Method on Utilization of Low Quality Biogas as a Fuel for 4 Stroke Spark Ignition Engine of Electric Generator

Abstract

Biogas quality in many installation of anaerobic digester for processing organic waste are found not optimum, especially in developing country where understanding of anaerobic processing is not well known. The methane content in the biogas are usually low that make it not possible to be utilized as a fuel of the engine. Biogas Purification usually will be introduced as a solution. But this idea is about complicated for simple or small anaerobic digester. Other solution is suggested by using enrichment of biogas by using other fuel such as hydrogen or blended with city gas such as LPG gas. But for preparing hydrogen gas or commercial will also costly. This research introduces simple technique for biogas enrichment by using denatured alcohol. The biogas contents were found around 30% vol. methane (CH4) and around 2% Carbon dioxide (CO2). The price of denatured alcohol is relative cheap because the selling tax is not as much as drinking alcohol. Engine with bigger combustion (420 cc) chamber was prepared for this purpose to make possible to be fueled with biogas. The compression was set to reach 10 bar. The clearance of the both intake and exhaust valve was set in order to be possible to be running by using biogas. The biogas-air mixer was design for this purpose. The carburetor was set for use of denatured alcohol. It is found that the engine is running well by using biogas fuel that is enriched by using denatured alcohol. The emission was found better comparing using gasoline for the same engine. The fuel consumption is reported for future economic analyses.