Browsing by Author "Sheehan, John, committee member"
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Item Open Access Bioplastic production from microalgae with fuel co-products: a techno-economic and life-cycle assessment(Colorado State University. Libraries, 2019) Beckstrom, Braden Dale, author; Quinn, Jason C., advisor; Marchese, Anthony, committee member; Sheehan, John, committee memberConcerns over depleting oil reserves and national security have spurred renewed vigor in developing bio-based products. One specific area of growing concern is the consumption of petroleum based plastics, which is expected to consume 20% of global annual oil by 2050. Algae systems represent a promising pathway for the development of a bioplastic feedstock but have many technological challenges. Algae-based plastics offer a promising alleviate that would decrease oil consumption, improve environmental impact, and in some cases even improve plastic performance. This study investigates the economic viability and environmental impact of an algae biorefinery that integrates the complementary functions of bioplastic and fuel production. The bioplastic and biofuel biorefinery modeled herein includes nine different production scenarios. Performance of the facility was validated based on experimental systems with modeling work focusing on mass and energy balances of all required sub-processes in the production pathway. Results show the minimum selling price of the bioplastic feedstock is within the realm of economic competition with prices as low as $970 USD tonne-1. Additionally, LCA results indicate drastic improvements in environmental performance of the produced bioplastic feedstock, with reductions ranging between 67-116% compared to petroleum based plastics. These results indicate that an algae biorefinery focused on bioplastic feedstock production and fuels has the potential to operate both economically and sustainably. Sensitivity analysis results, alternative co-products (given that fuels represent minimal value) and product market potential are discussed.Item Open Access Economic approaches to allocation of life cycle environmental burdens between beef production systems and ecosystem services(Colorado State University. Libraries, 2021) Haddix, Jilleen D., author; Dillon, Jasmine A., advisor; Ahola, Jason, committee member; Sheehan, John, committee memberBuck Island Ranch (BIR) is a cow-calf operation in central Florida that manages over 4,200 hectares of semi-native and improved pasture and produces over 2,000 calves each year. The operation has the unique distinction of being both a working ranch and a conservation site with extensive monitoring of everything from species diversity across taxa to nutrient dynamics in pastures and wetlands for the past 30 years. As a result of managing for profitable beef production and conservation, they provide key ecosystem services to their community through conservation oriented management practices. The primary goal of this project was to perform a cradle to farm gate life cycle assessment (LCA) of environmental impacts and resource consumption in the production of BIR live weight (LW) sold from the ranch. In addition, reproducible methods were developed for multi-functional allocation of environmental impacts between beef and conservation benefits. The LCA was conducted using four approaches to economic allocation of emissions between beef and ecosystem services: (1) allocate all emissions to beef; (2) multifunctional allocation using payments for conservation management practices through the USDA Conservation Stewardship Program (CSP); (3) multi-functional allocation using the "highest and best use" (HBU) price based on real estate evaluation of BIR land; (4) multi-functional allocation using conservation easement prices set by the USDA Agricultural Conservation Easement Program (ACEP). The results of the life cycle impact assessment were as follows: 1 kg LW leaving the farm gate to be sold used 322.22 L of water consumption, 43.97 m2 annual crop-eq, and 2.01 MJ energy surplus. The associated emissions were 12.27 kg CO2-eq/kg LW and 36.97 g N-eq/kg LW. When emissions were allocated between beef and ecosystem services, the impacts for beef were reduced 2% using the CSP approach, 39% using the HBU approach, and 42% using the ACEP approach.Item Open Access GWP* of U.S. beef and dairy systems(Colorado State University. Libraries, 2023) Molina Plaza, Erick, author; Dillon, Jasmine, advisor; Archibeque, Shawn, committee member; Denning, Scott, committee member; Sheehan, John, committee memberGlobal warming potential (GWP) is used to quantify the impact that greenhouse gases (GHG) have on the warming of the Earth's atmosphere relative to carbon dioxide (CO2). GWP* is a metric that is used to better quantify short-lived climate pollutants (SLCP) such as methane, hydrofluorocarbons, and sulfur dioxide. GWP* allows SLCP to be more consistently expressed by equating a change in the emission of the SLCP to a one-off pulse emission of CO2. Therefore, GWP* can be positive or negative. The objective of this work was to compare the GWP* and GWP100 for U.S. beef and dairy systems using livestock methane emissions data from the Food and Agriculture Organization (FAO) and the Environmental Protection Agency (EPA). Total methane emissions for this study are the sum of enteric and manure methane emissions. GWP100 was greater than GWP* for both beef and dairy systems using both datasets, with the exception GWP* for dairy using the EPA data. Dairy GWP* calculated using the EPA data was lower than GWP100 from 1990–2000, after which point on it became greater than GWP100 and continued increasing annually, because the emission factors used by the EPA increased annually, and the difference between weighted emissions from that year and the weighted emissions from 20 years prior surpassed the current emissions used in GWP100. Overall, the GWP* of EPA dairy increased by 507% from 1990–2020. The primary drivers of the differences in GWP* and GWP100 with the EPA dataset are the use of methane emission factors for manure