lettuceyj-x Germination rate of lettuce (Lactuca sativa var. Buttercrunch) after 10 days in a mixture of garden soil and x% of biochar

% Petri dishes in environment-controlled chamber at 22°C:16 hrs daytime /15°C: 8 hrs nighttime

Environment-controlled chamber

IBI (2012), OECD (1984), ISO 17126 (2005), Van Zwieten et al. (2010)

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Table 11. Comparison between analyses in this report and those of IBI (2012) and EBC (2012)

Parameter Allaire et al. IBI EBC General properties

Ash Given Required Required C Ctot, Corg, Cinorg and

Cgraph Ctot required Corg required

H/Corg Given Required Required O/C Given Required Not required

Physical properties BD Given Required Not required SD, TP Given Not required Not required SS Given Required Optional EC Given Required Required WCg Given Required Required CRx Given Optional Not required Particle-size distribution Several parameters Not required Required AR Given Not required Not required

Chemical properties pHH2O pHH2O Required,

pHCaCl2 Required, pHH2O

PT Given Not required Not required Exchangeable elements Given Not required CEC

suggested Soluble elements Given Not required Not required Heavy metals and metalloids

Given Required Required

PAH Given Required Required BCP Not measured Required Required PCDD/PCDF Not measured Required Required

Biological properties Earthworms Given Not required Suggested Lettuce Given Not required Required

IBI: International Biochar Initiative. EBC: European Biochar Certificate. PCDD: Dioxin and furans. N.B. Most of the analyses required by the IBI and EBC do not use the same methods. Properties measured by our team that are not listed in this table were neither required nor suggested by either IBI or EBC.

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4. Results and discussion

4.1. General properties

In the energy industry, ashes are useless and undesirable. A biochar containing more ash is generally less energy-efficient. However, for plant growth, ash can be considered a desirable mineral amendment as long as its heavy metal content does not exceed environmental standards. Agricultural applications of ashes are sometimes made. For the purposes of soil carbon sequestration or organic amendment, however, biochars should contain less ash and as much carbon as possible.

The percentage of ash in the biochars examined here varied between 1 and 54% of dry weight (Table 12). The biochars containing the least ash were two of the biochars manufactured with softwood (Airex-Res-427 and 454) and Coco-1000, which contains activated carbon, whereas the biochar that contained the most ash was made by Wood Ash Industries (Wood-Ash-1500). The latter result was no surprise, as this company uses a cogeneration plant that burns a wide range of materials, often containing contaminants such as sand, at high temperature. These ashes are sold as such. The biochars made with phragmites, cabbage, and pig slurry contained more than 18% ash. The biochars with the greatest ash content were not the same of those that showed the greatest variation in content. The biochars showing the greatest variability were BQ-Maple-500-3 and those manufactured by Airex with softwood sawdust. BQ-Maple-500-3 is made from anything that falls from timbers during and after pyrolysis into charcoal, including coal particles, bark, and sand.

Most of the biochars met the standards of the EBC, e.g., they contained more than 50% Ctot, the exceptions being one that was 30% C, manufactured using a cogeneration power plant (Table 12) and those manufactured with the Airex technology (Airex-Res-427 and 454) and recycled wood (Airex-RW-315 and 426). Only the activated-carbon biochar made with coconut (Coco-1000) contained more than 90% C, although BQ-Maple-500-1 contained about 80% C. The coefficients of variation (CV) of Ctot were very low. Relative to Ctot, Cgraph content was generally higher with hardwood, followed by non-coniferous softwood and coniferous softwood (Figure 1). The activated biochars (Nuchar-1000 and Coco-1000) contained the highest levels of Cgraph since the proportion of graphitic carbon generally increases with pyrolysis temperature. BQ-Maple-500-1 also contained more than 70% Cgraph (Table 12). Cinorg was present in much smaller proportions than Cgraph, but because it corresponds mainly to CaCO3. It could be useful for liming when present. Biochars made from recycled wood contained up to 9% Cinorg (Airex-RW-315), while those made from phragmites contained very little. Corg ranged between 1.5% for the BP-Willow-450-2014 and 45% for the BP-Birch-400. Relative to Ctot, the variation between biochars was lower among those made of hardwood. BP-Willow-450-2014 stood out with the highest H/Corg ratio because of its low Corg content. Maple wood biochars tended to provide relatively high values of H/Corg, as did biochars made at 500ºC. Biochars made of maple wood tended to give lower O/Ctot (Table 12), while non-woody materials tended to give somewhat higher values. However, the highest values were obtained with Airex-RW-315 and Airex-RW-426, followed by Wood-Ash-1500. These trends will be evaluated statistically in a future publication.

4.2. Physical properties

The bulk density (BD) of the biochars was very low (Max. 0.42 g cm-3), close to the values for peat and soil organic matter (Table 13). Those made from eucalyptus wood (B-Eu-300) and phragmites (BP-Phragmite-500) showed the highest BD values, while the biochars produced in the experimental laboratory (I-...) tended to give the lowest values. Low BD values are excellent for use in potting soils

29

or to loosen soils, but they increase transportation and bagging costs. Particle-size distribution influenced these BD values. SD density was similar between biochar except for Coco-1000 and Wood-ash that were higher. Only two biochars stood out, Wood-Ash-1500, since it contains a lot of ash, and Coco-1000. Based on BD and SD, TP values also tended toward somewhat higher values than those of peat. None of the values suggest potential problems for application to soil for vegetable, horticultural, or nursery production or for water filtration. Those produced in the laboratory tended to have greater porosity because of their very coarse grain size. Electrical conductivity (EC) varied little between the biochars, except for those manufactured in the laboratory using vegetable residues (I-Potato-300-24, I-Cabbage-300-48, I-Leek-300-48). Biochars manufactured by Pyrovac and Airex with softwood sawdust tended to have lower EC. Species and pyrolysis temperature appeared to influence the EC value. No biochars had a salinity level that could cause problems to plants when mixed with soil, unless used for greenhouse crops, where salinity can rapidly increase because of fertilization.

Hydraulic properties varied greatly between biochars (Table 14). These properties are much

influenced by particle size, internal and external porosity, and surface tension, which can make the biochar either hydrophilic or hydrophobic under different conditions. Initial water content depends mainly on the method of pyrolysis and method of storage. Therefore, these values are of little use for soil applications, being relevant primarily to handling and energy efficiency. Wood-Ash-1500 contained the highest water content, partly because it contained more ash (highly sorbent), but also because it had been exposed to air. Capillary rise leads some biochars to quickly sorb liquid water available around them (Fig. 2). For example, Nuchar-1000 and Wood-Ash-1500 sorbed water as soon as they came into contact with a wet, porous medium, whereas Pyr-Res-475 and I-Cabbage-300-48 were capable of sorbing a lot of water, but did so especially when the porous medium was soak but required more time; they sorbed much less when the soil was only moist. Other biochars, such as BQ-Maple-500-1 and Airex-Res-427, remained relatively dry even in very wet conditions. After 72 hrs, Wood-Ash-1500 sorbed up to 150 and 420% of its weight in water under soil tensions of -1.4 m (wet) and -0.05 m (soggy), respectively. Nuchar-1000 also sorbed a lot of water (275% at -0.05 m), as did BP-Willow-450-2014 (137%); comparativelyAirex-Res-427 sorbed only 12%.

Since it takes greater force to extract water from a drier environment, sorption rates under

higher tension are not as high as those under lower tension (-1.4 m vs. -0.05 m). The biochars also vary in their relative sorption abilities at different tensions. For example, BP-Willow-450-2014, which was among those that sorbed the most in wet conditions, was among the least sorbent in humid conditions (a little drier). Its behaviour resembled that of peat. As a result, not all biochars are able to sorb as much as water as the literature tends to say. Some are hydrophobic, much like peat, under drier conditions.

The sorption of water vapour from the air differs from that of liquid water from the ground.

Particle size is important for sorbing liquid water, but it is much less so for water vapour, where surface properties and salt are more important. Nuchar-1000 sorbed more than 100% of its weight from water vapour over 72 hrs, while I-potato-300-24 sorbed about 15% and the two biochars made by Pyrovac about 12 and 13%. This property will need to be considered for storage and bagging requirements. We must also be careful when applying them to the field under humid conditions to make sure that they do not clog the machinery.

Nuchar-1000 contained the largest proportion of fine particles, followed by the biochars

manufactured by Biopterre using Abri-Tech technology (Table 15). Biochars with very fine particles tend to produce a lot of dust, which is potentially harmful to workers and can also be very messy. Fine biochars cannot be mixed directly with compound fertilizers unless they are part of fertilizer granules,

30

Fines reduce the speed of drainage or clog drains. By contrast, the biochars made from vegetable residues (potato, cabbage, leek) and BQ-Maple-500-1 were too coarse to be mixed with fertilizers or incorporated into the soil. Other biochars were a good size for use in potting soil. The uniformity of the particle sizes varied greatly from one biochar to another (Fig. 3), depending on both the raw material and sieving before or after pyrolysis. The particle-size distribution curve shown in Figure 3 is spread, with great heterogeneity in particle size in some biochars (e.g., Award-Maple- 700 and Leaf-Maple-350). BQ-Maple-500-1, on the other hand, had a highly uniform particle size. Depending on intended use, a uniform particle size may be desirable, while in other cases heterogeneous granulometry may be required. It is generally desirable that the particle size remains the same during transport, handling, and time of use. The biochars with the finest particles and those pre-sieved were generally more resistant to break down (DMWD, Table 15), but this was not always true. Also, large particles tend to break more often (e.g., Leaf-Maple-350 and BQ-Maple 500-1), but this was not true for the biochars made from vegetable residues, which had very large and quit resistant particles.

