Industrial biochar systems for atmospheric carbon removal: a review

In the context of climate change, there is an urgent need for rapid and efficient methods to capture and sequester carbon from the atmosphere. For instance, production, use and storage of biochar are highly carbon negative, resulting in an estimated sequestration of 0.3-2 Gt CO2 year(-1) by 2050. Yet, biochar production requires more knowledge on feedstocks, thermochemical conversion and end applications. Herein, we review the design and development of biochar systems, and we investigate the carbon removal industry. Carbon removal efforts are currently promoted via the voluntary market. The major commercialized technologies for offering atmospheric carbon removal are forestation, direct air carbon capture utilization and storage, soil carbon sequestration, wooden building elements and biochar, with corresponding fees ranging from 10 to 895 GBP (British pounds) per ton CO2. Biochar fees range from 52 to 131 GBP per ton CO2, which indicates that biochar production is a realistic strategy that can be deployed at large scale. Carbon removal services via biochar are currently offered through robust marketplaces that require extensive certification, verification and monitoring, which adds an element of credibility and authenticity. Biochar eligibility is highly dependent on the type of feedstock utilized and processing conditions employed. Process optimization is imperative to produce an end product that meets application-specific requirements, environmental regulations and achieve ultimate stability for carbon sequestration purposes.