Margo Oge, a key player in the federal government’s push to decrease vehicle emissions and increase fuel efficiency, said she will retire at the end of this month.

Margo Oge, the high-level official for the U.S. Environmental Protection Agency who has spearheaded the agency’s efforts to reduce air pollution and greenhouse gas emissions from the U.S. transportation sector, is retiring from the agency where she worked for more than three decades.

The U.S. Environmental Protection Agency has called for the production of 1 billion gallons of biomass-based diesel as part of its 2012 national renewable fuel standard, up from 800 million gallons last year.

Ineffective oversight of the federal diesel emissions reduction grant program by the Environmental Protection Agency may have caused EPA to overstate the environmental benefits of the program, according to a new audit by the agency’s inspector general.