The US Environmental Protection Agency (EPA) has published a draft white paper discussing control techniques and other measures that could reduce greenhouse gas (GHG) emissions from combustion turbines and, by extension, from the power sector.

EPA’s draft white paper critically examines available and emerging options for reducing GHG emissions from combustion turbines, with significant focus on reducing the tons of GHGs emitted from natural gas-fired combustion turbines per unit of electricity generated. The paper notes that, in 2019, approximately 38 percent of the US’ net electricity was produced using natural gas, and that percentage is expected to grow in the coming years as the country moves away from its reliance on coal-fired generation. Though this is a technical paper, not a regulation, EPA requests public comments on the draft white paper “to gather perspectives from a broad group of stakeholders.”

EPA highlights a broad range of approaches, including:

• Turbine Efficiency: Combustion turbines can use less fuel and produce lower GHG emissions for the energy generated by improving their thermal efficiency through a keen focus on turbine design, pollution control design, and operating and maintenance practices, among other factors.

• Alternative Fuels: Some existing natural gas-fired combustion turbines can generate electricity using a mixture of natural gas and an alternative fuel, such as hydrogen. Increasing reliance on alternative fuels, including firing solely alternative fuels, can dramatically reduce GHG emissions.

• CCUS: Post-combustion carbon capture, utilization, and storage (CCUS) involves the separation and capture of carbon from emissions, which is then pressurized and transported either for long-term storage underground or for beneficial use, such as in the food processing industry.  

• Steam-Cycle Integrated Renewables: Solar thermal arrays (a system of large steel mirrors) can be collocated with natural gas-fired turbines. The solar thermal array is used to create steam that augments the steam created by the combustion of the natural gas, reducing reliance on natural gas, and correspondingly decreasing GHG emissions.

• Colocation with Energy Storage: Co-locating gas-fired combustion turbines with energy storage allows turbines to be cycled less, and operated at a more constant rate, by storing excess electricity and readily distributing that electricity in response to increased demand.

Earlier this year, EPA Administrator Michael Regan discussed the agency’s comprehensive power strategy, identifying the power sector as one of the largest stationary sources of GHG emissions. EPA’s draft white paper was developed as an integral part of that strategy.

EPA states in the draft white paper that it intends for the paper to assist state, Tribal, and local authorities as well as regulated entities in considering GHG emission reduction from combustion turbines. EPA notes that the “paper may also provide context for permit development” under the Prevention of Significant Deterioration program, including assessment of best available control technology (BACT). EPA further anticipates that the paper “may also be useful to EPA in future development of new source performance standards (NSPS).”

That appears to be a very real possibility. According to EPA’s unified agenda, EPA plans to propose rules for fossil fuel electric generating units to replace the Affordable Clean Energy Rule in July 2022, with rules finalized in 2023, and to revise NSPS for the same units in the same time frame.

But at this time, the paper expressly acknowledges that it “does not represent EPA endorsement of any particular control strategy for any particular purpose.” Critically, inclusion of a technology in this paper does not mean that the technology “meets the applicable standard for it to be required under any particular regulatory program.”

This is a particularly important acknowledgement for owners and operators of combustion turbines who are undertaking a BACT assessment — just because a technology appears in this paper does not mean that EPA has determined the technology may constitute BACT, today, for combustion turbines.  

EPA is accepting public comments through June 6, 2022.