Biochar: climate saving soils - Biochar Testing Protocol

Version 1.0, October 2013

1. Introduction

This document provides a set of test criteria for biochar materials and products. It includes analysis of biochar itself with respect to safety and

possible toxicants (section 2) as well as measurement of potentially beneficial properties (section 3). This information allows the user to

describe and define the properties of the biochar product. Information is also provided on the effects of biochar on receiving soils and on the

measurement of effects of biochar on plant growth. As far as practicable, information is provided on the analytical methods which can be used

for measuring the different criteria identified.

At the time of writing (October 2013), there are three main schemes available for assessment of biochar products. The International Biochar

Initiative (IBI)1 and the European Biochar Certificate (EBC)2 both published guidelines in 2012. In 2013, the Biochar Quality Mandate (BQM)3

was issued for consultation and, at the time of writing, is in process of finalisation; pending further discussions within the EU (see Table 1). A

major difference between IBI and EBC is in the definition of biochar. IBI sets out three categories of biochar with respect to their carbon

content: low carbon (>10<30%C), medium carbon (>30<60%C) and high carbon (>60%C). EBC meanwhile defines biochar as having a minimum

carbon content of 50%. There is a fair degree of overlap between the two schema with respect to Maximum Permissible Limits (MPLs) of

potentially toxic elements (heavy metals) which is not surprising since both rely upon existing experience and practice in setting regulatory

limits for possible toxicants in major jurisdictions, including Europe, North America and Australia. IBI provided a range of values which reflects

the range of values internationally. The EBC provided a two-tier system of Basic and Premium Grade biochar with different MPLs for some

toxicants as the distinguishing aspect. The BQM followed the EBC in adopting a two tier system (Standard and High Grade biochar) though the

upper MPLs used were from the top end of the IBI’s range as well as from the UK PAS100 composts standard. The lower MPLs (i.e. defining

High Grade biochar) were derived by analysis of naturally occurring quantities of potentially toxic elements (PTEs) in a range of non-poisonous

plant materials. Values were collected from databases including the Phyllis database4 and Plant Analysis 5 and averaged. The rationale is that if

X concentration of a PTE is naturally-occurring in non-poisonous plant material it should be regarded as environmentally acceptable. Since, on

average, 3kg of plant material produce 1kg of biochar, it was decided to multiple the mean concentration in plant matter by three times. Table

two compares the proposed MPLs for the three schemes for elements and organic compounds.

Table One: Comparison of the three schemes for biochar quality

Name Key Requirements Comparison of guidance Status, Certification and Labelling

International Biochar Initiative (IBI): Standardized Product Definition and Product Testing

Material definition; basic utility material properties; Toxicants (metals, organic contaminants, seed germination) ; optional advanced property testing; clean production; protocol for consistent testing ; details of accredited and modified analytical tests.

Ensures safe production of a consistent biochar that is not contaminated or an environmental hazard when added as a soil amendment. Minimum 10% C content.

IBI Biochar Certification Program is a voluntary certification program for biochar manufacturers. IBI Certified Biochar Seal Due to be launched 2013.

European Biochar Certificate (EBC)

As for IBI but also includes sustainability assessment of feedstocks and production operation; positive list.

Applies positive list of biomass (excludes dirty wastes); requires 50% carbon content. Basic and Premium Grades.

Now incorporated into Swiss Law. Third party accreditation process established.

Biochar Quality Mandate (BQM)

As for IBI and EBC but more comprehensive sustainability assessment; more detailed ‘end of waste’ to biochar product process outlined.

Applies to waste and non-waste feedstocks. Standard and Premium Grades.

Published and currently under consultation – and finalization anticipated late 2013. Certification process planned.

