An inventory analysis of sewage energy system

In this study, 13 types of sewage energy system are evaluated by using inventory analysis. Evaluation indexes are energy balance, greenhouse gas emission, and economic efficiency. The main ecmipment of those energy systems are three types of incineration, three types of solid fuel, two types of pyrolysis gasification, and five types of digestion. The range of evaluation is from sewage sludge to power generation. Inputs of those energy systems are electricity, city gas, light oil, and wood biomass, and outputs are production of electricity, CO₂ gas, and N₂O gas. The results from the viewpoint of energy balance show that only the systems with gasification furnace produce larger electricity generation than total consumption. The results about the greenhouse gas emission show that the lowest gas emission system is the system with solid fuel produced by drying. N2O gas emitted by solid fuel is lower than the others. The results about the economic efficiency show that the lowest cost system is the systems with solid fuel because the construction cost that holds most of total cost is much lower than the other systems.