Study On The Greenhouse Gas Methane Emissions Characteristic In The Typical MSW Landfill In China

In this paper, in order to improve the accuracy of the IPCC model for CH4emission estimation in MSW landfill site in China, the CH4emission flux from the landfill body surface and CH4dissolved in leachate were long-term monitored in a large landfill site in Beijing. And then, combined with the MSW landfill volume investigation, the CH4production and emission characteristics were revealed in this research. Through sampling and analysis the MSW samples in different landfill ages, the organic carbon degradation characteristics of landfill process were described, from which the half-life of landfill degradation were calculated. In addition, the in situ test method of CH4oxidation rate in cover layers was established base on the CH4and CO2emission flux, which was used to determine the CH4oxidation rate, and finally the CH4oxidation factor (OX) for the IPCC model were optimized. Comparison and analysis the IPCC model estimate results and field monitoring results, the modified IPCC model was verified in field scale. Finally, the CH4productions from MSW landfill in different area in China were estimated using the modified IPCC model.This research mainly obtains the following conclusion:(1) The CH4emission flux in the cover layer was shown as: the CH4emission fluxes changed a lot from the different monitoring points to the same points at different monitoring time. Meanwhile, the maximum value was17404.06mg C/(m2·h), while the minimum value was-10.34mg C/(m2·h).(2) For the hole emission on the covered HDPE membrane, the maximum value of CH4emission flux was1.8×109mg C/(m2·h), and the minimum value was-5.4×105mg C/(m2·h), in which the CH4and CO2emission flux had a significant positive correlation. (3) For the CH4concentration dissolved in leachate, it was higher in summer than that in winter, and the peak and the lowest value were4223.37and234.77mg C/L.(4) In2013, the estimation amount of CH4generation in the studied landfill site was15.63Gg C. In which, the proportion released trough the cover layer was15.05%; the proportion oxidized by the cover layer was7.41%; the proportion released by the HDPE membrane hole was0.02%, and the proportion recovered for energy or flaring was71.67%.(5) Using the established in-situ methane oxidation rate testing method, the average methane oxidation capacity in cover layers was813.3mg C/(m2-h), while the average methane oxidation rate was33%, which means the methane oxidation factor (OX) for the studied area was0.33, bigger than0.10of the IPCC recommended values.(6) Through the organic matter degradation curves analysis of MS W samples in different landfill ages, the organic matter degradation rate constant (k) was0.091, which means the waste degradation half-life (T1/2) was7.6years, close to7.7years of the IPCC recommended values.(7) When the impact factor: DOCf=0.5, landfill gas ratio of CH4(F)=0.4, the half-life (T1/2)=7.6year, the degradation rate constant (k)=0.091, the estimation amount of CH4production in this landfill site was15.73Gg C in2013, close to the15.63Gg C of the monitoring value in the field. Therefore, the value for the impact factors of the IPCC model was fit for the CH4generation estimation in this kind of landfill sites.(8) Using the modified IPCC model to estimate the CH4generation amount from the MSW landfill site in China, in2008the CH4generation was about507.35Gg C, while the amount of CH4generation was704.19Gg C in2012, the latter was1.39times than that of the former. Among them, the western provinces, such as Chongqing, Guizhou, Shaanxi, Sichuan etc. the CH4generation increased faster, while the eastern provinces, such as Beijing, Guangdong, Shandong, etc. the CH4generation had entered a period of slow growth.