Biochar carbon removal, also known as pyrogenic carbon capture and storage, is a method of reducing carbon in the atmosphere. This process starts with the heating of leftover plant material through a method called pyrolysis, which creates a substance called biochar. This biochar is then added to soil or used in long-lasting materials like cement and tar. Biochar changes carbon from plant matter into a stable, charcoal-like form that can remain in soil for hundreds to thousands of years, instead of returning to the air as carbon dioxide.

Studies show that biochar added to soil can stay there for hundreds to thousands of years, depending on factors such as the type of plant material used, how it is processed, how much is added, and the type of soil. Biochar and similar materials, like pyrogenic carbon, can also help reduce the release of greenhouse gases from soil and support plant growth.

Some studies and combined research have found that biochar can sometimes cause problems, such as breaking down faster than expected, increasing greenhouse gas emissions, or harming other carbon in the soil. Because of this, biochar carbon removal should be used carefully, with the right amount, type of plant material, and processing methods suited to the specific soil where it is used.

Definition

The term describes the process of making biochar from plant materials and other organic matter that are obtained in an environmentally responsible way. This biochar is then kept in storage for a very long time. The process uses photosynthesis, which is how plants take in carbon dioxide from the air as they grow. During biochar production, this carbon dioxide is locked inside the biochar and can remain stored for hundreds or even thousands of years.

Biochar Carbon Removal is a type of technology that helps remove carbon dioxide from the atmosphere. It is a method that can be quickly set up and is cost-effective, making it suitable for small-scale projects like farms. It also supports economic growth in rural areas of developing countries. This is mentioned in guidelines from the Science Based Targets initiative.

Scientists often call this process Pyrogenic Carbon Capture and Storage (PyCCS). The term "Biochar Carbon Removal" was first used by the European Biochar Industry Consortium in 2023 and has since been accepted by many organizations and experts.

Biochar Carbon Removal is also classified as a type of Biomass Carbon Removal and Storage (BiCRS).

In addition to capturing carbon, using biochar can have other benefits, such as helping plants grow more, increasing the amount of roots, improving how efficiently plants use water, and supporting the activity of soil microbes.

Biochar production

Biochar is made using a process called pyrolysis. Plant materials left over from farming or landscaping are broken into small pieces and heated to 350–900 °C (662–1,652 °F) in conditions with little oxygen. This creates solid biochar and other by-products, such as bio-oil and pyrogas. To help store more carbon in the soil, biochar production methods that reduce burning and prevent pyrogas from escaping into the air are usually used.

When organic materials are heated without much oxygen, they change into gases called pyrogas and solid materials called biochar. The pyrogas often turn into liquid bio-oil, which can be used for energy. Biochar is being studied as a way to store carbon in soil.

The global market for biochar is predicted to grow to US$368.85 million by 2028.

Around the world, several voluntary standards help control how biochar is made and its quality. These include:

• The European Biochar Certificate (EBC) and World Biochar Certificate (WBC), created by the Ithaka Institute
• The U.S. Environmental Protection Agency (EPA)
• The International Biochar Initiative

Carbon removal potential

During pyrolysis, three main carbon-based products are created. These products can be stored in different ways to reduce carbon in the air: solid biochar for various uses, a liquid called bio-oil that is pumped into old oil wells, and a gas called pyrogas (mainly carbon monoxide, hydrogen, and methane) that can be turned into carbon dioxide and stored underground after burning.

In 2022 and 2023, biochar helped remove 87 to 92 percent of all carbon taken out of the atmosphere.

Scientists are still studying how much carbon can be removed using biochar. Using waste from farming and forestry worldwide, it is estimated that about 6 percent of global emissions, or 3 billion tons of carbon dioxide, could be removed each year for 100 years. More broadly, the potential is estimated to be between 0.3 and 4.9 billion tons of carbon dioxide per year.

How long carbon stays stored in a material is an important measure of its quality and durability. Biochar is made by quickly turning organic matter into a specific type of material called maceral. Evidence shows that biochar made at temperatures above 600 degrees Celsius (1,112 degrees Fahrenheit) is very stable, similar to a type of material called inertinite. Studies suggest that the long-term storage and ability of biochar to remove carbon may be underestimated because some methods are too simple.

How much carbon dioxide is stored depends on how biochar is made and how it is used afterward. If made under certain conditions, 97 percent of the organic carbon in biochar becomes very hard to break down, meaning it can stay stored for a very long time. This shows that biochar can store carbon dioxide for a long time. Making biochar effectively is therefore important for long-term carbon storage.

There are several ways to store carbon dioxide for a long time:

• Soil application: When mixed into soil, biochar breaks into tiny pieces that can move deeper into the soil or into groundwater, where they are less likely to break down. Studies show that this type of carbon can stay stable for hundreds of years. Biochar can improve soil fertility, and it is estimated that using biochar in soil could store 2.5 billion tons of carbon dioxide each year.

• Additive for construction material (Cement Particleboards): Adding biochar to cement mixtures is still being tested, and exact calculations are not yet known. In general, biochar does not harm the usefulness of cement mixtures. Biochar is a porous material that can make cement lightweight, improve insulation, and help control humidity.

• Additive in asphalts: Biochar added to asphalt is still being studied, but early results are promising. Asphalt usually breaks down quickly when exposed to weather and has poor durability. Biochar can make asphalt more durable and more resistant to heat. One idea is to use agricultural waste, like crop straw, to make biochar for asphalt, which could increase the value of the waste and improve the asphalt’s quality.

• Additive in plastics, paper, and textiles: Adding biochar to plastic creates a combination of materials, with plastic as the main part and biochar as a reinforcement. This improves the plastic’s ability to resist heat and moisture. When added to recycled plastics, biochar makes the plastic stronger and stiffer. Combining plastics and biochar during production also lowers costs and improves efficiency.

Biochar-based carbon credits

Biochar carbon removal is becoming a hopeful method for reducing carbon emissions, especially for offsetting and carbon markets. Because biochar carbon removal has high costs for reducing carbon, biochar carbon credits are sold at prices much higher than credits from traditional methods like reducing emissions or using natural solutions. Some people believe biochar carbon credits are the best type of credit because they help companies save money and keep carbon locked in soil for hundreds or even thousands of years, preventing it from returning to the air.

Interest in biochar credits is growing, but trading these credits is still limited to a small number of companies that produce biochar and those that buy the credits. In 2024, most purchases of carbon dioxide removal (CDR) credits came from biochar projects, making up 86% of all credits bought that year.

To create biochar credits, several international standards and methods are used. Examples include:
• VERRA VM0044
• Puro.Earth Biochar Methodology (Finland)
• CSI Global Artisanal C-Sink
• Nori (USA)
• MoorFutures (Germany)
• max.moor (Switzerland)
• Compensate (Finland)

Many biochar production and credit standards set rules about which types of biomass can be used to make biochar. For example, the European Biochar Certificate (EBC) lists approved materials, such as agricultural waste, plant materials grown for use, wood waste from forests and sawmills, waste from landscaping, recycled materials, kitchen waste, food waste, textiles, waste from digestion processes, wastewater sludge, and animal by-products.

For a credit to be approved, companies must be carbon net-negative, meaning they capture more carbon than they use during the production and delivery of biochar.

More startups are working to expand biochar production in the Global South by selling carbon credits. For example, a company in Tanzania called Dark Earth Carbon (DEC) is supported by the UK Foreign, Commonwealth & Development Office’s Green Growth Facility (International Climate Finance). Many projects worldwide are now promoting biochar initiatives and selling carbon credits.