Microbes that feed on coal slowly produce natural gas. Using the right nutrients the microbes can be encouraged to speed up the process.
Luca Technologies, a startup based in Golden, CO, has raised $76 million to scale up a process that uses coal-digesting microorganisms to convert coal into methane. The process is designed to operate underground, inside coal beds. Methane, the key component of natural gas, can then be pumped out and used to generate electricity or power vehicles….
As little as one-hundredth of 1 percent of the coal in the United States converted into methane by microbes would supply the country’s current annual natural-gas demands, says Andrew Scott, a former professor of economic geology at the University of Texas at Austin. Source.
Since natural gas is so clean burning compared to other fuels it should become the fuel of choice.