Analysis on Carbon Emission from Different Sewage Sludge Treatment and Disposal Processes

The current technology roadmaps of sewage sludge treatment and disposal in China are bio-drying/land utilization process and heat drying/incineration process.Carbon dioxide emission from the processes was calculated and its emission budget was analyzed.The results indicate that the carbon dioxide emission and carbon footprint of bio-drying/land utilization process are lower,and those of heat drying/incineration process are 5.33 and 4.94 times those of bio-drying/land utilization process respectively.Using dried sludge as lawn substrate can reduce carbon emission and increase carbon sequestration,and the amounts of carbon dioxide emission reduction and absorption are 68.7 kg/t and 648 kg/t respectively.Considering net carbon emission,the heat drying/incineration process is characterized by high carbon emission of 372.9 kg/t,while the bio-drying/land utilization process has carbon emission reduction effect(-643.6 kg/t).The later meets the current policy and the future trend.