31

Table 12. General properties of biochars

Biochar Ash Ctot Cgraph Cinorg Corg H O H/Corg O/CTot % CV % CV % % % % CV % CV --- ---

Hardwood Leaf-Maple-350 11.9 8.4 68.0 1.6 57.8 1.71 8.5 2.35 3.5 9.6 2.6 0.28 0.14 BQ-Maple-500-1 5.10 19.3 79.5 0.4 71.7 1.17 6.7 2.57 0.4 10.0 4.1 0.39 0.13 BQ-Maple-500-2 12.5 2.5 68.2 0.9 53.5 2.50 12.2 2.41 3.2 13.1 3.5 0.20 0.19 BQ-Maple-500-3 12.2 38.5 69.4 0.5 48.4 0.74 20.2 2.68 1.8 10.0 3.7 0.13 0.14 Award-Maple-700 14.2 2.7 65.4 1.5 51.7 2.00 11.7 1.89 5.6 10.2 0.4 0.16 0.16 B-Eu-300 10.0 3.1 56.2 0.4 24.9 3.46 27.8 3.26 2.6 27.4 1.2 0.12 0.49 Nuchar-1000 5.40 3.1 77.4 0.7 66.8 0.49 10.2 0.97 1.3 11.0 0.8 0.10 0.14

Coniferous softwood BP-Res-400 13.8 2.2 66.3 0.3 42.2 1.73 22.3 3.63 2.1 16.2 12.9 0.16 0.24 BP-Res-500 10.7 9.0 72.0 0.4 60.0 1.09 10.9 2.70 2.1 11.0 1.5 0.25 0.15 Airex-Res-427 1.38 19.0 69.8 0.2 29.8 2.08 37.9 3.41 1.9 17.4 5.1 0.09 0.25 Airex-Res-454 1.56 23.3 74.9 0.2 60.3 NA 14.5 2.98 0.8 10.8 3.7 0.21 0.14 Pyr-Res-475 8.13 8.5 61.4 0.4 42.1 1.07 18.3 2.82 1.8 20.8 0.5 0.15 0.34 Pyr-Res-475-aged 9.91 18.6 60.2 1.4 40.2 1.14 18.9 2.45 5.3 21.0 2.1 0.13 0.35 Airex-RW-315 NA NA 43.5 2.8 10.7 9.17 23.7 4.99 2.7 33.1 1.6 0.21 0.76 Airex-RW-426 NA NA 45.2 0.5 16.0 3.47 25.7 3.35 0.6 23.3 2.9 0.13 0.52 I-RW-300-24 19.2 NA 60.5 0.7 25.5 1.35 33.6 3.18 1.1 22.1 0.5 0.09 0.37 I-RW-300-48 10.7 25.7 52.4 0.2 36.9 1.49 14.0 1.86 0.2 20.5 0.3 0.13 0.39 I-RW-300-48-2nd NA 8.6 54.7 0.9 22.8 2.64 29.2 2.69 0.9 22.3 11.8 0.09 0.41

Non-coniferous softwood BP-Willow-400 11.1 1.1 67.4 1.4 23.7 5.31 38.4 3.58 2.2 16.2 1.5 0.09 0.24 BP-Willow-450-2013 9.80 1.1 NA 1.6 NA NA NA 2.77 1.2 16.0 1.0 NA NA BP-Willow-450-2014 11.6 0.2 70.2 1.4 67.5 1.28 1.5 2.51 9.5 14.5 2.4 1.72 0.21

BP-Willow-500 12.2 4.57 71.5 0.2 61.6 0.96 8.9 2.62 1.1 13.7 0.9 0.29 0.19 BP-Willow-550 9.56 9.14 NA 1.3 NA NA NA 2.41 1.5 10.5 1.1 NA NA BP-Birch-400 7.26 0.89 71.8 1.5 24.6 2.54 44.7 4.03 3.3 17.0 0.5 0.09 0.24 BP-Birch-500 10.5 3.05 69.6 0.5 59.9 0.42 9.2 2.62 1.2 11.9 1.1 0.28 0.17 Coco-1000 1.11 9.84 91.5 0.2 84.8 0.85 5.8 0.10 0.0 3.2 0.4 0.02 0.04

Non-woody material BP-Phragmite-400 26.3 2.19 57.0 0.4 21.2 0.89 35.0 3.04 2.3 14.1 0.5 0.09 0.25 BP-Phragmite-500 28.6 3.55 56.3 1.7 43.2 0.48 12.6 2.45 5.3 14.7 12.4 0.19 0.26 I-Potato-300-24 9.88 4.69 62.8 1.8 24.8 1.32 36.8 4.28 3.4 20.6 1.8 0.12 0.33 I-Cabbage-300-48 20.0 2.49 55.4 0.2 21.8 3.21 30.4 4.16 2.1 20.8 1.2 0.14 0.38 I-Leek-300-48 18.1 1.66 54.7 0.1 10.1 3.21 41.5 4.30 0.2 18.8 1.4 0.10 0.34 B-Corn-300 5.28 1.22 68.8 0.7 37.7 1.32 29.7 3.83 2.1 14.7 0.2 0.13 0.21

Others Wood-Ash-1500 54.9 5.26 30.0 3.0 25.0 1.79 3.2 0.21 45.3 15.2 15.2 0.06 0.51 IRDA-Manure-500 21.7 8.49 52.4 0.4 23.5 3.88 25.1 3.06 0.1 19.3 1.1 0.12 0.37 CV = coefficient of variation (%). The properties that are not associated with CV have not been repeated. NA: Not Available

32

Figure 1. Relative content of C types in biochars (green: Corg, red: Cinorg, blue: Cgraph)

0%#

20%#

40%#

60%#

80%#

100%#

Leaf-Maple-350#

BQ-Maple-500-1#

BQ-Maple-500-2#

BQ-Maple-500-3#

Award-Maple-700#

B-Eu-300#

Nuchar-1000#

Conten

t&rela*

ve&to

&total&carbo

n&Hardwood&

Corg# Cinorg# Cgraph#

0%#

20%#

40%#

60%#

80%#

100%#

BP-Res-400#

BP-Res-500#

Airex-Res-427#

Airex-Res-454#

Pyr-Res-475#

Pyr-Res-475-aged#

Airex-RW

-315#

Airex-RW

-426#

I-RW-300-24#

I-RW-300-48#

I-RW-300-48-2nd#

Coniferous&so5wood&

0%#

20%#

40%#

60%#

80%#

100%#

BP-Willow-400#

BP-Willow-450-2014#

BP-Willow-500#

BP-Birch-400#

BP-Birch-500#

Coco-1000#

Conten

t&rela*

ve&to

&total&carbo

n&

Non7coniferous&so5wood&

0%#

20%#

40%#

60%#

80%#

100%#

BP-Phragmite-400#

BP-Phragmite-500#

I-Potato-300-24#

I-Cabbage-300-48#

I-Leek-300-48#

B-Corn-300#

Wood-Ash-1500#

IRDA-M

anure-500#

Non7woody&materials&

33

Table 13. General physical properties of biochars

Biochar BD SD TP EC

g cm-3 CV g cm-3 CV m3 m-3 CV dS m-1 CV Hardwood

Leaf-Maple-350 0.39 2.36 1.68 0.54 0.77 0.73 0.33 27.7 BQ-Maple-500-1 0.26 1.60 1.53 1.06 0.83 0.39 0.44 20.9 BQ-Maple-500-2 0.33 2.27 1.66 0.33 0.80 0.65 1.43 38.7 BQ-Maple-500-3 0.29 2.80 1.54 0.31 0.81 0.61 0.38 0.85 Award-Maple-700 0.35 3.44 1.77 1.57 0.80 0.49 0.48 34.2 B-Eu-300 0.46 1.26 1.63 0.77 0.72 0.19 0.68 0.97 Nuchar-1000 0.28 0.29 1.78 0.44 0.85 0.05 0.65 54.2

Coniferous softwood BP-Res-400 0.39 0.44 1.45 0.41 0.73 0.31 0.40 1.64 BP-Res-500 0.42 1.22 1.52 0.32 0.72 0.40 0.62 1.06 Airex-Res-427 0.21 1.51 1.48 0.75 0.86 0.29 0.10 13.2 Airex-Res-454 0.19 2.44 1.48 0.44 0.87 0.39 0.11 3.01 Pyr-Res-475 0.30 2.14 1.55 0.28 0.80 0.47 0.13 23.3 Pyr-Res-475-aged 0.31 3.23 1.54 0.60 0.80 0.77 0.15 0.01 Airex-RW-315 0.28 1.12 1.48 0.59 0.81 0.40 0.72 2.28 Airex-RW-426 0.26 10.7 1.52 1.83 0.83 1.89 0.88 3.72 I-RW-300-24 0.18 1.93 1.66 2.58 0.89 0.34 1.41 2.21 I-RW-300-48 0.18 3.03 1.63 2.87 0.89 0.74 1.57 4.64 I-RW-300-48-2nd 0.18 3.24 1.62 1.19 0.89 0.54 0.74 12.7

Non-coniferous softwood BP-Willow-400 0.34 1.97 1.46 0.29 0.77 0.55 0.37 33.6 BP-Willow-450-2013 0.31 2.28 1.57 0.88 0.80 0.64 1.20 32.5 BP-Willow-450-2014 0.36 3.37 1.51 0.21 0.76 1.11 0.73 36.4 BP-Willow-500 0.32 0.75 1.51 1.71 0.79 0.64 0.50 0.66 BP-Willow-550 0.31 6.07 1.61 1.40 0.81 1.41 2.09 12.1 BP-Birch-400 0.39 0.96 1.41 0.28 0.72 0.27 0.28 5.40 BP-Birch-500 0.40 1.29 1.53 0.69 0.74 0.71 0.44 1.30 Coco-1000 0.32 1.71 2.11 0.15 0.85 0.27 0.34 9.61

Non-woody materials BP-Phragmite-400 0.39 0.91 1.54 0.20 0.75 0.33 0.32 1.01 BP-Phragmite-500 0.42 1.08 1.59 0.31 0.74 0.49 0.33 1.99 I-Potato-300-24 0.13 12.1 1.25 0.46 0.90 1.43 3.61 32.6 I-Cabbage-300-48 0.18 3.26 1.39 0.32 0.87 0.49 4.81 12.6 I-Leek-300-48 0.17 0.77 1.38 1.07 0.88 0.28 3.10 40.6 B-Corn-300 0.33 1.91 1.62 1.15 0.79 0.21 0.25 2.27

Others Wood-Ash-1500 0.31 6.46 2.74 28.42 0.88 3.32 0.86 35.5 IRDA-Manure-500 0.33 1.51 1.59 0.73 0.79 0.47 1.53 29.0

CV = coefficient of variation (%).

