The U.S. Environmental Protection Agency (EPA) has awarded $8 million to reduce emissions from the nation’s existing fleet of diesel vehicles, including school buses, the agency announced on Friday.

The grants, issued through the EPA’s Diesel Emissions Reduction Act (DERA) program, will go to communities in 21 states and Puerto Rico. They will fund such projects as retrofitting and replacing older school buses to improve air quality, upgrading marine propulsion and agriculture engines, and replacing long-haul truck engines.

“Supporting clean diesel projects like these is one way EPA helps make a visible difference in communities across the country,” said Janet McCabe, acting assistant administrator for the EPA’s Office of Air and Radiation. “Cleaner trucks, buses, boats and heavy equipment keep local economies working and thriving while better protecting the health of the neighborhoods near ports and along delivery routes.”

The projects will receive funding through the EPA’s DERA fiscal year 2014 allocation. The DERA funding covers replacements, repowers and idle-reduction technologies to clean up a variety of older diesel engines.

Here are some of the school bus-related projects that were selected in the new round of grants:

• In California, the South Coast Air Quality Management District is replacing nine diesel school buses with compressed natural gas buses and one diesel school bus with a battery-electric vehicle.

• In Colorado, the Department of Public Health and Environment is retrofitting 36 school buses with technologies to cut soot and reduce idling.

• In Idaho, the Franklin Soil and Water Conservation District is replacing three school buses.

• In several Midwestern states, Leonardo Academy is replacing two school buses and retrofitting five buses.

• In Missouri, St. Louis Clean Cities is replacing six school buses.

For the full list of grant recipients, go here.

DERA funding has also been used for the EPA’s School Bus Replacement Rebate Program, which recently awarded $3 million in rebates to help replace older diesel school buses in 76 fleets across the nation.