Sep 30, 2011
What Do We Know and What Can We Know?
Published in: Environmental Science and Technology, v. 44, no. 6, 2010, p. 1895-1901
Posted on RAND.org on December 31, 2009
The generation and distribution of electricity comprises nearly 40% of U.S. CO2 emissions, as well as large shares of SO2, NOx, small particulates, and other toxins. Thus, correctly accounting for these electricity-related environmental releases is of great importance in life cycle assessment of products and processes. Unfortunately, there is no agreed-upon protocol for accounting for the environmental emissions associated with electricity, as well as significant uncertainty in the estimates. Here, we explore the limits of current knowledge about grid electricity in LCA and carbon footprinting for the U.S. electrical grid, and show that differences in standards, protocols, and reporting organizations can lead to important differences in estimates of CO2, SO2, and NOx emissions factors. We find a considerable divergence in published values for grid emissions factor in the U.S. We discuss the implications of this divergence and list recommendations for a standardized approach to accounting for air pollution emissions in life cycle assessment and policy analyses in a world with incomplete and uncertain information.