Corporate Travel Management has signed a three-year agreement with Delta Air Lines to buy sustainable aviation fuel, the carrier announced.

The terms and amount of fuel involved in the agreement was not disclosed, but Delta said over three years it would cut lifecycle emissions of carbon dioxide by 209 metric tons, the equivalent of the work of 256 acres of forest. Delta has signed sustainable aviation fuel agreements with other travel management companies and corporate partners—including BCD Travel, CWT, Deloitte, Nike and Takeda—but the agreement with CTM is the first to span multiple years, according to Delta.

In aggregate, all of Delta’s sustainable fuel agreements with corporate partners so far account for the purchase of 300,000 gallons of fuel.

The World Economic Forum, meanwhile, on Thursday announced that it has developed a new accounting tool to help claim emission reductions related to the purchase of sustainable aviation fuel. Its Sustainable Aviation Fuel Certificate system will be able to track and verify such purchases, similar to accounting systems in renewable electricity markets.

Over the next year, the organization plans to conduct pilot transactions with the certificate and eventually have a full emissions accounting system.