But we are sitting on rich and unexploited seams of coal, much of which would burn cleanly.

They are non-toxic and burn cleanly without emitting soot.

The fuels that are easiest to burn cleanly are typically liquids and gases.

Beeswax for candles and olive oil for lamps are preferred because they are natural and burn cleanly.

Hydrogen has been touted as a potential solution because it burns cleanly.