Sewage treatment is an important issue in a country for public health and environmental protection. The treatment
process not only consumes energy but also emits CO2
. In this research, the idea of streamlined life cycle assessment was
applied. The CO2
emission from sewage treatment was assessed from direct energy consumption of four major sewage
treatment plants in Taiwan. The results showed that the CO2
emission at in-plant sewage treatment stage takes more
than 95% of total CO2
emission for most plants. The results suggested that CO2
emission of sewage treatment can be
calculated from energy consumption at in-plant sewage treatment stage to simplify the calculation. The CO2
emission
of sewage treatment was then assessed from sewage plants in Taiwan using in-plant electricity consumption. The unit
CO2
emission of sewage treatment in Taiwan is 0.216 kg-CO2
/m3
. This database will be an important reference for water
resource research and future government environmental policies.