Rapid start-up and humification of kitchen waste composting by an innovative biodrying-enhanced process

Abstract

An innovative biodrying-enhanced composting (BEC) system that applies biodrying to composting process as its start-up stage was developed to rapidly process kitchen waste (KW) into highly maturate products. The BEC performance and potential mechanisms of rapid start-up and humification were explored through a continuous pilot experiment. The results showed that the BEC system was designed and operated with 9 d retention time, achieving highly maturate products with a germination index of 91.85%–112.08% and a humification index of 6.21–6.36. The 24 h biodrying stage could markedly accelerate KW dehydration and start-up of the composting process. The stage-enriched Corynebacterium (45.61%–66.91%) and Pichia (76.72%–92.33%) rapidly decomposed macromolecular substances (i.e., methoxylated polysaccharides) and generated humic acid (HA) precursors (especially methoxy groups and residual aromatic-like components). The precursors were utilized to rapidly synthesize HA skeletons and stable HA by thermophilic Firmicutes and Ascomycota in the humification stage. The Maillard reaction and lignin-protein theory contributed greatly to HA elongation, while the “methoxy-aromatic nucleus” pathway might improve HA stabilization during BEC as an alternative to polyphenol humification pathway. BEC technology can be enhanced by reducing the residence time and plant areas required for composting, improving the prospects for recycling organic waste in engineering applications.