Frequently asked questions
Get answers to the most frequently asked questions about biochar.
About biochar
What is biochar?
Biochar (short for “biological charcoal”) is a stable, carbon-rich, solid material produced through the pyrolysis of biomass. Common biomass used to make biochar includes wood residues, crop waste, manure, and other organic waste. Biochar made from wood looks and feels much like charcoal.
How is biochar made?
Biochar is made through either pyrolysis or gasification, thermochemical processes in which biomass is heated in a low-oxygen environment, typically between 400°C and 700°C. Because there’s very little to no oxygen, the material doesn’t combust. Instead, it decomposes into three outputs: a solid carbon-rich product (biochar), non-condensable gases (syngas), and condensable vapors (which can be refined into bio-oil).
Is biochar the same as charcoal?
Biochar and charcoal are both produced through pyrolysis, but they have different uses, specifications, and quality control.
Charcoal is made mainly from wood, used as a fuel, and its production is focused on maximizing burn efficiency and energy content. Biochar can be made from nearly any waste biomass and is designed to be used as a soil amendment or in other materials like concrete, potting media, and stormwater filtration media.
Has biochar really been around for centuries?
Yes! The practice of incorporating charred biomass into soil dates back more than 2,000 years to Indigenous communities. First rediscovered in the Amazon Basin more than 50 years ago, soils where biochar had been applied by ancient societies is known as “dark earth” or terra preta de indio. These soils were highly sought after for their high fertility compared to surrounding soils. Since then, archaeologists have discovered that biochar was used by ancient societies around the world to improve soil quality and increase crop yields before the advent of chemical fertilizers.
What is biochar made from?
Biochar is made from biomass — organic waste from agricultural or forestry residues, or other sources like manure. Common feedstocks include wood chips, sawdust, forest thinnings, crop residues (such as corn cobs, rice husks, or wheat straw), livestock waste like chicken or cow manure, and even biosolids from wastewater treatment plants.
The type of feedstock affects the chemical and physical properties of the biochar, such as carbon content, nutrient composition and retention, ash content, and pH. Because biochar is often used in agricultural applications, feedstock should be free of contaminants such as treated wood, plastics, or hazardous waste, and the resulting biochar should always be verified through appropriate testing standards.
Who uses biochar and for what purpose?
Biochar is used across agriculture, horticulture, infrastructure, environmental treatment, and more. These are some of the core biochar end-uses today:
Large-scale agriculture and corporate producers
Commercial farms and food companies use biochar to improve soil health, water retention, and nutrient efficiency. Because biochar persists in soils for hundreds of years, it can support long-term increases in yield, and be a part of regenerative land management, helping improve soil quality over time. On-farm biochar production is also a circular approach to managing waste biomass such as orchard trimmings, in-field residues, and agricultural processing wastes like nut shells and rice hulls.
Small-scale agriculture and specialty growers
Market farms, orchards, vineyards, and greenhouse operations incorporate biochar into soils and compost blends to improve moisture management, increase yields and nutrient holding capacity, and reduce fertilizer and input costs. Application rates and benefits vary by crop type and soil conditions. Many small scale orchards and vineyards can also produce biochar on site and then reincorporate that material into soil.
Retail and consumer products
Biochar is sold in soil blends, fertilizer products, and horticultural amendments for gardeners, landscapers, and turf managers. Retail uses typically focus on soil conditioning for gardening and improving growing media performance for potted plants. Biochar can also be a key component of sustainable peat-free and perlite-free potting media blends.
NGOs and public agencies
Municipalities, conservation organizations, and land managers use biochar in tree planting and turf management, stormwater systems, and soil restoration projects. It can support water quality management, waste diversion, and local biomass utilization initiatives that deliver community-level benefits. These organizations can also become biochar producers, providing an opportunity to upcycle waste biomass such as arborist trimmings in urban areas.
Forestry and land management
Biochar can be produced from wood products, manufacturing waste, in-forest residues, thinning operations related to wildfire mitigation, and invasive species removal initiatives. Converting excess woody biomass into biochar provides an alternative to pile burning, reducing harmful particulate air pollution. Biochar produced from this material can also generate carbon credit revenue and be sold for other uses, creating an economic opportunity from this otherwise low value material, and supporting fuel load reduction and forest management strategies.Construction
Biochar is being incorporated into concrete, asphalt, and other building materials to develop greener construction products and new material formulations for critical infrastructure and housing. Some biochar formulations are being developed to produce high performance concrete and asphalt blends.
What are the benefits of biochar?
One of biochar’s defining benefits is its longevity – persisting for hundreds to thousands of years. The stable structure formed during pyrolysis decomposes very slowly, so its structural and functional properties can remain effective long after application, unlike many organic amendments that break down relatively quickly in soils.
