Graduate Thesis Or Dissertation

 

Integrated Spatio-temporal Sustainability Analysis of Biofuels Using Biogeochemistry, Economic and Life Cycle Analysis Public Deposited

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  • Fossil fuels have been the main source of energy for a long period but due to growing concerns over climate change, oil depletion and energy security, the development of renewable sources of energy such as biofuels have been flourishing over the past few decades. Despite the fact that biofuels are perceived to be more sustainable than fossil fuels, three important issues should be considered if agricultural products are used to produce fuel. First, the environmental impacts of producing biofuels vary greatly with feedstock type and growing location. The second issue is the dilemma between food and fuel such that if food crops are used to make biofuels, food prices can increase dramatically. Third, if there is an increase in demand for a particular crop, non-agricultural land (e.g. forest, grassland, peatland) can be converted to agricultural land which increases the greenhouse gas emissions (GHG) due to land use change (LUC). In order to capture the effect of regional factors on life cycle assessment of biofuels,agroecosystem process-based models which can model soil emissions and predict yield can be used. Life cycle assessment (LCA) is a systematic set of procedures for compiling and examining the inputs and outputs of materials and energy and the associated environmental impacts directly attributable to the functioning of a product or service system throughout its life cycle. In the first objective of this study, the effect of regional factors on LCA of camelina seed production and camelina methyl ester production was assessed. While general conclusions from LCA studies point to lower environmental impacts of biofuels, it has been shown in many studies that the environmental impacts are dependent on location, production practices and even local weather variations. A cradle to farm gate and well to pump approaches were used to conduct the LCA. To demonstrate the impact of agro-climatic and management factors (weather condition, soil characteristics, and management practices) on the overall emissions for four different regions including Corvallis, OR, Pendleton, OR, Pullman, WA and Sheridan, WY, field emissions were simulated using the DeNitrification-DeComposition (DNDC) model. openLCA v.1.4.2 software was used to quantify the environmental impacts of camelina seed and camelina methyl ester production. The results showed that GHG emissions during camelina production in different regions vary between 49.39 to 472.51 kg CO2-eq. ha due to differences in agro-climatic and weather variations. The GHG emissions for 1 kg of camelina produced in Corvallis, Pendleton, Pullman, and Sheridan were 0.76±11%, 0.55±10%, 0.47±18% and 1.26±6% kg CO2-eq., respectively. The GHG emissions for 1000 MJ of camelina biodiesel using camelina produced in Corvallis, Pendleton, Pullman, and Sheridan were 53.60±5%, 48.87±5%, 44.33±7% and 78.88±4% kg CO2-eq., respectively. Other impact categories such as acidification and ecotoxicityfor 1000 MJ of camelina biodiesel varied across the regions by 43% and 103%, respectively. Since the results of LCA are highly site-specific, and it is recommended that conclusions from LCA studies be presented in the context of site-specific data. The second objective of this study was to model the soil emissions during camelina and wheat production in a three-year cycle in the Pacific North West region of the United States considering spatial variations in agro-climatic factors. DNDC model was used to estimate the soil emissions in different regions, and openLCA software was used to conduct a regional LCA for camelina biodiesel production in the State of Oregon. The results showed that change in soil organic carbon (dSOC) did vary across different locations and in most locations, lower initial SOC resulted in lower CO2 emissions. The global warming potential of camelina biodiesel varied between 39 to 84 kg CO2-eq. 1000 MJ across different locations and scenarios. Uncertainty analysis was carried out using Monte Carlo method, and the results showed that there could be up to 23% variation in soil emissions due to variation in air temperature and SOC. The break-even cost for a three-year crop rotation (winter wheat-fallow-camelina) was estimated to be 1715 $ ha 3years; therefore, locations with income equal or more than the break-even cost and low environmental impacts are suitable for the winter wheat-fallow-camelina rotation system. The last objective of this study was to integrate DNDC with LCA model using a GIS-based platform software, ENVISION. The integrated model helps LCA practitioners to conduct LCA in large regions while capturing the variability of soil emissions due to variation in regional factors during producing crops or biofuel feedstocks. In order to evaluate the integrated model, the corn-soybean cropping system in Eagle Creek Watershed, Indiana was studied and our integrated model was used to first model the soilemissions and then calculate the LCA as well as economic parameters based on the model results. The results showed that within one location, the variation in soil emissions due to variation in weather is high. Weather variability caused some locations to be carbon sink in some years and source of CO2 in other years. In order to test the model under different scenarios, two tillage scenarios were defined: 1) conventional tillage (CT) and 2) no tillage (NT) and analyzed with the model. The overall GHG emissions for the corn-soybean cropping system was simulated and results showed that the NT scenario has lower soil GHG emissions compared to CT scenario. Moreover, global warming potential (GWP) of corn ethanol from well to wheel varied between 57 and 92 g CO2-eq. MJ while GWP under the NT system was lower than that of the CT system. The cost break-even point was calculated as $3612.5 for each hectare of the 2 year corn-soybean cropping system and the results showed that under low and medium prices for corn and soybean most of the farms did not meet the break-even point.
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