Turning food waste into climate solutions: New study shows biochar can cut emissions at low cost

A new study reveals that converting food waste into biochar could offer a powerful and affordable way to remove greenhouse gases while addressing a growing waste management challenge.

Researchers investigated how digestate, a byproduct of anaerobic digestion of food waste, can be transformed into stable biochar and applied to agricultural soils. Their findings show that this process can lock carbon into the ground for the long term while significantly reducing overall emissions.

“Food waste is often seen as a disposal problem, but our results show it can become part of the climate solution,” said lead author Dr. Disni Gamaralalage. “By converting digestate into biochar, we can both manage waste more sustainably and remove carbon dioxide from the atmosphere.”

Food waste is produced in vast quantities worldwide and is commonly treated through anaerobic digestion. While this process generates renewable energy, it also produces digestate, a wet residual material that is difficult to reuse due to contamination and high moisture content. As a result, it is often incinerated, leading to additional emissions and lost resource value.

The study demonstrates that hydrothermal carbonization followed by high temperature processing can efficiently convert this digestate into biochar, a carbon rich material known for its stability in soils. The resulting biochar contains a highly stable carbon fraction that resists degradation and can remain stored in soil for centuries.

According to the research, each tonne of biochar produced can remove between 1.15 and 1.20 tonnes of carbon dioxide equivalent from the atmosphere. This is largely due to the long term storage of carbon within the biochar structure.

Importantly, the team found that the process can be economically competitive. When biochar production facilities are located close to existing anaerobic digestion plants, greenhouse gas removal can be achieved at costs below £100 per tonne of carbon dioxide equivalent. This makes the approach comparable or even favorable relative to many other carbon removal technologies.

The analysis highlights that transportation plays a key role in both cost and emissions. Moving wet digestate over long distances significantly increases costs, suggesting that decentralized, co located systems offer the best performance.

Beyond climate benefits, applying biochar to agricultural soils may also improve soil quality. Biochar can enhance water retention, support nutrient availability, and potentially reduce the need for synthetic fertilizers. However, the study notes that more research is needed to fully quantify these additional benefits under real world conditions.

The researchers also explored future deployment scenarios in the United Kingdom. They estimate that using half of the country’s projected food waste digestate by 2030 could remove around 93 thousand tonnes of carbon dioxide equivalent per year, requiring a network of biochar production facilities.

Globally, the potential is even greater. With over one billion tonnes of food waste generated annually, scaling this approach could contribute meaningfully to climate mitigation efforts.

The study emphasizes that policy and economic incentives will be crucial for widespread adoption. In particular, the ability to charge a gate fee for processing waste plays a major role in making the technology financially viable.

“This work shows that waste derived biochar can be both a climate and economic opportunity,” said the authors. “With the right infrastructure and policy support, it could become an important tool in achieving net zero goals.”

The findings provide new insights into how waste management systems can be integrated with climate strategies, offering a practical pathway toward a more circular and low carbon economy.

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Journal Reference: Gamaralalage, D., Rodgers, S., Gill, A. et al. Biowaste to biochar: a techno-economic and life cycle assessment of biochar production from food-waste digestate and its agricultural field application. Biochar 7, 50 (2025).   

https://doi.org/10.1007/s42773-025-00456-0   

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About Biochar

Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field. 

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