WASHINGTON, D.C. — Up to $20 million in grants is available for projects aimed at reducing pollution from the nation's existing fleet of diesel engines, the U.S. EPA announced on Friday.

In addition to these FY 2012 grants, approximately $9 million will be available through direct state allocations. The EPA estimates that for every $1 spent on clean diesel funding, up to $13 of public health benefit is realized.

"Technology has evolved to make diesel engines more efficient and cleaner than ever," said Gina McCarthy, assistant administrator for the EPA’s Office of Air and Radiation. "These grants enable owners of older diesel vehicles to make investments that modernize their vehicles while making the air in their communities cleaner and healthier to breathe.”

This is the first competition since the Diesel Emission Reduction Program (also known as DERA) was reauthorized in 2011. The program cleans up existing diesel vehicles by targeting projects that utilize the most cost-effective clean diesel strategies. By reducing diesel emissions in areas that have significant air quality issues, the program can have a direct impact on community health, officials said.

The EPA has standards in place that make new diesels more than 90 percent cleaner. However, older diesels that predate these standards emit large amounts of air pollutants, such as nitrogen oxides and particulate matter. Nearly 11 million older diesels still operate throughout the nation's transportation system.

States, tribes, local governments and non-profits are eligible to apply for the grants. Projects can reduce air pollution from older school buses, transit buses, heavy-duty diesel trucks, marine engines, locomotives and other diesel engines. The closing date for receipt of proposals is June 4, 2012.

DERA was enacted in 2005. Since it was first funded in FY 2008, the EPA has awarded more than 500 grants nationwide. Officials said that these projects have reduced hundreds of thousands of tons of air pollution and saved millions of gallons of fuel.

For request for proposals forms and related documents, go here.