Study On The Changes Of Nitrogenous Compounds And Microbial Community Characteristics During Food Waste Composting

Food waste is an important source of village/town-scale domestic waste after waste classification.The in-situ composting of village/town-scale domestic waste is a crucial step for their reduction,stabilization,and resource recovery.This thesis aimed to investigate the changes of proteinaceous compouds like proteins and amino acids during composting of food waste,and the key nitrogenous compounds related with the efficiency of agricultural fertilizer will be identified.The positive effects of bulking agents on the composting process in terms of the changes of nitrogenous compounds and microbial community will be revealed.A pilot-scale composting plant,located in Xiaogang Village of Fengyang Town(Anhui Province,China),was chosen to investigate the characteristics of compost product.The main findings include:1.The key nitrogenous substances which affect the composting efficiency of food wasteUsing chicken manure as the inoculum and wood chips as the bulking agent,0,0.1,0.3,0.5 g/g dry weight(Total solids,TS)food waste were added respectively.The results indicated that the addition of 0.3 g/g TS of food waste was the optimum condition.The highest seed germination index of the compost product was 267.6%.the protein content decreased to 73.2%,and the highest increase of the proline content was 176.57mmol/kg.Experiments on plant germination and hydroponics found that compared with the treatment without proline,the highest increases of seed germination rate and shoot length of single proline treatment,as well as the root and leaf biomass of seedlings were 27.78%,10.45%,81.8%,and 76.30%,respectively.The activities of superoxide dismutase,peroxidase and malondialdehyde content treated with single proline were lower than those without proline,which proved that proline would not cause oxidative damage to plants.Proline showed a positive effect on seed germination and seedling growth,and was a key nitrogenous substance that affected the agricultural value of compost products.2.Straw bulking agents promoted the transformation of key nitrogenous substances and the characteristics of microbial community during the composting of food wasteUse maize stalks,rice stalks,rape stalks and wheat stalks as bulking agents,and the proportion of food waste is 0.3 g/g(dry base).After 35 days of composting,the maximum temperature during the group without bulking agents did not reach 50 ~oC,the final NH4~+content was 1.91 mg/g,and the seed germination index was only 51%,which did not meet the compost maturity requirements.In comparison,stalks treatments all met requirements.Among them,the compost with maize stalks has the best effect.It was found that the addition of fillers promoted the enrichment of Proteobacteria(7.9-11%)and Bacteroidetes(5.3-11%).Compared with the initial stage of composting,after adding maize stalks,the relative abundance of amino acid metabolic sequences in the maturity stage increased by 8.9%.And the results of the study showed that the increase of proline content was the highest,increasing to 129.69 mmol/kg at the maturity stage(adding maize stalks).3.The characteristics of nitrogenous compounds and the distribution of microplastics in a pilot-scale composting project located in Xiaogang VillageThe domestic waste in Xiaogang Village showed a high moisture content(75.98%),a low calorific value(2829 k J/kg),and a relatively high proportion of food waste(73.3%).The results of the in-site production test of the compost demonstration project showed that the total nutrient content of the compost output was 5.8%,the roundworm mortality rate was 100%,the seed germination index was 144%,and the content of heavy metals and other toxic and harmful substances was far low compared with the standard limit.It met the standard requirements of“Organic Fertilizer NY525-2012”,met the maturity standard,being non-toxic to plants,and finally can be applied to farmland.This thesis revealed the changes of nitrogenous substances such as protein and amino acids during the composting process of food waste,and clarified the positive effects of bulking agents on the aerobic composting process of food waste.The results gained from this study provided fundamental basis for the establishment of a demonstration project of food waste composting and the resource utilization of food waste.