Evaluating Biochar Crediting Protocols for Durable Carbon Removal

Shreya Mukhopadhyay, Xiaodong Gao, Julia Seay, Thembelihle Chaza, Saran Sohi, Caroline Masiello, Kenneth B. Medlock III

As biochar expands as a source of carbon credits it has become increasingly clear that there are major differences among biochar protocols. This variation can make it challenging for producers to choose protocols and can make it difficult for buyers to understand the comparative value of different certified biochar credits, and in both these cases investor confidence is jeopardized. Here we comparatively review eight voluntary biochar crediting protocols, evaluating their approaches to six parameters: feedstock eligibility, production conditions, application criteria, permanence, reversal risk, and monitoring, reporting, and verification (MRV). We find that all protocols have three common types of requirements: restrictions on eligible biomass feedstocks, controls in thermochemical conversion, and documentation of end uses associated with carbon storage. However, we also find protocols have major differences in how they operationalize permanence and carbon crediting integrity. Some methodologies treat permanence as a material quality and use compositional indicators such as H:Corg ratios to define permanence. Others adopt a temporal or end use approach, quantifying the fraction of carbon expected to remain stored over a specific time period given the final use. Also, requirements for lifecycle assessment, chain of custody documentation, and non-soil application vary considerably. Finally, we identify three key scientific and methodological uncertainties that may present future challenges for all biochar protocols: biochar loss during fire, landscape mobility and erosion, and biochar induced priming of native soil-carbon. We conclude that more harmonized, evidence-based approaches to durability, full life-cycle emissions and uncertainty management are needed to improve credibility and support high integrity biochar CDR markets.