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Frequently Asked Questions (FAQs) about the IBI Biochar Standards

These FAQs are divided into the following categories:

Process for Producing the IBI Biochar Standards
Questions Specific to Tests, Test Methods, and Test Laboratories
Questions Specific to Biochar Producers
Questions Specific to Biochar Users
Technical Questions Pertinent to the IBI Biochar Standards

Process for Producing the IBI Biochar Standards

What is IBI’s goal for these IBI Biochar Standards? The Standardized Product Definition and Product Testing Guidelines for Biochar That Is Used in Soil were created to encourage further development of the biochar industry by providing standardized information regarding the characterization of biochar materials to assist in achieving more consistent levels of product quality. In addition to providing product definition and qualitative specification guidelines, this document has been developed to assist biochar producers in providing consumers with consistent access to credible information regarding qualitative and physicochemical properties of biochar. The IBI Biochar Standards are designed to support an IBI Biochar Certification program. Separately, the IBI Biochar Standards are also intended for use by various national and regional product standards bodies, and national and regional biochar groups for their own local adaptation and use, and as a reference in regulatory situations, as may be appropriate. Any use of the IBI Biochar Standards for commercial purposes requires the permission of IBI, the copyright holder.

What was IBI’s role in the document development process? IBI initiated and undertook the process as an international leader and convening authority in the biochar field, and utilized the expertise of the global biochar community and an external consultant—in this, case, Leading Carbon Ltd.—to develop a biochar characterization document in a process that was fully transparent, open, and global in scope, and that comports with processes used by international standard-setting bodies such as the International Standards Organization (ISO). IBI provided the leadership and oversight for the process, and utilized its vast network of stakeholders to ensure that the process was open to the global biochar community, transparent, and fully documented.

Why did IBI lead the IBI Biochar Standards development process? IBI specifically sought to undertake a globally inclusive, open, and transparent process that would facilitate the involvement and collaboration of process and substance experts in the field and the wider biochar community and stakeholders. IBI ensured that the process was science-based and that adequate information and quality assurances were provided throughout the IBI Biochar Standards development process. The end-goal of this process was to create a document that will be applicable to commercial biochar production worldwide, and will supply regulatory agencies and end-users with adequate information regarding product quality and reliability. IBI recognizes that this is the first iteration of these IBI Biochar Standards, and fully anticipates that the IBI Biochar Standards will be updated and improved over time as experience and science further progress.

Who provided input into this document? IBI utilized its vast network of contacts and organizations in the global biochar community to publicize and promote the process and to encourage participation in the process. Every version of the IBI Biochar Standards was made publicly available for public comment and input, and IBI promoted continued engagement through its monthly electronic newsletter, which goes out to thousands of individuals and organizations. Each live posting of the document was followed by public comment collection through the IBI website and various contact e-mail addresses, as well as open public webinars to permit real-time questions, comments, and feedback from the public. Comments were encouraged throughout the process, and all comments were taken into consideration during revisions.

Who participated in the balloting process? During the balloting process, which was open from April 23 – May 6, 2012, all IBI members who were in good account standing could participate in the vote to accept or reject the IBI Biochar Standards. To register for an IBI membership, please go to the IBI Membership page, at:

How can the public supply comments to the IBI Biochar Standards now that they are final? Comments are welcome at any time. Please send comments to IBI will periodically revise the IBI Biochar Standards over time.

Questions Specific to Tests, Test Methods, and Test Laboratories

Why was the organic carbon (Corg) test method changed in Version 1.1 of the IBI Biochar Standards? After further review by the Expert Panel that provided input in the development of the IBI Biochar Standards, IBI changed the test method utilized to determine Corg to the “pressure calcimeter method” because of this method is preferred by the majority of professional soil testing laboratories and is a lower cost method.

Can different test methods be used instead of the referenced methods in the IBI Biochar Standards? No. In order to ensure that biochar samples are consistently assessed in a uniform and reliable way, standardized test methodologies must be used when analyzing biochars. This will ensure that all biochar analyses adhere to a standardized approach to analysis and reporting of outcomes. This will also serve to help biochar users compare different biochars using a common set of characteristics and test methods in order to determine which biochar is best-suited to their needs.

