Browsing by Subject "Life Cycle Assessment"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Evaluating Lifecycle Assessment models in a Low Carbon Fuel Standard
    (Hubert H. Humphrey Institute of Public Affairs, 2009-05-28) Warner, Ethan
    To avoid and/or reduce the risk of the various potential irreversible impacts associated with global climate change, many policies have been proposed to create reductions in greenhouse gas (GHG) emissions in all sectors of the United State’s economy. Several US States and the Federal government are considering, or have already considered, adopting a policy called a low carbon fuel standard (LCFS) that seeks to reduce the average GHG intensity of fuels measured across the full fuel cycle. There is significant controversy over the selection of a life cycle assessment (LCA) model to measure full fuel cycle emissions because of the potential impacts on an LCFS policy. There is a debate over whether or not full fuel cycle emissions are useful standards for use in policies designed to set and reach GHG emission reduction goals. This paper compares structural differences within existing LCA models, and the impacts of the emission intensity scores produced by these models. It then introduces these results into a LCFS policy in a system dynamics (SD) model of the Minnesota transportation sector. A comparison between the full fuel cycle intensity emissions as produced by LCA models show that full fuel cycle emissions matter in evaluating fuel choices under the LCFS and differ with regard to pollutants, fuel choice, and jobs created from fuel choices. From the SD modeling scenarios, criteria were developed to help policy makers select an LCA model for use in an LCFS (or potentially other policies). Selection of an LCA model is driven by situation specific issues, values, and goals of policy makers; therefore, criteria developed in this paper will be helpful in determining which LCA model should be adopted under different political and social contracts.
  • Thumbnail Image
    Item
    Improving Sustainability Management Decisions with Modified Life Cycle Assessment Methods
    (2016-12) Pelton, Rylie
    Across the globe, organizations and institutions have publicly committed to reducing the environmental impacts associated with their operations. Despite these commitments, progress in integrating sustainability measurement information into core business processes and decision criteria has been limited. To avoid many of the ecological tipping points that society currently faces, it is essential that sustainability measurement systems and decision support tools are improved to be more practically incorporated into business operations and decisions. This dissertation explores the specific sustainability challenges and information gaps that are faced by core business operations in three separate case studies, thereby expanding the sustainability operations management literature in the areas of environmentally preferable procurement, sustainable manufacturing, and green supply chain management. Modified life cycle assessment (LCA) methods are demonstrated in the methodological designs of the respective case studies, which help reduce the complexity of environmental information and the costs of assessment, and increase the specificity to organizations by considering spatial and temporal aspects of operations. Altogether, methods enable optimal management options and trade-offs to be identified, priorities to be set, and increases overall understanding of and ability to manage risks. These elements greatly enhance the actionability of sustainability information to organizational decision makers, helping to lower the barriers for integrating into core organizational processes for reducing the environmental burden of production and consumption systems.
  • Thumbnail Image
    Item
    Performance Measures of Direct Metal Laser Sintering Hybrid Milling: Mechanical Properties and Environmental Performance Indicators
    (2019-07) Ahmad, Nabeel
    Applications of metal additive manufacturing (AM) has increased substantially because it allows cost and resources efficient small-scale production required in industries such as aerospace and mold and die manufacturing. Geometric and dimensional accuracy of parts produced by AM is still subpar compared to conventional subtractive approaches. Recently, hybrid additive-subtractive called direct metal laser sintering hybrid milling (DMLS-HM) technology has been introduced which combines strengths and robustness of both additive and subtractive units. This thesis explores the adoption consequences and impacts of DMLS-HM through relative performance measures of mechanical and metallurgical properties as well as environmental impact assessment. This was achieved by first characterizing mechanical properties of Maraging steel powder and comparing it with conventional DMLS to understand the degree of variability. It was found out that DMLS-HM has superior mechanical properties for impact toughness and surface finish; however, tensile strength and hardness values were similar with DMLS. Environmental performance assessment was achieved by first identifying and finding the energy requirements in subsystems (additive and subtractive) of DMLS-HM and then converting into equivalent carbon emission. Carbon emission results for DMLS-HM printed geometry were compared with two other manufacturing approaches namely electron beam melting and conventional milling which fabricated the same geometry. The DMLS-HM process showed higher energy consumption during the part production stage with an average 84% more than EBM and CM processes. However, the CM was dominant in energy consumption during the procurement stage with an around 70% more energy than DMLS-HM and EBM processes. The outcome of this research project will contribute to the understanding of basic physics of energy consumption in AM and can be used in suitable process selection and setting sustainable manufacturing goals.