The energy consumption throughout the world has increased substantially over the past few years and the trend is projected to continue indefinitely. The primary sources of energy are conventional fuels such as oil, natural gas and coal. The most apparent negative impacts of these conventional fuels are global warming, poor air-quality, and adverse health effects. Considering these negative impacts, it is necessary to develop and use non-conventional sources of energy. Landfill gas (LFG) generated at landfills can serve as a source of cleaner energy. LFG has substantial energy generation potential and, if cleaned of certain impurities, can be used for several applications such as electricity generation and conversion to high Btu gas. This thesis considers another application of LFG, which consists of using it as a vehicular fuel for refuse trucks. Currently, limited research has been performed on the development of such a methodology to evaluate the application of LFG as a vehicular fuel for refuse truck operations. The purpose of this thesis is to develop a methodology that can be used to evaluate the use of LFG generated at landfills as a Liquefied Natural Gas (LNG) fuel source for refuse trucks in Texas. The methodology simulates the gas generation process at a landfill by using standard models developed by the Environmental Protection Agency. The operations of a refuse truck fleet are replicated by using generic drive cycles developed as part of this research. The economic feasibility is evaluated by estimating the costs required for cleaning the LFG and converting the truck fleet from diesel to LNG as well as quantifying the benefits obtained due to change in fuel consumption and emission generation by the refuse trucks. The methodology was applied to a potential landfill in Texas. The results show that the methodology offers an innovative tool that allows the stakeholders to evaluate the economic feasibility of using LFG for refuse truck operations. The methodology also provides a flexible framework wherein each component can be changed or tailored to meet the specific needs of the stakeholders.

M. Ing. / The overall purpose of this research project was to develop a proposed maintenance strategy for generator sets utilised in biogas applications. One specific biogas application, involving the use of landfill gas (LFG) to generate electrical energy, was the focal point of the research project. This is due to the fact that the author’s organisation is extensively involved with landfills and power generation through the use of LFG.

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Microbial oxidation of methane has attracted interest as an alternative process for treating landfill gas emissions. Approaches have included enhanced landfill cover layers and biocovers, passive gas drainage and biofiltration, and active gas extraction and biofiltration. Previous research has shown that microbial methane oxidation is affected by a number of factors, many of which are dependent on the environment in which the process is occurring. The aim of this research was to evaluate the behaviour and performance of a passive landfill gas drainage and biofiltration system operating in a temperate climate, and to identify and quantify the factors that determine the behaviour and performance of the system under such conditions. To achieve this a series of field trials were undertaken in Sydney, Australia, over a period of 4 years. The trials were designed to evaluate the effect of a range of factors, including landfill gas loading rate, temperature and moisture content of the biofilter media, biofilter media characteristics, and climatic conditions. The results of the field trials showed that a passive gas drainage and biofiltration system operating in a temperate climate can achieve methane oxidation efficiencies > 90% and that the behaviour and performance of a passive gas drainage and biofiltration system is primarily dependent on 3 factors: the landfill gas loading rate, which varies; the temperature of the biofilter media, which is affected by the temperature of the landfill gas being treated, the level of microbial activity occurring in the biofilter, and local climatic conditions; and the moisture conditions within of the biofilter media, which is affected by local climatic conditions and the characteristics of the biofilter media. Relationships between these factors and the performance of a passive biofilter operating in a temperate climate were developed, where able. A number of design concepts for passive landfill gas drainage and biofiltration were developed. A process for assessing the feasibility of applying the concepts and designing a passive landfill gas drainage and biofiltration system was also developed. In addition, guidelines and recommendations for the design of a passive landfill gas drainage and biofiltration system operating in temperate climate were developed.

