The US Environmental Protection Agency released additional thoughts for comment in late October on some of the more controversial aspects of its June plan to reduce carbon dioxide emissions from existing power plants that use fossil fuels.

Comments are due by December 1, 2014, a date that may be challenging for some states that had closely-contested governors’ races. The June plan set individual state goals for reducing carbon dioxide emissions (expressed in lbs CO2/MWh) and listed measures states could use to cut emissions.

The June plan also suggested that states could convert these goals expressed in emissions per megawatt hour into tons of CO2 emissions per year, which would be easier to implement for states that develop or enter into cap-and-trade programs.

Although the ultimate targets in the June plan would not need to be achieved until 2030, there are interim targets to take stock of how states are doing in 2020. EPA suggested use of the following four measures (also termed “building blocks”) to reach the emissions targets: improved heat rates at coal-fired power plants, increased use of low-emitting power sources like natural gas, increased use of zero- and low-emitting power sources like solar energy and increased demand-side energy efficiency. EPA is required to finalize the plan by June 1, 2015.

Critics of the plan complain that meeting the 2020 interim targets does not allow states enough flexibility to choose how best to cut emissions. The plan also appeared to assume that some states could readily increase the use of combined-cycle natural gas-fired power plants by dispatching those power plants up to about a 70% capacity factor. EPA is now suggesting that states could count early reductions for puposes of demonstrating compliance with the 2020 targets. Such reductions may be in the form of energy efficiency programs implemented before 2020 and would give states more time to phase in other reduction measures. EPA is also suggesting phasing in improvements of heat rates at coal-fired power plants and increases in the dispatch rates of natural gas-fired power plants.

The agency also passed along in October some suggestions that some people who commented on the June plan made for how states might incorporate the use of new natural gas-fired power plants and co-firing of natural gas in existing coal-fired boilers to meet the required emissions targets. EPA said it might also look at the regional availability of renewable energy to set state renewable energy targets.

The emissions goals set in the June plan were based on 2012 power sector data. Some have suggested that this baseline may not have been representative, so the agency released data for years 2010 and 2011 and is taking comments on whether state emissions targets should be based on an average of several years of information.

— contributed by Sue Cowell in Washington