In recent decades, advances in low NOₓ coal combustion and increasingly strict CO₂ reduction mandates have changed power plant boiler operations quite significantly. As a result of these necessary efforts, the characteristics of fly ash generated at many power plants have also changed. In particular, increases in unburned carbon content have been observed with detrimental implications on the utility of these fly ashes in concrete applications. Over the same time period, the combustion of biomass for energy generation has received increased attention due to the potential benefits of reducing CO₂ emissions and improved sustainability when compared to fossil fuel combustion. Biomass is directly burned, gasified, or co-fired with coal to achieve this goal. Currently, close to 120 million metric tons of coal combustion by products are produced in the U.S. annually. As with coal combustion, production of energy from biomass combustion/gasification results in significant by-product generation that must either be productively reused or geologically disposed. While much research effort has been devoted to understanding the properties and potential productive reuse alternatives for coal combustion residuals, relatively little work has been done on the by-products of biomass combustion. This study investigated the properties and engineering behavior of sixteen ash samples that were produced in eleven different power plants. Specifically, three high carbon content Class F fly ashes, eight coal and biomass co-fired ashes, three pure biomass ash samples, and two high quality, low carbon content ash samples, one of which is commercially marketed (for reference) were chosen. The various ash samples were characterized by means of: electron microscopy; laser diffraction and dry sieve particle size analysis; loss on ignition and total organic carbon analysis; specific surface area analysis; as well as x-ray fluorescence and x-ray diffraction. The ash samples were also investigated for their potential engineering application in the fired clay brick industry, as low-cost adsorptive agents, and in alkali activated geopolymer synthesis for geotechnical and geoenvironmental applications. Results from physical and chemical characterization of the ash samples show no significant differences between pure coal ash and coal co-fired with biomass ash samples from the same power plant. However, there are significant morphological, chemical, and mineralogical differences between coal ash and pure biomass ash. Unlike pure coal ash, biomass ash is not composed primarily of aluminosilicate glass cenospheres but rather consists mainly of charred, fibrous woody remnants with elevated calcite content as compared to coal ash. Bench scale fired bricks produced by partial replacement of clay material with high carbon coal ash, co-fired ash, and pure biomass ash, respectively, was successful. Physical properties of a number of the mix designs exceeded the highest ASTM weathering grade requirements. As sorptive agents, high carbon concentrates from coal and co-fired ash samples, along with all the biomass ash samples, showed significant uptake of lead. The unaltered as- received ash samples (i.e. no acid or steam activation) showed only moderate arsenic (V) and selenium (VI) sorption capacity. Finally, solidification/stabilization by geopolymerization of high carbon content, co-fired ash with as little as 3 molar NaOH in the activator solution was successful, possibly paving the way for various geotechnical and geoenvironmental applications in ground improvement and soil/ash-pond stabilization.

A Reverse Production System (RPS) is a network of transportation logistics and processing functions that collects, refurbishes, and demanufactures for reuse/recycle used or end-of-life products. In this thesis, I focus on the RPS strategic decisions of a processor and collectors when the collection network and contracts for materials can be co-designed. The research problem is motivated by the need of material processors to ensure a consistent flow of material from collectors at a cost that will enable them to be competitive with virgin raw materials. The failure to develop a cost-effective collection network can lead to poor overall economics where expensive processing assets are not fully utilized. The three key problems from the processor s point of view are: 1) how to design a strategic collection network; 2) how to be competitive in the collected materials market place when significant investment is at risk; and 3) how to avoid overpaying for materials when collectors are in regions with different volumes and costs. The multiple goals of this research are: 1) to integrate the contract and strategic network design in RPS; 2) to develop contract mechanism designs to improve the performance under incomplete information and study the value of information (complete vs. incomplete); and 3) to introduce and analyze new strategic network models for effectiveness in solution quality and time. Concepts of mathematical optimization, contract theory, and game theory are utilized in proposing models that couple contract and network problems, including lump sum and variable volume contracts.

The catalytic depolymerization/pyrolysis of nylon 6 and 66 were investigated with the prospect of helping to curb the amount of carpet landfilled. Thermogravimetric analysis was used to determine which catalysts (and their nylon/catalyst ratio) were most suited for the depolymerization. By adding bases, the onset of degradation for some bases was 100 aC lower than that of the pure nylons. Potassium hydroxide and sodium hydroxide were found to be the most effective catalysts at a catalyst ratio of 100:1 of nylon 6 and nylon 66 to catalyst, respectively. After determining the most efficient catalyst, kinetic models/parameters from the TGA data were determined. These parameters were used in a reactive extrusion model for depolymerizing nylon 6 in carpet. Data from the model was then used to do cost analysis for the process. It was found that to get a Present Value Ratio greater than 1, the flow rate has to be greater than or equal to 500 lb/hr. At even higher flow rates up to the model¡¦s limit (1500 lb/hr), the Net Present Value shows that this process is economically viable. Extrusion of a 100:1 ratio of pure N6 and KOH was done in a 30 mm counter-rotating non-intermeshing twin screw extruder. The material collected from the vents of the extruder was tested with a gas chromatograph- mass spectrum (GC-MS) in tandem. There was only one significant peak from the GC and the primary molecular weight on the MS was 113, the molecular weight of caprolactam. This shows that the process could be profitable and require little purification if done industrially.

