Optimization of Production for Certification of Biochar for Carbon Dioxide Removal based on Pyrolysis Conditions

Meeting the long-term temperature goals of the UN Paris Agreement requires greenhouse gas (GHG) emission reductions and carbon dioxide removal (CDR) from the atmosphere. Biochar’s role as a new CDR technology is currently being discussed. Particularly, with the Intergovernmental Panel on Climate Change (IPCC) revising the national GHG inventory guidelines in 2019, related research has increased following the publishing of methodologies for quantifying the role of biochar as a CDR following its sequestration in soil. Therefore, this study aimed to scientifically evaluate the CDR methodology for biochar proposed by the IPCC and establish a methodology that reaches the Tier-2 level to calculate GHG reduction effects. For this, the conditions that satisfy the certification criteria for biochar at the earliest stage were determined, and the conditions of biochar production that maximize carbon removal were evaluated. The results of this study showed that, depending on the biomass type, biochar produced via pyrolysis at 400°C for at least 30 min met the certification criteria, with an organic carbon content (C_org) of at least 10% and a H/C_org molar ratio of less than 0.7. However, for sewage sludge, the certification criteria were met only in the case of pyrolysis at 550°C for at least 30 min. The manufacturing conditions with the largest organic carbon yield that met the certification seemed to be the most appropriate for maximizing carbon removal.