Effect of biochar amendment during composting and compost storage on greenhouse gas emissions, N losses and P availability

We tested the effect of adding 10% biochar (on a dry weight base) in a mixture of green waste and the organic fraction of municipal solid waste before processing in a composting plant. Focus is on compost quality, fate of nutrients and on the environmental impact during composting (emission of greenhouse gasses). As a consequence of biochar amendment, the <10mm fraction was proportionally higher in the biochar-blended compost. In this full scale experiment, mixing biochar in the feedstock mixture strongly affected the oxygen uptake rate and nutrient availability during the first weeks of the
bio-oxidative phase. A higher organic matter decomposition, a higher dry matter content and lower P, SO4 and NH4-N concentrations were observed for fraction <10 mm of the biochar-blended compost. After 27 days a clearly lower oxygen uptake rate was detected for the biochar-blended compost.