In the past few decades, globalization has led to a world economy with unbounded consumption. In addition to the consequential impoverishment of natural resources, this large consumption produces copious amounts of waste and requires high energy use. Proper end-of-life strategies can help to reduce the global impact of these inefficiencies. The objective of this thesis is to demonstrate, through life-cycles analyses of an automotive transfer case and a gear, the positive environmental impact of remanufacturing strategies compared to recycling and disposal end-of-life strategies. In this study, the energy consumption, the air emissions and the wastes resulting from the entire supply chain s engineering processes will be quantitatively evaluated through calculations and also industrial or governmental data. In disposal end-of-life strategies, the analysis will begin with the ore mining phase, will go through material refining and processing; and eventually end with the final parts machining. In recycling scenarios and remanufacturing scenarios, the analysis will begin with the used material collection, will go through material s reprocessing or refurbishing and will finally end with the new or renewed parts machining. This study will show the significant impact of high energy consumption processes such as electrolysis of aluminum and metal melting. It will also show how shipping and collection phases can dramatically change or annihilate the advantage of sustainable reuse scenarios depending on the sorting strategies adopted in the supply chain. To conclude, the goal of this research is to demonstrate how remanufacturing strategies can reduce the energy consumption, air emissions and waste. This thesis will also show how inappropriate supply chain management can negate the impact of these savings.

The purpose of this study was to analyze the developing organizational and management paradigms in the aluminum packaging and container industry, where reverse channels of distribution offer an excellent vehicle for studying organizations which are "closing the distribution circle." Based on the analysis, several conclusions are offered. 1. The extent to which primary manufacturers have entered aluminum packaging and container recycling and subsequently developed effective reverse channels of distribution is contingent upon needs for resources. 2. The most successful recycling programs are those which have decentralized organizations. 3. Central to beverage producers' decisions to develop extensive reverse channels of distribution is the belief that recycling is (1) a deterrent to container legislation, (2) a source of favorable publicity, (3) a source of company profits, and (4) can improve supply relationships with primary aluminum suppliers. 4. Regional beverage companies in the environmentally conscious Far West have the most successful and comprehensive recycling operations. 5. Loose organizational federations such as those of the soft drink franchise do not seem amenable to the development of reverse channels of distribution. 6. Where i t serves the needs of the enterprise, firms are developing sophisticated and efficient reverse channels of distribution. The institution of reverse channel intermediary functions reflects a new management and organizational paradigm based on environmental considerations. 7. A major stumbling block to further reverse channel development is the uncertainty caused by proposed container legislation.

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The growth of the construction industry in Brazil has resulted in increasing of construction and demolition wastes generation (CDW). Given this fact, various studies and researches have been conducted in order to mitigate or even extinguish the undesirable impacts caused by improper disposal of these wastes on the environment. On the other hand, the road infrastructure constructions, in general, consume large amounts of natural resources, that have become scarce in many regions of the country. But fortunately, it is worth noting that this construction area has a favorable history about incorporation of wastes in your construction process, and CDW is the most prominent. Against this background, with this research sought to evaluate the geotechnical properties of CDW recycled aggregates produced by a recycling plant in the Aracaju metropolitan region (AMR), preparing mixtures of these materials with two typically soils of Sergipe state. Therefore, tests were conducted to evaluate the composition and percentage of impurities, gradation, Atterberg limits, absorption, abrasion resistance, bulk density, grain form, compaction, degradation, califórnia bearing ratio and resiliente modulus. Based on results, obtained using the intermediate compaction energy, it was found that the CDW recycled aggregates provided significant improvements in the soils properties, expressed by satisfactory mechanical performance observed in the CBR and RM parameters of mixtures. The results presented in this research indicate and ratify the technical feasibility of using the CDW in base and sub-base pavements layers, which can contribute to sustainable development, increasing the materials supply and a application methodology in AMR and Sergipe urban roads constructions, in addition to resulting in decreased extraction of natural materials and areas of final disposal of such wastes. / O crescimento da indústria da construção civil no Brasil tem resultado no aumento crescente da geração de resíduos de construção e demolição (RCD). Diante desse fato, diversos estudos e pesquisas têm sido realizados com a finalidade de amenizar ou até mesmo extinguir os impactos indesejáveis causados pela deposição inadequada desses resíduos no meio ambiente. Por outro lado, as obras de infraestrutura rodoviária, em geral, consomem grandes quantidades de recursos naturais, que já se tornam escassos em diversas regiões do país. Mas, felizmente, cabe destacar que essa área da construção já possui um favorável histórico de incorporação de resíduos no seu processo construtivo, sendo o RCD o de maior destaque. Diante deste cenário, com esta pesquisa procurou-se avaliar as propriedades geotécnicas de agregados reciclados de RCD produzidos em uma usina recicladora da região metropolitana de Aracaju (RMA), preparando-se misturas desses materiais com dois solos tipicamente encontrados no Estado de Sergipe. Dessa forma, foram realizados ensaios para se avaliar a composição e porcentagem de materiais indesejáveis, granulometria, limites de Atterberg, absorção, desgaste por abrasão, massa específica, índice de forma, compactação, degradação, índice de suporte califórnia e módulo de resiliência. Com base nos resultados obtidos, utilizando-se a energia intermediária de compactação, verificou-se que os agregados reciclados de RCD proporcionaram significativas melhorias nas propriedades dos solos, expressa pelo desempenho mecânico satisfatório observado nos parâmetros ISC e MR das misturas. Os resultados apresentados nesta pesquisa indicam e ratificam a viabilidade técnica do uso do RCD em camadas de base e sub-base de pavimentos, o que pode contribuir para o desenvolvimento sustentável, o aumento da oferta de materiais e uma metodologia de aplicação na construção de vias urbanas da RMA e do Estado de Sergipe, além de resultar na diminuição da extração de materiais naturais de jazidas e das áreas de disposição final desses resíduos.

