ATLANTA – CoalTek, a startup company focused on patented technology to make coal burning more cleanly, has closed on $33 million in a third round of venture capital financing, according to Venture Wire.

CoalTek has raised some $18 million in earlier financing.

Lightspeed Venture Partners led the latest round.

The move reflects growing investor interest in clean fuel and alternative fuel technology.

CoalTek has developed technology that uses electromagnetic energy to reduce moisture, ash, sulfur and mercury in coal, thus allowing it to burn more cleanly.