Potential of greenhouse gas emissions from sewage sludge management: a case study of Taiwan

Sludge management is a critical part for reduction of greenhouse gas (GHG) emissions from wastewater treatment plants. Five sewage sludge management scenarios were conducted in this study: landfilling, incineration, reuse in bricks, reuse in cement, and reuse as fertilizers. The GHG emissions inventory for these scenarios, including both on-site (direct carbon dioxide, methane, and nitrous oxide emissions) and off-site sources (electricity, fuel and chemical usages), were developed. Annual GHG emission from sewage sludge management at Taiwan's wastewater treatment plants was c.a. 21 × 106 kg CO2-eq/yr. In terms of dehydration of sewage sludge, dewatering emits the lowest amount of GHGs, followed by drying with flue gas and direct heating. Manufacturing bricks is recommended among the three reusing scenarios with regards to GHG mitigations. Sludge incineration produced the largest GHG emissions (223,020 kg CO2-eq/tonne) in this study. Using fertilizers with nitrogen and phosphorus nutrients are mainly contributed to carbon dioxide and nitrous oxide emissions, respectively. The approach developed in this study for sewage sludge management should be applicable to other wastewater treatment plants and it should be helpful for reduction of GHG emissions and for development of sludge-to-energy alternatives. [Display omitted] •GHG emissions from sewage sludge management were evaluated.•Sludge incineration produced more GHG emissions.•Bricks manufacturing is recommended with regards to GHG mitigations.•Content of the fertilizers affects their GHG emissions.