Is pyrolysis technology an advisable choice for municipal solid waste treatment from a low carbon perspective?

Abstract

With worldwide concern about climate change, waste-to-fuel technologies have been revived in the argument over whether waste-to-energy is still the best choice. A process-oriented life cycle assessment for municipal solid waste (MSW) was performed on the basis of full-scale operational data to compare the carbon footprints of the pyrolysis technology enhanced by mechanical and biological treatment (MBT) and incineration technology. Material and carbon flow analyses reveal that MBT produces refuse-derived fuels (RDFs) of 330 kg/ton MSW for pyrolysis, in which 67% of the carbon ends up in tar and char. Based on the Chinese energy structure in 2020 and MSW composition with 13% plastics, incineration and MBT–pyrolysis provide similar net carbon savings around 200 kg CO2-eq/ton. As the MSW contains more plastic fraction and the energy system becomes greener, the carbon savings from MBT–pyrolysis are less affected compared with those from incineration. The full-scale MBT–pyrolysis was verily optimised to maximise the RDF production and yield more tar and less syngas by identifying the important parameters, resulting in 30% higher savings in carbon footprint. With the energy structure at year 2050, the carbon footprints from MBT–pyrolysis are completely superior to that from incineration, regardless of the waste composition and heat recovery. From the low carbon perspective, fuel recovery with MBT − pyrolysis deserves priority over electricity recovery with incineration. This potential difference between waste-to-fuel and waste-to-energy technologies is for the first time quantitatively identified, and thus calls for a reconsideration on the long-term waste management and technological improvements.