methane, which increase yearly, and the use of a larger dairy population estimate than FAO. The EPA emission factors increase yearly based on the trend towards larger farm sizes managing more liquid manure, therefore produce more manure methane emissions. The dairy GWP* using EPA data was greater than the beef GWP* every year, despite greater total methane emissions for beef than for dairy, because the average rate of change for dairy (29.8 kt of CH4/yr) was greater than the average rate of change for beef (9.4 kt of CH4/yr). Accounting methods play a key role in the amount of methane emissions that are calculated, and thus how GWP100 and GWP* are calculated. The EPA larger population estimate and annual increase in manure methane emission factors led to greater GWP* and GWP100 values for the EPA data than for the FAO data for both beef and dairy systems. Data source is critical to the policy implications of GWP* and GWP100 for livestock systems, as evidenced by the differences in GWP* and GWP100 results between datasets.Item Open Access Methane emissions from gathering pipeline networks, distribution systems, agriculture, waste management and natural sources(Colorado State University. Libraries, 2016) Pickering, Cody, author; Bradley, Thomas, advisor; Zimmerle, Daniel, advisor; Sheehan, John, committee memberClimate change has influenced United States policymakers and industry professionals alike to minimize greenhouse gas emissions; including methane, the second most abundant greenhouse gas. The recent focus on quantifying methane emissions is not only motivated by its abundance but also the high global warming potential of the gas, which is 86 times greater than that of carbon dioxide on a 20-year timescale. Techniques to quantify methane emissions can be broken into three categories: component level, facility level, and basin level. In this study component level measurements and published emission estimates were used in Monte Carlo models to estimate regional methane emissions from three different source categories: natural gas gathering pipeline networks, natural gas distributions systems, and non-oil and gas sources such as: agriculture, waste management, lakes, ponds, rivers, wetlands and geological seepage. These estimates are designed to support a regional estimate including all methane sources for comparison against top-down emission estimates from aircraft measurements in the same region. Gathering pipeline networks are a sector of the natural gas supply chain for which little methane emissions data are available. In this study leak detection was performed on 96 kilometers of underground plastic pipeline and above-ground components including 56 pigging facilities and 39 block valves. Only one leak was located on an underground pipeline, however, it accounted for 83% of total measured emissions. Methane emissions estimated using a Monte-Carlo model for the 4684 km of gathering pipeline in the study area were 400 [+214%/-87%] kg/h (95% CI). This estimate is statistically similar to estimates based on emission factors from EPA’s 2015 Greenhouse Gas Reporting Program and is approximately 1% [0.1% to 3.2%] of the 39 Mg/h estimated in a prior aircraft measurement of the study region. The wide uncertainty range is due to two factors: one, the small sample size relative to the total gathering system in the study area and two, the presence of only one underground pipeline leak to characterize a range of possible emissions. The study also investigates what fraction of gathering pipelines in a basin must be measured to understand the maximum probable impact gathering line emissions could have on a basin level emission estimate. Distribution systems are a sector of the natural gas supply chain that has been analyzed and measured in recent years due to the attention they received in a 1992 study showing that they contribute approximately 25% of total methane emissions from the natural gas supply chain. The only distribution company in the study region provided data and access to their system for measurement during this study. During the field campaign, 129 of 239 metering and regulating stations were visited and 34 of 87 documented leaks from PHMSA surveys were visited. When scaling measured emissions to the eight counties in the study region, pneumatic emissions dominate, accounting for 2.8 [+37%/-31%] kg/h (95% CI) or 53% [42%-64%] of total emissions from measured sources. When including customer meters, the total distribution system in the 8 county study region contributes approximately 0.05% [0.02% to 0.12%] of the 39 Mg/h found in a prior aircraft measurement of the study region. While this study shows that the distribution system measurements are not a major contributor of emissions in this basin, it does not imply emissions are negligible on a national scale, since the rural regions in the study area had relatively little distribution infrastructure, and other distribution systems that may be older or constructed with materials that have higher leak rates, such as cast iron or unprotected steel. A detailed emission estimate from non-oil and gas sources was performed including poultry, cattle, swine, rice cultivation, landfills, wastewater treatment, wetlands, rivers, ponds and lakes, and geological seepage. This analysis supported emission estimates of previous work suggesting that cattle are the largest source of biogenic methane in this region. This analysis also indicates the importance of understanding geological seepage due to the large contribution that it may have to methane emissions from non-oil and gas sources. This analysis concludes that methane emissions from gathering pipeline networks, distributions systems, agricultural practices, waste management systems and natural sources contribute a small, but non-negligible, fraction of total methane emissions for this particular region which includes large-scale natural gas production. While methane emissions from the analyzed sources are proportionally low in the study region they are not necessarily proportionally small on a state, national or global scale.