Wood Ash as an Additive in Biomass Pyrolysis: Effects on Biochar Yield, Properties, and Agricultural Performance

Summary

The use of wood ash as an additive in biochar production was shown to increase biochar yields and was suggested to improve the recycling of ash-derived nutrients.However, there is limited knowledge on the interaction of ash addition with pyrolysis conditions and their effects on biochar yield and properties.Here, we performed experimental pyrolysis in an auger reactor applying different ash concentrations, temperatures, and residence times.Biochar yield (dry and ash-free) increased by 26% and carbon-conversion efficiency of pyrolysis by 36% when 9 wt % ash was added to softwood.Up to this concentration, yield increase was correlated linearly, while higher ash concentrations did not further increase yield significantly.The ash-induced yield increase was lower at 400 C than for 425-500 C.Bio