Analyzing and advancing maize and sugarcane biorefinery systems

Fossil fuels are considered one of the most significant contributors to anthropogenic greenhouse gas (GHG) emissions, and renewable energy derived from biomass has potential to displace fossil fuels and to significantly reduce the CO2 emissions. One example of the conversion of biomass into renewable energy is the production of biofuels such as ethanol and biodiesel. Nowadays, producing a green product with lower cost is challenging because of production cost and environmental impacts of the manufacturing process that involve expensive technologies and significant amounts of emission. While much research in this area has been published over the last few decades, gaps remain with respect to understanding sustainability and environmental impact of ethanol production. These gaps can be explained by techno-economic analysis designed to optimize one process, and by life cycle assessment, a tool for assessing environmental performance of complex systems. The principal objective of this dissertation was to investigate the feasibility of certain processes in the ethanol production chain to fill in some existing deficiencies in the literature related to different aspects of ethanol production and its coproducts. Four sub-objectives were developed: to investigate how storage time, storage temperature, and particle size influence chemical and nutritional properties of corn distillers dried grains with solubles (DDGS); to analyze the economic feasibility of substituting evaporation process for a flocculation technology in a corn-based ethanol plant through Life Cycle Assessment (LCA) and Techno-Economic Analysis (TEA); to determine the proximate analysis and to predict the ultimate analysis of sugarcane bagasse and corn stover (leaves, stalks, cobs, and raw material); and to evaluate the economic feasibility of low-moisture anhydrous ammonia (LMAA) pretreatment in five different scenarios for ethanol production from sugarcane bagasse. Because the United States is considered the largest producer and exporter of grain-based ethanol and DDGS in the world, a study investigating how storage time, storage temperature, and particle size affect some properties of corn DDGS was conducted. Additionally, the feed industry has expressed concerns related to nutritional components of DDGS in the U.S. feed market, and the analysis revealed that among these properties only storage temperature did not affect the properties of DDGS. To achieve the second sub-objective, LCA and TEA were conducted to analyze the economic feasibility of using a flocculation process in substitution of an evaporation system in a corn-based ethanol plant, with results showing that utility costs were lower for the flocculation process than for the evaporation system. However, none of the simulated scenarios were profitable, and from sensitivity analysis, it was observed that feedstock cost was the most sensitive parameter with respect to DDGS, distillers wet grains with solubles (DWGS), and corn oil production cost. With respect to environmental aspects, the flocculation process also presented the lowest Global Warming Potential (GWP) emissions and a significant reduction in CO2-equivalent emissions. To achieve the sub-objective, from the study for determining the proximate analysis and for predicting the ultimate analysis of sugarcane bagasse and corn stover, it could be concluded that experimental data from the proximate analysis produced values similar to those found in the literature, and ultimate analysis could be successfully estimated using published models based on the proximate analysis. Finally, to accomplish the last sub-objective, LCA and TEA were conducted to evaluate economic feasibility and environmental impact of the use of LMAA pretreatment for five different scenarios for ethanol production from sugarcane bagasse. As a result, materials and utility costs were found to be the most impactful costs for all simulated scenarios, and from sensitivity analysis it could be observed that ethanol sale price was the most sensitive parameter, followed by feedstock cost and ammonia cost. On the other hand, LCA results revealed significant reduction in GHG emissions, and the scenario with the lowest feedstock amount to be processed presented the lowest GHG emissions, an expected result due to the utilization of the equipment with lower capacity that required less energy consumption