Summary
This experimental study investigated wood ash as a process additive during biomass pyrolysis to enhance biochar production efficiency and nutrient recycling. Addition of 9 wt% ash to softwood increased biochar yield by 26% and carbon-conversion efficiency by 36%, with linear yield increases up to this concentration; higher ash concentrations showed no further benefit. Whilst ash amendment reduced micropore surface area and thermal stability, it increased electron exchange capacity, elevated potassium content, and promoted plant growth, whilst maintaining contaminant levels well below safety thresholds, suggesting ash-amended biochar is suitable for soil application.
UK applicability
The findings are potentially applicable to UK biomass pyrolysis operations seeking to improve char yield and nutrient recovery from forestry and agricultural residues. However, the study used softwood under controlled laboratory conditions; validation across UK-relevant hardwood species, feedstock blends, and commercial-scale pyrolysis systems would strengthen applicability to UK soil amendment and carbon sequestration programmes.
Key measures
Biochar yield (dry and ash-free basis), carbon-conversion efficiency, polycyclic aromatic hydrocarbon content, polychlorinated organic pollutant content, electron exchange capacity, micropore specific surface area, thermal stability, potassium content, sunflower growth promotion
Outcomes reported
The study measured biochar yield, carbon-conversion efficiency, contaminant content, electron exchange capacity, micropore surface area, and thermal stability as functions of ash concentration, pyrolysis temperature, and residence time. Agricultural performance was assessed through sunflower growth trials.
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