Enterprise Holdings, owner and operator of the Enterprise Rent-A-Car, National Car Rental and Alamo Rent A Car brands, has converted more of its airport shuttle buses to 20% biodiesel (B20) and exploring other clean fuel options for its buses, the company announced June 14. The company says it has converted its fleet of buses to biodiesel in more than 50 North American markets, including airport locations within five miles of a biodiesel station.

Overall, more than 70% of its buses now run on biodiesel, with approximately 50% using 5% biodiesel (B5), and more than 20% using B20. By the end of the year, the company’s older buses will be replaced with new B20-compatible models and more than 80% of its total shuttle bus fleet will run on biodiesel, Enterprise reported.

“We are steadily converting our shuttle fleet as biodiesel becomes accessible to more and more of our airport locations,” said Lee Broughton, head of corporate sustainability, Enterprise Holdings.

Biodiesel is an alternative fuel produced from domestic, renewable resources such as plant oils, animal fats, algae and used cooking oil. According to the National Biodiesel Board (NBB), switching to biodiesel reduces greenhouse gases by more than 85% and particulate-matter emissions by more than 45%, as well as decreases hydrocarbon emissions by 75%. The NBB also states that for every unit of fossil energy it takes to produce biodiesel, 5.5 units of renewable energy are returned.

In addition to embracing biodiesel, Enterprise operates 30 buses fueled by compressed natural gas (CNG) in Southern California, and plans to add 10 new CNG-fueled buses this year — four in Southern California and six at Lambert-St. Louis International Airport.