34

Table 14. Physical properties related to water

Biochar WC Capillary rise RH Regression curve CR RH80 m b R2 CR-1.4 m CR-0.05 m % CV g g-1 h-1 g g-1 h-1 --- % CV % CV % CV

Hardwood Leaf-Maple-350 2.42 0.46 -0.0006 0.005 0.92 15.5 8.3 23.5 18.3 5.90 1.9 BQ-Maple-500-1 2.04 0.60 -0.0004 0.004 0.90 13.8 18.0 21.3 12.1 5.98 6.2 BQ-Maple-500-2 1.04 0.33 -0.0056 0.029 0.86 23.3 32.3 43.8 17.0 6.14 0.4 BQ-Maple-500-3 4.19 3.2 NA NA NA NA NA NA NA 5.24 1.9 Award-Maple-700 2.42 0.25 -0.0005 0.005 0.94 14.9 15.9 23.0 16.2 5.93 3.3 B-Eu-300 5.19 10.3 NA NA NA NA NA NA NA 6.14 6.4 Nuchar-1000 6.44 2.24 -0.0072 0.055 0.61 86.3 8.3 275 0.6 102.8 1.7

Coniferous softwood BP-Res-400 0.0 NA NA NA NA NA NA NA NA 5.67 1.8 BP-Res-500 0.16 200 NA NA NA NA NA NA NA 6.04 3.4 Airex-Res-427 5.64 0.06 -0.0004 0.003 0.97 7.7 0.4 12.3 10.4 6.11 5.4 Airex-Res-454 3.41 5.5 NA NA NA NA NA NA NA 6.79 2.1 Pyr-Res-475 5.98 2.0 -0.0098 0.047 0.94 6.8 51.5 121 32.4 12.44 1.2 Pyr-Res-475-aged 7.86 21 NA NA NA NA NA NA NA 13.17 0.5 Airex-RW-315 0.76 18 NA NA NA NA NA NA NA 9.90 6.4 Airex-RW-426 0.77 100 NA NA NA NA NA NA NA 5.94 1.5 I-RW-300-24 3.19 5.4 -0.0012 0.007 0.97 10.0 9.4 21.1 11.6 8.42 6.1 I-RW-300-48 5.94 32 -0.0061 0.029 0.89 5.7 9.4 14.5 10.0 8.65 1.8 I-RW-300-48-2nd 2.23 20 NA NA NA NA NA NA NA 7.04 11.4

Non-coniferous softwood BP-Willow-400 1.17 9.4 NA NA NA NA NA NA NA 6.72 1.6 BP-Willow-450-2013

0.73 NA -0.0059 0.033 0.78 20.0 55.8 40 4.3 NA NA

BP-Willow-450-2014

0.56 8.51 -0.0098 0.048 0.88 6.5 66.1 137 20.4 5.62 7.7

BP-Willow-500 0.4 82 NA NA NA NA NA NA NA 7.62 8.0 BP-Willow-550 0.70 NA -0.0059 0.032 0.88 15.9 41.6 124 7.0 NA NA BP-Birch-400 0.01 150 NA NA NA NA NA NA NA 5.29 0.5 BP-Birch-500 0.22 173 NA NA NA NA NA NA NA 6.58 2.4 Coco-1000 2.95 1.70 -0.0039 0.031 0.62 43.5 58.9 149 1.2 NA NA

Non-woody material BP-Phragmite-400 0.0 100 NA NA NA NA NA NA NA 5.71 1.6 BP-Phragmite-500 0.0 100 NA NA NA NA NA NA NA 6.20 2.6 I-Potato-300-24 1.00 8.40 -0.0028 0.018 0.97 24.4 5.8 64.2 3.8 14.58 11.3 I-Cabbage-300-48 0.80 16.4 -0.0069 0.039 0.98 39.8 9.4 106 10.0 11.12 2.2 I-Leek-300-48 1.36 9.16 -0.0013 0.020 0.95 28.7 14.8 64.7 30.1 12.75 4.0 B-Corn-300 5.07 3.3 NA NA NA NA NA NA NA 6.17 0.7

Others Wood-Ash-1500 16.8 6.64 -0.0224 0.127 0.92 150.7 130.4 420 93.8 5.89 6.7 IRDA-Manure-500 2.48 1.1 -0.0011 0.009 0.88 19.4 16.8 41.8 16.7 9.25 12.1 CV = coefficient of variation (%). The capillary rise curves were completed with replicates using the equation y = m ln(x)+b, where y = sorption of water g g-1 h-1, x = tension (-m), and b = asymptote g g-1 h-1. Therefore, there is no CV for m and b. Capillary rise (CR-1.4 or CR-0.05) indicates the mass of water sorbed per biochar mass during 72 hrs under different tensions (-1.4 m = humid, -0.05 m = wet). Sorption of relative humidity (RH80) is the mass of water sorbed in vapour form per biochar mass during 72 hrs under a RH of 80% at 22°C. NA: Not Available

35

Figure 2. Capillary rise of different biochars under tensions of -0.05 m (very wet) to -1.4 m (humid)

0.00#

0.01#

0.02#

0.03#

0.04#

(1.50# (1.25# (1.00# (0.75# (0.50# (0.25# 0.00#

Sorp%on

'rate'(g''g

-1'h

-1)' Hardwood'

Leaf(Maple(350#

BQ(Maple(500(1#

BQ(Maple(500(2#

Award(Maple(700#

Nuchar(1000#

0.00#

0.01#

0.02#

0.03#

0.04#

(1.50# (1.25# (1.00# (0.75# (0.50# (0.25# 0.00#

Coniferous'so9wood'Airex(Res(427#

Pyr(Res(475#

I(RW(300(24#

I(RW(300(48#

0.00#

0.01#

0.02#

0.03#

0.04#

(1.50# (1.25# (1.00# (0.75# (0.50# (0.25# 0.00#

Sorp%on

'rate'(g''g

-1'h

-1)'

Tension'(m)'

Non-coniferous'so9wood'BP(Willow(450(2013#

BP(Willow(450(2014#

BP(Willow(550#

Coco(1000#

0.00#

0.01#

0.02#

0.03#

0.04#

(1.50# (1.25# (1.00# (0.75# (0.50# (0.25# 0.00#Tension'(m)'

Non-woody'materials'I(Potato(300(24#

I(Cabbage(300(48#

I(Leek(300(48#

Wood(Ash(1500#

IRDA(Manure(500#

36

Table 15. Physical properties related to particle-size distribution and abrasion resistance of biochars

Biochar Before After abrasion MWD UI (D60/D10) UI (D95/D10) DMWD DUI

(D60/D10) µm CV -- CV -- CV µm CV --

Hardwood Leaf-Maple-350 1397 9 6.34 10 19.22 18 -280 46 25.7 BQ-Maple-500-1 6107 0.6 1.60 0.5 2.33 0.1 -655 24 7.46 BQ-Maple-500-2 287 5 2.20 14 2.95 15 -14.8 180 2.32 BQ-Maple-500-3 2191 3 2.06 0.7 3.37 4 NA NA NA Award-Maple-700 1242 12 6.42 10 21.93 9 -93.7 190 23.6 B-Eu-300 138 5 8.30 71 22.93 60 NA NA NA Nuchar-1000 171 14 1.89 9 2.86 27 -3.50 645 3.47

Coniferous softwood BP-Res-400 189 2 2.74 3 5.39 4 NA NA NA BP-Res-500 204 3 2.20 14 3.18 16 NA NA NA Airex-Res-427 961 7 3.91 5 19.66 6 -62.0 332 19.2 Airex-Res-454 884 5 4.09 3 10.42 8 NA NA NA Pyr-Res-475 1302 5 5.45 2 21.27 3 -96.8 144 24.8 Pyr-Res-475-aged 1543 4 6.93 5 22.47 3 NA NA NA Airex-RW-315 901 2 4.82 1 10.66 0.9 NA NA NA Airex-RW-426 1210 4 14.91 2 47.44 8 NA NA NA I-RW-300-24 1837 7 4.98 8 11.13 13 -71.7 6 13.2 I-RW-300-48 1814 4 5.47 70 12.13 7 -150 18 17.2 I-RW-300-48-2nd 1592 2 4.88 6 11.75 8 NA NA NA