Table Two: Comparison of the Maximum Permissible Limits (MPLs) with respect to Elements and Compounds for Three Schema: IBI, EBC

and BQM

Heavy Metal

IBI MPL (mg/kg dry matter), 1.1 (issue: 11.04.2013; IBI-STD-01.1)

PAS 100 (for composts) MPL (mg/kg dry matter) (UK-based standard)

European Biochar Certificate basic biochar (mg/kg dry matter)

European Biochar Certificate premium biochar (mg/kg dry matter)

Biochar Quality Mandate –High Grade (mg/kg dry matter)

Biochar Quality Mandate – Standard Grade (mg/kg dry matter)

Arsenic 12-100 n/a n/a n/a 10 100

Cadmium 1.4-39 1.5 1.5 1 3 39

Chromium 64-1200 100 90 80 15 100

Cobalt 40-150

Copper 63-1500 200 100 100 40 1500

Lead 70-500 200 150 120 60 500

Mercury 1-17 1 1 1 1 17

Manganese n/a n/a n/a n/a 3500

Molybdenum 5 - 20 n/a n/a n/a 10 20

Nickel 47-600 50 50 30 10 600

Selenium 1-36 n/a n/a n/a 5 36

Zinc 200-7000 400 400 400 150 2800

Boron Declaration

Chloride Declaration

Sodium Declaration

Organic compounds

PAHs 6 - 20 12 4 20 20

PCBs 0.2 – 0.5 0.2 0.2 0.5 0.5

PCDDs (dioxins) / PCDFs (furans

9 ng/kg 20 ng/kg 20 ng/kg 20 ng/kg 20 ng/kg

Note: The BQM advocates testing for PCBs, PCDDS and PCDFs only in the situation where there is a reasonable risk of sufficient chlorine in the feedstocks to

constitute a risk that these chemicals could be produced during pyrolysis or gasification.

2. Suggested Necessary Basic Biochar Testing

It is advised that all biochar samples should be tested against the criteria set out in Table Three. This includes properties which allow a basic

characterisation of the material to be made, as well as those properties likely to be beneficial as well as potentially negative properties. The

methods proposed are not definitive but rather indicative and it is suggested that those requiring testing talk to potential providers to

establish the most suitable options. The table includes variables from all the published biochar standards but they are not necessarily required

by all three approaches.

Table Three: Criteria Recommended for Basic Biochar Testing

STANDARD BIOCHAR PROPERTIES

CRITERIA UNIT Indicative methods

pH Declaration pH DIN 10390; BS EN13037; TMECC6 modified by

Rajkovich et al. (2011)7;

Moisture at time of delivery

Declaration % by dry mass ASTM D1762-84 (105c); BS EN 13040BS EN 13040

(1050C for 24 hours)

Organic Carbon (Corg) ≥10%, irrespective of the quality biochar grade (IBI basic)

% of dry mass ASTM D4373-02. Organic C calculated as Total C – Inorganic C; BS EN 13039

BS EN 13039

Inorganic Carbon Declaration % of dry mass As calcium carbonate BS 7755-3.10, ASTM D4373-02. or

Inorganic carbon calculated as Total C-Organic C (after

HCl pre-treatment

Total Carbon (C) Declaration % of dry mass BS EN 15104; ASTM D5291

Elemental analyser by dry combustion

Hydrogen (H) Declaration % of dry mass BS EN 15104; ASTM D5291

Elemental analyser by dry combustion 15104

Oxygen (O) Declaration % of dry mass BS EN 15104; ASTM D5291 Elemental analyser by dry combustion

H:Corg 0.7 (maximum) irrespective of the quality biochar grade H/C ratio <0.6 8

Molar ratio C and H ratio elemental analyser by dry combustion, BS EN 15104, ASTM D5291. Degree of carbonization (Chun et al., 2004) as described by Schimmelpfennig & Glaser (2012)8.

oxygen (O)/C ratios (Van

Krevelen diagrams)

O/C ratio <0.4, 8 Molar ration maturity and decomposition rate Hammes et al., 2006) as described by Schimmelpfennig & Glaser (2012)8

Total Nitrogen (N) Declaration % of dry mass BS EN 15104; SASTM D5291

Elemental analyser by dry combustion

Total Sulphur (S) Declaration % of dry mass BS EN 15104; ASTM D4239 (Method B) ;

Elemental analyser by dry combustion

Carbon / nitrogen ratio Declaration Molar ratio Total C and N BS EN 15104; ASTM D5291. Elemental

analyser by dry combustion )

Total Ash Declaration % of dry mass ASTM D1762-84 (750c); BS EN 13039; ASTM D4442

(Method a)

Total Phosphorus (P) Declaration (IBI Advanced) % of dry mass Modified dry ashing method followed by ICP (Enders and Lehmann 2012)9 BS EN 13650

Total Potassium (K) Declaration (IBI Advanced) % of dry mass Modified dry ashing method followed by ICP (Enders

and Lehmann 2012)9; BS EN 13650

Potentially toxic elements (PTEs) (as listed in Table Two).

