Biochar

Risks and Controversies

2 min read

Risks and Controversies

Permanence science divergence

Decomposition-model camp (IPCC, models soil GHG from biochar, Puro CORC200+, Isometric 200y) vs inertinite/Ro camp (Sanei et al.; Isometric 1000y; CSI upper class). Critiques argue inertinite proxies can overstate absolute permanence or that two-pool models mis-specify chemistry. See Permanence Science for Credits and Consensus vs Debates.

Leakage & land-use

  • Market leakage if biomass is diverted from higher-carbon uses (timber, mulch, animal feed)
  • Harvesting that depletes ecosystem carbon stocks (non–waste biomass) undermines net removal
  • Residue removal can harm soil protection (also flagged in NRCS soil carbon amendment in US ag)

Contamination & agronomic harm

PAHs, dioxins, heavy metals, high salts (manure chars), excessive liming on alkaline soils; dust/albedo/erosion on slopes. Standards respond with EBC/WBC limits; NRCS excludes biosolids chars over PFAS concerns. See Contaminants and Quality.

Double counting

Same tonne claimed as product footprint reduction, voluntary credit, and compliance instrument; unclear ownership along grower → pyrolyzer → farmer → buyer chain; overlap with soil-carbon farming methodologies. See Double Counting and Credit Ownership.

Overstated yields / MRV gaps

Crediting before application; weak retail chain-of-custody; optimistic permanence factors; ignoring CH₄ from pyrolysis or biomass storage. Delivery vs contracted volume gaps create expectation risk (CDR.fyi(https://www.cdr.fyi/blog/biochar-carbon-removal-market-snapshot-2025)).

Greenwashing critiques

NGOs (e.g., Fern, Carbon Market Watch) criticize carbon-removal certification frameworks—including biochar under EU CRCF drafts—for weak life-cycle boundaries, land-sector interactions, or insufficient safeguards. Marketing “carbon-negative fertilizer” without retired, unique registry tonnes is a separate risk.

Buyer concentration

Microsoft and a few others dominate BCR volume—see Buyers and Offtakes · Market Volumes and Pricing · Historical Deals. Q1 2026 intermediaries facilitated 74% of contracted tonnes (CDR.fyi).

Graph View

Backlinks