Reducing nitrogen loss during kitchen waste composting using a bioaugmented mechanical process with low pH and enhanced ammonia assimilation

Exploring the regulation of nitrogen transformation in bioaugmented mechanical composting (BMC) process for rural kitchen waste (KW) is essential to avoid the not-in-my-backyard phenomenon caused by nitrogen loss. Herein, nitrogen transformation and loss in BMC versus conventional pile composting (CPC) of KW were compared. The results showed that the total nitrogen loss in the BMC was 6.87-39.32 % lower than that in the CPC. The main pathways to prevent nitrogen loss in the BMC were reducing NH3 by avoiding a sharp increase in pH followed by transforming the preserved NH4+-N into recalcitrant nitrogen reservoir via enhanced ammonia assimilation. The enriched thermophilic bacteria with mineralization capacities (e.g., Bacillus and Corynebacte-rium) during rapid dehydration and heating in the BMC accumulated organic acids and easy-to-use carbon sources, which could lead to lower pH and ammonia assimilation enhancement, respectively. This study provides new ideas for formulating low-cost nitrogen conservation strategies in decentralized KW composting.

Automated summary

This study compares nitrogen transformation and loss between bioaugmented mechanical composting (BMC) and conventional pile composting (CPC), finding that the total nitrogen loss in BMC is 6.87-39.32% lower than that in CPC. The main pathways to prevent nitrogen loss in BMC include reducing NH3 by avoiding a sharp increase in pH and transforming preserved NH4+-N into recalcitrant nitrogen reservoir via enhanced ammonia assimilation.