There’s a common criticism of biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More as a climate solution: that it simply moves carbon from one short-term reservoir, the biosphere, to another, the soil, without truly reducing atmospheric CO₂. This perspective, however, misunderstands the fundamental nature of the global carbon cycle and the specific role biochar plays within it. A review published in the journal BiomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More and Bioenergy, authored by David Chiaramonti, Franco Berruti, Johannes Lehmann, and their colleagues, aims to provide a clear, scientifically supported framework for understanding biochar as a durable carbon dioxide removal (CDR) solution.

The Earth’s carbon cycle involves the movement of carbon between different reservoirs—the atmosphere, biosphere, and geosphere—through various biological, chemical, and geological processes. While the biosphere consists of living organisms, plant residues, and active soil organic matter with short residence times (weeks to decades), the geosphere, which begins with soils and sediments, stores carbon for much longer periods, from centuries to millions of years. The key distinction isn’t physical location, but whether the carbon is accessible to biological degradation.

PyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More, the process of making biochar, is a critical step in a two-part process that converts short-lived carbon into a durable, geospheric form. First, plants use photosynthesis to capture atmospheric CO₂ and store it as biomass. This biomass would typically decompose, returning the carbon to the atmosphere over a short period. However, when biomass is subjected to thermochemical conversion—pyrolysis—it undergoes dehydration and condensation. This process creates highly condensed aromatic structures similar to those found in coal, which are far more resistant to microbial decomposition than unpyrolyzed biomass. Biochar can be seen as a way to shift the residence timeResidence time refers to the duration that the biomass is heated during the pyrolysis process. The residence time can influence the properties of the biochar produced.   More of carbon. Instead of returning to the atmosphere within decades through decomposition, a significant portion of this carbon is converted into a highly stable form with residence times on the scale of centuries to millennia. For biochar made with proper production conditions, specifically at a maximum carbonization temperature of 550–600°C, the carbon is converted to a highly durable form, with a minimal risk of re-release over hundreds of years. Long-term field experiments have even confirmed that the most permanent fractions of biochar remain unaltered after 15 years of conventional farming.

The authors also address concerns about the lack of permanence in some biochar applications. They point out that scientific studies showing significant degradation have often used insufficiently carbonized biochar, produced at temperatures below 550°C, or have incorrectly parameterized decay models. There is no danger of a sudden carbon re-release if the biochar is properly characterized. The amount of durable carbon can be predicted from its properties. The fact that there is a scientific field dedicated to this makes it more valid.

When implemented in a sustainable system where harvested biomass is replaced through regrowth, biochar adds an additional, long-term storage pathway that doesn’t diminish the biosphere’s natural role as a carbon sink. By diverting a fraction of biomass away from short-term decay and into long-term geological storage, biochar systems achieve a net atmospheric carbon removal. This process also has agronomic co-benefits, as it can improve soil health and productivity, making the agricultural system more photosynthetically efficient.

In conclusion, the authors argue that biochar is a valid and robust CDR solution. It’s a two-step process that combines the power of photosynthesis with advanced carbonization technologies to create a new, long-term carbon reservoir. This dual-action approach not only diverts carbon from the atmosphere but also enhances agricultural systems, highlighting biochar’s potential as a critical tool in the fight against climate change.

Source: Chiaramonti, D.; Berruti, F.; Lehmann, J.; Masek, O.; Petersen, H.I.; Perez, M.G.; Sanei, H.; Vaccari, F.P. Biochar and its impact on the carbon cycle. Biomass and Bioenergy 2025, 203, 108365.