Life Cycle Environmental and Cost Evaluation of Bioenergy Systems

• Main Author: Zhang, Yimin
• Other Authors: MacLean, Heather L.
• Language: en_ca
• Published: 2010
• Subjects: Civil Engineering; 0543
• Online Access: http://hdl.handle.net/1807/24921

Energy derived from biomass has been proposed as a means to attain various environmental, economic and social goals. However, bioenergy production and utilization may also result in undesirable environmental and social consequences. This thesis investigates, from a life cycle perspective, environmental and cost implications of near-term bioenergy applications in the transportation and electricity sectors. Key tradeoffs related to the attributes of the systems are elucidated. Three case studies are conducted to consider the site-specific nature of bioenergy systems. The first two studies analyze the environmental and cost implications of displacing coal with biomass for electricity generation in Ontario’s coal generating stations. The third study examines implications of replacing gasoline with ethanol for use in California’s light-duty vehicle fleet to meet the State’s Low Carbon Fuel Standard (LCFS). The Ontario studies show that, relative to coal-based electricity generation, electricity generated from co-firing 10% (energy input) biomass with coal reduces greenhouse gas (GHG) emissions by 8% at a cost of $22/tonne CO2 equivalent for agricultural residues ($50/dry tonne residues delivered), and by 9% at a cost of $70-$84/tonne CO2 equivalent for wood pellets ($160/tonne pellets delivered), on the basis of one kWh of electricity generated (all costs are in U.S. dollars). One hundred percent pellet firing reduces GHG emissions by 91% compared to the coal system; however, the cost of GHG reduction is $99-$106/tonne CO2 equivalent. Displacing a portion of gasoline with ethanol is a feasible option to meet California’s LCFS, which calls for a 10% carbon intensity reduction of the State’s transportation fuels by 2020. Assuming current production methods and an indirect land use change effect of 30 g CO2/MJ, average Midwest corn ethanol is ruled out as an option to meet the LCFS. Using lignocellulosic ethanol to meet the LCFS is more attractive than using Brazilian sugarcane ethanol due to lower direct agricultural land requirement, dependence on imported energy, projected ethanol cost, required refuelling infrastructure modifications, and penetration of flexible fuel E85 vehicles. The thesis demonstrates that a life cycle approach is useful for analyzing and comparing different bioenergy applications, and providing insights into tradeoffs necessary in decision making for the development of next generation energy systems.