Date of Award

2018

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy in Chemical Engineering (PhD)

Administrative Home Department

Department of Chemical Engineering

Advisor 1

David Shonnard

Advisor 2

Robert Handler

Committee Member 1

Alex Mayer

Committee Member 2

Wen Zhou

Abstract

Liquid transportation biofuels are viewed as a promising alternative to fossil fuels to address energy security and climate change mitigation. Algae biomass and rapeseed were considering among the promising sources for renewable diesel and hydrotreated renewable jet (HRJ) fuel production. However, there are many challenges and technical barriers to implementation of a viable commercial process to produce biofuels from algae/oilseed. Biofuels production must typically go through a complicated series of unit processes for cultivation, harvesting, oil extraction, conversion, and other logistical steps. The impacts of their production pathway in terms of greenhouse gas (GHG) emission, land use impact, fossil energy demand have not been comprehensively studied and concerns have been raised about that large-scale biofuel production may place pressure on fresh water supplies and water quality, biodiversity, soil quality, and other sustainability impacts.

Chapter 2 investigated the GHG emission impacts of algae biofuel when evaluating several potential uses for the lipid-extracted algae (LEA) generated as a co-product of algae biofuel production to substitute for the use of animal feed. Results indicated that the benefit from displacing animal feed does not outweigh the incremental burdens associated with replacing the requirements that LEA currently satisfies associated with the biofuel process, resulting in higher GHG emissions for the algae biofuels life cycle. Chapter 3 assessed the LUC impacts using IPCC Tier 1 methodology to assess potential emissions resulting from the conversion of proposed algae facility sites in the U.S. Gulf Coast. Direct LUC impacts appear to be important, which is roughly 6.3% and 12.5% of the total GHG emission over the entire algae renewable diesel life cycle without considering the LUC. Chapter 4 investigated the environmental impacts associated with the novel algae harvesting and oil extraction technologies. Results show that all novel technologies appear to have the potential to provide at least modest decreases in GHG compared to current default algae process technologies. The selection of a particular technology for a unit operation can have consequences that affect other stages of the full biofuels life cycle, both upstream and downstream from the unit operation in question. Chapter 5 developed a life cycle water footprint (WF) analysis informed by inputs from multiple models for rapeseed HRJ fuel production in North Dakota, and evaluated the environmental impacts on water utilization and water quality due to large scale jet production. WF analysis, when combined with water-focused LCA, can be an effective system analysis tool for water sustainability. Discussions also carried out the importance of incorporating allocation within a life cycle approach when conducting biofuel WF analysis. Chapter 6 employed a model-based approach to conduct LCA of HRJ fuel produced from rotation of rapeseed with grain crops (mostly wheat) to replace the fallow period. Results show that introducing fuel oilseeds to existing crop rotations have significant advantages in terms of GHG emissions reductions compared to the current cropping practices. SOC sequestration and N2O emissions vary along the oilseed price points, and are influenced by the fertilizer application, tillage system, crop rotations, and other management actions. The total energy demand for rapeseed HRJ production is larger than fossil jet fuel, however, most of the energy inputs are from renewable biomass and HRJ requires less fossil energy comparing to fossil jet. These results provide some insights on the potential impacts of expanded biofuel production systems in regional and national contexts compared to the current cropping systems and answered the questions of what is the best practice to enhance the sustainability of biofuel production.

Available for download on Friday, August 24, 2018

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