What is biochar?
We define biochar as a porous, carbon-rich solid produced by the thermochemical conversion of organic materials under oxygen-limited conditions. Biochar possesses unique physicochemical properties that make it suitable for the safe, long-term sequestration of carbon in the environment, as well as for potential soil enhancement and other environmental applications. This definition is intentionally flexible, encompassing both the production process and the various applications of biochar.
A sustainable biochar system is one that:
a) produces and applies biochar in a manner that is safe and minimizes the emission of non-CO2 greenhouse gases (such as methane and nitrous oxide);
b) contributes to a net reduction in radiative forcing; and
c) promotes equitable access to resources without exacerbating social inequalities.
While such systems are rare at commercial or demonstration scales, they represent the ideal toward which biochar technology should strive. It is important to note that traditional charcoal production, unless it includes effective mitigation of fugitive emissions and soot removal, does not meet the criteria of a sustainable biochar system.
Biochar's structure is predominantly amorphous, with regions of local crystalline organization comprised of highly conjugated aromatic compounds. These crystalline regions are typically nanoscale in size, featuring turbostratically arranged graphite-like layers (i.e., the layers are not perfectly aligned). Beyond these graphene-like structures, biochar also contains a complex mixture of aromatic and aliphatic organic compounds, as well as inorganic minerals derived from the original biomass. Additionally, biochar's structure includes various voids, such as macro-, meso-, and micropores, which originate from the cellular structure of the biomass. This unique combination of properties gives biochar its distinctive characteristics, including its resistance to microbial decomposition, making it an effective and durable carbon sink.