Declaration mg kg-1 DIN EN ISO17294-2 (E29); Modified dry ashing method

followed by ICP (Enders and Lehmann 2012)9 BS EN

13650; aqua regia extraction (BS7755) followed by ICP-

AES (BS ISO 22036) ; Also see sludge code of practice10

and EU waste and fertilizer report 11

PAHs Declaration

mg kg-1 DIN/BS EN: 15527:2008-09; DIN ISO 13877: 1995-06

(principle B with GC-MS; Toluene with accelerated

solvent extraction (ASE) (recommended Hilber et al,

2012)12.

Dioxins and Furans Declaration

ng kg-1 AIR DF 100 HMRS; BS EN 1948 series

PCBs Declaration

ng kg-1 AIR DF 100 HMRS; BS EN 1948 series

Water holding capacity Declaration (EBC Premium)

ml g_1 Funnel and filter paper method; Hilgard paper cup

method; DIN 51718; TGA 701 D4C

Bulk density Declaration t m-3 Mass and volume determination

Particle size distribution Declaration mm and µm Progressive dry sieving with 4760μm, 2380μm and 420μm sieves, as outlined in ASTM D2862-10 Method for activated carbon.

Boron Declaration mgkg-1 TIMECC13

Sodium Declaration mg kg-1 dry wt

TIMECC13

Chlorine Declaration % of dry mass ASTM E776 (Cl)

3. Suggested Additional Testing Criteria

Listed in Table Four are a range of other biochar properties which might be measured as part of product development.

Table Four: Additional properties of biochar which may provide additional beneficial information to product developers

ADDITIONAL BIOCHAR PROPERTIES CRITERIA UNIT INDICATIVE METHOD

Micro-nutrients (Zn, Ca, Fe, Ni, Se, Mo,

Mg, Mn, Fe, etc.)

Optional mg kg-1 DIN EN ISO 17294 – 2 (E29); EPA method 3053 (microwave digestion followed by AA)

Neutralising Capacity (liming if pH above 7)

(IBI basic) % CaCO3 Rayment & Higginson (1992)

Liming (carbonate value) Declaration % CaCO3 ASTM D 4373

Electrical Conductivity (IBI basic) dSm-1 Rajkovich et al. (2011) BS EN 13038; TIMECC (modified)

Cation Exchange Capacity (K, Ca, Mg, Na)

Optional cmol+kg-1 Ammonium-acetate (EPA 9080)(extraction) then ICP-OES

Porosity Optional e.g. mercury intrusion porosimetry

Specific Surface area / total surface area

Optional (EBC Premium)

N2 gas adsorption method (e.g. BET) ; ASTM D 6556-10; ISO 9277

Labile carbon content / volatile matter

% of dry mass Incubation studies (Cross & Sohi, 2011)14 / ASTM D1762-84

Long-term stable carbon % of dry mass Accelerated ageing (oxidative) method (Cross & Sohi, 2013)15

Available P mg/kg 2% formic acid followed by spectrophotometry as described by Wang et al (2012)16 after Rajan et al (1992)17 and AOAC (2005)18

Mineral N (NO3-N) (IBI Advanced) Declaration

% of dry mass or mg/kg

KCl xtraction followed by spectrophotometry/ ICP (Rayment and Higginson 1992)19

Release dynamics of nutrients (P, K, N)

Soil column leaching experiments modified by Angst & Sohi 201320

Impact on soil aggregation

Soil water potential (available water content)

g/g or g/cm3 Tension table and pressure plate

Priming potential (impacts on SOC) % / % Incubation studies

Thermal analysis Optional stability indices Exo1 and Exo2

ratio Thermogravimetric analysis (TGA); Thermogravimetry-differential scanning calorimetry (TG-DSC) % labile (exo1)and % recalcitrant C (exo2) over % OC (% weight loss under oxidation contitions)21,22

Ammonia (NH4-N) Declaration mg kg-1 Rayment and Higginson 1992

4. Properties of Soils

In many cases it will be useful and important to know about the properties of the soil in to which biochar is added, either or both prior to and

after biochar addition. Table Five lists some of the dimensions of the soil which may be useful to characterise.

