Keywords

Landfill gases

Abstract

Municipal solid waste (MSW) management strategies typically include a combination of three approaches, recycling, combustion, and landfill disposal. In the US approximately 54% of the generated MSW was landfilled in 2008, mainly because of its simplicity and cost-effectiveness. However, landfills remain a major concern due to potential landfill gas (LFG) emissions, generated from the chemical and biological processes occurring in the disposed waste. The main components of LFG are methane (50-60%) and carbon dioxide (40-50%). Although LFG poses a threat to the environment, if managed properly it is a valuable energy resource due to the methane content. Currently there are over 550 active LFG to energy (LFGTE) facilities in the US, producing renewable energy from LFG. A major challenge in designing/operating a LFGTE facility is the uncertainty in LFG generation rate predictions. LFG generation rates are currently estimated using models that are dependent upon the waste disposal history, moisture content, cover type, and gas collection system, which are associated with significant uncertainties. The objectives of this research were to:  Evaluate various approaches of estimating LFG generation and to quantify the uncertainty of the model outcomes based on case-study analysis,  Present a methodology to predict long-term LFGTE potential under various operating practices on a regional scale, and  Investigate costs and benefits of emitting vs. collecting LFG emissions with regards to operation strategies and regulations. iii The first-order empirical model appeared to be insensitive to the approach taken in quantifying the model parameters, suggesting that the model may be inadequate to accurately describe LFG generation and collection. The uncertainty values for the model were, in general, at their lowest within five years after waste placement ended. Because of the exponential nature, the uncertainty increased as LFG generation declined to low values decades after the end of waste placement. A methodology was presented to estimate LFGTE potential on a regional scale over a 25-year timeframe with consideration of modeling uncertainties. The methodology was demonstrated for the US state of Florida, and showed that Florida could increase the annual LFGTE production by more than threefold by 2035 through installation of LFGTE facilities at all landfills. Results showed that diverting food waste could significantly reduce fugitive LFG emissions, while having minimal effect on the LFGTE potential. Estimates showed that with enhanced landfill operation and energy production practices, LFGTE power density could be comparable to technologies such as wind, tidal, and geothermal. More aggressive operations must be considered to avoid fugitive LFG emissions, which could significantly affect the economic viability of landfills. With little economic motivation for US landfill owners to voluntarily reduce fugitive emissions, regulations are necessary to increase the cost of emitting GHGs. In light of the recent economic recession, it is not likely that a carbon tax will be established; while a carbon trading program will enforce emission caps and provide a tool to offset some costs and improve emission-reduction systems. Immediate action establishing a iv US carbon trading market with carbon credit pricing and trading supervised by the federal government may be the solution. Costs of achieving high lifetime LFG collection efficiencies are unlikely to be covered with revenues from tipping fee, electricity sales, tax credits, or carbon credit trading. Under scenarios of highly regulated LFG emissions, sustainable landfilling will require research, development, and application of technologies to reduce the marginal abatement cost, including:  Diverting rapidly decomposable waste to alternative treatment methods,  Reducing fugitive emissions through usage daily/intermediate covers with high oxidation potential,  Increasing the lifetime LFG collection efficiency, and  Increasing LFG energy value – for instance by producing high-methane gas through biologically altering the LFG generation pathway

Notes

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Graduation Date

2011

Semester

Summer

Advisor

Reinhart, Debra R.

Degree

Doctor of Philosophy (Ph.D.)

College

College of Engineering and Computer Science

Department

Civil, Environmental, and Construction Engineering

Format

application/pdf

Identifier

CFE0003960

URL

http://purl.fcla.edu/fcla/etd/CFE0003960

Language

English

Length of Campus-only Access

None

Access Status

Doctoral Dissertation (Open Access)

Subjects

Dissertations, Academic -- Engineering and Computer Science, Engineering and Computer Science -- Dissertations, Academic

Included in

Engineering Commons

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