Achieving Low Emissions From a Biogas Fueled SI Engine Using a Catalytic Converter

Utilization of biogas is attractive from a greenhouse gas standpoint since it is carbon neutral due to the use of renewable resources. One source of biogas is anaerobic digestors. The biogas produced could be used to power IC engine-generator sets to produce electric power and heat on farms and in rural and northern communities. Use of local energy sources is particularly attractive in remote regions where liquid fuels must be shipped in via difficult terrain. Whatever the fuel, the engine must meet stringent exhaust emission standards. Biogas is typically used in spark ignition engines, where stoichiometric engine operation coupled to a three-way catalyst is a proven technology for achieving low emissions. An appropriate three-way catalyst was selected on the basis of tests with natural gas. A flow mixing system was used to create simulated biogas mixtures consisting of varying concentrations of methane, carbon dioxide, hydrogen and nitrogen. The effectiveness of the catalyst in achieving low emissions when the engine was fueled by the various simulated biogas mixtures was assessed.