The amending potential of vermicompost, compost and digestate from urban biowaste: Evaluation using biochemical, Rock-Eval? thermal analyses and transmission electronic microscopy

Organic fraction of municipal solid waste can be recovered using a variety of processes including composting, anaerobic digestion and vermicomposting. The impact of these products was evaluated using an innovative approach combining quantitative and qualitative analyses. Chemical analysis showed that the organic matter content of dry compost, digestate and vermicompost was 76 %, 67.2 % and 41.7 %, respectively. Index of Recalcitrant Organic Carbon (IROC) was higher for vermicompost (87.2 %) than for compost (77.9 %) or digestate (66.9 %). The Rock-Eval (R) approach was correlated to the IROC with its R -index (R2 = 0.97). Transmission electron microscopy was used to describe the microbial activity, the decomposition state and we observed more advanced maturity from vermicompost, compost to digestate. Finally, the digestate is predicted to have a fertilizing effect whereas the compost should have more an amending effect in the medium/long term. Due to a higher degree of stability, the vermicompost could have both a fertilizing and amending effect.