Evaluation of carbon fixation during carbonization of municipal solid waste

Carbonization is a promising method of carbon fixation, but there has been little research on municipal solid waste (MSW) carbonization as a carbon capture, use, and storage technology. We focused on biomass- and fossil-derived carbon in samples produced at the Saikai City Carbonization Center and evaluated carbon fixation through the MSW carbonization process. We found that the total C content of carbonized fuels is approximately 50%, with fossil C accounting for 9.1–14.4%. Fossil carbon in MSW was considered to be derived mainly from polyethylene and polyamide (nylon 6–6). In terms of the carbon mass balance, negative emissions of 71,300–108,000 kg-CO₂/month can be achieved from carbonized fuels that are not burned, such as soil amendments, compared to the case wherein all carbon in MSW is released into the atmosphere. The fossil C content of carbonized fuels is affected by the composition of the input MSW, while the influences of waste quality, desalination time, and pyrolysis temperature changes of several tens of degrees Celsius are small. Landfill disposal of carbonized fuels is limited by the capacity of the final disposal sites. The consumption of this capacity can be reduced through the use of carbonized fuels as a soil amendment.