What is Biochar?

Biochar terminology includes the application of charred organic matter in settings outside of agriculture. “Char” is a term used interchangeably with charcoal, but it can also refer to a material that is charred to a lesser extent than charcoal, typically as a product of fire. Biochar is derived from diverse feedstocks and can be created with various technologies, but its climate benefits depend on multiple factors. If fossil fuel energy is used in production, it may reduce or eliminate biochar’s greenhouse gas (GHG) benefits. Similarly, using low-technology methods can produce excess methane, which counters the long-term sequestration benefits of biochar.

Biochar is a solid carbon-rich material produced through thermochemical processes, either pyrolysis or gasification, which convert biomass into charcoal in an oxygen-limited environment. When used in soil applications, such as soil amendment in agricultural lands, or non-soil applications, such as cement and asphalt, biochar is regarded as a carbon sink demonstrating carbon stability over time. The total GHG benefits of biochar depend on the type of feedstocks, the technology used, and the potential fossil fuel inputs used to create the final product. Biochar GHG accounting is complex, and existing biochar certification programs, such as the European Biochar Certificate (EBC), limit feedstock types, technology, and product types that qualify.

Biochar can help retain water and nutrients in the soil for plants to grow due to its adsorption ability. Some biochar’s can immobilize heavy metals, pesticides, herbicides, and hormones, prevent nitrate leaching and fecal bacteria into waterways, and reduce N2O and CH4 emissions from soils. Using biochar production for waste management instead of open burning in fields or landfills can also recover the heat and carriers of renewable energy co-produced during the process to meet the energy needs of local communities, additionally, biochar’s soil stability can range from centennial to millennial timescales.

From Pollution to Capturing CO2

Disregarding animal and crop wastes in agriculture can lead to severe environmental pollution. Biochar can address these wastes and reduce their volume and weight. Green urban and clean industrial wastes can also be used for biochar production, which offers economic opportunities and helps mitigate climate change by decreasing methane emissions, reducing energy use, recovering energy from waste, enhancing carbon sequestration in forests, and decreasing energy used in long-distance waste transport.

Biochar quality control is necessary, but pyrolysis removes pathogens and heavy metals from waste. Unlike manure or compost, biochar does not need to be applied annually, reducing the risk of heavy metal accumulation. Adding biochar to soils is a way to capture carbon dioxide from the atmosphere. For this to work, plants must be grown at the same rate as they are being charred. Biochar decomposes quickly and releases carbon into the atmosphere. Several estimates have been made of the potential of biochar sequestration to reduce atmospheric CO2.

Biochar is a solid material formed through the pyrolysis of organic matter, and its physical characteristics depend on the type of biomass used and the processing conditions. The biomass feedstock’s chemical composition also affects the biochar’s physical nature. For instance, the proportions of some components will influence the degree of reactivity and physical structure modification during processing. The temperature at which the pyrolysis occurs is the most critical factor in determining the physical properties of the biochar. Heating rates and pressures also affect its physical properties.

Biochar Benefits

Adding biochar to soil has multiple motivations, including improving soil productivity, mitigating climate change, reducing off-site pollution, and managing waste on an economically viable basis. Biochar addition to soil can improve crop productivity by increasing cation retention or decreasing acidity in highly weathered soil minerals. This may benefit soils that are degraded by long-term continuous cultivation. In some cases, soil productivity improvement is the primary objective, and biochar production is optimized for its ability to improve soils rather than capture energy.

In other situations, climate change mitigation may be the main incentive, and energy capture during pyrolysis is central to reducing greenhouse gas emissions and economic viability. Biochar production is also motivated by upgrading and facilitating the transportation of low-grade wastes, such as green waste. Converting some green waste into biochar and energy may improve product quality and reduce transportation costs. Biochar management may make use of all four mentioned outcomes. Still, specific locations may pose constraints regarding soil type, crop, biomass availability, energy needs, and any regulatory or economic framework. Ultimately, adding biochar to the soil will depend on the producer’s primary objective.

CO2 Removal Certification

Puro CO2 removal certificates (CORC) are digital certificates that show how much carbon dioxide (CO2) a product has removed from the environment. Products like biochar or wooden building elements with a net-negative impact on the environment can earn these certificates. The Puro Standard checks and certifies these products, and a third party verifies the amount of CO2 removed. The producer can sell these certificates to make revenue and finance their investments. CORCs buyers such as Microsoft and Shopify can use these certificates to show that they support sustainability or net-zero claims. This ensures transparency and prevents double claims.


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