Compilation of Published Reservoir and Lake Greenhouse Gas Emission Data and Preliminary Assessment of Potential Annual GHG Emissions from the Oroville Facilities

摘要

This paper presents results of a recent study commissioned by the California Department of Water Resources (Department) that reviewed historical data underlying recent concerns that the hydropower industry may be contributing to global warming through greenhouse gas (GHG) emissions associated with reservoir and power plant operations. It presents a summary of the relevant reservoir GHG studies and data, discusses the variability of these published data, and identifies key factors influencing GHG emissions from rivers, lakes and reservoirs. The compilation of data reveals a wide variation among reported results, with factors such as site location and associated watershed geography and climate, reservoir age and characteristics, water residence time, water chemistry, wind speed, microbial productivity and biomass all influencing emissions and thus contributing to the wide variability in measured data. With such variability, attempts to draw industry-wide generalizations on greenhouse gas emissions from reservoirs can be difficult and misleading. Included within this data set were results from an independent study of selected western United States (U.S.) reservoirs conducted in 2001 and published in a 2004 report by Soumis, et al, that included limited measurements of GHG emissions at the Department's Lake Oroville. The 2004 report data for Lake Oroville were extrapolated by the authors of this paper to estimate the range of potential annual GHG emissions per kWh for the Oroville Facilities and then compare these values on a unit basis with other sources of power generation. Even with the wide variation in measurements from published data, this large hydropower project appears to produce minimal GHG emissions per kWh generated, equal to only a fraction of the emissions from fossil fuel-fired generation alternatives. The range of GHG emissions from the Oroville Facilities was estimated to be only from 6 to 31 grams carbon dioxide (CO_2) equivalent per kWh. This compares with 940-1,340 grams for coal and 650-770 grams for natural gas. In addition, the Oroville Facilities appear to produce equal to or less than published GHG emissions per kWh from other renewable energy sources such as wind, solar, or biomass, which range from a low of 7 to a high of 260 grams CO_2 equivalent per kWh. Based on the studies reviewed for this paper, hydropower generation is comparable to the best alternatives available in the marketplace with respect to minimizing GHG emissions. The paper concludes with recommendations on how more in-depth studies could contribute to a better understanding of a particular hydropower project's carbon footprint.