Evaluating Options for a Sustainable Energy Future: Biofuels and Electricity

The term “sustainability” has become a popular catch phrase in recent years. Many definitions of sustainable energy emphasize the importance of meeting the energy needs of both present and future generations while addressing social, environmental, economic, and technological limitations. Most of the energy consumed in the US is used for transportation or to generate electricity (EIA 2014a). Analyzing the sustainability of the current transportation sector and possible alternatives, as well as the electricity generation sector is an important step toward developing a more sustainable energy system in the US. In the first analysis, the transportation sector is addressed by modeling the cost of delivering forest biomass chips to produce biofuel using a new production pathway developed at the University of Maine. In the second analysis, the electricity generation sector is addressed through a multi-criteria decision analysis (MCDA) of 13 different electricity generation technologies using six different criteria spanning the four areas of sustainability. In the first analysis, an economic biomass supply chain model for Maine was developed to estimate the delivered cost of biomass chips using the stumpage price paid to the landowner for the biomass, the cost of harvesting and chipping the logging residues, and the cost of transporting the biomass chips to a theoretical biorefinery. Harvesting costs were estimated using Maine-specific productivity equations, harvesting assumptions, and hourly costs. Transportation costs were estimated using round trip distance to the potential biorefinery. The delivered cost of biomass was estimated for multiple scenarios, including variation in the machine cost rate, variables impacting machine productivity, transport distance, and stand characteristics. The delivered cost of biomass was found to be below the current biomass chip price when biomass was treated as a waste product and within the range of the current price or higher when harvesting costs were included. The results of this analysis will serve as a portion of the overall sustainability assessment of the new biofuel pathway. In the second analysis, MCDA was used to compare the technical, economic, environmental, and social sustainability of 13 commercially available electricity generation technologies in the US using the criteria of job creation, levelized cost of energy (LCOE), greenhouse gas emissions, water consumption, land use, and capacity factor. Using MCDA, weights were assigned for each criterion to indicate the relative importance to the decision maker and then the weighted scores were used to rank the technologies. The resulting sustainability ranking is a helpful tool for comparing electricity generation technologies across sustainability criteria, which can be useful for policy making. Five different sets of weights were used to simulate the following potential decision-maker preference scenarios: all equal; jobs and LCOE; environmental; climate change; and climate change and economy. Changing the weights used substantially changed the technology rankings, as different measures of sustainability were deemed more or less important. These two analyses address sustainable energy use in electricity and transportation sectors which may overlap in energy feedstocks such as biomass. Sustainability analysis at the national and regional level can be used by decision makers to compare alternatives