Biochar from animal manure: A critical assessment on technical feasibility, economic viability, and ecological impact

Summary

This review examines pyrolysis as a thermochemical treatment for surplus animal manure in regions with intensive livestock farming, evaluating its capacity to address contamination, pathogen, and climate risks while producing energy and biochar. Manure pyrolysis reduces bioavailability of potentially toxic elements, eliminates pathogens and micropollutants, and lowers greenhouse gas emissions compared to conventional storage and application. However, the authors identify substantial knowledge gaps regarding nutrient mass balances and crop yield effects, and note that nitrogen losses during pyrolysis require mitigation through pretreatment strategies such as liquid–solid separation or ammonia stripping.

UK applicability

The United Kingdom has intensive livestock regions with manure surplus constraints under nutrient management regulations; pyrolysis could address restrictions on manure field application, particularly in areas with high stocking densities. However, the review's call for more field trials with standardised nutrient accounting suggests UK-specific trials would be needed to validate crop productivity and economic returns under British soil and climate conditions.

Key measures

Bioavailability of potentially toxic elements (PTEs); elimination of pathogenic microorganisms and organic micropollutants; greenhouse gas emissions reduction; nitrogen loss during pyrolysis; crop yield and fertilisation efficiency; technical feasibility and economic viability of pyrolysis systems

Outcomes reported

This review assessed the technical feasibility, economic viability, and ecological impact of converting animal manure via pyrolysis into biochar and energy. The authors evaluated how manure pyrolysis affects contaminant reduction, greenhouse gas emissions, nitrogen losses, and crop productivity relative to conventional manure management.

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