The US Environmental Protection Agency (EPA) has proposed Clean Air Act standards to reduce CO2 emissions from fossil-fuel fired power plants (electric utility generating units, EGUs). For purposes of this rule, fossil fuel-fired EGUs include utility boilers, IGCC units and certain natural gas-fired stationary combustion turbine EGUs that generate electricity for sale and are larger than 25 megawatts (MW). In addition, EPA said it is working with state, tribal, and local governments, industry and labor leaders, non-profits, and others to establish CO2 standards for existing power plants.
The proposed rulemaking establishes separate standards for natural gas and coal plants. The proposed limits for natural gas units are based on the performance of modern natural gas combined cycle (NGCC) units. New large (>850 mmBtu/h) natural gas-fired turbines would need to meet a limit of 1,000 pounds of CO2 per megawatt-hour, while new small (≤850mmBtu/h) natural gas-fired turbines would need to meet a limit of 1,100 pounds of CO2 per megawatt-hour.
The proposed limits for fossil fuel-fired utility boilers and IGCC (Integrated Gasification Combined Cycle) units (i.e., coal units) are based on the performance of a new efficient coal unit implementing partial carbon capture and storage (CCS).
EPA is proposing two limits for these units, depending on the compliance period that best suits the unit. These limits require capture of only a portion of the CO2 from the new unit.
1,100 lb CO2/MWh-gross over a 12-operating month period; or
1,000-1,050 lb CO2/MWh over an 84-operating month (7-year) period.
The longer compliance period option provides flexibility by allowing sources to phase in the use of partial CCS. The owner/operator can use some or all of the initial 84-operating month period to optimize the system. EPA is soliciting comment on what the standard should be within the proposed range.
According to the DOE/NETL estimates EPA cited in the proposed rulemaking, a new efficient subcritical pulverized coal (PC) unit firing bituminous coal currently would emit approximately 1,800 lb CO2/MWh; a new supercritical PC (SCPC) unit using bituminous coal would emit nearly 1,700 lb CO2/MWh, and a new IGCC unit would emit about 1,450 lb CO2/MWh.
The rule does not apply to any existing EGUs; units undergoing modifications or to reconstructed units; liquid oil-fired stationary combustion turbine EGUs; new EGUs that do not burn fossil fuels (e.g., those that burn biomass only); or low capacity factor EGUs that sell less than 1/3 of their power to the grid.
EPA said that the current and planned implementation of CCS projects, combined with the widespread availability and capacity of geological storage sites, makes it clear that the technology is feasible.
Background. In the decision in Massachusetts v. EPA in 2007, the 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.
In December 2009, the EPA Administrator found that the current and projected concentrations of greenhouse gases endanger the public health and welfare; one year later, EPA announced a proposed settlement agreement to issue rules that would address GHG pollution from certain fossil fuel-fired EGUs.
In 2012, EPA issued a proposed standard for EGUs. (Earlier post.) That proposal established an output-based limit of 1,000 pounds of CO2 per megawatt‐hour. With the issuance of the new proposed rulemaking, EPA is withdrawing its earlier proposal.
Power plants are the largest concentrated source of emissions in the United States, together accounting for roughly one-third of all domestic greenhouse gas emissions. While the United States has limits in place for arsenic, mercury and lead pollution that power plants can emit, currently, there are no national limits on the amount of CO2 new power plants can emit.
Currently, nearly a dozen states have already implemented or are implementing their own market-based programs to reduceCO2 emissions. In addition, more than 25 states have set energy efficiency targets, and more than 35 have set renewable energy targets.
The agency is seeking comment and information on the proposed rulemaking, including holding a public hearing.