impact

The generation of electricity, and the consumption of energy in general, often result in adverse effects on the environment. Coal-fired power plants generate over half of the electricity used in the U.S., and therefore play a significant role in any discussion of energy and the environment. By cofiring biomass, currently-operating coal plants have an opportunity to reduce the impact they have, but to what degree, and with what trade-offs? A life cycle assessment (LCA) has been conducted on a coal-fired power system that cofires wood residue.

Biomass is a significant contributor to the US economy--agriculture, forest and paper products, food and related products account for 5% of our GDP. While the forest products industry self generates some of their energy, other sectors are importers. Bioenergy can contribute to economic development and to the environment. Examples of bioenergy routes suggest that atmospheric carbon can be cycled through biofuels in carefully designed systems for sustainability. Significant potential exists for these options. Research and development of integrated biomass reduction and conversion systems, as currently being performed in the Biomass for Rural Development Program, can help verify the potential energy, economic, and environmental benefits and advance biomass and bioenergy into the 21st century.

The U.S. Department of Energy has supported a research and development program for the establishment of renewable, biomass-derived, liquid fuels for the better part of the last twenty years. These 'biofuels' represent opportunities to respond to uncertainties about our energy security and the future health of our environment. Throughout its history, the Biofuels Program has experienced an ongoing fiscal 'roller coaster'. Funding has ebbed and flowed with changing political and public attitudes about energy. The program was initiated in a flood of funding in the late 1970s related to the energy shortages experienced in that period. The flooding turned rapidly to drought as falling oil prices dissipated public concern about energy supplies. In the late 1980s, funding for the program slowly increased, driven by national security issues.

Power generation emits significant amounts of greenhouse gases (GHGs), mainly carbon dioxide (CO2). Sequestering CO2 from the power plant flue gas can significantly reduce the GHGs from the power plant itself, but this is not the total picture. CO2 capture and sequestration consumes additional energy, thus lowering the plant's fuel-to-electricity efficiency. To compensate for this, more fossil fuel must be procured and consumed to make up for lost capacity. Taking this into consideration, the global warming potential (GWP), which is a combination of CO2, methane (CH4), and nitrous oxide (N2O) emissions, and energy balance of the system need to be examined using a life cycle approach. This takes into account the upstream processes which remain constant after CO2 sequestration as well as the steps required for additional power generation.

To determine the environmental implications of producing electricity from biomass and coal, life cycle assessments (LCA) have been conducted on systems based on three power generation options: (1) a biomass-fired integrated gasification combined cycle (IGCC) system, (2) three coal-fired power plant technologies, and (3) a system cofiring waste biomass with coal.

The harvest of corn stover or herbaceous crops as feedstocks for bioenergy purposes has been shown to have significant benefits from energy and climate change perspectives. There is a potential, however, to adversely impact water and soil quality, especially in Midwestern states where the biomass feedstock production would predominantly occur. The overall goal of this research is to provide a thorough and mechanistic understanding of the relationship between stover and/or herbaceous crop production management practices and resulting range of impacts on soil and water quality, with a focus on Eastern Iowa. The production of these bioenergy crops is compared to corn and corn-soybean rotations on eight different soils representative of the region. The APEX model, which predicts crop, water, nutrient, carbon and soil flows within an integrated agricultural and hydrological system, provides a means to quantify sustainability metrics and is used to generate sufficient data to provide a greater understanding of the particular variables that affect water and soil quality than previously possible. The sustainability metrics include total nutrient emissions to ground and surface water, total soil losses due to wind and water erosion, and cumulative soil carbon losses, all normalized to acreage and crop production. As expected, the results clearly show the superiority of switchgrass from a soil and water quality perspective. They also show, however, that compared to corn-soybean rotations with conventional tillage, soil and water quality degradation can be reduced at the same time stover is collected under certain soil types and no-till agricultural practices.