Photos: Clean-tech start-ups swing for the fences

The biofuel industry is booming, with production of ethanol and biodiesel forecast to continue growing rapidly in the coming years. One of the issues with biorefineries is dealing with residual products after the fuel is made. These bottles show separated diesel fuel and the small amount of glycerol that is left after production.

AC Fox is a start-up that has developed a furnace that can burn glycerol, a byproduct of biodiesel production. Glycerol actually has about two-thirds of the energy of biodiesel, and it can be used to power biorefineries, according to Jim Cosgrave, the company's CEO.

The heat from burning the "glyc fuel" can be sold to neighboring buildings, such as hotels, that need heat for hot water as well, he said. The name of the company comes from a process it uses to separate the glycerol: activated carbon facilitated oxidation.