In a comprehensive analysis published in EarthArXiv, Mukhopadhyay et al. systematically evaluated how eight prominent voluntary carbon market protocols measure, quantify, and verify carbon removal through biochar. The study examined foundational protocols including Verra VM0044, Isometric, Puro.earth, Climate Action Reserve, European Biochar Certificate, World Biochar Certificate, Global Biochar Carbon Sink, and Global Artisan Carbon Sink. The authors found that while all eight frameworks share a fundamental baseline—requiring non-purpose-grown biogenic waste, controlled pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More heating parameters, and traceable end-use applications—they diverge significantly in how they define and account for carbon durability.

The primary divergence identified in the review lies between material-based and temporal crediting methodologies. Standards like the European Biochar Certificate and World Biochar Certificate evaluate durability primarily as an inherent property of material quality, using hydrogen-to-organic-carbon ratios to confirm structural recalcitrance. In contrast, project-focused protocols such as Verra VM0044, Puro.earth, Climate Action Reserve, and Isometric treat permanence as a variable timeline, applying complex decay curves to estimate how much carbon remains after one hundred to one thousand years in specific soil environments. These conflicting approaches generate wide variations in calculated carbon removal totals for identical batches of biochar.

In addition to foundational accounting differences, the study highlights critical gaps in handling environmental risks and lifecycle accounting. Protocols differ sharply in their full life-cycle assessment boundaries, with some ignoring energy inputs or transport emissions altogether. Furthermore, the review outlines three major scientific uncertainties that threaten credit integrity: physical transport of biochar through wind and water erosion, accelerated oxidation during forest fires, and altered native soil carbon decomposition through chemical priming. Most protocols currently lack robust buffer pools or physical management rules to account for these post-application losses.

The resulting fragmentation creates substantial market friction, driving credit prices from ninety dollars to six hundred dollars per ton of carbon dioxide equivalent removed. This price spread forces buyers to perform expensive secondary due diligence to verify actual credit value. Additionally, compliance hurdles and steep verification fees leave more than fifty percent of global biochar producers uncertified, preventing smaller operators from accessing carbon finance. The authors conclude that establishing unified carbon accounting rules and standardizing testing protocols will be vital to restoring market transparency, lowering entry barriers, and scaling high-integrity carbon removal.

Source: Mukhopadhyay, S., et al. (2026). Evaluating biochar crediting protocols for durable carbon removal. EarthArXiv.