Non-coniferous softwood BP-Willow-400 194 2 2.23 8 3.03 9 NA NA NA BP-Willow-450-2013 192 0.5 1.71 0.8 2.20 1 NA 16 2.10 BP-Willow-450-2014 202 3 1.75 8 2.53 9 NA 112 2.31 BP-Willow-500 194 1 2.06 3 2.74 4 NA NA NA BP-Willow-550 202 2 1.72 0.7 2.22 0.9 -3.83 126 2.10 BP-Birch-400 226 7 2.69 5 6.10 10 NA NA NA BP-Birch-500 236 3 1.78 0.8 3.67 2. NA NA NA Coco-1000 197 0.2 1.65 0.2 2.11 0.3 NA 398 2.10

Non-woody materials BP-Phragmite-400 198 5 2.27 10 3.12 13 NA NA NA BP-Phragmite-500 203 3 1.80 9 2.34 10 NA NA NA I-Potato-300-24 6017 2 49.42 6 58.95 6 -1062 5 109.6 I-Cabbage-300-48 2102 4 3.63 0.7 9.26 2 -402 12 15.5 I-Leek-300-48 2594 16 3.62 7 9.38 12 -853 36 21.8 B-Corn-300 253 1 2.47 8 6.70 8 NA NA NA

Others Wood-Ash-1500 1214 0.4 12.33 30 88.39 31 -60.7 23 68.3 IRDA-Manure-500 1014 30 3.64 10 18.94 36 -123 24 24.3


37

Figure 3. Cumulative particle-size distribution of biochars

0"

20"

40"

60"

80"

100"

1" 10" 100" 1000" 10000"

Par$cles)fine

r)than

)(%))

Hardwood)Leaf,Maple,350"

BQ,Maple,500,1"

BQ,Maple,500,2"

BQ,Maple,500,3"

Award,Maple,700"

B,Eu,300"

Nuchar,1000"

0"

20"

40"

60"

80"

100"

1" 10" 100" 1000" 10000"

Coniferous)so9wood)BP,Res,400"BP,Res,500"Airex,Res,427"Airex,Res,454"Pyr,Res,475"Pyr,Res,475,aged"Airex,RW,315"Airex,RW,426"I,RW,300,24"I,RW,300,48"I,RW,300,48,2nd"

0"

20"

40"

60"

80"

100"

1" 10" 100" 1000" 10000"

Par$cles)fine

r)than

)(%))

Particle size (µm)

Non;coniferous)so9wood)

BP,Willow,400"BP,Willow,450,2013"BP,Willow,450,2014"BP,Willow,500"BP,Willow,550"BP,Birch,400"BP,Birch,500"Coco,1000"

0"

20"

40"

60"

80"

100"

1" 10" 100" 1000" 10000"Par$le)size)(µm))

Non;woody)materials)

BP,Phragmite,400"BP,Phragmite,500"I,Potato,300,24"I,Cabbage,300,48"I,Leek,300,48"B,Corn,300"

38

4.3. Chemical properties

The pH values of the biochars ranged from 4.8 for Nuchar-1000 to 10.4 for Wood-Ash-1500, i.e., from relatively acid to very strongly basic (Table 16). However, neither of these biochars was typical, the first being activated and the second containing much ash. The latter one is used as a liming agent. The hardwood biochars tended to be rather basic, with pH values between 7.5 and 8.5, while those made of softwood tended to be a bit more neutral or even slightly acid. The biochars made of non-coniferous wood and other soft materials also tended to be basic, with pH values above 7.5, especially those made of vegetable residues, which had pH values above 9.

The biochars with the highest buffer capacity (PTpH4) were Wood-Ash-1500, BQ-Maple-500-2,

and BP-Res-500, followed by I-Cabbage-300-48, which had a large CV. Essentially, the same biochars also had the highest PTpH7 values. Despite the frequent claim that biochars have excellent buffer capacity, some of the biochars we examined, such as Airex-Res-454, Airex-Res-427, and Nuchar-1000, did not. In fact, although the pH of most of the biochars was basic, most had little buffer capacity and would quickly change their pH in contact with more acidic substances such as peat or decaying organic matter.

As nitrogen (N) is generally volatilized during pyrolysis, most biochars have very low N

concentrations and thus cannot be regarded as nitrogen fertilizer. However, those made from vegetables (I-Potato-300-24, I-Cabbage-300-48, I-Leek-300-48) were composed 2 to 5.7% of N (Table 17), while the pig manure biochar (IRDA-Manure-500) contained about 4.5%. The large particle size of the feedstock and low temperature during pyrolysis of the vegetable residues promote greater nitrogen retention. By contrast, several of the biochars contained a significant amount of total P. The IRDA-Manure-500 biochar had the highest P content, which was unsurprising as Quebec hog manure contains a lot of P. Nuchar-1000 followed closely with 18 682 mg kg-1, while the Coco-1000 and I-RW-300-48 contained very little. Some biochars can therefore be used as a P amendment for plants, while others may be preferred when redistribution of P in the environment must be avoided. Sulphur content (S) was low in almost all biochars, but may be high enough to serve as a micronutrient for plants. I-RW-300-48 contained slightly more S, at 5.8%. The N and S contents of the biochars in this study were therefore insufficient to cause detrimental effects on plants or the environment.

The exchangeable micro- and macro- nutrient contents of the biochars are given in Table 18.

The contents greatly varied from one biochar to another, but in general the biochars contained all or most nutrients without exceeding most standards, and thus could be considered suitable as soil amendments in respect to the environment. The biochars made of vegetable residues had the highest potassium content (K), while biochars made of recycled wood (Airex-RW-315 and Airex-RW-426) had the lowest levels. The Ca content also greatly varied between biochars, with those made of recycled wood tending to contain slightly more. There was no obvious trend in Mg content among biochar types. The biochars made of recycled wood, Wood-Ash-1500, and IRDA-Manure-500 contained comparatively high levels of sodium (Na), while Nuchar-1000 and I-Cabbage-300-48 stood out for their very high Na content, which could cause problems when applied in high concentrations, as in potting soils. However, Na is easily soluble and does not remain in the biochar if large amounts of water are applied, as in greenhouse and nursery potting soils. The sum of exchangeable elements varied from 6.43 cmol + kg-1 for Airex-Res-427 to more than 120 cmol + kg-1 for biochars made of vegetable residues, which offers an interesting range for plant growth and environmental applications.

The total content in heavy metal and other elements (Table 19) varied as much as that of soluble

and exchangeable elements. Mercury (Hg) was not detected in any biochar and thus is not listed in

39

Tables 20 and 21. Only 6 biochars contained arsenic (As). Airex-RW-315 contained the highest proportion because it was made of recycled wood and thus probably contained As associated with old paint or wood treatments. Cadmium (Cd) was detected in 10 of 34 biochars, but in small quantities. Cobalt (Co) was present in the majority of biochars in relatively small amounts. Only BP-Phragmite-400 and IRDA-Slurry-500 contained more than 15 mg kg-1. Chromium (Cr) was detected in nearly all biochars. BP-Willow-450-2013 contained the most, followed by Airex-BR-277. The others contained little. Cupper (Cu) was detected throughout the samples. The biochar made from pig manure contained as much as 556 mg kg-1 (pigs receive both Cu and zinc (Zn) in their diet, and more than 99% is excreted in their feces). Molybdenum (Mo) was found in only 3 biochars, and in small quantities. By contrast, only 4 biochars did not contain nickel (Ni). The biochar made from phragmites and the BP-Willow-450-2013 contained the most. More than half of the biochars had no lead (Pb). Among those that did contain Pb, all of the biochars made from recycled wood (Airex-RW-315 and -426 and I-RW-300-24 and -300-48) contained more than 45 mg kg-1, probably because of old paint and other wood treatments. Only 8 biochars showed a detectable selenium (Se) content. Airex-RW-426 contained the highest level, followed by BP-Phragmite-500. Zn was found in all biochars. Those made of willow tended to contain significantly more than the others, as did the biochar made of pig manure. The biochars made from non-woody materials or coniferous softwood contained only a little Zn.

Data on PAH contents were available for only six of the biochars at the time this report was

written (Table 22). Among those biochars, only BP-Willow-450 exceeded the level permitted by regulations and thus cannot be used for applications in the field. Three others, BQ-Maple-500-1, Wood-Ash-1500, and I-Leek-300-48, would receive the ‘B’ classification according to the MDDELCC criterion (1998).

The chemical properties of the biochars will be compared and classified with respect to Quebec

regulations and the IBI and EBC criteria in a future paper. The implications for plant growth of the macro- and micronutrient contents of the biochars will be discussed in another paper.

