Application of seasonal freeze-thaw to pretreat raw material for accelerating green waste composting.

ABSTRACT

The recalcitrance of green waste, caused by its high lignocellulose content, is a technical challenge for accelerating green waste composting. However, because lignocellulose degradation in litter (similar to green waste) can be promoted during the freeze-thaw season, and the composting is difficult to implement in this period (due to the low temperature); seasonal freeze-thaw was intended to be used as a pretreatment strategy for the existing technical challenge in the winter of cold regions. In this process, green waste was pretreated with seasonal freeze-thaw to enhance its lignocellulose degradation for subsequent composting. To verify this assumption, two strategies for the pretreatment were used the green waste was either drenched or immersed in water during the freeze-thaw season, and the effects on subsequent composting were evaluated. The results demonstrated that both strategies can significantly promote the mineralization of TOC (total organic carbon, by 2.73%-8.01% compared with the control, the following comparisons were all based on the control), TN (total nitrogen, by 0.21%-0.52%), and lignocellulose (lignin degradation was promoted by 3.52%-3.73%, cellulose degradation was promoted by 13.23%-14.26%) during composting and that the synthesis of humus was also enhanced (by 19.19%-21.43%). Furthermore, since the loss of NH4+N and NO3-N was significantly less in the drenched treatment than in the immersed treatment (by 9.15% for the loss of NH4+N and 7.66% for the loss of NO3-N), drenching the green waste during the freeze-thaw season might be a better strategy than immersing for nitrogen conservation. An additional advantage of drenching compared to immersing is water conservation.