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Approximately 136,000 refuse trucks were in operation in the United States in 2007. These trucks burn approximately 1.2 billion gallons of diesel fuel a year, releasing almost 27 billion pounds of greenhouse gases. In addition to contributing to global climate change, diesel-fueled refuse trucks are one of the most concentrated sources of health-threatening air pollution in most cities. The landfills that they ultimately place their waste in are the second largest source of human-related methane emissions in the United States, accounting for approximately 23 percent of these emissions in 2007. At the same time, methane emissions from landfills represent a lost opportunity to capture and use a significant energy resource. Many landfill-gas-to-energy (LFGTE) projects are underway in an attempt to curb emissions and make better use of this energy. The methane that is extracted from these landfills can be converted into a transportation fuel, sold as a pipeline-quality natural gas, operate turbines for electricity, or be flared. The unique relationship that occurs between refuse trucks' constant visits to the landfill and the ability of the landfill itself to produce a transportation fuel creates an ability to accomplish emissions reduction in two sectors with the implementation of using landfill gas to fuel refuse trucks. Landfill owners and operators are very reluctant to invest in large capital LFGTE projects without knowing their long-term feasibility. The costs and benefits associated with each LFGTE project have been presented in such a way that owners/operators can make informed decisions based on economics while also implementing clean energy technology. Owners/operators benefit from larger economic returns, and the citizens of the surrounding cities benefit from better air quality. This research focused on six scenarios: converting landfill gas (LFG) to liquefied natural gas (LNG) for use as a transportation fuel, converting LFG to compressed natural gas (CNG) for use as a transportation fuel, converting LFG to pipeline-quality natural gas, converting LFG to electricity, flaring LFG, and doing nothing. For the test case of a 280-acre landfill, the option of converting LFG to CNG for use as a transportation fuel provided the best benefit-cost ratio at 5.63. Other significant benefit-cost findings involved the LFG-to-LNG option, providing a 5.51 benefit-cost ratio. Currently, the most commonly used LFGTE option of converting LFG to electricity provides only a 1.35 benefit-cost ratio while flaring which is the most common mitigation strategy provides a 1.21, further providing evidence that converting LFG to LNG/CNG for use as a transportation fuel provides greater economic benefits than the most common LFGTE option or mitigation strategy.

Countries around the world face social, economic, and ecological damage from escalating natural disasters caused by climate change. In an effort to curtail climate change impacts, local and regional governments are beginning to employ green house gas (GHG) mitigation strategies to reduce their carbon footprint. These strategies work to eliminate a range of GHG emissions from entering the atmosphere. Apart from carbon dioxide (CO₂), the most prevalent GHG is methane. In terms of global warming, methane is approximately 21 times more harmful to the atmosphere than CO₂. Natural gas systems, coal mining, manure management, rice cultivation, wastewater treatment, and landfills all contribute to methane generation. According to the US Environmental Protection Agency's 2011 US GHG inventory, landfills generate 1.5% of total GHG emissions in carbon dioxide equivalents. Recognizing the global impacts of its policies and operations, municipalities are working to reduce their GHG emissions. Coalitions like the C40 Cities Climate Leadership Group were created to specifically address GHG reductions, which will result in a 248 million MT reduction in GHGs released to the atmosphere by 2020. Guided by existing literature, this Master's Report calculates methane generation and transport to determine the effectiveness of applying two methane mitigation alternatives--passive methane oxidation biocovers (PMOBs) and landfill gas to energy technologies (LFGTE)--at an inactive landfill site to reduce GHG emissions. LFGTE generates energy for direct use such as space heating or industrial processes or for electricity generation. Cost-saving strategies abound for landfills which utilize LFGTE. PMOBs optimize the landfill surface soil cover environment to promote microbial growth of bacteria, called methanotrophs, which convert methane into carbon dioxide. When employed, these mitigation alternatives are designed to significantly reduce methane emissions from landfills. The EPA has developed a computer modeling program (LANDGEM) to aid in the calculation of landfill gas generation. A hypothetical case study of a one million ton landfill was created and modeled for methane generation over a 35 year period. With methane generation rates calculated, assessment of potential LFGTE was performed and methane oxidation rate calculations were made to determine the impact of a PMOB and LFGTE on net GHG emissions at the landfill. The overall GHG reductions with these engineering controls were two-thirds of the level a landfill without controls would emit. These results indicate that implementing methane mitigation steps at closed landfills throughout the world would yield significant reductions in GHG emissions. / text

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