Effects of percolate recirculation frequency on the organic matter composition after solid-state anaerobic digestion of straw and pig slurry

Abstract

Restoring humus in soil represents a key factor for improving soil quality. Digestates from anaerobic digestion (AD) can be successfully applied as soil amendments. Here, we investigated changes of the organic matter (OM) composition of digestates from solid-state anaerobic digestion (AD) of straw and pig slurry at different percolate recirculation frequency. Atomic ratios, thermostability indexes, O-alkyl C/alkyl C ratio and Py-GC/MS results consistently showed a positive effect of the highest number (4) of percolate recirculations per day on OM features, resulting in a more stable OM in digestate.