Biochar is frequently cited as one of the most cost-competitive carbon dioxide removal pathways. Costs of $50–200 per tonne CO₂ are achievable at scale — far below direct air capture at $400–1,000+ per tonne, and competitive with enhanced weathering at larger deployment volumes.
But there’s a catch: not all biochar is equal. The gap between high-quality and low-quality biochar is large enough to determine whether a buyer is purchasing centuries of durable carbon storage or a product that will degrade meaningfully within decades.
A new whitepaper from Climeworks and Carbonfuture breaks down what “high-quality biochar” actually means in practice — and why it matters for anyone building a credible CDR portfolio.
What Biochar Is and How It Works
Biochar is produced by heating organic material (biomass feedstock) at high temperature in the absence of oxygen — a process called pyrolysis. Under these conditions, rather than combusting, the carbon in the biomass is transformed into a stable, porous solid material.
When incorporated into soil, high-quality biochar resists biological decomposition for centuries to millennia. This is the mechanism of carbon removal: carbon that would have returned to the atmosphere as CO₂ through decomposition is instead locked into a stable solid form.
The co-benefits are real: biochar improves soil water retention, increases microbial activity, and can reduce agricultural emissions of nitrous oxide (N₂O). But the primary claim in the CDR market is carbon permanence — and that’s where quality differentiation matters most.
The Variables That Determine Quality
Several factors determine whether a given batch of biochar delivers durable carbon removal:
Feedstock type. High-lignin feedstocks — wood, agricultural residues like straw and husks — produce more stable biochar than low-lignin materials. Sewage sludge biochar, for instance, has different stability characteristics and may contain contaminants that disqualify it for soil application in certain jurisdictions.
Pyrolysis temperature. Higher temperatures (above 500°C) produce more stable biochar with higher aromatic carbon content. Below 450°C, the H/C organic ratio — the key proxy for carbon stability — rises, indicating more labile carbon that will decompose faster. The relationship is not perfectly linear, and optimal temperature varies by feedstock, but the rule of thumb holds: hotter is more stable.
H/C organic ratio (H/Corg). This is the most widely used proxy for biochar stability. The European Biochar Certificate (EBC) and International Biochar Initiative (IBI) both specify maximum H/Corg thresholds for certified biochar. At H/Corg below 0.4, carbon is considered highly stable with a mean residence time in the centuries range. Above 0.7, the carbon is significantly less stable.
Certified permanence and chain of custody. The most credible biochar credits in the market come with third-party certification against EBC or IBI standards, including documentation of feedstock origin, pyrolysis process parameters, and the H/Corg ratio of the final product. Buyers who don’t verify this chain of custody are not buying what they think they’re buying.
What Low-Quality Biochar Looks Like
The voluntary carbon market has had quality problems with biochar. Early biochar projects used whatever feedstock was locally available, run at suboptimal temperatures, with minimal process monitoring. The resulting products had elevated H/Corg ratios and, in some cases, contained polycyclic aromatic hydrocarbons (PAHs) at levels that raised soil safety questions.
Buyers who purchased these credits without auditing the process parameters acquired exposure to credits that may not represent durable removal — and, in some cases, exposure to soil contamination liability.
This is the biochar field’s credibility problem: the pathway is scientifically sound when done correctly, but the market has historically had limited ability to distinguish high-quality from low-quality production at the point of purchase.
How the Market Is Improving
The EBC and IBI certification systems are the primary tools for quality differentiation, but compliance varies. The most rigorous buyers now require:
- Process documentation: Feedstock type, origin, pyrolysis temperature range, and equipment specifications
- Product analysis: H/Corg ratio, total carbon content, PAH levels, heavy metals
- Third-party verification: Not self-reported, independently audited
- Chain of custody: From feedstock to application site
CDI portfolio companies Syncraft and Cotierra are built around exactly this kind of rigorous process control. Syncraft operates wood gasification systems in Central Europe and the Alpine region, producing biochar as a co-product with independently verified stability characteristics. Cotierra builds soil carbon and biochar pathways in Latin America, where agricultural feedstock availability and tropical conditions create strong conditions for high-quality, cost-competitive production.
In a market where quality signals are still being established, that differentiation matters — not just for reputational reasons, but because the buyers with the largest and most scrutinized portfolios are increasingly requiring it.
The Bottom Line for Buyers
Biochar can deliver cost-effective, durable carbon removal. The cost advantage is real. But the quality range is wide enough that “biochar credit” is not a sufficient description of what you’re buying.
Before purchasing, verify: what was the feedstock? What temperature was it processed at? What is the H/Corg ratio? Is it EBC or IBI certified? Who audited it?
If a supplier can’t answer those questions clearly, you’re not buying durable CDR — you’re buying a claim.
For a detailed look at how biochar production works at different scales and what the economics look like across production models, see the CDI blog post: How to Make Biochar at Different Scales.
Source: Climeworks/Carbonfuture whitepaper on biochar quality standards, via Climeworks on X, April 1, 2026.