Dublin City School District officials are anticipating a drop in bus-fleet maintenance costs, thanks to the addition of compressed-natural-gas buses.

The district received Dublin Board of Education approval to purchase five CNG buses for $588,300 and eight new diesel buses for $675,400, said Jeff Stark, the school district's director of business operations.

Those purchases will be offset by a $200,000 rebate the district will receive from the Environmental Protection Agency for scrapping 10 of its diesel buses, Stark said.

The EPA rebate is part of its School Bus Replacement and Retrofit Funding Opportunity, which gives school districts the opportunity to receive funding to replace or retrofit school buses to lower harmful fuel emission.

The district applied to be eligible for the EPA rebate last fall, and learned it was granted in January, Stark said.

The district has 146 buses in its fleet, he said, and replaces between 12 and 15 buses per year.

Over the next couple of years, the district's operational excellence team will measure the total return on investment of the CNG purchase, Stark said.

CNG engines reduce greenhouse gas emissions by up to 20 percent compared to diesel engines, and CNG vehicles also require less overall maintenance, Stark said.

"It will come out to be a huge savings." he said.

The district plans to work with the city to use Dublin's natural-gas fueling station at 6351 Shier Rings Road, and both entities still are working out infrastructure sharing details, Stark said.

The district is making its foray into using cleaner fuels for its buses, Stark said. Long-term, district officials want to continue either using natural gas or electric vehicles to be more environmentally friendly and energy efficient.

The school district is not alone in its use of CNG vehicles.

The Central Ohio Transportation Authority in 2013 committed to phasing out diesel-powered vehicles out of its fleet in favor of CNG vehicles, said COTA spokeswoman Lisa Myers.

As a result, 150 of COTA's 321 buses now are powered by CNG, Myers said.

The switch has also resulted in cost savings.

COTA has saved approximately $10 million in fuel costs by transitioning to CNG since 2013.