Over a year ago, the US Environmental Protection Agency announced that it would start the process of implementing rules that would limit the carbon dioxide emissions from newly built power plants. The intended rules would put a uniform limit on fossil-fuel burning plants of 1,000 pounds of CO 2 for each Megawatt-hour of electricity produced.

Today, the EPA has announced a revised set of rules to replace last year's effort. The revised versions split the single standard and only hold large natural gas plants to the 1,000 lbs/MW-hr figure. Coal and smaller plants will only have to meet a less stringent 1,100 lbs/MW-hr standard. If a new plant is built that does not meet these standards, its operators will have seven years to bring it into compliance—possibly enough time to develop carbon capture and storage technology.

Based on figures from the US Energy Administration, natural gas plants nearly meet the proposed standards already, while coal is nowhere close. But given the low cost of natural gas, nobody was planning to build a coal plant anyway, something explicitly recognized by the EPA's proposal: "existing and anticipated economic conditions mean that few, if any, solid fossil fuel-fired EGUs will be built in the foreseeable future." As such, the new rule is unlikely to have much of an impact, something that's also recognized by the EPA: "the EPA projects that this proposed rule will result in negligible CO 2 emission changes, quantified benefits, and costs."

So why bother proposing the rule at all? Because past decisions will now compel the EPA to formulate rules that limit carbon dioxide emissions from existing power plants. The stakes there will obviously be much higher, and the ensuing fight will be far more challenging. By setting precedents with these rules, the EPA will undoubtedly lay important foundations for putting general emissions controls in place.

The public and any other interested parties will now have 60 days to comment on the rules, including at a public hearing. At the end of that period, the EPA may either amend the rules again or attempt to put them into effect. Even though utilities and other interested parties have been extensively consulted while the rules were formulated, legal challenges are almost certain to delay the actual implementation.