The importance of biochar quality and pyrolysis yield for soil carbon sequestration in practice

Summary

This meta-analysis synthesises published data on biochar to develop a practical metric combining biochar quality and pyrolysis yield for assessing carbon sequestration efficiency in soil. The authors find that stable biochar achieves 25–50% feedstock carbon sequestration, with optimal efficiency (41.4% ± 4.5%) occurring when plant-based feedstocks are pyrolysed at 500–550°C to achieve H/Corg ratios of 0.38–0.44. The findings provide evidence-based guidance for large-scale biochar application under emerging EU regulations and international quality standards.

UK applicability

These findings are directly applicable to UK agricultural practice, particularly given alignment with EU regulation 2021/2088 and international biochar certification schemes increasingly adopted in UK soil carbon schemes and regenerative farming programmes. UK farmers and policymakers can use the identified optimal pyrolysis temperature range (500–550°C) to select or produce biochar with verified sequestration potential.

Key measures

Carbon sequestration efficiency (percentage of feedstock carbon sequestered over 100 years); hydrogen-to-organic carbon (H/Corg) ratio; pyrolysis temperature; carbon yield; fraction of biochar carbon remaining in soil (Fperm)

Outcomes reported

The study evaluated biochar carbon sequestration efficiency by analysing published data compliant with International Biochar Initiative and European Biochar Certificate guidelines, calculating the fraction of biochar carbon remaining in soil after 100 years as a function of the hydrogen-to-organic carbon ratio and feedstock type. The research identified optimal pyrolysis conditions for maximising soil carbon sequestration from plant-based feedstocks.

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