Climate change impact of the development in household waste management in China
June 5 – 10, 2022
China has experienced significant economic growth over the last few decades – as reflected in the amount of municipal solid waste the country generates. According to national annual data, the quantity of municipal solid waste increased from 148 million tons in 2006 to 235 million tons in 2020. In 2006, 81% of municipal solid waste was landfilled, 15% was incinerated and 4% biologically treated. In contrast, in 2020, 33% of municipal solid waste was landfilled, 62% was incinerated and 5% biologically treated. LCA modelling shows that the current development away from landfilling and towards incineration with energy recovery is beneficial with respect to climate change. Landfilling is a net load with respect to climate change: The methane slip from the degradation of the food waste is high (39%, resulting in around 250 kg CO2-eq/ton wet household waste) but even though carbon sequestration of the residual waste in the landfill is a saving (around 100 kg CO2-eq/ton wet household waste), the net value is a high load. Incinerating all the household waste is a small net saving with respect to climate change. However, the net value is the difference between a very large load and a very large saving (both around 400 kg CO2-eq/ton wet household waste).The load is from incineration of plastic and the saving is from recovered electricity substituting for fossil-based electricity. Any uncertainty related to one or both of these numbers easily could affect the net value. This also shows a potential for improvement, if the waste contained less plastic or more electricity could be recovered. Source-separation of the food waste at the current 20% rate contributes with additional savings of about 5-10 kg CO2-eq/ton wet household waste. Here recovery of the oil fraction and producing electricity from biogas is the better way of biorefining. However, the difference is very small. Variations in household waste composition, due to current geographical variations or due to future consumption patterns, illustrated with four different waste compositions, add variation to the net results of the order of 40 kg CO2-eq/ton wet household waste as illustrated for a technological configuration of incineration and biorefining of 20% collected food waste. However, this variation does not challenge the conclusion that incineration is better than landfilling with the current recovery and substitution of electricity. Increasing the source-sorting efficiency of the food waste, for example from the current 20% to 60%, which we consider very high, provides an additional saving of 20 kg CO2-eq/ton wet household waste. This may seem a small benefit of a large effort. As China implements increasing use of renewable energy sources, the exchange of energy between the waste system and the energy system may change. It is impossible to predict what the long-term marginal technology will be and when the long-term marginal technology will change. Fossil-based energy sources could be the affected marginal if implementation of renewable energy sources cannot meet the needs in the market, but one day renewable energy sources may become the affected marginal. Our results then reveal a completely different picture: Incineration has much higher loads than landfilling with respect to climate change. This is due to the fact that the recovery of energy provides very low savings in climate change impacts. This does not indicate that landfills again become attractive from a climate change of view, because of the methane issue. With the urgency of climate mitigation, a 20-year perspective on methane reveals very high climate change impacts from landfilling. The results, however, stress the importance of considering how to reduce the direct load from incineration. There are three options: Use bioplastic instead of fossil-based plastic, recycling of plastic instead of incineration, or introduce carbon capture and storage to remove carbon dioxide from the flue gas. While the two first options will reduce the load from incineration, carbon capture and storage may make incineration a net saving. These issue must be specifically assessed, but our results show that although the current development in Chinese household waste management is contributing to reduce climate change, new challenges must be addressed as the energy system change to renewable energy sources.
Thomas H. C hristensen and Huimin Changb, "Climate change impact of the development in household waste management in China" in "WasteLCA_3: Life Cycle Sustainability Assessment For Waste Management And Resource Optimization", Umberto Arena, University of Campania “Luigi Vanvitelli”, Italy; Thomas Astrup, University of Denmark, Denmark Eds, ECI Symposium Series, (2022). https://dc.engconfintl.org/lca_waste_3/52