OREANDA-NEWS. Congress gave the US Environmental Protection Agency significant flexibility in determining how best to reduce CO2 emissions from the power sector, government lawyers said.

The section of the Clean Air Act used to issue the Clean Power Plan for existing power plants grants the agency the ability to look beyond what can be done at individual facilities in determining the "best system of emission reduction," EPA lawyers said in a 22 April court filling. The word system in particular means the agency can look at a "broad scope" of potential measures, such as "generation shifting," or moving to less carbon-intensive electricity sources, EPA said.

"This broad statutory language shows that Congress was directing EPA to consider a wide range of measures to reduce emissions from sources," the agency said.

Supporting the use of generation shifting is the fact that "power plants can, and do, apply these measures to reduce their emissions," EPA said.

The use of generation shifting is one of the biggest issues in the case, with EPA and its opponents arguing back-and-forth over its use in court filings over the past month. The states, generators and industry groups suing EPA say the Clean Air Act limits the agency to setting standards that can be achieved by individual units.

The carbon standards are being challenged by 26 states, along with dozens of utilities, coal producers and industry groups.

EPA's filing last week, along with those from parties supporting the agency, marks the end of the legal briefing for the case. Next up, the court will hear oral arguments on 2 June, with a decision likely to be issued in late summer or early fall. The US Supreme Court in February put the Clean Power Plan on hold until the litigation is resolved.

The Clean Power Plan requires each state's power sector to meet CO2 targets for 2020-2030.

EPA set the targets based on a series of "building blocks," such as improving power plant heat rates, relying more on existing natural gas-fired generation and building new renewable energy generation. The agency says states can comply using a wide range of measures, not just those included in the building blocks.