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

Summary

This review examines pyrolysis—thermochemical conversion under oxygen-limited conditions—as an alternative treatment for animal manure in regions with intensive livestock production. The authors assess pyrolysis's capacity to reduce bioavailability of potentially toxic elements, eliminate pathogens and micropollutants, reduce greenhouse gas emissions, and provide energy recovery, whilst identifying critical gaps in evidence on nutrient mass balances and crop productivity outcomes. The review concludes that whilst manure pyrolysis shows promise, standardised field experiments with livestock unit equivalent comparisons are essential to establish practical agronomic value.

UK applicability

Given the United Kingdom's intensive livestock farming regions and increasingly stringent manure application restrictions due to pollution concerns, pyrolysis technology could address regulatory constraints and surplus manure management challenges. However, applicability depends on whether commercial-scale pyrolysis infrastructure can achieve the economic and environmental benefits identified in this review, and on establishing crop performance data relevant to UK soil and climate conditions.

Key measures

Bioavailability of potentially toxic elements (PTEs); pathogenic microorganism elimination; organic micropollutant degradation; greenhouse gas emissions; nitrogen loss; crop yield; fertilisation efficiency

Outcomes reported

The review assessed pyrolysis as an alternative treatment for animal manure, evaluating its effects on bioavailability of potentially toxic elements, pathogenic microorganism elimination, organic micropollutant destruction, greenhouse gas emissions reduction, and nitrogen loss mitigation. It identified gaps in evidence regarding crop yield and fertilisation efficiency outcomes when comparing manure and manure biochar applications.

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