Biochar C-Sink
The Global Biochar C-Sink Standard was introduced in 2020 as the EBC C-Sink Standard — the first certification standard for biochar-based carbon sinks and, at the time, the first operational standard for any form of geological carbon removal. Now in version 4.0 (2026), it provides the methodology for calculating, tracking, and certifying the carbon sequestered when biochar is applied to soil or incorporated into durable materials. Every certified C-sink is registered in the Global C-Sink Registry.
The standard requires that biochar used for C-sink certification is produced under EBC or WBC certification, guaranteeing the sustainability of biomass sourcing and the pyrolysis process. From there, it follows the carbon through every step — transport, processing, trading, matrix incorporation, and final application — using a mandatory digital MRV system that ensures no carbon is counted that cannot be verified.
At the core of the methodology is a probabilistic persistence model that divides biochar carbon into two pools. The geologically persistent carbon (GPC) fraction — the highly aromatic core of the biochar — is modelled to persist beyond 1,000 years and qualifies as a geological C-sink. The semi-persistent carbon (SPC) fraction decays more slowly than uncombusted biomass but faster than GPC, following a modelled decay function. Two persistence classes (upper and lower) are assigned based on analytical proxies — the H/Corg molar ratio, Random Reflectance, and hydrogen pyrolysis (HyPy) — which characterise the degree of carbonisation and aromaticity of the biochar. These proxies, refined in version 4.0, determine the certified C-sink value over defined time horizons (C-Sink_100, C-Sink_200, C-Sink_1000+).
All greenhouse gas emissions associated with the entire chain — from biomass production through pyrolysis, transport, processing, and application — must be fully documented in an emission portfolio and offset before the C-sink can be registered. This ensures that every registered biochar C-sink represents verified net carbon removal, not gross removal with hidden emissions.
The standard certifies biochar carbon sinks across multiple application pathways. Soil application creates geological C-sinks. Biochar incorporated into mineral-bound construction materials (concrete, asphalt) is fully protected from degradation for the lifetime of the structure. Biochar in composite materials, animal farming substrates, and other approved matrices creates temporary C-sinks whose duration depends on the matrix. For each pathway, the standard defines specific persistence rules and end-of-life accounting.
Version 4.0 introduces a methodology for methane offsetting using biochar-based temporary carbon sinks. Based on the total climate effect (TCE) framework, the methodology matches the time-dependent cooling of a carbon sink to the warming impact of a methane emission over defined horizons. This enables biochar C-sinks to be used not only for CO₂ compensation but also for the offsetting of methane from agriculture and waste management.
The standard and its certification are operated by Carbon Standards International. The Ithaka Institute develops and curates the standard.
Link to Global Biochar C-Sink Standard v4.0 (PDF)
Link to Carbon Standards International for further information