Isamu WATANABE

Evaluation of Anaerobic Co-digestion System of Sewage Sludge and Garbage

by Life Cycle Assessment

Toshiya KOMATSU Shuji HIMENO Shoichi FUJITA


Anaerobic digestion of garbage using sludge digesters in sewage treatment plant is expected to be an effective energy recovery method from garbage.
In this study , we tried to evaluate anaerobic co-digestion system of sewage sludge and garbage by Life Cycle Assessment. We presumed the city population of 200,000 and compared five scenarios for garbage treatment : Ⅰincineration, incineration after anaerobic co-digestion( treatment ratio rate of garbageⅡ30 ％ ,Ⅲ80 ％ ) , composting after anaerobic co-digestion ( treatment ratio of garbage Ⅳ30 ％ ,Ⅴ80 ％).

As categories for evaluation , we set up the cost , amount of energy consumption , and emission of CO2・NOX・SOX・dioxins・heavy metals. As the results , there was no remarkable difference between scenarios in cost. In case of the environmental loads , the scenarioⅤ was the smallest.

Furthermore , we integrated assessment among the environmental impact categories by the Distance to Target method. The scenarioⅤ was also the most excellent in this evaluation method.

It is concluded that the anaerobic co-digestion system is effective in case that treatment ratio of garbage is high and composting after co-digestion is applied.