40

Table 16. Chemical properties of biochars related to acidity

Biochar pHH2O PTpH4 PTpH7 --- CV Meq

HCl CV Meq

HCl CV

Hardwood Leaf-Maple-350 8.58 0.88 0.59 13.06 0.03 0.01 BQ-Maple-500-1 7.56 0.67 0.21 4.42 0.01 0.01 BQ-Maple-500-2 8.89 0.58 1.57 3.01 0.10 20.41 BQ-Maple-500-3 7.78 0.61 0.26 2.41 0.05 4.42 Award-Maple-700 8.39 7.38 0.95 8.59 0.05 0.01 B-Eu-300 8.08 0.66 0.19 7.64 0.04 6.15 Nuchar-1000 4.80 0.49 0.06 6.80 ND NA

Coniferous softwood BP-Res-400 8.56 0.06 0.27 0.88 0.08 3.01 BP-Res-500 9.75 0.10 1.54 0.76 0.74 1.59 Airex-Res-427 5.50 0.45 0.02 20.41 NA NA Airex-Res-454 7.21 0.43 0.06 8.08 0.01 0.01 Pyr-Res-475 5.97 1.81 0.21 17.82 ND NA Pyr-Res-475-aged 6.37 2.07 0.27 5.24 ND NA Airex-RW-315 6.86 0.07 0.26 1.84 ND NA Airex-RW-426 7.71 0.12 0.60 0.00 0.08 0.01 I-RW-300-24 6.09 0.67 0.19 1.61 ND NA I-RW-300-48 5.64 1.06 0.13 31.70 ND NA I-RW-300-48-2nd 6.11 1.23 0.29 12.56 ND NA

Non-coniferous softwood BP-Willow-400 8.10 0.17 0.32 0.00 0.07 0.01 BP-Willow-450-2013 NA NA NA NA NA NA BP-Willow-450-2014 9.56 1.13 0.63 3.72 0.12 9.39 BP-Willow -500 8.99 1.20 0.96 1.77 0.34 5.31 BP-Willow -550 NA NA NA NA NA NA BP-Birch-400 7.64 0.31 0.12 2.02 0.01 0.01 BP-Birch-500 8.78 2.15 1.03 2.28 0.31 5.69 Coco-1000 8.91 0.06 0.22 7.78 0.06 4.16

Non-woody material BP-Phragmite-400 7.55 0.06 0.21 1.14 0.04 0.01 BP-Phragmite-500 7.72 0.42 0.15 4.88 0.03 4.04 I-Potato-300-24 9.29 0.18 0.78 6.02 0.20 0.01 I-Cabbage-300-48 9.94 2.31 1.38 9.09 0.37 4.11 I-Leek-300-48 9.45 0.05 1.05 0.00 0.24 4.88 B-Corn-300 7.69 0.40 0.64 0.37 0.10 2.28

Others Wood-Ash-1500 10.42 0.90 2.20 6.43 0.23 36.42 IRDA-Manure-500 9.69 0.51 1.17 17.61 0.11 10.88 CV = coefficient of variation (%). Nd: Not Determined a siniitla pH > 7. Na: Not Available

41

Table 17. Biochar contents in N, P, and S

Biochar Ntotal Ptotal Stotal % CV mg kg-1 CV %

Hardwood Leaf-Maple-350 0.63 3.50 1043 0.7 3.35 BQ-Maple-500-1 0.55 0.35 550 5.0 0.00 BQ-Maple-500-2 0.57 3.16 1453 3.2 3.64 BQ-Maple-500-3 0.77 1.75 NA NA 0.00 Award-Maple-700 0.58 5.57 806 22.3 1.51 B-Eu-300 0.47 2.56 1659 3.0 0.00 Nuchar-1000 0.33 1.30 18682 6.2 3.58

Coniferous softwood BP-Res-400 1.23 2.14 1110 27.4 0.00 BP-Res-500 1.28 2.11 NA NA 0.00 Airex-Res-427 0.31 1.88 221 45.3 3.90 Airex-Res-454 0.21 0.84 NA NA 0.00 Pyr-Res-475 0.48 1.76 755 24.3 3.73 Pyr-Res-475-aged 0.49 5.28 NA NA 0.00 Airex-RW-315 0.47 2.66 NA NA 0.00 Airex-RW-426 0.46 0.60 NA NA 0.00 I-RW-300-24 0.71 1.11 241 NA 3.99 I-RW-300-48 0.93 0.22 72 63.4 5.83 I-RW-300-48-2nd 0.89 0.86 NA 36.6 0.00

Non-coniferous softwood BP-Willow-400 1.00 2.17 756 8.0 0.00 BP-Willow-450-2013 1.08 1.21 1699 65.8 3.14 BP-Willow-450-2014 0.95 9.45 1033 9.2 2.88 BP-Willow-500 1.06 1.09 NA NA NA BP-Willow-550 1.16 1.45 1620 11.7 3.28 BP-Birch-400 0.94 3.30 1415 4.0 0.00 BP-Birch-500 0.98 1.18 NA NA NA Coco-1000 0.27 0.00 169 4.3 2.56

Non-woody materials BP-Phragmite-400 1.19 2.26 1383 7.7 0.00 BP-Phragmite-500 1.15 5.28 NA NA NA I-Potato-300-24 2.92 3.43 10544 5.1 3.54 I-Cabbage-300-48 3.73 2.14 9348 7.1 5.72 I-Leek-300-48 5.71 0.24 7029 0.3 1.41 B-Corn-300 0.88 2.14 1780 2.0 0.00

Others Wood-Ash-1500 0.32 45.3 2676 14.5 2.69 IRDA-Manure-500 4.49 0.07 22796 2.9 3.91

NA = Not available.

42

Table 18. Biochar contents in exchangeable macro- and micronutrients (related to plants)

Biochar K Ca Mg Na Total cmol+

kg-1 CV cmol+

kg-1 CV cmol+

kg-1 CV cmol+

kg-1 CV cmol+

kg-1

Hardwood Leaf-Maple-350 7.30 7.84 9.04 5.98 2.17 7.79 2.10 5.69 20.61 BQ-Maple-500-1 2.75 19.83 4.63 50.35 0.45 15.33 0.44 10.14 8.27 BQ-Maple-500-2 18.42 0.66 23.35 0.69 11.14 0.75 2.15 2.31 55.06 BQ-Maple-500-3 6.27 5.68 11.08 3.38 1.30 4.08 0.16 6.54 18.81 Award-Maple-700 8.10 4.07 13.90 9.41 2.23 8.32 2.04 2.18 26.27 B-Eu-300 7.54 32.77 14.73 16.16 1.02 34.45 0.96 31.26 24.24 Nuchar-1000 0.40 3.46 1.44 1.30 0.18 0.65 33.52 28.81 35.54

Coniferous softwood BP-Res-400 15.27 1.60 9.91 1.97 1.48 2.45 0.79 2.98 27.46 BP-Res-500 13.36 21.54 8.93 15.08 1.25 16.97 0.71 18.14 24.25 Airex-Res-427 4.59 1.19 1.31 4.04 0.03 15.81 0.50 7.68 6.43 Airex-Res-454 3.56 4.60 3.45 7.48 0.64 7.89 0.20 4.07 7.85 Pyr-Res-475 10.93 95.70 63.47 92.27 6.62 97.40 1.62 7.35 82.63 Pyr-Res-475-aged 10.27 14.67 47.16 3.81 4.12 2.28 0.57 2.15 62.12 Airex-RW-315 2.84 0.47 21.21 6.04 1.57 2.31 2.33 2.11 27.96 Airex-RW-426 3.45 9.26 19.89 10.76 0.82 9.19 2.93 10.29 27.09 I-RW-300-24 2.87 1.58 25.56 2.47 0.94 5.90 4.86 2.80 34.22 I-RW-300-48 3.98 7.51 23.53 38.05 1.01 25.25 5.43 7.33 33.96 I-RW-300-48-2nd 2.41 3.15 15.43 5.79 0.53 3.19 3.43 2.46 21.79

Non-coniferous softwood BP-Willow-400 10.85 4.24 17.17 1.93 1.22 2.37 0.52 4.23 29.76 BP-Willow-450-2013 31.99 9.72 17.44 7.42 2.61 9.95 4.33 2.06 56.36 BP-Willow-450-2014 24.39 2.63 10.76 0.31 1.28 2.06 0.49 1.72 36.92 BP-Willow-500 27.31 1.06 21.37 3.60 1.66 3.03 0.52 3.02 50.86 BP-Willow-550 28.48 8.62 6.07 10.08 1.15 12.02 3.50 5.46 39.20 BP-Birch-400 4.80 2.32 8.93 1.08 0.96 0.56 0.26 4.12 14.95 BP-Birch-500 16.49 2.89 17.88 1.53 1.19 1.71 0.56 2.87 36.13 Coco-1000 7.84 0.48 2.18 2.36 1.14 1.46 0.90 0.33 12.05

Non-woody materials BP-Phragmite-400 10.83 3.41 13.54 0.93 0.99 1.99 1.36 2.17 26.72 BP-Phragmite-500 12.00 1.42 5.98 0.86 0.62 0.69 1.52 1.12 20.11 I-Potato-300-24 117.38 2.57 0.39 1.35 1.71 1.33 0.43 1.53 119.90 I-Cabbage-300-48 138.51 1.14 21.47 0.97 6.17 3.04 18.63 1.46 184.77 I-Leek-300-48 137.41 1.10 14.40 4.08 6.96 3.34 1.22 1.30 159.98 B-Corn-300 26.47 6.79 0.81 2.29 0.78 4.75 0.50 6.50 28.55

Others Wood-Ash-1500 28.40 10.59 62.83 4.05 2.24 9.46 4.60 7.71 98.07 IRDA-Manure-500 30.87 7.09 8.16 7.14 4.72 11.99 6.49 8.94 50.24


43

Table 19. Biochar contents in soluble macro- and micronutrients (related to transport of contaminants and plants)

Biochar K Ca Mg Na Mn Fe Al Cu Zn mg kg-1 CV mg kg-1 CV mg kg-1 CV mg kg-1 CV mg kg-1 CV mg kg-1 CV mg kg-1 CV mg kg-1 CV mg kg-1 CV X 103 X 102 X 102 X 102

