Effects of brown sugar and calcium superphosphate on the secondary fermentation of green waste

► A two-stage composting (with primary and secondary fermentations) is described. ► Brown sugar and calcium superphosphate are evaluated as fermentation additives. ► Maturity time is shortened and maximum of fermentation temperature is attained twice. ► Physico-chemical characteristics explain the rapid decomposition of green waste. ► pH, C/N ratio, organic matter, GI value, void ratio, and particle size are optimized. The generation of green waste is increasing rapidly with population growth in China, and green waste is commonly treated by composting. The objective of this work was to study the physical and chemical characteristics of composted green waste as affected by a two-stage composting process and by the addition of brown sugar (at 0.0%, 0.5%, and 1%) and calcium superphosphate (Ca(H2PO4)2·H2O) (at 0%, 3%, and 6%) during the second stage. With or without these additives, all the composts displayed two peaks in fermentation temperature and matured in only 30days. Compared to traditional industrial composting, the composting method described here increased the duration of high-temperature fermentation period, reduced the maturity time, and reduced costs. Addition of 0.5% brown sugar plus 6% calcium superphosphate produced the highest quality compost with respect to C/N ratio, pH, organic matter content, electrical conductivity, particle-size distribution, and other characteristics.