Biochar stability validation – reaching a new level of understanding and transparency

Biochar can store carbon in soils for centuries, but uncertainties about its long-term stability have limited its integration into carbon removal frameworks. This project addressed that challenge by consolidating global datasets, conducting laboratory incubations and field trials in Sweden, and developing models that estimate how much biochar carbon remains in soil over time.

The results show that biochar stability can be predicted from measurable properties such as the hydrogen-to-carbon (H/C) ratio and mean annual temperature. The project also produced a public dataset and Python code on GitHub, enabling transparent and reproducible calculations of biochar durability.

Together, these outcomes strengthen the scientific foundation for using biochar as a credible carbon dioxide removal method and provide practical tools for researchers, policymakers, and market actors.

The long-term field trial at Ultuna will continue beyond the project period to generate new data on biochar persistence under natural conditions.

The project has included dialogue with a wide range of biochar actors in Sweden and internationally, including public authorities in Sweden and the European commission regarding new EU legislation, as well as the Greenhouse Gas Protocol for organizational climate reporting.

A statement prepared with the aim to synthesize current understanding of the durability of biochar carbon storage was published in June 2023: On The Durability Of Biochar Carbon Storage.