What is biochar?

Generally speaking, biochar is the product of turning biomass into gas or oil with the intention of adding it to crop and forest production systems as a soil amendment. The definition of biochar is more about its creation and intended application rather than what it is composed of. Both charcoal and biochar are produced through an energy conversion process called pyrolysis, which is essentially the heating of biomass in the complete or near absence of oxygen.

Pyrolysis of biomass produces char, oils, and gases. The amount of these materials produced depends on processing conditions. What makes biochar different from charcoal is that the biochar product is created for use as a soil amendment. Biochar can be produced from a variety of biomass feedstocks, but is generally designated as biochar only if it produces a useable co-product for soil improvement. The oils and gases from pyrolysis can be used for energy production. The biochar and energy created can provide a carbon-negative energy source and a useable co-product for soil improvement. However, not all biochars are created equal. The efficiency and effectiveness of the process of its creation and use can vary and the specific biomass sources used can affect the characterization and usability of the biochar.

Complex ongoing research is striving for a more uniform and standard biochar that will limit potential environmental problems associated with biochar production and application to soils. Creating a standardization of biochars may make it possible for people who buy biochar to depend on uniform attributes. Issues such as what should be the ideal moisture and ash content of standard biochar are relatively easy to measure and standardize, but tests for metals and alkalinity are not. Some of the attributes that might be expected from biochars can go beyond just physical characteristics to issues of whether the feedstock used in its creation was from a renewable feedstock, whether its production reduced greenhouse gas emissions and whether the biochar can improve soil quality in a reliable way.

From a practical perspective, biochar can benefit farmers and ranchers because it serves as a soil amendment that can enhance fertility and reduce the need for more costly fertilizers. It also helps retain moisture in the soil, and it may have the potential to significantly mitigate greenhouse gas emissions and slow climate change.

You can learn much more about this topic in the ATTRA publication Biochar and Sustainable Agriculture. This publication reviews the current research and issues surrounding the production and use of this emerging biomass energy technology and explore how biochar can contribute to sustainable agriculture.