Hardwood Leaf-Maple-350 2.1 14 3.0 6.4 0.69 13 0.34 9.3 1.2 14 2.7 24 6.4 21 0.24 58 0.08 45 BQ-Maple-500-1 1.6 43 5.2 90 1.5 104 0.11 78 6.8 63 0.89 41 5.6 7.9 0.16 14 0.03 43 BQ-Maple-500-2 4.3 2.0 9.6 1.5 5.2 1.8 0.32 1.6 5.6 6.0 0.22 26 6.6 2.4 0.14 30 0.05 15 BQ-Maple-500-3 2.0 2.1 7.4 2.5 1.6 0.8 0.28 15 29 1.9 0.60 11 0.5 14 0.25 14 0.09 19 Award-Maple-700 1.9 3.6 3.8 12 0.07 7.6 0.26 1.4 0.2 12 0.94 12 14 5.8 0.13 39 0.01 62 B-Eu-300 0.9 2.0 4.0 4.5 1.9 1.6 1.8 1.0 12 7.7 2.7 29 1.4 11 0.34 22 0.07 29 Nuchar-1000 0.04 8.9 1.6 68 NA NA 55 1.5 0.1 55 41 1.0 27 0.92 0.34 41 0.31 21

Coniferous softwood BP-Res-400 2.6 1.9 3.0 2.3 1.5 1.3 1.4 1.3 0.9 2.9 1.1 5.3 0.7 24 0.20 76 0.06 0.00 BP-Res-500 5.2 0.4 2.3 4.8 0.7 5.5 1.4 1.4 0.3 57 0.62 2.1 4.3 7.3 0.10 18 0.07 11 Airex-Res-427 0.2 1.1 0.09 52 0.02 64 0.04 9.6 0.3 14.0 1.9 2.5 1.8 3.4 0.25 44 0.13 29 Airex-Res-454 0.4 0.6 1.8 1.8 0.42 1.1 0.23 7.9 3.2 29 0.48 34 0.29 35.4 0.11 17 0.05 44 Pyr-Res-475 0.9 128 1.9 128 0.33 125 0.1 51 3.8 108 1.7 17 6.2 13.2 0.11 17 0.03 55 Pyr-Res-475-aged 0.6 2.9 2.4 2.4 0.47 2.9 0.7 9.9 4.4 43 1.8 33 0.43 24.9 0.26 30 0.15 32 Airex-RW-315 0.7 5.1 33 1.1 1.3 3.2 71 3.0 7.5 5.1 1.2 8.4 0.93 20 0.62 60 0.10 17 Airex-RW-426 0.8 0.9 24 5.0 1.8 4.4 59 1.2 21 2.1 3.7 6.2 2.1 6.1 0.68 16 0.55 6 I-RW-300-24 0.1 1.1 74 7.0 1.2 4.9 38 1.4 11 4.9 0.43 2.4 0.19 13 0.76 13 1.46 8 I-RW-300-48 0.4 11 46 25 1.4 4.3 16 8.0 17 17 14 12 11 31 0.57 34 2.75 39 I-RW-300-48-2nd 0.08 49 3.0 18 0.54 1.1 2.3 95 8.6 35 0.54 137 0.69 119 0.84 51 0.83 78

Non-coniferous softwood BP-Willow-400 2.3 1.4 1.1 1.3 1.7 1.9 1.1 0.7 2.9 11 1.0 8.2 0.31 40 0.39 28 0.21 14 BP-Willow-450-2013 3.4 13 3.8 6.6 0.61 9.7 0.35 14 0.2 95 0.67 6.0 2.6 1.2 0.14 5.18 0.03 12 BP-Willow-450-2014 4.4 2.6 3.1 1.1 1.2 3.8 0.85 2.6 0.4 17 0.41 9.0 8.7 29 0.17 19 0.19 13 BP-Willow-500 3.7 0.3 8.4 1.5 1.4 1.4 0.66 3.9 0.6 6.2 0.64 5.2 0.20 28 0.30 74 0.13 4.23 BP-Willow-550 5.6 1.5 0.6 3.9 0.42 2.3 0.47 0.4 0.04 17 0.26 19 5.9 2.5 0.15 19 0.04 11 BP-Birch-400 1.2 9.7 0.5 7.6 1.2 9.3 0.58 8.0 2.0 10 0.72 7.0 0.16 7.0 0.32 31 0.18 19 BP-Birch-500 3.3 3.4 0.6 5.8 1.0 7.9 0.99 8.7 0.2 12 0.45 15 0.20 13 0.23 47 0.31 18 Coco-1000 1.8 0.7 0.1 14 0.02 7.5 1.9 1.0 NA NA 0.20 2.9 0.19 4.0 0.11 8 0.18 37

Non-woody materials BP-Phragmite-400 1.4 0.3 5.0 1.3 1.1 0.7 2.0 2.0 4.0 1.7 0.71 18 0.15 36 0.20 63 0.07 28 BP-Phragmite-500 1.7 2.0 3.0 2.7 0.57 0.9 2.3 2.4 6.7 1.9 1.1 9 0.06 127 0.29 72 0.18 37 I-Potato-300-24 20 2.0 0.03 10 0.45 2.5 0.37 3.3 0.4 10 7.1 15 15 1.5 4.18 2 1.23 19 I-Cabbage-300-48 42 1.3 5.2 6.4 1.6 8.1 35 0.6 0.3 113 9.4 5.4 60 6.1 1.08 17 0.61 5 I-Leek-300-48 38 3.1 2.7 3.6 1.3 2.4 2.1 2.0 1.3 4.0 29 3.5 60 1.6 1.51 19 1.64 7 B-Corn-300 5.5 2.1 0.2 47 0.32 11 0.94 0.8 0.6 35 7.8 6.1 5.0 13 0.60 27 0.52 12

Others Wood-Ash-1500 5.5 13 3.5 9.2 0.12 30 8.8 0.02 1.7 28 5.6 25 252 3.6 0.48 24 0.45 17 IRDA-Manure-500 9.8 4.7 0.06 0.44 5.7 1.1 18 6.7 1.1 31 4.0 6.2 0.08 80 1.18 29 0.51 6 CV = coefficient of variation (%). NA: Not Available

44

Table 20. Biochar total contents in other elements (related to the environment) (Part 1)

Biochar As Cd Co Cr Cu mg kg-1 CV mg kg-1 CV mg kg-1 CV mg kg-1 CV mg kg-1 CV

Hardwood Leaf-Maple-350 ND 0 5.33 9 ND 0 3.42 29 19.7 13 BQ-Maple-500-1 ND 0 0.67 141 ND 0 5.21 50 10.3 40 BQ-Maple-500-2 ND 0 2.99 1 1.33 71 3.48 18 21.7 8 BQ-Maple-500-3 ND 0 ND 0 0.26 141 0.65 0 6.1 20 Award-Maple-700 ND 0 5.33 18 0.67 141 3.48 7 21.3 19 B-Eu-300 ND 0 ND 0 3.52 5 1.19 4 9.5 7 Nuchar-1000 ND 0 ND 0 ND 0 3.36 5 4.2 29

Coniferous softwood BP-Res-400 ND 0 ND 0 3.35 14 6.35 27 17.0 5 BP-Res-500 ND 0 ND 0 ND 0 6.21 6 13.5 6 Airex-Res-427 ND 0 ND 0 ND 0 3.72 39 12.7 10 Airex-Res-454 ND 0 ND 0 ND 0 0.00 0 3.4 20 Pyr-Res-475 ND 0 ND 0 ND 0 6.39 16 15.3 11 Pyr-Res-475-aged ND 0 ND 0 ND 0 ND 0 9.4 30 Airex-RW-315 2.5 141 ND 0 1.70 54 3.81 46 10.5 13 Airex-RW-426 72.1 84 ND 0 2.69 17 22.6 61 54.9 49 I-RW-300-24 60.8 9 0.16 141 5.53 34 14.5 13 70.7 29 I-RW-300-48 40.6 40 ND 0 1.66 39 4.89 71 24.1 46 I-RW-300-48-2nd 27.0 84 ND 0 ND 0 1.30 62 41.3 111

Non-coniferous softwood BP-Willow-400 18.9 21 1.17 3 7.08 6 17.7 14 86.4 1 BP-Willow-450-2013 ND 0 3.24 17 2.33 20 33.0 49 72.0 12

BP-Willow-450-2014

ND 0 0.43 4 4.34 4 6.91 18 27.8 2

BP-Willow-500 ND 0 ND 0 ND 0 5.88 16 20.0 3 BP-Willow-550 ND 0 1.78 32 1.00 141 23.1 28 74.7 25 BP-Birch-400 ND 0 ND 0 1.70 4 4.10 8 11.1 1 BP-Birch-500 ND 0 ND 0 0.26 141 5.14 5 26.8 24 Coco-1000 ND 0 ND 0 0.82 19 1.50 1 15.0 6

Non-woody materials BP-Phragmite-400 ND 0 ND 0 12.99 6 20.8 7 27.7 7 BP-Phragmite-500 ND 0 ND 0 1.61 5 22.3 6 23.5 11 I-Potato-300-24 ND 0 ND 0 ND 0 ND 0 29.8 25 I-Cabbage-300-48 ND 0 ND 0 1.33 7 ND 0 6.0 6 I-Leek-300-48 ND 0 ND 0 1.07 11 0.42 9 12.9 6 B-Corn-300 ND 0 ND 0 1.38 8 0.22 6 6.1 5

Others Wood-Ash-1500 ND 0 0.40 35 9.84 7 3.57 11 57.8 26 IRDA-Manure-500 ND 0 ND 0 15.89 1 1.37 12 556 2

Hg was not detected. CV = coefficient of variation (%). ND = Not detected (< limit of detection)

45

Table 21. Biochar content in other elements (related to the environment) (Part 2)

CV = coefficient of variation (%). ND= not detected (< Limit of detection).

