Effects of waste lime and Chinese medicinal herbal residue amendments on physical, chemical, and microbial properties during green waste composting

Abstract

Traditional composting is time-consuming and often results in a low-quality product. The objective of this study was to determine the effects of waste lime (WL; at 0, 2.5, and 3.5%) and/or Chinese medicinal herbal residues (CMHRs; at 0, 10, and 20%) as amendments on the two-stage composting of green waste (GW). The combination of WL and CMHRs improved compost particle-size distribution and pH, decreased nitrogen loss, and increased cation exchange capacity (CEC), nutrient content, and microbial numbers. The combination of WL and CMHRs also accelerated organic matter humification and lignocellulose degradation and therefore increased the germination index of the final compost. Relative to the non-amended compost, the optimal amendment (2.5% WL and 20% CMHRs) increased the percentage of particles of ideal size from 23.8 to 66.9%, the pH from 6.69 to 7.17, the CEC from 52 to 169 cmol/kg, the humic acid to fulvic acid ratio from 1.32 to 2.49, the hemicellulose degradation rate from 42 to 87%, and the cellulose degradation rate from 20 to 61%. The treatment with addition of 2.5% WL and 20% CMHRs to GW required only 21 days to generate the highest quality compost product.