In its regulatory impact assessment of the proposed rulemaking, EPA noted that other GHGs such as nitrous oxide (N₂O) (and to a lesser extent, methane (CH₄)) may be emitted from fossil-fuel-fired EGUs, especially from coal-fired circulating fluidized bed combustors and from units with selective catalytic reduction and selective non-catalytic reduction systems installed for nitrogen oxide (NO_x) control. EPA is not proposing separate N₂O or CH₄ emission limits or an equivalent CO₂ emission limit because of a lack of available data for these affected sources.

For purposes of this rule, fossil-fuel-fired EGUs include fossil-fuel-fired boilers, integrated gasification combined cycle (IGCC) units and stationary combined cycle turbine units that generate electricity for sale and are larger than 25 megawatts (MW).

Although emissions vary by plant and with the specific type of fuel, EPA provided illustrative examples of CO₂ emissions from EGUs:

• Conventional coal: 1,800 lbs CO₂/MWh
• Natural Gas Combined Cycle: 820 lbs CO₂/MWh
• Coal with carbon capture and storage (CCS): 200 lbs CO₂/MWh

According to the EPA, new natural gas combined cycle (NGCC) power plant units should be able to meet the proposed standard without add‐on controls. Based on available data, EPA believes that nearly all (95%) of the NGCC units built recently (since 2005) would meet the standard.

EPA suggests that new power plants that are designed to use coal or petroleum coke would be able to incorporate technology to reduce carbon dioxide emissions to meet the standard, such as carbon capture and storage (CCS).

The proposed standard provides flexibilities for new power plants to phase in technology to reduce carbon pollution:

• New power plants that use CCS would have the option to use a 30‐year average of CO₂ emissions to meet the proposed standard, rather than meeting the annual standard each year.

• Plants that install and operate CCS right away would have the flexibility to emit more CO₂ in the early years as they learn how to best optimize the controls.

• A company could build a coal‐fired plant and add CCS later. For example, a new power plant could emit more CO₂ for the first 10 years and then emit less for the next 20 years, as long as the average of those emissions met the standard.

• CCS is expected to become more widely available, which should lead to lower costs and improved performance over time.

The EPA will accept comment on this proposed rule for 60 days following publication in the Federal Register. EPA will also hold public hearings on this proposal. The dates, times, and locations of the public hearings will be available soon.

Background. Currently, there is no uniform national limit on the amount of greenhouse gases new power plants can emit. On 2 April 2007, in the Massachusetts v. EPA decision, the US Supreme Court determined that greenhouse gases, including carbon dioxide, are air pollutants under the Clean Air Act and EPA must determine if they threaten public health and welfare. On 15 December 2009, the EPA Administrator found that the current and projected concentrations of greenhouse gases endanger the public health and welfare of current and future generations. On 23 December 2010, EPA announced a proposed settlement agreement to issue rules that would address GHG pollution from certain fossil fuel‐fired EGUs. This agreement addressed, in part, EPA’s September 2007 remand of its February 2006 final decision not to set standards for boilers.

The proposed standard relies on the deployment of the same types of technologies and steps that power companies are already taking to build the next generation of power plants. EPA says that its proposal is in line with these investments. Even without the proposed rulemaking, EPA suggests, the power plants that are currently projected to be built going forward would already comply with the standard. As a result, EPA does not project additional cost for industry to comply with this standard. 

...energy market data and projections support the conclusion that, even in the absence of this rule, existing and anticipated economic conditions in the marketplace will lead electricity generators to choose technologies that meet the proposed standards. Therefore...EPA anticipates that the proposed EGU GHG NSPS will result in negligible CO₂ emission changes, energy impacts, quantified benefits, costs, and economic impacts by 2020. Accordingly, EPA also does not anticipate this rule will have any impacts on the price of electricity, employment or labor markets, or the US economy.

—EPA Regulatory Impact Analysis

Resources

• Standards of Performance for Greenhouse Gas Emissions for New Stationary Sources: Electric Utility Generating Units

• Regulatory Impact Analysis