Biochar Mo Ni Pb Se Zn mg kg-1 CV mg kg-1 CV mg kg-1 CV mg kg-1 CV mg kg-1 CV Hardwood Leaf-Maple-350 ND 0 7.00 12 1.97 141 ND 0 289 0 BQ-Maple-500-1 ND 0 4.67 36 1.56 141 ND 0 29.3 15 BQ-Maple-500-2 ND 0 9.33 22 4.90 141 ND 0 185 6 BQ-Maple-500-3 ND 0 2.66 24 ND 0 16.0 23 26.5 29 Award-Maple-700 ND 0 6.33 7 7.12 50 ND 0 301 21 B-Eu-300 ND 0 0.00 0 ND 0 ND 0 18.0 8 Nuchar-1000 2.74 9 2.67 29 ND 0 ND 0 ND 0 Coniferous softwood BP-Res-400 ND 0 34.9 12 ND 0 ND 0 54.2 2 BP-Res-500 ND 0 23.0 5 ND 0 14.0 5 73.9 4 Airex-Res-427 ND 0 4.67 20 ND 0 ND 0 27.0 18 Airex-Res-454 ND 0 1.51 141 ND 0 ND 0 13.1 11 Pyr-Res-475 ND 0 8.33 34 4.37 71 ND 0 195 12 Pyr-Res-475-aged ND 0 4.50 35 ND 0 19.9 27 63.3 31 Airex-RW-315 ND 0 6.70 38 66.6 35 9.1 10 40.0 45 Airex-RW-426 ND 0 23.6 12 184 13 27.5 45 130 15 I-RW-300-24 ND 0 22.4 123 180 82 ND 0 149 96 I-RW-300-48 ND 0 2.03 34 51.0 76 ND 0 151 116 I-RW-300-48-2nd ND 0 1.96 40 45.1 40 ND 0 20.4 10 Non-coniferous softwood BP-Willow-400 ND 0 40.2 7 207 2 ND 0 290 1 BP-Willow-450-2013 ND 0 63.3 3 1.71 141 ND 0 379 10 BP-Willow-450-2014 ND 0 38.7 3 ND 0 ND 0 151 4 BP-Willow-500 ND 0 22.0 3 1.54 141 11.5 2 136 5 BP-Willow-550 ND 0 43.0 17 ND 0 ND 0 455 8 BP-Birch-400 ND 0 12.5 4 ND 0 ND 0 55.3 5 BP-Birch-500 ND 0 35.1 3 ND 0 13.0 2 87.5 7 Coco-1000 ND 0 4.39 5 ND 0 ND 0 ND 0 Non-woody materials BP-Phragmite-400 1.19 12 51.6 2 4.58 4 ND 0 42.2 14 BP-Phragmite-500 ND 0 67.8 1 5.75 8 25.7 4 93.2 2 I-Potato-300-24 ND 0 1.95 48 15.4 4 ND 0 30.7 5 I-Cabbage-300-48 ND 0 1.90 10 ND 0 ND 0 6.6 21 I-Leek-300-48 ND 0 0.42 141 ND 0 ND 0 47.7 5 B-Corn-300 ND 0 ND 0 ND 0 ND 0 139 4 Others Wood-Ash-1500 ND 0 ND 0 6.68 14 ND 0 81.9 23 IRDA-Manure-500 3.28 2 ND 0 ND 0 ND 0 326 5

46

Table 22. Biochar contents in PAH (related to the environment)

PAH Criteria Biochars

MD

DEL

CC

(A)

MD

DEL

CC

(B)

BQ

-Map

le-5

00-1

Pyr-

Res

-500

BP-

Will

ow-4

50-2

014

Nuc

har-

1000

Woo

d-A

sh-1

500

I-R

W-3

00-4

8

I-Po

ireau

-300

-48

Acenaphtene 0.1 10 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Acenaphtylene 0.1 10 <0.1 <0.1 <0.1 <0.1 0.5 <0.1 <0.1 Anthracene 0.1 10 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Benzo(a)anthracene 0.1 1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Benzo(a)pyrene 0.1 1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Benzo(e)pyrene --- --- <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Benzo(b+j+k)fluoranthene 0.1 1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Benzo(c)phenanthrene 0.1 1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Benzo(g,h,i)perylene 0.1 1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Chrysene 0.1 1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Dibenzo(a,h)anthracene 0.1 1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Dibenzo(a,i)pyrene 0.1 1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Dibenzo(a,h)pyrene 0.1 1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Dibenzo(a,l)pyrene 0.1 1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Dimethyl-7,12 benzo(a)anthracene 0.1 1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Fluoranthene 0.1 10 0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Fluorene 0.1 10 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Indeno(1,2,3-cd)pyrene 0.1 1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Methyl-3 cholanthrene 0.1 1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Naphtalene 0.1 5 1.5 <0.1 2.0 <0.1 3.5 <0.1 0.4 Phenanthrene 0.1 5 0.3 <0.1 0.2 <0.1 <0.1 <0.1 <0.1 Pyrene 0.1 10 0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Methyl-1 naphtalene 0.1 1 0.5 <0.1 0.7 <0.1 0.2 <0.1 0.1 Methyl-2 naphtalene 0.1 1 0.6 <0.1 1.0 <0.1 0.1 <0.1 <0.1 Dimethyl-1,3 naphtalene 0.1 1 0.3 <0.1 0.4 <0.1 <0.1 <0.1 <0.1 Trimethyl-2,3,5 naphtalene 0.1 1 0.2 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Yellow: Downgraded to B; Red: Downgraded to C

47

4.4. Biological properties

Only two biological properties were measured (Table 23, Figs. 4-7). Earthworms did not want to live in soil containing activated biochars (Nuchar-1000 and Coco-1000) regardless of concentration. Among all biochars, they preferred those made of non-woody materials, especially when the mixture contained only 10% biochar, which they preferred to garden soil alone (Fig. 4). When the soil contained 50% biochar, they preferred garden soil without biochar except in the case of hardwood biochars.

The lettuce germination tests had not all been completed by the time we wrote this report. Among those that were completed, germination was found to occur in all biochars. However, the speed and germination rate varied. In mixtures of soil containing 10% biochar, IRDA-Manure-500 and two of the biochars made of vegetables showed a slight delay in germination, but in all cases germination in the biochars was completed within 10 days. In mixtures of soil containing 50% biochar, the speed and rate of germination in biochars made from non-woody material was delayed, except in the case of the Wood-Ash-1500. Little difference was observed in the germination of lettuce in mixtures containing 50% of the other biochars, except for BQ-Maple-500.

These tests demonstrate that the biochars we examined are not toxic for earthworms (excepted activated ones) and lettuce, two sensitive species. The tests also show, however, that biochars can cause problems in extremely high concentrations, as in mixtures containing 50% biochar. Interpretation of these results will be completed later.

5. Conclusion and future work

The average, minima, and maxima values found for most properties are given in Tables 24 to 26.

The list of biochar analysis methods outlined in this report will be of value to all individuals and organizations interested in the potential uses of biochar. The wide variety of physico-chemical properties of the biochars found in Quebec, also documented here, will also be of great interest. This report also serves to identify the biochar companies in Quebec and to compare the properties of their biochars with those of some of the others found around the world. One can, from these data, assess how a single method of pyrolysis can produce different biochars with different materials (e.g., Airex biochars and BP biochars), how the same material makes very different biochars when subjected to different pyrolysis methods (e.g., all maple biochars, BP biochars made of willow), and the potential of unusual materials for pyrolysis (e.g., manure, phragmites).

Interpretation of these results, and classification of the biochars and their potential uses in agriculture and the environment, will be the subject of later papers by our team. Team members are also conducting specific studies of the leaching of elements from biochars and of the structure and carbon composition of biochars in relation to pyrolysis methods. The correlations between methods of pyrolysis and biochar properties are now the subject of statistical analysis. Finally, the effect of biochars on the growth of a variety of plants under a range of conditions (field, greenhouse, nursery, mines, buffer strips) is also under study by our team. Publications will follow. Several documents will become available in 2015, while others will be published in 2016.

48

Table 23. Percentage of earthworms that chose the mixture of garden soil with 10% biochar compared to soil alone, or with 50% biochar compared to soil alone, and germination rate of

lettuce after 3 and 6 days in the same mixtures (related to biological toxicity)

CV = coefficient of variation. NA: Not Available

Biochar Earthworm Lettuce 10% biochar 50% biochar 10% biochar 50% biochar % CV % CV 3 days 6 days 3 days 6 days

Hardwood Leaf-Maple-350 63.3 20 60.0 14 78.3 95.0 61.7 86.7 BQ-Maple-500-1 76.7 25 79.6 10 83.3 90.0 26.7 73.3 BQ-Maple-500-2 46.7 20 56.7 22 70.0 93.3 3.3 75.0 BQ-Maple-500-3 63.3 27 NA NA NA NA NA NA Award-Maple-700 50.0 43 56.3 24 68.3 88.3 66.7 93.3 B-Eu-300 56.7 8 NA NA NA NA NA NA Nuchar-1000 0.0 0 0.0 0 81.7 91.7 73.3 90.0

Coniferous softwood BP-Res-400 36.7 56 NA NA NA NA NA NA BP-Res-500 43.3 29 NA NA NA NA NA NA Airex-Res-427 40.0 20 33.3 28 73.3 88.3 85.0 93.3 Airex-Res-454 53.3 23 NA NA NA NA NA NA Pyr-Res-475 NA NA 33.3 14 80.0 91.7 51.7 93.3 Pyr-Res-475-aged 30.0 27 NA NA NA NA NA NA Airex-RW-315 70.0 12 NA NA NA NA NA NA Airex-RW-426 76.7 6 NA NA NA NA NA NA I-RW-300-24 56.7 8 40.0 NA 78.3 95.0 58.3 93.3 I-RW-300-48 26.7 47 26.7 0 85.0 90.0 51.7 93.3 I-RW-300-48-2nd 66.7 14 NA 18 NA NA NA NA

