Reza Broun

ORCID Identifier(s)

0000-0002-2871-633X

Graduation Semester and Year

2016

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering

Department

Civil Engineering

First Advisor

Melanie L Sattler

Abstract

Despite the decreasing rate of landfilled waste due to increases in reuse and recycling, landfilling remains an enormous part of the waste industry of the United States due to population and economic growth. In addition, certain wastes are not easily recycled due to their mixed composition (i.e. a cardboard carton with a plastic lining) or their contamination (i.e. diapers). The primary goal of this research is to develop a comprehensive framework that can help landfill designers chose the best type of landfill (conventional, bioreactor, or aerobic) for a given situation based on greenhouse gas (GHG) emissions, traditional air pollutants and costs (internal and external). This study focuses on estimation of life cycle costs (LCC), appraisal of life cycle inventory (LCI) of air emissions, and estimation of external costs arising from environmental damages during disposal of solid waste into landfills. The study fills several gaps in the existing literature: • Several life cycle inventories of air pollutant and greenhouse gas emissions have been conducted to date for landfills outside the United States. Generally, the studies focus on direct emissions from landfills. Few studies include infrastructure construction or transportation of required material for construction in the analysis. Furthermore, these international studies do not necessarily apply to US conditions. • Previous studies have reported useful methodologies for assessing the economic performance of landfills and implementing landfill gas-to energy (LFGtE) projects, but they have typically not considered the role of solid waste acceptance rate and the effect of cost amortization over the lifetime of landfill. In addition, a cost function for each phase of life cycle of landfill has not been provided in the context of the US. • In many studies about landfill-biogas-to energy, landfill biogas collection efficiency has been assumed to be a single value rather than a temporally weighted collection efficiency depending on the stage of landfill operation. Additionally, the combination of internal combustion engines that convert biogas to electricity have been chosen arbitrarily, so that the effect of upper and lower bounds of required rate of biogas flow entering to run such engines were not taken into account. Specific objectives of the study are: 1. To develop a landfill life cycle internal cost model for all types of landfills for raw materials acquisition, construction, operation, closure and post-closure phases of 3 types of landfills (conventional, bioreactor, and aerobic). 2. For the use/operation phase of landfill-gas-to-energy systems, including fugitive methane emissions escaping through landfill covers, to determine the quantities of GHG emissions, traditional air pollutants , potential electricity generation and internal costs from LFGtE implementation in conventional and bioreactor landfills and subsequent revenue from electricity sales within a 100-year time horizon. 3. To quantify greenhouse gas emissions and air pollutant emissions for all types of landfills from landfill raw materials acquisition, construction, operation and end of life. 4. To integrate environmental damage-based external costs from GHGs and air pollutants, and internal costs estimated by LCC, for the all types of landfills. To determine the LCC associated with different types of landfills, a Landfill Life Cycle Cost model (2L2C) was developed using LCC methodology and economic elements of pre-construction and construction, operation and end of life of phases of landfill to estimate costs within estimation range defined by Association for the Advancement of Cost Engineering (AACE). The range of total annual life cycle cost of a conventional landfill was found to be $25 to $43 per ton of landfilled waste based on the type of landfill and waste acceptance rate. The operational phase was responsible for the majority of the costs (40 to 50%), largely from equipment costs and, particularly for conventional landfills, from leachate treatment costs. The construction phase contributed in the range of 30% to 50%, of which the excavation costs contribute around 25- 35% of the construction costs. Finally, end-of-life activities were responsible for 13 to 20% of the total annual life cycle costs, owing mainly to the final cover costs and especially post-closure care for conventional landfills. To determine the quantities of GHG emissions, traditional air pollutants and potential electricity generation from conventional and bioreactor landfills during operation phase of landfill-gas-to-energy ( LFGtE) system, a model was developed to incorporate environmental factors such as biogas generation, impacts of various collection efficiencies, converting the methane portion of biogas to electricity, offsetting fossil fuel based-electricity by burning recovered methane, methane oxidation through the landfill soil cover and emission inventories of biogas control devices. The average electricity production for bioreactor landfill and conventional landfill was estimated to be 4993 and 3153 MWh per million ton of waste in place. In bioreactor landfills, the annual revenue ranged from $8.50 to $24.77 per ton of waste based on acceptance rate. Also, total GHG emission in the most realistic case ranged from 168 and 371 kg CO2e per 1 t of landfilled MSW. To quantify greenhouse gas emissions and air pollutant emissions from landfill raw materials acquisition, construction, operation and end of life, the sub-stages of the construction and operational and end of life stages (including LFGtE system) of MSW landfills were identified. Using the LCI method, GHG and traditional air pollutant emissions inventories were performed for a generic “national average” landfill. The analyses revealed that construction and operation phases make up about 75% of total CO2e emissions within the entire life cycle of landfill. Manufacturing of materials for construction phase and equipment use during operational phase account for the majority of emissions to the atmosphere. To integrate environmental damage-based external costs from GHGs and air pollutants, and internal costs estimated by LCC, for the 3 types of landfills, the contributions of the emissions to external costs and internal costs over the life cycle of landfills was combined. Direct emissions from the landfilling system represented the major contributor to overall GHG emissions, whereas emissions from LCI of the landfill were determined to be responsible for nearly 2%, which is extremely low. External system costs, for a landfill with a low waste acceptance rate, did not exceed $1.35 per ton of waste. This value never went below $0.77 per ton waste for an aerobic landfill. If average LFG collection efficiency were installed in bioreactor and conventional landfills, the aerobic landfill would have more sustainable performance in terms of GHG emissions and traditional air pollutants. In the case of high LFG collection efficiency considered for bioreactor and conventional landfills, the bioreactor landfill was recognized to have the lowest total cost including Internal and external costs compared to other types of landfills.

Keywords

Solid waste landfills, Economic assessment, Life cycle assessment, GHG emissions

Disciplines

Civil and Environmental Engineering | Civil Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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