Degree Type

Dissertation

Date of Award

2011

Degree Name

Doctor of Philosophy

Department

Agricultural and Biosystems Engineering

First Advisor

D. R. Raman

Abstract

Development and extraction of energy sources, energy production and energy use have huge economic, environmental and geopolitical impacts. Increasing energy demands in tandem with reductions in fossil fuel production has led to significant investments in research into alternative forms of energy. One that is promising but yet not commercially established is the production of biofuel from algae. This research quantitatively assessed the potential of algae biofuel production by examining its cost and environmental impacts. First, two models developed by the RAND corporation were employed to assess Cost Growth defined as the ratio of actual costs to estimated costs, and Plant Performance defined as the ratio of actual production levels to design performance, of three algal biofuel production technologies. The three algal biofuel production technologies examined to open raceway ponds (ORPs), photobioreactors (PBRs), and a system that couples PBRs to ORPs (PBR-ORPs). Though these analyses lack precision due to uncertainty, the results highlight the risks associated with implementing algal biofuel systems, as all scenarios examined were predicted to have Cost Growth, ranging from 1.2 to 1.8, and Plant Performance was projected as less than 50% of design performance for all cases. Second, the Framework the Evaluation of Biomass Energy Feedstocks (FEBEF) was used to assess the cost and environmental impacts of biodiesel produced from three algal production technologies. When these results were compared with ethanol from corn and biodiesel from soybeans, biodiesel from algae produced from the different technologies were estimated to be more expensive, suffered from low energy gains, and did not result in lower greenhouse gas emissions. To identify likely routes to making algal biofuels more competitive, a third study was undertaken. In this case, FEBEF was employed to examine pinch-points (defined as the most costly, energy consuming, greenhouse gas producing processes), in three algal production and fuel conversion scenarios, and then to estimate the improvement to cost and environmental impacts of proposed solutions to the pinch-points. These results illuminated significant opportunities to improve the economics and environmental impacts from producing algal biofuels produced in ORP, PBR, and PBR-ORPs. No single solution examined appeared to be sufficient to reduce the cost of fuel energy from algae to a competitive level with current petroleum diesel prices (4.20 $/gal, ca. $28/GJ). However, if multiple pinch-points are overcome, e.g., simultaneous increases in (1) radiation use efficiency and (2) oil content or simultaneous decreases in (3) irrigation, (4) harvesting, (5) labor and (6)PBR costs are achieved then low Fuel Energy Costs (the ratio of total production and conversion costs to total energy available in the fuel) and low Total Energy Costs (the ratio of total production and conversion costs to total energy available in the fuel and co-products) are possible; with estimates ranging from 48 to 11 $/GJ.

Copyright Owner

Katrina Lea Christiansen

Language

en

Date Available

2012-04-30

File Format

application/pdf

File Size

181 pages

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