We literally looked at every option we could think of, with several key parameters in mind, Emil Jacobs, vice president for research and development at Exxon’s research and engineering unit told the the New York Times, adding that scale was the first.

For transportation fuels, if you can’t see whether you can scale a technology up, then you have to question whether you need to be involved at all, Jacobs told the paper.

Exxon fended off proposals related to renewable fuels at an investors meeting in May.

Certainly for the foreseeable future, the world is going to continue to rely on fossil fuels, chief executive officer, Rex Tillerson said.