Landfill gas with hydrogen addition – A fuel for SI engines

Abstract

The recent quest to replace fossil fuels with renewable and sustainable energy sources has increased interest on utilization of landfill and bio gases. It is further augmented due to environment concerns and global warming caused by burning of conventional fossil fuels, energy security concerns and high cost of crude oil, and renewable nature of these gases. The main portion of landfill gas or biogas is comprised of methane and carbon dioxide with some other gases in small proportions. Methane if released directly to the atmosphere causes about 21 times global warming effects than carbon dioxide. Thus landfill gas is generally flared, where the energy recovery is not in place in practice. Using landfill gas to generate energy not only encourages more efficient collection reducing emissions into the atmosphere but also generates revenues for operators and local governments. However, use of landfill gases for energy production is not always perceived as an attractive option because of some disadvantages. Thus it becomes necessary to address these disadvantages involved by studying landfill gases in a technological perspective and motivate utilization of landfill gas for future energy needs. This paper discussed landfill gas as a fuel for a spark ignition engine to produce power in an effective way. It has been shown that though the performance and combustion characteristics of the landfill gas fueled engine deteriorated in comparison with methane operation, increasing compression ratio and advancing spark timing improved the performance of the landfill gas operation in par with methane operation. The effects due to composition changes in the landfill gas were found more pronounced at lean and rich mixture operation than at stoichiometry. In addition, the effects of additions of hydrogen up to 30% in the landfill gas were studied. Addition of even small quantities of hydrogen such as 3–5% delivered better performance improvement particularly at the lean and rich limit operations and extended the operational limits. Additions of hydrogen also improved the combustion characteristics and reduced cyclic variations of landfill gas operations especially at the lean and rich mixtures.