GHG Emissions Pattern From MSW Sector And The Potential Reduction Processes

Municipal solid waste has been regarded as one of the main non-CO2 GHG anthropogenic sources,and the GHG emissions estimation and the potential reduction process should be identified,to meet the Intended Nationally Determined Contributions(INDC).The GHG emissions accounting for urban solid waste sources could provide a new eye for the assessment of the operation level of the MSW management system.Due to the high organic matter content,high water content and the heterogeneous mixture of the MSW in China,the default IPCC cannot be applied directly.Shanghai,as the megacities,MSW generation amounts increased greatly in the past 30 years,and waste compositions also changed greatly with the rapid urbanization process and the increase of the living levels.In this work,waste management pattern of Shanghai was summarized according to the official statistics data and the onsite survey.GHG emissions estimation were carried out using the combined method of IPCC and bottom-up method,which can finely illustrate the emissions pattern.The potential GHG emissions scenarios were proposed finally according to the local plan on waste sector.The main findings were shown as bellows:(1)By reviewing the management history of MSW in Shanghai,a relationship between time and the disposal pattern of waste sector was established.Around 77.89 Million tons of MSW were generated from 2005 to 2015,and disposed in landfill,incineration and composting,with the corresponding rates of 94.62%.Landfill predominated in the MSW disposed,with the percentage of 64.19%,followed by incineration(20.51%).Composting was almost neglected.(2)Based on the GHG estimation emissions under 2006 IPCC guideline combined with bottom-up methods,GHG emissions pattern from waste sector in Shanghai had been estimated using the local data of each disposal facility and the waste compositions.A total of 25.06 Mt CO2-eq was emitted from the MSW disposal in Shanghai from 2005 to 2015.Landfill sites were the major source,accounting for 81.88% of the total emissions,and Laogang Refuse landfill was the main contributors.Besides,annual GHG emissions increased year by year from waste sector,with the increasing rate of 3.9%.The peak year was found in2014,with a total of 2.58 Mt CO2-eq.(3)The GHGs emission pattern of Shanghai Laogang Domestic Waste Landfill were estimated and summarized here,as the largest landfills in the world.Laogang Refuse landfill could be categorized into three phases,namely Phase I-III of the old landfills from 1989-2008,Phase IV of new landfill from 2005 to now,and Phase V of comprehensive compartments from 2013 to now.The total amount of MSW disposed in landfill was 41.76 Mt in phase I-III,and total emissions,until 2015,were 23.24 Mt CO2-eq.The annual emissions peak occurred in 2003,with the value of 1.75 Mt CO2-eq.With regards to the GHG emissions per ton waste landfilled,it was found that the GHG emissions per ton MSW from Phase IV was only 42% of that from Phase I-III.As the closure of phase I-III in Laogang landfill and the fresh garbage landfilling in Laogang phase IV,Phase IV had already been the main GHG sources during 2010-2011.(4)GHGs emissions varied with the different disposal processes,among which,potential GHG generation per ton MSW for landfill,reaching to 1183 kg CO2-eq/t wet MSW,was the highest.Potential GHG generation for Bio-treatment(191 kg CO2-eq/t wet MSW)was the lowest one,next to the potential GHG generation for incineration(515 kg CO2-eq/t wet MSW).However,consider the deduction of bio-carbon emissions,only 160 kg CO2-eq/t wet MSW released from incineration disposal.Combined with GHG impact factors,per ton GHGs emission pattern was established.During 2005-2015,the average amount of GHG emissions per ton MSW was 434 kg CO2-eq/t wet MSW for landfill,160 kg CO2-eq/t wet MSW under incineration disposal,and 191 kg CO2-eq/t wet MSW under bio-treatment disposal.Annual emissions per ton from landfill was on the rise,with the increasing rate of 6%,and “turning points” appeared in 2010 and 2015.After 2015,GHG emissions from landfill decreased gradually with the fall of landfill amount in Phase IV and the aging of Phase I-III.Meanwhile,with the improvement of the efficiency of the new-built incineration plants,annual emissions per ton declined slowly at an annual decline rate of 1%.Further analysis on landfills on different conditions showed the gap between GHG emissions per ton from each landfill sites in Shanghai,from 102 kg CO2-eq/t wet MSW to 557 kg CO2-eq/t wet MSW.And the annual GHG emissions account for 9%-51% of potential GHG generation,which showed that GHG mitigation measures,including functional solid cover,landfill gas collection and flaring,played an active role on GHG mitigation.(5)Based on the Waste Plan of Shanghai and the implementation of the source separation program,the waste compositions and generation amounts will change greatly.New scenario of waste management system in 2020 was proposed,and the corresponding GHG emissions patterns was established and compared under the BAU and NP scenarios.It was found that waste source separation will influence the waste disposal process greatly due to the reduction of both final disposal amount and the organic matter content in the final disposal process.And with the development of the full amount of incineration,GHG emissions in Shanghai will decrease shapely in the next 5-10 years after the reduction of aging landfills.With the implementation of all these policies,the total GHGs emission will reduce around 20%.