# Biochar Turning biomass into charcoal ## What you need to know about biochar 1. Biochar is the output of heating biomass to high temperatures in an oxygen-poor environment, a process known as pyrolysis. 2. The end result is a charcoal that is chemically stable, rich in carbon, and can be used as a soil additive and for other purposes. 3. The feedstock biomass can be any plant matter, but to be additional, projects need to use waste biomass (without another use) as their feedstock. 4. Different types of plant feedstock create biochar with different amounts of carbon and durability. 5. The pyrolysis process also creates combustible gases including methane and CO₂ as byproducts, which can be captured and used for fuel. ## Turning biomass into charcoal When organic matter is burned or left to decay, it releases its carbon content back into the atmosphere as CO₂. However, biochar projects circumvent this natural process by heating organic matter (biomass) in the absence of oxygen so that no carbon is released, thereby becoming a method of carbon dioxide removal (CDR). Biochar is the charcoal-like substance that results from this process, and it could hold the key to removing vast amounts of CO₂ from the atmosphere while also offering a host of other benefits: it reduces nitrous oxide emissions in soil, improves soil health, and can be a vector for clean energy production. When biochar is applied as a soil enrichment, it helps soils form better aggregates, which helps them retain more water and nutrients. In turn, this supports plant growth, decreases dependence on chemical fertilizers, and reduces leaching and runoff. Applying biochar can improve crop yields while reducing emissions of the land used by about 12%. Experts estimate that widespread use of biochar could durably sequester 2.5 gigatonnes of CO₂ each year. ## Project showcase webinar: Biochar We hosted a webinar with Novocarbo and Climate Farmers to understand how biochar can both sequester carbon and revitalize soil health. ## Carbon credits and biochar Biochar is currently the most market-ready form of carbon dioxide removal. To date, biochar projects are responsible for 89% of engineered CDR retirements, and are increasingly being sold as ex-post credits (indicating that many projects are mature enough to sustain themselves and scale without advance financing). Biochar is frequently compared to afforestation, reforestation, and revegetation (ARR), as this is another CDR option that issues ex-post credits. Unlike biochar, ARR projects have more serious potential for risk of reversal due to natural ecosystem events like wildfires or pest outbreaks, and the natural lifespan of trees is limited. ARR projects also typically have a durability of decades, compared to biochar, which can be stable for hundreds of years. ## The history of biochar Archaeological records point to biochar use in indigenous Amazonian cultures as far back as 2,500 years ago. Known by the Portuguese term "terra preta" (meaning "black earth"), biochar use in agriculture in South America is also referred to by scholars as Amazonian dark earth (ADE). Amazonian communities would ignite a mixture of organic materials, certain tree trunks, and soil, then bury it for combustion, producing biochar, which they’d use as soil fertilizer. However, the earliest biochar practitioners may have been Australian Aborigines, who practiced "fire-stick farming" — igniting moist plant matter to encourage crop growth — as much as 10,000 years ago. Evidence of the Aboriginal use of oven mounds containing charcoal, minerals, organic matter, and clay has been discovered in southeast Australia. Biochar has also been used for centuries in Japan and China to maintain soil fertility. ## How is biochar produced? While there are multiple methods of producing biochar, the principle behind production is consistent: plants absorb carbon dioxide through photosynthesis. Even on working farms or thriving forests, there will inevitably be waste plant biomass (i.e. corn husks, thinned trees, animal manure). This waste biomass becomes the feedstock for biochar production. The feedstock undergoes pyrolysis, becoming biochar. Gases including methane and CO₂ are released as byproducts during pyrolysis, which can be captured for use or storage. The biochar itself is then reused or stored. This process creates three byproducts: - Biochar - Natural gas — can be sold or sequestered underground - Carbon credits ## Types of feedstock used to create biochar Biochar can be versatile as a climate solution since many types of biomass can be used as feedstock for pyrolysis. Different feedstocks have different chemistry, impacting the stability and carbon composition of the biochar created. Higher stability in biochar means carbon is less likely to interact with its environment and be released back into the atmosphere. This is known as "risk of reversal," a risk of biochar when used for CDR. Broadly speaking, there are two main categories of biomass used as feedstock in most biochar projects today: ### Wood Wood tends to produce the most stable, highest-carbon content biochar — especially when exposed to high temperatures during pyrolysis. This means more carbon is stored and therefore less risk of reversal. Wood used as biochar feedstock should be biomass from a local forest that would otherwise be left to burn or decay, collected in a way that aligns with ecological principles and overall ecosystem health. ### Agricultural residue Farming creates a large amount of waste biomass. This includes crop residue like corn stalks or plant parts that aren’t commercially used. Animal manure is another possible feedstock. Biochar created from agricultural residue usually has lower carbon content compared to wood feedstock. ## Biochar stability and permanence Feedstock exposed to different temperatures can also have different stabilities. Higher pyrolysis temperatures tend to create more stable biochar, as more volatile gasses are lost during the process. For biochar, higher stability equals higher "permanence" — the length of time carbon is sequestered. Scientists estimate that biochar can be durable for up to or exceeding 1,000 years, depending on factors including feedstock materials, heat of pyrolysis, and environmental conditions. Many projects are rated with permanence levels of hundreds of years or more, exceeding the permanence of forestry projects. ## Biomass sourcing All carbon projects need to account for lifecycle emissions, including those from transport. Biochar projects need abundant feedstock, ideally co-located near the pyrolysis facility or kilns to minimize transportation emissions and costs. Additionally, biomass used as feedstock for biochar shouldn’t compete with land for other productive uses like sustainable agriculture or forestry. ## Biochar leakage and additionality If a biochar project uses feedstock that could be productively used elsewhere, this causes "leakage." Leakage refers to the possibility for carbon avoided or removed by a climate project to shift or "leak" to another location or process. Carbon credits are financially additional when a project can demonstrate its viability is due to revenues from sales of carbon credits. Biochar produces revenue streams beyond the sale of carbon credits, including: - The actual biochar, which can be sold to improve soil quality - Combustible gas like methane, which can be sold as fuel - Biochar carbon credits, sold to support project viability ## The varying scales of biochar projects ### Industrial pyrolysis projects These are industrial-scale projects relying on large-scale, automated pyrolyzers or gasifiers capable of mass-producing biochar. They’re highly efficient, sequestering CO₂ at scale while effectively capturing gases emitted as byproducts. ### Artisanal kiln systems Individuals can produce biochar using small kilns or open fires, creating small quantities of material. Although labor-intensive and with higher process-level emissions, these projects support economic opportunities for small communities and can be installed directly on farms. ### Batch systems These systems are between industrial and artisanal methodologies, using kilns for small batches of biochar and achieving a blend of efficiency and co-benefits. ## Capture of methane and other process-related gas The pyrolysis of biomass to create biochar generates combustible gases made from the combination of methane, CO₂, and similar compounds. Biochar projects can either capture all greenhouse gasses emitted during production or account for emissions losses in the final carbon audit. Large-scale pyrolyzers are typically efficient at capturing gases, but some residual emissions always occur.