Biochar also has a highly porous structure with significant internal surface area, combined with reactive surface properties, giving it strong absorption capacity. This makes it effective in farming, stormwater management, filtration systems, and other applications where retaining nutrients, contaminants, or even odors is important.
The porous structure of biochar allows it to hold up to five times its weight in water, providing water for healthy plant growth even during droughts. Larger pores are also home to microbes and fungi, improving soil health.
Biochar also contains important nutrients and compounds, primarily in the ash fraction of the material. The ash fraction can contain micro and macro-nutrients including phosphorus, potassium, calcium, magnesium, silica, and more. The minerals in the ash can also provide liming, offsetting the costs of lime applications.
Does biochar need to be “charged” before being used in soil?
Pre-conditioning (often called “charging”) involves blending biochar with compost, fertilizer solutions, manure, or nutrient-rich organic materials before application. This allows the pore structure of biochar to fill with nutrients and microbial life, supporting more predictable plant performance. One of the best approaches is to mix biochar with other organic materials or manure at the beginning of the composting process, improving the quality of the biochar and the resulting compost.
Charging biochar is considered a best practice before using biochar as a soil amendment, but it is not required in every situation. Raw biochar provides many initial benefits, including improved water and nutrient retention, micro and macro-nutrients in the ash fraction, and improved soil health.
Over time, raw biochar ages in the soil as microbes slowly degrade the outsides of the individual particles. This process increases the cation exchange capacity of the biochar, making it more effective for retaining nutrients so that biochar improves over time.
What are the impacts of biochar on soil nitrogen?
Biochar, unlike most high carbon soil amendments, does not “lock up” soil nitrogen. Because the carbon in biochar is stable, and is only very slowly decomposed by microbes, it does not decompose and immobilize nitrogen. A small amount of the carbon in biochar can be readily degraded, so there can be some tie up of nitrogen, but this is usually less than a few percent of the carbon.
Further, in most soils, and particularly those with sandier texture, biochar can significantly increase the retention of nitrogen, boosting nutrient uptake and nitrogen use efficiency. Thus, the net effect of biochar addition on soil nitrogen is almost always to increase plant available nitrogen, which can help increase crop yields or reduce the cost of fertilizer applications.
How is biochar applied?
The application method is determined by sector and intended use. Other factors that impact the process are soil conditions, system design, and regulatory requirements.
Large-scale agriculture and corporate producers
Biochar can be spread and incorporated into soil often before planting or alongside compost and nutrient additives. For large-scale use, it’s commonly added to soil using field equipment, like lime, manure, or compost spreaders. It can also be applied using specialized biochar application equipment that has been developed over the past decade.
Some biochar and fertilizer companies also produce biochar enhanced fertilizers that are designed to be applied using standard fertilizer applicators.
Small-scale agriculture and specialty growers
Growers often blend biochar into compost, potting mixes (substrates), raised beds, or planting rows. For smaller scale use, it can be added to soil by hand or using a spreader.
Retail and horticulture
Biochar is usually pre-blended into bagged soil products, compost, or specialty growing media for consumer use. It’s also sometimes sold in pure form for soil improvement.
Public agencies and infrastructure
In public infrastructure projects, biochar is incorporated into stormwater systems in biochar bags (or “filter socks”) or in swales, urban greenery installations, and soil restoration efforts. It is also used as an amendment to tree planting and surface applied as a turf amendment. Biochar can increasingly be sourced from local soil suppliers in urban areas.
Forestry and land management
Biochar may be applied to restoration sites following thinning or wildfire mitigation treatments, often incorporated back into soils during site restoration work. For wildwires, using wood waste to create biochar and then return it to the land is a circularly beneficial process, and can reduce the complexities and logistics associated with transporting biochar offsite from remote in-woods locations.
Construction
Biochar is integrated directly into material formulations, such as concrete or composite building products.
Is biochar safe?
Yes. Biochar produced from clean feedstocks and tested to meet appropriate quality standards is safe to use in approved applications.
As with any material, correct specification, testing, and quality assurance are essential to ensure safe and effective use.
What standards or certifications exist in the biochar industry?
There are multiple established international and region-specific standards and certifications, and more are in development. At ABI, we work to develop standards tailored for the American biochar industry, aligning with applicable laboratory methods and regulatory frameworks.
Check out the Biochar Standards page to learn more about currently available standards.
About American Biochar Institute
What is the American Biochar Institute (ABI)?
American Biochar Institute (ABI) is a 501(c)(3) educational nonprofit dedicated to expanding the effective use of biochar as a sustainable material across agriculture, industry, and the built environment.
What does ABI do?
We support the growth of reliable biochar markets through standards development, education, technical assistance, and industry collaboration. Our work helps ensure biochar is produced, tested, and applied with consistency and transparency.