If a laboratory does not know how to do some of these tests, where can they get the information they need? Each of the identified biochar characteristics and constituents within the levels corresponds to a specific identified test methodology. These methodologies (ASTM International (formerly known as the American Society for Testing and Materials), US Environmental Protection Agency, or another) are documented and referenced in the document, including information on how to appropriately conduct the analyses.

Are there reference materials available to help labs with quality assurance? Quality Assurance/Quality Control (QAQC) procedures are often standard practice within laboratories. Although IBI does not have specific recommendations for QAQC reference materials, there are a wide variety of resources available, and the majority of chemistry societies (AOAC - Association of Analytical Communities, ASTM International, etc.) should have standard QAQC documents.

Will IBI have a quality assurance program for labs? IBI does not have plans at this time to develop a quality assurance program for laboratories.

If a laboratory doesn’t have the capacity to conduct all the analyses within the IBI Biochar Standards document, how can they run all the necessary tests? Laboratories may share responsibilities with, or sub-contract with other laboratories to address analyses that they may not perform in-house. As long as proper QAQC practices are followed, it should not matter that two labs are conducting biochar analyses by splitting analytical responsibilities among different tests (e.g. Lab 1 conducts all physical properties, metals and toxic analyses but sub-contracts Lab 2 to assess PAH, PCBs, and dioxins). Alternatively, a producer can simply submit samples to two or more qualified laboratories to conduct specific tests.

Questions Specific to Biochar Producers

What labs can do all of these tests? University or government soil labs are often capable of conducting the tests listed within the IBI Biochar Standards. Additionally, there are likely to be other analytical laboratories that specialize in soil, agricultural, and environmental analyses that will be capable of conducting the IBI Biochar Standards tests.

Will these tests help meet the regulatory requirements for soil amendments in a particular country? It was the intention of the document development process that these requirements would assist in meeting regulatory requirements by following standard, already accepted regulatory reporting levels, and prescribed methodologies. Following the IBI Biochar Standards does not ensure that national soil amendment regulations will be met. It is the responsibility of the user of this document, and the producers and users or consumers of biochar, to establish appropriate safety and health practices and determine the applicability of any national, state or provincial, and local regulatory limitations prior to use.

How can small producers and developing country producers perform the tests in the IBI Biochar Standards without adequate resources or access to laboratories? Recognizing that this is a new industry in which many businesses are struggling for economic viability, IBI has tried to narrow the range of required tests to what is necessary. The IBI Biochar Standards have been structured to address costs as much as possible by providing both required and optional test categories. However, the purpose of the IBI Biochar Standards is to provide market certainty for commercial producers of biochar. The IBI Biochar Standards were not developed for producers in certain developing countries where some of the lab tests are simply unavailable. If funding allows, IBI intends to develop a set of IBI Biochar Standards specifically for developing countries and small producers.

Why are the testing requirements for Processed Feedstocks more stringent than the requirements for Unprocessed Feedstocks? Processed Feedstocks are defined in the IBI Biochar Standards as biomass that has gone through chemical or biological processing or as biomass material that may have been grown on soils contaminated with heavy metals or other toxicants. By definition, these feedstocks will have more exposure to potential toxicants and must undergo toxicant testing on a more frequent basis than Unprocessed Feedstocks.

If a production facility uses several different kinds of feedstock on a rotating basis, must the facility retest the biochar material every time it switches between feedstocks, even if it has already tested that feedstock during a given 12-month period? If tests have been conducted for a feedstock or a specific feedstock mixture during a given 12-month period, additional tests will not be necessary if a producer switches back and forth between already tested feedstocks or feedstock mixtures, as long as the processing parameters of temperature and time have not changed.

Is Municipal Solid Waste (MSW) an eligible feedstock for biochar under the IBI Biochar Standards? Unsorted MSW is not an eligible feedstock. The IBI Biochar Standards use the following definition for MSW:
Municipal Waste/Municipal Solid Waste (MSW): solid non-hazardous refuse that originates from residential, industrial, commercial, institutional, demolition, land clearing, or construction sources (Canadian Council of Ministers of the Environment 2005). Municipal solid waste includes durable goods, non-durable goods, containers and packaging, food wastes and yard trimmings, and miscellaneous inorganic wastes. (US Environmental Protection Agency, 2011)
Some portion of MSW is biomass waste. This biomass fraction can be separated at the source or sorted out later. As long as the MSW contains no hazardous waste that might leach onto the biomass fraction, the separated biomass fraction is eligible to use as a “processed” feedstock for biochar. No biochar feedstock may contain more than two percent contaminants (defined as glass, metals, plastics and other fossil-fuel derived materials.

