Comparative assessment of dewatered sludge recycling systems based on cost-effectiveness

Abstract

Some rural sewage treatment plants, which are
located near a cement plant, select a recycling system to input dewatered
sludge dilectly in cement kiln. In terms of energy recovery from organic matter
contained in sewage sludge, this system (direct cement feedstock system, DCFS)
is not defined as an energy recovery measure and targeted for revision. On the
other hand, an analysis of energy balances and greenhouse gas emissions for
this system was not conducted, so information for deciding whether this system
should be continued or not is lacking. In this study, I evaluated the
cost-effectiveness [kg-CO2eq/1,000 Yen] for the measures to changing from DCFS
to sludge carbonization system (SCS) in Gun-ma and Tochigi prefectures. The
evaluated cost-effectiveness values of measures for changing from DCFS to SCS
were smaller than the other GHG reduction measures in the field of sludge
recycling. It is concluded that continuation of DCFS in rural area is a
responsible decision.