No description available.

The essentiality for waste reduction in society is prompted by the depletion of natural resources. Internationally, five waste management strategies have been identified, namely reduction of waste (waste prevention), re-use of waste, recycling of waste, recovery of energy and disposal to landfill. In Polokwane Declaration of September 2001, South Africa’s Department of Environmental Affairs and Tourism committed itself to achieve a 50 percent reduction in the volume of waste generated by 2012 and to be landfilled and have a zero waste plan implemented by 2022. Through the National Waste Management Act, No. 59 of 2008, the South African government also committed itself to provide protection of health, well-being and the environment through measures to avoid and minimise the generation of waste. Even though several policies and legislative documents are available that address waste minimisation and recycling, individual community members are however still reluctant to participate in these activities. This study therefore investigated the current levels of understanding, education and commitment to recycling and waste minimisation in a selected South African community. The target respondents of the study were members of a local church who are representative of the various peoples that reside in the communities serviced by the selected municipality. A convenience sample of 70 participants from that church was selected to complete the questionnaires. Seventy (70) questionnaires were distributed, and all 70 questionnaires were returned. Interviews were also conducted with two managers from the Waste Management Department of the selected municipality. The data analyses conducted, included descriptive statistics and content analysis of the interview transcripts. The empirical results revealed among others that: (1) recycling removal service is limited to pre-selected recyclables; (2) the municipality contributes to local entrepreneurial opportunities; (3) public participation is a pre-requisite in the success of the programmes; (4) participation is determined by convenience; (5) enforcement of legislation assists with compliance; (6) environmental sustainability is supported by environmental concerned consumers; (7) mismatch of opinions around separation at source of generation and (8) continuous education is instrumental in waste management. The main recommendations of the study include: (1) municipalities need to provide exciting and innovative recycling and waste minimisation programmes, continuously; (2) positive attitude and behaviour of all the stakeholders determines the success of waste minimisation and recycling; and (3) society, industry and government need to join forces in ensuring success in waste management. By implementing these recommendations, stakeholders in this field of interest will go a long way in improving waste management in South Africa communities.

There has been considerable interest in finding and explaining the basic elements that can drive product quality up. In the literature this is largely done by modelling the effects of investing in learning and process improvement, and of cost reduction. In the first essay, demand is modelled as a function of price and quality. With this demand function, the firm should produce output of higher quality, the increase in quality being dependent on consumers’ sensitivity to quality and to price, and the effect of technological improvement on product price and quality are very different from those when the demand is a function of price alone. Some twenty states in the U.S. have passed recycling laws which mandate consumption of old newspaper by the newsprint industry. To study the effect of regulation, a model is used in which two firms compete under the regulatory constraint—one firm producing the recycled product, the other the virgin product. Assuming the regulatory constraint is binding, and the demand for the recycled product is derived solely from the legislation, interesting results such as the two firms share equal profits, and consumers pay higher average price in competitive equilibrium than the cartel price, are obtained in the second essay. The two firm model is generalized to include n firms which compete under the same kind of regulatory constraint in the third essay. Results similar to the two firm case are obtained. When the recycled product and the virgin product are partially substitutable, regulation that mandates consumption of the recycled product results in infinitely many equilibria. A dominating equilibrium exists if the demand parameters satisfy a certain condition, otherwise it is not clear how to select an equilibrium. On the other hand, a suitable tax on the virgin product, or its producer, serves to induce compliance with the recycling policy and equilibrium selection. The equilibrium prices and profits of the two firms under the schemes of production tax, excessive consumption tax and progressive profit tax are examined and compared in the fourth essay. It is interesting to find that the tax rate for excessive consumption is comparatively low and, in equilibrium, this tax scheme collects no tax payment. / Business, Sauder School of / Graduate