Estimate of energy generation and of greenhouse gas emission on biogas recovery from wastewater treatment plant

The use of biogas from treatment of domestic sewage, animal waste and solid waste disposal is an alternative to generate electricity with great potential for expansion in Brazil. The aim of this paper is quantifying the energy from the biogas produced in a wastewater treatment plant (WWTP) and estimating the greenhouse gas emission avoided with the biogas recovery. The WWTP evaluated has flow 33,220.8 m(3).d(-1) and COD 14,617.1 kg.d(-1) and serves about 190,000 inhabitants. It was used monitoring data from August/2012 to March/2013 to quantify the following parameters: COD converted into biomass; sulfate converted to sulfide; COD converted to methane; methane loss (liquid and gas); potential energy available; electrical power available; avoided emissions of methane. The following results were obtained: average treatment efficiency of 65.6%; methane production of 1,427.2 m(3).d(-1); average electricity available of 65,280.3 kWh.month-1 (59% of the average monthly energy demand of the WWTP); avoided emissions of 941.9 kgCH(4.)d(-1) and 17,189.7 kgCO(2eq.)d(-1). Therefore, it can be concluded that the biogas recovery of in Santa Quiteria WWTP can result in economic and environmental benefits.