Sewage Biogas Conversion into Electricity by Using Small Systems

This article intends to present some considerations about electricity generation with 30 kW (ISO) microturbines, using biogas generated by a sewage treatment process at SABESP (Basic Sanitation Company of São Paulo State), located in Barueri, Brazil. This project, pioneer in Latin America, is being accomplished together with BUN – Biomass Users Network of Brazil (proponent), in association with CENBIO – Brazilian Reference Center on Biomass (executer), with patronage of FINEP/CT-ENERG (financial backer), by means of CONVENTION No: 23.01.0653.00, regarding to ENERG-BIOG Project – “Installation and Tests of an Electric Energy Generation Demonstration Unit from Biogas Sewage Treatment”. The study is being held at Barueri Sewage Treatment Plant. This plant operates with anaerobic digestion process, which has as mainly products biogas (composed mainly by methane) and sludge. Currently, part of the methane produced is burnt in a boiler being used to increase the digesters temperature and so, the process efficiency. The methane remnant is burnt in flare to reduce the impacts caused by gases emissions. An alternative to burn it in flare is the biogas conversion into electricity through engines or microturbines. This paper describes the proposed system to convert biogas in electricity and heat using microturbine. Thus, this article presents some technical, financial and environmental project results, related to the exploitation of sewer biogas for power generation, as well as more details about purification, compression and electricity generation systems (biogas microturbine), used in the facility. It is possible to conclude that the purification system projected takes care of the fuel specifications, demanded by the microturbine, but the costs analysis on using microturbines are not positive when compared with a conventional generator of equal power. Until the present moment, the data obtained will serve to baseline for the accomplishment of future environmental impact comparative studies, between engines (Otto – Cycle) and microturbines.