Non-coniferous softwood BP-Willow-400 40.0 0.0 NA NA NA NA NA NA BP-Willow-450-2013 NA NA NA NA NA NA NA NA BP-Willow-450-2014 33.3 51 60.0 0 83.3 95.0 70.0 91.7 BP-Willow-500 56.7 30 NA NA NA NA NA NA BP-Willow-550 NA NA NA NA NA NA NA NA BP-Birch-400 36.7 46 NA NA NA NA NA NA BP-Birch-500 66.7 26 NA NA NA NA NA NA Coco-1000 NA NA 0.0 0 86.7 93.3 33.3 90.0

Non-woody materials BP-Phragmite-400 30.0 0 NA NA NA NA NA NA BP-Phragmite-500 13.3 94 NA NA NA NA NA NA I-Potato-300-24 72.3 18 70.0 11.7 73.3 95.0 0.0 25.0 I-Cabbage-300-48 90.0 0 0.0 0 45.0 90.0 0.0 0.0 I-Leek-300-48 73.3 10 38.2 30 66.7 88.3 0.0 16.7 B-Corn-300 46.7 10 NA NA NA NA NA NA

Others Wood-Ash-1500 NA NA 3.3 141 88.3 98.3 48.3 88.3 IRDA-Manure-500 80.0 10 13.3 94 61.7 95.0 0.0 45.0

49

Figure 4. Preference of earthworms for garden soil alone (0% biochar) or a mixture of garden

soil with 10% v/v biochar

0"

20"

40"

60"

80"

100"

Leaf,Maple,350"

BQ,Maple,500,1"

BQ,Maple,500,2"

BQ,Maple,500,3"

Award,Maple,700"

B,Eu,300"

Nuchar,1000"

Distrib

u(on

+of+w

orms+(%)+

Hardwood+

10%+ 0%+

0"

20"

40"

60"

80"

100"

BP,Res,400"

BP,Res,500"

Airex,Res,427"

Airex,eés,454"

Pyr,Res,475,aged"

Airex,RW,315"

Airex,RW,426"

I,RW,300,24"

I,RW,300,48"

I,RW,300,48,2nd"

Coniferous+so9wood+

0"

20"

40"

60"

80"

100"

BP,Willow,400"

BP,Willow,450,2014"

BP,Willow,500"

BP,Birch,400"

BP,Birch,500"

Distrib

u(on

+of+w

orms+(%)+

Non;coniferous+so9wood+

0"

20"

40"

60"

80"

100"

BP,Phragmite,400"

BP,Phragmite,500"

I,Potato,300,24"

I,Cabbage,300,48"

I,Leek,300,48"

B,Corn,300"

IRDA,Manure,500"

Non;woody+materials+

50

Figure 5. Preference of earthworms for garden soil alone (0% biochar) or a mixture of garden

soil with 50% v/v biochar

0"

20"

40"

60"

80"

100"

Leaf,M

aple,35

0"

BQ,Ma

ple,500

,1"

BQ,Ma

ple,500

,2"

Award

,Maple,

700"

Nuchar

,1000"

Distrib

u(on

+of+w

orms+(%)+

Hardwood+

50%+ 0%+

0"

20"

40"

60"

80"

100"

Airex,R

es,427"

Pyr,Re

s,475"

I,RW,30

0,24"

I,RW,30

0,48"

Coniferous+so9wood+

0"

20"

40"

60"

80"

100"

BP,Willow

,450,2

014"

Coco,1

000"

Distrib

u(on

+of+w

orms+(%)+

Non;coniferous+so9wood+

0"

20"

40"

60"

80"

100"

I,Potato

,300,2

4"

I,Cabba

ge,300

,48"

I,Leek,3

00,48"

Wood,As

h,1500

"

IRDA,M

anure,5

00"

Non;woody+materials+

51

Figure 6. Germination rate of lettuce in garden soil amended with 10% biochar

0"

20"

40"

60"

80"

100"

0" 2" 4" 6" 8" 10"

Germ

ina(

on*(%

)*Hardwood*

Leaf,Maple,350"

BQ,Maple,500,1"

BQ,Maple,500,2"

Award,Maple,700"

Nuchar,1000"

0"

20"

40"

60"

80"

100"

0" 2" 4" 6" 8" 10"

Coniferous*so5wood*

Airex,Res,427"

Pyr,Res,475"

I,RW,300,24"

I,RW,300,48"

0"

20"

40"

60"

80"

100"

0" 2" 4" 6" 8" 10"

Germ

ina(

on*(%

)*

Time*(days)*

Non9coniferous*so5wood*

BP,Willow,450,2014"

Coco,1000"

0"

20"

40"

60"

80"

100"

0" 2" 4" 6" 8" 10"

Time*(days)*

Non9woody*materials*

I,Potato,300,24"

I,Cabbage,300,48"

I,Leek,300,48"

Wood,Ash,1500"

IRDA,Manure,500"

52

Figure 7. Germination rate of lettuce in garden soil amended with 50% biochar

0"

20"

40"

60"

80"

100"

0" 2" 4" 6" 8" 10"

Germ

ina(

on*(%

)*Hardwood*

Leaf,Maple,350"

BQ,Maple,500,1"

BQ,Maple,500,2"

Award,Maple,700"

Nuchar,1000"

0"

20"

40"

60"

80"

100"

0" 2" 4" 6" 8" 10"

Coniferous*so5wood*

Airex,Res,427"

Pyr,Res,475"

I,RW,300,24"

I,RW,300,48"

0"

20"

40"

60"

80"

100"

0" 2" 4" 6" 8" 10" 12"

Germ

ina(

on*(%

)*

Time*(days)*

Non9coniferous*so5wood*

BP,Willow,450,2014"

Coco,1000"

0"

20"

40"

60"

80"

100"

0" 2" 4" 6" 8" 10"

Time*(days)*

Non9woody*materials*

I,Potato,300,24"

I,Cabbage,300,48"

I,Leek,300,48"

Wood,Ash,1500"

IRDA,Manure,500"

53

Table 24. Summary of general and physical properties of biochars

Property Units Min Max Mean General properties

Ash % 1.11 54.9 13.1 Ctot % 23 91.5 63.3 Cgraph % 10.1 84.8 40.3 Cinorg % 0.4 9.2 2.1 Corg % 1.5 44.5 20.9 H % 0.1 5 2.8 O % 3.2 33.1 16.2 H/Corg --- 0.02 1.7 0.2 O/Ctot --- 0.04 0.76 0.28

Physical properties BD m3 m-3 0.13 0.46 0.3 SD m3 m-3 1.25 2.74 1.6 TP m3 m-3 0.72 0.9 0.81 EC dS m-1 0.1 4.81 0.94 WC % (mass) 0 9.3 2.4 CRm g g-1 h-1 -0.0224 -0.0004 -0.0051 CRb g g-1 h-1 0.003 0.127 0.03 CR1.4 % (mass) 5.7 130 30.8 CR-0.05 % (mass) 12.3 419 100 RH90 % (mass) 5.24 102 10.7 MWD µm 138 6106 1153 UI (D95/D10) -- 2.1 109.6 21.4 DMWD µm -1062 5.62 -218

54

Table 25. Summary of chemical properties of biochars

Property Units Min Max Mean Properties relative to acidity

pHH2O --- 4.8 10.4 7.79 PTpH4 meq 0.02 2.2 0.58 PTpH7 meq 0.01 0.74 0.14

Basic elements NTotal % 0.2 5.1 1.2 Ptotal mg kg-1 4.58 207 42.5 Stotal % 0 5.8 3.3

Exchangeable nutrients K cmol+ kg-1 0.4 138 22.9 Ca cmol+ kg-1 0.39 63.5 16.1 Mg cmol+ kg-1 0.03 11.1 2.14 Na cmol+ kg-1 0.16 33.5 3.25 Echg. tot cmol+ kg-1 6.43 185 44.4

Soluble nutrients K mg kg-1 34 42 508 51 112 Ca mg kg-1 2.95 9938 926 Mg mg kg-1 1.16 579 119 Na mg kg-1 3.3 5 589 508 Mn mg kg-1 0.03 31 4.7 Fe mg kg-1 0.16 41.6 4.26 Al mg kg-1 ND 264 14.7 Cu mg kg-1 0.04 4.25 0.51 Zn mg kg-1 0.006 5.76 0.40

Other elements As mg kg-1 ND 72.1 6.53 Cd mg kg-1 ND 5.33 0.63 Co mg kg-1 ND 15.9 2.42 Cr mg kg-1 ND 33 6.96 Cu mg kg-1 3.42 556 41.7 Mo mg kg-1 ND 3.28 0.21 Ni mg kg-1 ND 67.8 16.2 Pb mg kg-1 ND 207 23.2 Se mg kg-1 ND 27.5 4.02 Zn mg kg-1 ND 455 120

ND: Not Detected (< Limit of detection)

55

Table 26. Summary of biological properties of biochars

Percentage biochar

Time (days) Min Max Mean

Earthworms 10% 10 0.0 90 51.6 50% 10 0.0 79 36

Lettuce 10% 3 45 88 75 6 88 98 92 50% 3 0.0 85 39 6 0.0 9 72

N.B. The values do not add up, they are only min, max and mean of all observations.

56

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