Emission Characteristics And Control Of Odorous Gas In Aerobic Composting Of Food Waste

The reduction,recycling and harmless treatment of food waste are the important needs of social development.Aerobic composting is a mature recycling technology for food waste,but there are odor emission such as Volatile Organic pollutants（VOCs）in the process.In addition,the high content of meat,eggs and other protein substances in food waste leads to the high potential of producing NH₃,H₂S and other malodorous gases in compost,which not only causes environmental pollution,but also leads to the loss of nitrogen and sulfur in compost products.Therefore,this paper took Food waste composting as the research object and used stable isotope labeling technology to study the emission characteristics of VOCs,NH₃ and H₂S in aerobic composting process.At the same time,illite was used as an additive to explore the emission reduction effect of controlling odor gases such as NH₃ and H₂S in the aerobic composting process of Food waste.The main research results are as follows:1)VOCs emission characteristics in aerobic composting processes of Household Food Waste（HFW）and Restaurant Food Waste（RFW）.The results showed that the types of VOCs emitted during the composting of HFW and RFW were similar,but the emission concentration and peak time were different.VOCs emission in HFW compost mainly concentrated in high temperature periods,and the main odor gases were 2-butanone,ethyl acetate,vinyl acetate and acetone.Oxygenated Volatile Organic Compounds（OVOCs）accounted for the highest proportion,reaching 94.0%.VOCs emissions in RFW compost were mainly concentrated in the warming and high temperature periods,and the main odor gases were 2-butanone,n-heptane and carbon disulfide.OVOCs,Volatile Sulfurous Organic Compounds（VSOCs）and Aliphatic Hydrocarbon（Al H）account for 69.4%,19.3%and 9.8%,respectively.Correlation analysis showed that the emission of OVOCs in HFW was related to the degradation of polysaccharides by microorganisms such as Lactobacillus and Ureibacillus,while the emission of carbon disulfide in RFW was related to the degradation of proteins and polysaccharides by microorganisms such as Weissella and Leuconostoc.2)NH₃ and H₂S emission and nitrogen transformation mechanism in aerobic composting process of RFW.The nitrogen conversion and contribution of NH₃release in aerobic composting process of RFW was investigated by using glutamic acid as stable isotope ¹⁵N label.It was found that the concentration of NH₄⁺-N increased rapidly in the warming period and high temperature period,and a large amount of NH₃ was released in the high temperature period,and the emission rate reached 61.37 mg·dry kg^-1·h^-1,which was significantly positively correlated with temperature（P<0.05,f=0.812）.The cumulative emission of NH₃ during composting was 9.57 g·dry kg^-1,accounting for 70.49%of the total nitrogen loss,indicating that NH₃ release was an important route for nitrogen loss.In addition,the nitrogen loss caused by the release of glutamic acid nitrogen in the form of NH₃accounted for 74.76%of the total nitrogen loss in the composting process,and the NH₃ emission and nitrogen loss mainly concentrated in the high temperature stage,accounting for 89.3%.At the same time,The release of H₂S in RFW compost was mainly concentrated in the high temperature period,accounting for 70.93%.The cumulative H₂S emission during composting was 25.32 mg·dry·kg^-1,accounting for4.01%of the total sulfur loss.3)Study on the reduction of NH₃ and H₂S emission by illite addition in RFW aerobic composting process.The results showed that the addition of illite was beneficial to compost maturity and emission reduction.After illite was added,the reactor temperature was increased by 6.2℃,the duration of high temperature period was extended for 3 days,and the seed germination index was increased by 12%.In addition,the cumulative release of NH₃ in the reactor was 8.65 g·kg^-1,41.29%lower than that in the control group.The cumulative H₂S emission in illite addition group was 132.19μg·dry kg^-1,which was 38.93%lower than that in control group.The microbial community analysis showed that the illite addition reactor showed high microbial diversity and Bacillaceae abundance increased during high temperature period.In conclusion,the odorous gases released by HFW compost are mainly OVOCs,while those released by RFW are mainly NH₃,H₂S and OVOCs.The odorous gas release time is closely related to the temperature and stage of the heap.Adding illite can improve the compost maturity and reduce the emission of NH₃ and H₂S.This paper provides an important reference for elucidating odor emission characteristics and odor pollution control in aerobic composting of food waste.