Table Five: Testing Soil Properties

Variable Unit Test method

Soil organic carbon % dry weight e.g. ISO 13878 - Dumas – dry combustion (with HCl pre-treatment for calcareous soils)

pH In de-ionised water(Allen, 1989).ISO 10390

Total Nitrogen % dry weight or mg/kg

ISO 13878 - Dumas – dry combustión

BS EN 15104

Extractable Mineral nitrogen (nitrate, nitrite, ammonium)

mg/kg e.g. 0.5 KCl extraction; ISO 14256-2

Extractable Phosphorus Olsen Method

Soil moisture % dry weight Dry at 105oC for 24 hours

CEC (exchangeable K, Na, Ca, Mg)

cmol+/kg Ammonium-acetate then ICP-OES 23

Saturated hydraulic conductivity (SHC)

μm/s soil water movement (using Darcy’s law)24

Soil water potential / available water content

g/g Tension table and pressure plate 24

Soil texture (clay, fine silt, coarse silt, fine sand, coarse sand)

Separation by sieving (ASTM) and sedimentation(Pipette method 25

5. Measuring the Plant Response

Some possible measures of plant responses to biochar soil amendment are presented in Table Six.

Table Six: Measuring Plant Response to Soil Amendments such as Biochar

Variables : Basic Unit Indicator Detail

Total biomass yield - above and below ground

kg (DW) per m2 Total plant response

Harvestable biomass kg (DW) per m2 grain, vegetable leaves, edible stems, edible roots

Useable / saleable part of crop

Leaf chlorophyll SPAD meter Indicates chlorophyll content

Nitrogen content % Crude protein Leaves / stems

Crude fibre % ? Leaves / stems

Starch % Starch Tubers

Xylem sap flow (XSF) water uptake by plant

Micro-nutrients mg per kg (DW) e.g. Zn, Mn, B, Mg, Na, Fe In edible parts of plant

Other nutriitional properties and indicators

e.g. nutritional value per kg or area ?

References

1. the International Biochar Initiative’s (IBI) Guidelines for biochar that is used in soils. http://www.biochar-

international.org/characterizationstandard (version 1.1, published May 2012, updated 11th April 2013, accessed on 16th October 2013)

2. The European Biochar Certificate (EBC). (Delinat Institute, Switzerland). http://www.european-biochar.org/en/ct/1-Guidelines-for-the-

European-Biochar-Certificate (4.6 version, published 2nd April 2013, accessed on 16th October 2013)

3. Biochar Quality mandate (BQM), v.1 (2013). http://biocharbraf.files.wordpress.com/2013/06/bqm-v-1-0-version-for-public-

consultation1.pdf (published 15.06.2013, accessed on 16th October 2013)

4. Phyllis database (ECN, 2007) https://www.ecn.nl/phyllis2/

5. Reuter, D., Robinson, J.P. (editors), Plant Analysis An Interpretation Manual, CSIRO, Australia. .

6. US Composting Council and US Department of Agriculture (2001) Test methods for the 29 examination of composting and compost.

(TMECC) Thompson W.H. (ed.) http://compostingcouncil.org/tmecc/. (Accessed January 2012).

7. Rajkovich, S., Enders, A., Hanley, K., Hyland, C., Zimmerman, A.R., and Lehmann, J. (2011).Corn growth and nitrogen nutrition after

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8. Schimmelpfennig S.; Glaser B. (2012). One Step Forward toward Characterization: Some Important Material Properties to Distinguish

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9. Enders, A. and Lehmann, J. (2012) Comparison of wet digestion and dry ashing methods for total elemental analysis of biochar.

Communications in Soil Science and Plant Analysis. 43:1042–1052.

10. Sludge Code of Practice, available at: http://archive.defra.gov.uk/environment/quality/water/waterquality/sewage/documents/sludge-

cop.pdf. Methods as listed in “Index of Methods for the Examination of Waters and Associated Materials 1976-1992” (ISBN

011752669X).

11. Amlinger, F., Faroino, E., and Pollack, M. (2004) EU Heavy Metals and Organic Compounds from Waste Used as Organic Fertilizers Final

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12. Hilber, I, Bucheli, TD, Blum, F, Leifeld, J, Schmidt, HP Quantitative determination of PAHs in biochar – a prerequisite to assure its quality

and safe application. J. Agric. Food Chem. 2012

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Books, Australia/ Inkata Press, Port Melbourne.

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