سود و زیان کاهش تولید گازهای گلخانه ای از بخش برق

Recent federal policy proposals to reduce emissions of sulfur dioxide (SO2), nitrogen oxides (NOx), and mercury from the US electricity sector promise important improvements in air quality and reductions in acid deposition. The cost of achieving these reductions depends on the form and stringency of the regulation. In this research, we analyze the economic benefits and costs of the US Environmental Protection Agency's (EPA's) Clean Air Interstate Rule (CAIR) as characterized in the supplemental rule proposed in June 2004, and the Clean Air Mercury Rule (CAMR) as proposed in February 2004. The assessment integrates a model of the electricity sector, two models of atmospheric transport of air pollutants, and a model of environmental and public health endpoints affected by pollution. We model explicitly the emissions of SO2, NOx, mercury and carbon dioxide (CO2) and the effects of changes in emissions of SO2 and NOx on environmental and public health. The manner in which mercury emissions are regulated will have important implications not only for the cost of the regulation, but also for emission levels for SO2 and NOx and where those emissions are located. We find the economic benefits of CAIR and CAMR are far greater than the costs. Recent estimates of benefits of reductions in mercury and acidification indicate that our model captures the lion's share of quantifiable benefits. We also find that the EPA would have been justified on economic grounds in pursuing additional SO2 emissions reductions beyond the requirements of CAIR.

The electricity sector is a major source of several air pollutants including sulfur dioxide (SO2), which contributes to acid rain and fine particle concentrations in the atmosphere, nitrogen oxides (NOx) which contribute to both of these pollution problems and to ground-level ozone, mercury, which is a toxic substance linked to neurological and other health problems, and carbon dioxide (CO2), which contributes to global warming. The electricity sector contributes roughly 68% of national emissions of SO2 emissions, 22% of NOx, 40% of mercury, and 40% of CO2. The environmental effects of SO2 and NOx emissions are particularly strong in the northeast, which is downwind of the large number of coal-fired generators located in the Mid-Atlantic States and the Ohio Valley. Recent federal policy proposals to reduce emissions of SO2, NOx, and mercury from the electricity sector promise important improvements in air quality and reductions in acid deposition. The cost of achieving these reductions depends on the form as well as the stringency of the regulation. In particular, the fact that technologies designed to reduce SO2 and NOx can reduce mercury emissions as well has important implications for how producers respond to different types of mercury regulation and for the cost of multipollutant policies aimed at all three pollutants. In this research, we analyze alternatives for federal policy to examine how well they will protect the environment and public health. We analyze the economic costs and benefits of the Environmental Protection Agency's (EPA's) Clean Air Interstate Rule (CAIR) as characterized in the supplemental rule proposed in June 2004 and the Clean Air Mercury Rule (CAMR) as proposed in February 2004, which differ in only small ways from the final rules issued in March 2005. Our assessment integrates a model of the electricity sector, two models of atmospheric transport of air pollutants, and a model of environmental and public health endpoints affected by pollution. We model explicitly the emissions of SO2, NOx, mercury and CO2 and the effects of changes in emissions of SO2 and NOx on public health. We do not model directly the effects of acidification or of mercury emissions, but we augment the modeling with estimates from other recent studies.1

The four policies regulating multiple pollutants from the electricity sector that we investigate all would deliver benefits that exceed the costs of those policies by a significant factor even under cautious assumptions about inputs to the benefits calculation that are expected to yield relatively low estimates of benefits. Contrary to EPA's findings, we find CAIR as originally proposed would not keep summer emissions of NOx from electricity generators in the SIP region below the current SIP seasonal NOx Cap. In the final rule EPA added a seasonal NOx cap to address seasonal ozone problems. Our results show that CAIR with the seasonal NOx cap yields higher net benefits. Unfortunately our findings do not translate into an endorsement of the EPA multipollutant rules. Our modeling indicates that additional SO2 emissions reductions beyond those called for by the EPA rules would yield benefits that substantially exceed the additional cost. Further, a more precise accounting of the benefits of reduced mercury emissions could sway the recommendation in favor of more stringent mercury controls. Three primary limitations to our analysis should be kept in mind. First, we focus on the electricity sector, and thus are unable to account for the general equilibrium social costs of the different policies, which could significantly raise the estimate of costs. Second, except in our uncertainty analysis, we do not assign monetary values to changes that would result from the reduction in acid deposition, visibility improvements or other ecological effects from reduced particulate matter and ozone. And, most importantly we do not value the benefits of a reduction in mercury. The benefits of mercury reductions are the reason for considering the alternative mercury policies. Quantifying and valuing these pathways could significantly raise the estimate of benefits as the Rice and Hammitt (2005) findings suggest.