The Effects of Biogas Fuel in an Electric Generator on Greenhouse Gas Emissions, Power Output, and Fuel Consumption

Abstract

Abstract. The rising cost of fossil fuels, global warming from greenhouse gas (GHG) emissions, unreliable grid supply electricity, and overdependence on hydropower electricity have resulted in low electricity per capita in Nigeria. This study was undertaken to produce, purify, and use biogas as a fuel to generate electricity with a 3.5 kW spark-ignition engine generator and determine its effect on GHG emissions, power output, and fuel consumption. Unpurified and purified biogas were used as fuels. The biogas was purified in water and in a calcium chloride solution. The fuels used to power the generator were gasoline, unpurified biogas, water-purified biogas, and calcium chloride-purified biogas. The GHGs measured were carbon monoxide, carbon dioxide, nitrogen oxide, and sulfur dioxide. The biogas was produced with a 3 m3 capacity floating-drum biogas plant. The total solids concentration and carbon/nitrogen ratio of the influent and effluent slurries were determined. The effects of fuel type on GHG emissions were determined in a 4 × 4 factorial experiment with three replicates in a completely randomized design. The effects of fuel type on power output and fuel consumption of the generator were determined in a 4 × 2 factorial experiment with three replicates in a completely randomized design. The results were analyzed using analysis of variance at p = 0.05. Duncan’s new multiple range test was used to separate means when there was significant difference. The results obtained showed that carbon dioxide emission was not affected by purification of the biogas because the carbon dioxide emissions from the fuel types were not significantly different. The carbon monoxide emission was much higher from the unpurified biogas than from the purified biogas fuels, although gasoline had the highest carbon monoxide emission. The water-purified biogas had the least carbon monoxide and sulfur dioxide emissions. The unpurified biogas had the least nitrogen oxide emission compared to the purified biogas fuels and gasoline. The power output from the unpurified biogas was not significantly different from that of gasoline and was higher than the purified biogas fuels. The fuel consumptions of the purified biogas fuels were not significantly different. The water-purified biogas is recommended for use as fuel for the production of electricity from a spark-ignition engine generator. Keywords: Biogas, Effects, Electricity, Fuel consumption, Greenhouse gas emissions, Power output.