Biochar’s Permanence in Long-Term Soil Carbon Sequestration

The durability of biochar as a method of carbon removal has long been a topic of scientific debate. How permanent is biochar carbon removal (BCR)? A new, peer-reviewed study[1] provides groundbreaking insights: inertinite—a stable, carbon-rich component of biochar—demonstrates remarkable resistance to decomposition in soils, representing a permanent carbon removal and soil health solution.

What is Inertinite?

Inertinite is a specific carbon fraction characterized by its chemical stability and resistance to decomposition. Researchers Hamed Sanei and Henrik I. Petersen have developed methods to precisely measure this fraction, addressing long-standing concerns about biochar's long-term stability. Previous studies typically relied on short-term laboratory incubation experiments, which often depicted biochar decay rates inappropriately, leading to incomplete understanding of its permanence.

Real-World Proof of Biochar's Durability

In 2009, researchers applied biochar to a Tuscan vineyard at a rate of 22 tons per hectare (about 9 tons per acre). Fifteen years later, they carefully unearthed and analyzed the biochar using advanced scientific techniques. The goal was to understand its long-term behavior under real agricultural conditions.

The results were compelling. Despite exposure to typical farming practices like tillage and fertilization, the biochar showed remarkable stability. The ratio of fixed carbon to total carbon varied by only about 8%, with the inertinite fraction remaining fundamentally unchanged.

Agricultural Implications of Biochar's Stability

From an agricultural perspective, this research offers compelling insights beyond carbon sequestration, highlighting biochar's potential to transform soil management. The remarkable stability demonstrated by minimal changes in carbon composition over 15 years suggests profound benefits for agricultural systems. The near-constant inertinite fraction indicates that biochar can provide long-term soil structure improvements, enhanced water retention, and sustained nutrient availability.

By maintaining its physical and chemical properties over extended periods, biochar acts as a persistent soil amendment that not only sequesters carbon but also improves overall soil quality. This durability means farmers might see sustained benefits from a single application, including improved soil fertility, reduced erosion, and potentially increased crop resilience to environmental stresses—all while contributing to carbon removal strategies.

Biochar as a Carbon Removal Strategy

This study marks a significant step forward in understanding biochar’s potential as a powerful tool for carbon removal and soil health. It provides verifiable evidence that high-quality biochar can meet durability standards required by emerging climate policies. As the debate around biochar’s durability continues, this study offers compelling evidence that high-quality biochar, composed largely of inertinite, does not decay in soils. The question is no longer whether biochar is a viable carbon removal tool—it is. The challenge now is scaling its use and integrating it into global CDR policies and practices. For anyone dedicated to advancing sustainable agriculture and tackling climate change, the path forward is unmistakable.

[1] Note: Chiaramonti, D., Lotti, G., Vaccari, F. P., & Sanei, H. (2024). Assessment of long-lived carbon permanence in agricultural soil: Unearthing 15 years-old biochar from long-term field experiment in Vineyard. Biomass and Bioenergy, 191, 107484. https://doi.org/10.1016/j.biombioe.2024.107484