Reduction Technologies Of Typical Pollutional Gaseous Emissions During Kitchen Waste Composting And Life Cycle Assessment Of Management

In most places of China, municipal solid waste (MSW) was processed with unsource-separation system and fuzziness management model at presetent, resulting in difficulty to the end-processing and waste recycling. In view of the situation, this study investigated the optimizing technology and management of MSW based on factory and region scales. On factory scale, the reduction technologies of typical pollution gases during kitchen waste composting were studied, including technological parameters controlling, addition of bulking agents and chemical additives, etc.; On region scale, the sourth region of Dongcheng and Xicheng Districts of Beijing was taken as the object. Five scenarios were builded and estimated using Life Cycle Assessment (LCA) based on the current situation. The results could provide an optimal MSW management scheme to the decision makers or government. Results of this study showed that:(1) In the co-composting of kitchen waste and cornstalks with different C/N ratio (15,20,25), moisture content (60%,65%,70%) and ventilation rate (0.2,0.4,0.6L·kg-1DM·min-1). Ventilation rate was negatively correlated with CH4emissions, and positively correlated with N2O and NH3emissions; the C/N ratio had a negative correlation with CH4and NH3emissions. However, the significant relation between C/N ratio and N2O emissions was not found. The significant relationshiop between moisture content and gaseous emissions was also not found in this study. Composting with ventilation rate of0.4L·kg-1DM·min-1, C/N ratio of25and moisture content of60%had a minimum greenhouse gas (GHG).(2) In the co-composting system of kitchen waste and cornstalks, treatment of intermittent ventilation (between on and off every30min) decreased CH4and NH3emissions by23.5%and21.5%, compared with continuous ventilation. However, the continuous ventilation had a slight advantage on decreasing N2O emissions (by6.5%, per ton dry matter).(3) Treatments of mature compost (weighed10%of composting materials, wet basis) covered on the surface of composting pile and mixed with composting materials, could decreased CH4emissions by36.2%and44.8%respectively, compared with CK treatment; N2O emissions decreased by37.7%and73.6%respectively. Mixed treatment decreased NH3emissions by22.2%(per ton dry matter), while NH3emissions from covered treatment showed no significant difference with CK treatment.(4) Adding phosphogypsum and superphosphate with5%of initial materials (dry basis) decreased CH4by85.8%and80.5%, NH3by23.5%and28.9%, while N2O increased by3.2%and14.8%(per ton dry matter).(5) Addition of cornstalks, saw dust and spent mushromm substrate as composting bulking agents, which weighed15%of initial composting materials (wet basis), could decrease CH4emissions by59.2%,55.0%and66.6%respectively, compared with CK treatment; N2O emissions decreased by46.7%,73.1%and44.7%; NH3missions decreased by30.9%,40.5%and41.5%(per ton dry matter); All of the three kinds of bulking agents could avoid leachate production during composting completely. The CH4and NH3emissions were negatively correlated with the adding proportions of spent mushromm substrate,35%SMS addition could increase N2O emissions obviouly; while only the treatment with15%of spent mushromm substrate decreased CH4, N2O and NH3simultaneously by60.6%,29.0%and14.8%(per ton dry matter), compared with CK treatment.(6) Life cycle assessment results of different MSW management scenarios indicated that the source-seperation system decreased the comprehensive environmental potential. Furthermore, adopting mtigation technologies of typical gaseous emissions during composting decreased the Global Warming Potential.