Global climate change mitigation scenarios for solid waste management

The waste sector is an important contributor to climate change. CH4 produced at solid waste disposal sites contributes approximately 3-4 percent to the annual global anthropogenic greenhouse gas emissions. Emissions from solid waste disposal are expected to increase with increasing global population and GDP. On the other hand, many cost-efficient emission reduction options are available. The rate of waste degradation in landfills depends on waste composition, climate and conditions in the landfill. Because the duration of CH4 generation is several decades, estimation of emissions from landfills requires modelling of waste disposal prior to the year whose emissions are of interest. In this study, country- or region-specific first-order decay (FOD) models based on the 2006 IPCC Guidelines are used to estimate emissions from municipal solid waste disposal in landfills. In addition, IPCC methodology is used to estimate emissions from waste incineration. Five global scenarios are compiled from 1990 to 2050. These scenarios take into account political decision making and changes in the waste management system. In the Baseline scenario, waste generation is assumed to follow past and current trends using population and GDP as drivers. In the other scenarios, effects of increased incineration, increased recycling and increased landfill gas recovery on greenhouse gas (GHG) emissions are assessed. Economic maximum emission reduction potentials for these waste management options are estimated at different marginal cost levels for the year 2030 by using the Global TIMES model. Global emissions from landfills are projected to increase from 340 Tg CO2 eq in 1990 to 1500 Tg CO2 eq by 2030 and 2900 Tg CO2 eq by 2050 in the Baseline scenario. The emission reduction scenarios give emissions reductions from 5% (9%) to 21% (27%) compared to the Baseline in 2030 (2050). As each scenario considered one mitigation option, the results are largely additive, and the total mitigation potential can be assumed to be up to 30% in 2030 and 50% in 2050.The most favourable mitigation scenario was High landfill gas recovery scenario where increased rates of landfill gas recovery were assumed in developed and developing countries. In developing countries CDM type activities have appeared to be favourable mechanisms to stimulate this development. Due to the time lag in the emissions from landfills, the impact of increased recycling and incineration in mitigating the emissions from the waste sector is seen more slowly than that of landfill gas recovery. According to the calculations of economic potentials, one third of global CH4 emissions from landfills could be reduced at zero to negative costs in 2030. Below 10-20 USD/t CO2 eq, more than half of the emissions could be reduced. The economic maximum potential would be approximately 75% in 2030 when compared with the Baseline, but due to the time lag between waste disposal and emissions, this would be reached only if measures with very high marginal cost levels could be implemented in 2010. These assessments of potentials based on specific assumptions are appropriate for generalized global comparisons; however, more accurate assessment of the potentials would need more detailed consideration of regional and local conditions.