The Environmental Protection Agency (EPA) is reconsidering its decision to incorporate indirect land use changes in calculating the impact of biofuel production on greenhouse gas emissions for the Renewable Fuel Standard 2 (RFS 2).

The agency, which is charged with implementing the RFS 2 in the energy bill passed by Congress in 2007, has decided to “carefully quantify and consider the uncertainties surrounding lifecycle greenhouse gases (GHG) for biofuels,” EPA Administrator Lisa Jackson said in a letter to Iowa Sen. Tom Harkin.

Harkin, former chairman of the Senate Agriculture Committee, and six other senators had introduced an amendment to the Senate Interior-Environment Appropriations bill that would prohibit the EPA, for one year, from spending funds to include international indirect land use change emissions in the implementation of the RFS 2.

Grant Gustafson, press aide for Harkin, said the senator had decided to withdraw the amendment because of the EPA administrator’s letter.

The letter stated that “Administrator Jackson recognizes the uncertainty in calculating the indirect effects on land-use change from greater biofuels production,” said Gustafson, who added she had committed to carefully quantify and consider uncertainties surrounding GHG.

“In light of the EPA letter, and because EPA had said it would delay issuing regulations to establish renewable fuel volume biofuel requirements for 2010, Sen. Harkin decided not to press the amendment,” Gustafson said.

“The senator considers setting those fuel requirements in a timely manner as critically important to our national strategy for reducing our dangerous dependence on imported oil.”