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Construction and Demolition (C&D) wastes are materials produced in the process of construction, renovation, or demolition of structures (buildings and roads). It also includes materials generated as a result of natural disasters (EPA, 2009). Preliminary estimates from the U.S. Environmental Protection Agency (EPA) show that the nation generated more than 160 million tons of building related C&D wastes in 2003. Also, Pennsylvania Department of Environmental Protection (PADEP) estimated that in 2005, Pennsylvania disposed over 2.25 million tons of C&D wastes in its municipal and C&D landfills (PADEP, 2009).Though previous studies have shown that it is cost-effective and environmentally friendly for contractors or construction managers to recycle C&D wastes rather than disposing them in landfills, these previous studies, however, paid little or no attention to detailed cost of recycling C&D wastes in a particular geographical area or region as compared to the availability of market for recycled materials or monetary value of the recycled materials. Hence, the objective of this study was to develop a mathematical model that helps stakeholders in construction business to evaluate the potential cost of recycling C&D waste components in their geographical area or region, and the potential revenue from the recycled materials. The model developed in this thesis will enable private companies or individuals to identify, invest and participate in the recycling of C&D waste components that yield good profits in their region or area. It will also enable Government to identify, sponsor or provide incentives for the recycling of C&D waste components that yield no or less profit in order to reduce environmental pollution and generate jobs. A case study is conducted in Pennsylvania to test the model developed in this thesis and the test has been successful. Based on the mathematical model and logic structure for selecting C&D waste components for recycling, drywall, roofing shingles and wood are identified as the components whose recycling will yield good profit and thus may not need government's support or incentives. Moreover, C&D waste components such as concrete, brick, block and asphalt, have been identified as components whose recycling will not be profitable enough and therefore would require government's support or incentives. The result of the case study also shows that the quantity of non-ferrous metals in C&D wastes are very small and their recycling will not yield any significant profit. / Civil Engineering

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This dissertation explores technical regulations (sanitary and phytosanitary (SPS) measures, technical barriers to trade, and geographical indications) in Central American agricultural and food trade. In the first part, a framework to systematically evaluate the broad issues for developing countries is presented. Evaluation of the issues for Central America is based on interviews with about 100 persons in the region and in the United States (US), and on secondary sources. The topic is of significance in Central America, especially when related to SPS measures. The World Trade Organization (WTO) Agreements have had relatively little direct impact in improving Central America's response to technical regulations, while homologous Central American regional institutions may have been more successful, with indirect support from the WTO and the US, in reducing the incidence of illegitimate regulations in intra-regional trade. Central America may implement illegitimate barriers more against others in the region than against the US. Although the Central America Free Trade Agreement (CAFTA) may support Central America's capacity to meet more stringent technical regulations, the improvement may not be sufficiently perceptible. The potential for Central American greenhouse tomato exports to the US is analytically evaluated in the second part. These tomatoes may be admitted as the ban based on the risk of introduction of the Mediterranean fruit fly is partially lifted, due in part on discussions in the CAFTA negotiations. Mature green, vine-ripe and greenhouse tomatoes are heterogeneous in demand, and vine-ripe tomatoes are but greenhouse tomatoes are not heterogeneous by origin. A static partial equilibrium model is constructed for the US tomato market, where demand is based on multi-stage budgeting and supply is a function of own tomato price. When the Central American greenhouse excess supply function is introduced to the model, the region exports to the US, the aggregate greenhouse quantity increases, and its prices decrease. As greenhouse preference increases, greenhouse quantity and prices also increase. Changes are perceptible but small in the mature green and vine-ripe markets in the expected direction. Access by Central America is particularly beneficial when US consumer preferences shift further toward greenhouse over other tomatoes. / Ph. D.

This thesis examines the effects on demand, supply, imports, and prices of partial easing of sanitary and phytosanitary (SPS) barriers to trade in the U.S. market in the case of Mexican avocados. The SPS Agreement plays a role in the avocado market studied here through its implications for negotiations between countries that have not utilized the formal channels of the WTO for resolving disputes. A quarantine in place from 1914 until very recently banned entry of Mexican avocados into the U.S. market on grounds of risk of pest infestation. Since the early 1970s this quarantine has been a cause of dispute between the Mexican and U.S. governments, resulting in elaborate evaluations of possible pest risks and risk mitigation procedures that might be carried out. However, after the initiation of negotiations for the North American Free Trade Agreement (NAFTA) in 1991, the import ban was partially eased in 1995 allowing Mexico access to the Northeastern part of the U.S. during four winter months. After three years of successfully exporting without any pest outbreaks, Mexico requested increased access to an additional part of the U.S. market, which it was granted in 2001. This study develops a partial equilibrium trade model to investigate the effects that this increased access will have on the avocados markets. Hypothesized further increases in access are described, and their potential effects are evaluated as well. / Master of Science

Municipal solid waste landfills are convenient means of disposing of society's waste; once closed, they become a liability to the community due to attributes which contribute to soil and water contamination. Regulations state that adequate vegetation be used to maintain the integrity of the soil trash cover. Alternatives to leaving a landfill derelict include establishing meadow-type communities that enrich floristic diversity while providing adequate cover to protect the soil cap over the trash. In 1993, an experimental study was conducted at the Roanoke Regional Landfill where a mixture of native wildflowers and grasses and the standard revegetation mixture were sown on plots on varying aspects at the landfill. In 1993, the plots sown with the native mixture had a higher average species richness than the plots planted with the native mixture. Plots with the standard revegetation mixture had higher cover than plots planted with the native mixture. In 1993 and 1994, an observational study was conducted at the Chancellorsville landfill in Spotsylvania county. Wildflowers had been seeded on part of the landfill in 1992. It was observed that the wildflower mixture decreased in species richness. The areas revegetated with the standard revegetation mixture had high richness due to the presence of invasive plants. Average cover over time was higher in areas planted with the standard revegetation mixture. Without regulations quantifying standards for aboveground cover, other methods should be implemented to determine to what extent revegetation mixtures are maintaining the integrity of a soil cap. / Master of Science

The possibility of acetone shock loadings to phenol acclimated systems resulting in sequential substrate utilization and increased effluent phenol concentrations was evaluated. Phenol acclimated batch and continuous-flow systems, developed with seed from a municipal wastewater treatment plant, were shock loaded with acetone, bacto-peptone, and domestic primary effluent. Phenol and acetone utilization rates were then monitored using direct injection gas-liquid chromatography. The results of the investigation indicated that, under the described experimental conditions, qualitative shock loading of phenol acclimated/utilizing cultures had no significant effect on effluent phenol concentrations. Variations of system pH, however, were found to have extreme effects. / Master of Science

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