Carbon footprints of incineration, pyrolysis, and gasification for sewage sludge treatment

Thermal technologies have gained increasing attention in sludge management. This study applied life cycle assessment to assess the impacts to climate change of ten technological configurations (TCs) treating sludge with incineration, gasification, and pyrolysis. We used distributions of process parameters for quantifying the associated uncertainties and considered different energy exchanges. In a 55 %-fossil energy system, the TCs with various thermal processes showed impacts to climate change in a wide range of -2000 to 2000 kg CO2 eq/t total solid. A probabilistic comparison indicated that with a 10 %-fossil energy system, TCs with gasification and pyrolysis showed a > 95 % probability of performing better than TCs with incineration. Energy consumption and dewatering parameters contributed significantly to the uncertainty due to their large variation and sensitivity. This study emphasized the potential of optimizing key parameters and provided evidence from a climate change perspective for better technological selection and development in sludge management.