If a producer blends its biochar with minerals and microbes before packaging and sale, at what point in the manufacturing process must the tests be performed? If biochar is to be blended or mixed with another substance (excluding water used for quenching), the biochar must be tested after the thermochemical reaction is complete and before blending or mixing. In some cases minerals may be deliberately added to feedstocks during the production process. Those minerals are considered to be diluents and must be declared if they constitute 10 percent or more of the total feedstock.

Can a producer use the IBI Biochar Standards test results to produce recommendations for uses of its product? The IBI Biochar Standards do not prescribe uses for biochar materials, nor provide guidance on what biochar can or should be used for. It is the responsibility of producers to make it clear to users that any recommendations for product use are made by the producer and not by IBI.

Can a producer use the IBI logo in its marketing materials? IBI will develop a logo to be made available for marketing purposes as part of its IBI Biochar Certification program. The certification program will supply official guidance on how, when, and where the specific logo can be used for marketing IBI-certified biochar.

Questions Specific to Biochar Users

How does the consumer know that the manufacturer really did these tests? A chain-of-custody reporting and documentation structure for test results will be developed as part of the IBI Biochar Certification process. This documentation will ensure that a manufacturer has verifiable proof that the biochar material has been tested as reported.

How will these tests help consumers? Will they help determine what the biochar is good for and how to use it? These test results will assist users in determining that biochar is safe for use as a soil amendment, and for determining where biochar will be beneficially used by providing a better understanding of certain physical and chemical characteristics of the biochar, including by identifying potential beneficial components that may be present. These test results will assist the knowledgeable user in decision-making about how best to utilize a biochar product.   

Why is there no information in the IBI Biochar Standards on how biochar was produced, like temperature and processing or residence time? The IBI Biochar Standards are material guidelines intended to identify and test for certain specific components of the biochar end-product that are important to its safety and utilization as a soil amendment. This document does not address or certify biochar production processes or technologies, and was intentionally created to be process-neutral, and to focus only on the product material.

Do the IBI Biochar Standards allow biochar to be made from old tires, coal or plastic? As indicated in the section on feedstock contents, the IBI Biochar Standards will permit no more than 2% contaminants in feedstock. Contaminants include petroleum- and fossil-fuel-derived materials such as tires, coal, or plastic. Biochar feedstocks must come from a biomass source.

Will hydrochar from hydrothermal carbonization qualify as biochar? Material that passes the tests and meets the required reporting standards will qualify as biochar.  The IBI Biochar Standards are intentionally process-neutral.

Do the IBI Biochar Standards specify that biochar must be made sustainably from sustainably harvested feedstocks? The IBI Biochar Standards are process neutral and do not address issues of feedstock or process sustainability.

Technical Questions Pertinent to the IBI Biochar Standards

What are the major revisions in Version 1.1? 1) The organic carbon content test method was changed. 2) The earthworm avoidance test was removed (see the next FAQ for further info). 3) A new section titled “Revisions to the IBI Biochar Standards” was added. 4) In Test Category B – Toxicant Reporting, a) maximum toxicant thresholds for metals were updated based on guidance from international regulatory agencies, and b) the reporting units were changed for PAHs and PCBs (see V1.1 Section 4.2 and Appendix 3 for further details). 5) Additional product specifications were added to the biochar labeling requirements (see V1.1 Section 5.1 and Appendix 1). 6) Numerous minor editorial clarifications and typographical corrections were made.

Why was the earthworm avoidance test removed from Version 1.1 of the IBI Biochar Standards? After further review by the Expert Panel that provided input during development of Version 1.0 of the IBI Biochar Standards, IBI removed the earthworm avoidance test from Version 1.1 because 1) the required testing of and Maximum Allowed Thresholds for dioxins, PAHs, PCBs, and metals, in addition to the required germination inhibition assay, makes the earthworm avoidance test redundant, and 2) after polling numerous professional soil testing laboratories IBI has determined that there is a dearth of accredited labs that conduct the earthworm avoidance test.

