A comparative life cycle assessment approach of 5 alternative technologies for converting municipal solid waste (MSW) into chemicals and electricity in the UK

This study develops a systematic life cycle assessment approach for 5 alternative technologies that can be used to convert municipal solid waste (MSW) into chemicals and electricity. Particular attention is given to the combustion and gasification as the main conversion processes and the UK’s MSW is used here as the case study. The investigation focusses on 5 different scenarios: (1) combustion and electricity generation, (2) gasification and electricity generation, (3) methanol synthesis from syngas with electricity co-production (4), dimethyl ether (DME) synthesis from produced methanol by syngas (indirect synthesis) and power generation, and (5) DME synthesis from syngas (direct synthesis) and electricity co-production. The unreacted gas left from the methanol or DME synthesis process can also be employed as a fuel gas for the electricity generation. As the result, it is interesting to find out which method is the most appropriate and optimal to convert the UK’s MSW. The environmental impacts are evaluated by IMPACT2002+ method using Ecoinvent 3 as a database. The results show that scenario 5 (direct DME synthesis with electricity co-production) causes the least climate change impact (532 kg CO2 eq.) and resource impact (-5560 MJ primary), followed by scenario 4 (544 kg CO2 eq. and -5250 MJ primary), scenario 3 (569 kg CO2 eq. and - 4820 MJ primary), scenario 1 (591 kg CO2 eq. and -3880 MJ primary) and scenario 2 (881 kg CO2 eq. and -3900 MJ primary) respectively. However, the study also demonstrates that the scenarios involving methanol and DME synthesis have more impacts on human health category due to the required metal oxide catalysts. The impact of a change in total yield of methanol and DME synthesis is also investigated and analysed along with the associated potential environmental benefits.