In carbon markets, permanence is one of pivotal metrics that define credibility. It is a measurement of how long carbon stays locked away once removed from the atmosphere. Here comes biochar, and its permanence. When properly produced and applied, biochar stabilises carbon into forms that resist microbial breakdown for centuries to millennia. This makes it one of the most commercially promising pathways in the carbon removal portfolio.

The Science of Permanence

Research shows that two carbon pools exist in biochar. About 75% is Persistent Aromatic Carbon (PAC), with mean residence times (MRT) of 1,000 years or more, largely independent of soil type or climate. The remaining ~25% is Semi-Persistent Carbon (SPC), which typically persists 50–100 years. Biochar produced at more than 550 °C with a molar H:C ratio below 0.4 reliably creates high PAC content. Feedstocks with more lignin (woody residues) tend to yield more stable carbon than crop residues or manures. Additionally, soil interactions help. Mineral binding, pore protection, and organo-mineral complexes further protect biochar carbon against degradation. Field evidence backs this up: ancient char-rich soils such as Amazonian Terra Preta still hold carbon thousands of years later.

In simpler terms, about three-quarters of the carbon in well-made biochar is so stable that it can stay locked in the soil for a thousand years or more, regardless of climate or soil type. The rest lasts for decades, which is still much longer than compost or crop waste. High-temperature production from woody materials makes biochar more durable, and once in the soil, natural processes give it extra protection. That’s why charred soils from ancient civilizations still hold carbon today.

So what one might ask - 

Why does this matter beyond the lab? Because permanence is what sets biochar apart:

1. Compared to compost or crop residues, biochar creates a carbon sink measured in centuries, not seasons.

2. Compared to reforestation or soil carbon practices, biochar carries a much lower risk of reversal.

3. Compared to engineered removals, biochar achieves near-geological permanence at a fraction of the cost.

So what one might ask again- 

Permanence makes biochar scientifically credible, and commercially differentiating.

The Commercial Value of Permanence

1. Premium Credits: Durable carbon is a scarce commodity. A biochar credit backed by >75% long-lived carbon (>1,000 years) carries more weight, and commands a higher price than a credit from practices that last only 10 to 20 years.

2. Investor Confidence: Permanence reduces the risk of reversal, a key concern in carbon markets. Investors and financiers prefer assets with durability, because they’re less likely to lose value if practices change or conditions shift.

3. Farmer Benefits: Permanence is amplified by biochar’s co-benefits. While carbon stays locked away, farmers see gains in soil fertility, water and nutrient retention, and microbial health. 

Therefore: 

Biochar is not “just carbon in soil.” It is a carbon product with two defined pools, one lasting decades to centuries, the other millennia. The Persistent Aromatic Carbon fraction is essentially permanent at human timescales, while the Semi-Persistent fraction is still far more durable than most alternatives.

Permanence is not a side benefit, it is biochar’s strongest commercial proposition. Developers who can produce high-quality, PAC-rich biochar and credibly verify its permanence will command premium pricing, investor trust, and long-term leadership in both agriculture and carbon markets.