Why was the H:Corg ratio chosen as a measure of carbon stability rather than the “proximate analysis” that identifies stable and labile carbon components? Experts involved in the IBI Biochar Standards development process indicated that the “proximate analysis” from ASTM International is not very reproducible or reliable for biochar. The H:Corg ratio (ratio of hydrogen to organic carbon) was chosen as the measure of carbon stability because H and C are elements that can be accurately quantified as opposed to the less-well-defined “volatile matter” that is meant to be measured in the “proximate analysis.” For more technical background information on the use of H:Corg to measure carbon stability, see the IBI Biochar Standards Appendix 5 – The Use of H:Corg to Indicate C Stability.

Why do the IBI Biochar Standards require that all biochar materials be tested for dioxins and PAH? What evidence is there that these toxicants may be present in biochar? The term “dioxins” is used to refer to a family of dozens of compounds that includes polychlorinated dibenzo dioxins (PCDDs) and polychlorinated dibenzo furans (PCDFs). PAH refers to a family of hundreds of compounds known as polyaromatic hydrocarbons. Not all of the dioxins and PAHs are toxic and the testing and reporting methods in the IBI Biochar Standards will identify and limit only those compounds that are of concern. It is important to test biochar for toxic dioxins and PAH because unlike other toxicants such as heavy metals, which may be present in feedstocks, these compounds may be produced by thermochemical conversion processes. The IBI Biochar Standards make no specifications regarding thermochemical conversion processes, leaving open the possibility of toxicant formation during production. While it is likely that most thermochemical processes used to make biochar will not result in the presence of these toxicants at levels of concern, it is important to recognize that biochar is a new industrial material, and compared to better-known materials, relatively few biochar samples have been tested for PAH and dioxins. Because the potential for toxicant formation does exist, regulatory bodies will require more information about the potential presence of these toxicants. One important purpose of the IBI Biochar Standards is to demonstrate to national and international regulatory bodies that biochar is safe for use as a soil amendment. For a more detailed discussion please review the IBI White Paper – Implications and Risks of Potential Dioxin Presence in Biochar.


  • Downie, A., Munroe, P., Cowie, A., Van Zweiten, L. and Lau, D. (2012) Biochar as a Geoengineering Climate Solution: Hazard Identification and Risk Management. Critical Reviews in Environmental Science and Technology 42(3):225-250
  • Garcia-Perez, M. (2008) The formation of polyaromatic hydrocarbons and dioxins during pyrolysis: A review of the literature with descriptions of biomass composition, fast pyrolysis technologies and thermochemical reactions. Washington State University
  • Hale, S., Lehmann, J., Rutherford, D., Zimmerman, A., Bachmann, R.T., Shitumbanuma, V., O'Toole, A., Sundqvist, K.L., Arp, H.P.H., and Cornelissen, G. (2012). Quantifying the total and bioavailable polycyclic aromatic hydrocarbons and dioxins in biochars. Environ. Sci. Technol., 46 (5), pp 2830–2838. DOI: 10.1021/es203984k

Why do the IBI Biochar Standards require the germination inhibition assay in addition to all of the laboratory analysis tests for chemical toxicants? Chemical analysis is limited to the chemicals specified in the Category B tests, which are those chemicals that are known to be found in some biochars. Bioassays, such as the germination inhibition assay, are able to detect unknown toxic chemicals that could be present in biochar. Also, a chemical concentration determined by lab analysis may not indicate the bioavailability of the chemical in soil. The bioassays provide an indicator of bioavailable toxicants. The use of bioassays was internationally standardized by the Organization for Economic Cooperation and Development (OECD) in 1984. The use of bioassays has expanded greatly since that time. They are used to assess soil contamination and to identify and characterize potential hazards of new and existing chemical substances. Recent work using bioassays to help characterize biochar as a soil amendment confirms that methods for conducting the germination inhibition assay can be used successfully to assess biochar safety as a soil amendment.


  • Busch, D., Kammann, C., Grunhage, L., and Muller, C. (2011) Simple biotoxicity test for evaluation of carbonaceous soil additives: establishment and reproducibility of four test procedures. J. Environ. Qual. 40: 1-10
  • Van Gestel, C. A. M. (2012) Soil ecotoxicology: state of the art and future directions. ZooKeys 176: 275–296
  • Van Zwieten, L., Kimber, S., Morris, S., Chan, K.Y., Downie, A., Rust, J., Joseph, S., and Cowie, A. (2010) Effects of biochar from slow pyrolysis of papermill waste on agronomic performance and soil fertility. Plant Soil 327: 235-246