Coskata’s semi-commercial plant will demonstrate three different types of bioreactor: one proprietary bioreactor that uses strawlike membranes to deliver the gases, and two conventional bioreactors. It will also demonstrate two gasifiers and two methods for concentrating the ethanol: a conventional distillation process and a membrane-based process that can use less energy.
Companies will be able to license different combinations of technologies to build commercial plants, Bolson says. The plan to license the technology is a departure from Coskata’s original plan, which was to build its own commercial plants. The company’s plan to move directly from a plant that produces tens of thousands of gallons of ethanol to commercial production is unconventional. Typically companies first build demonstration plants that produce one million or two million gallons of ethanol.
One of the main challenges with Coskata’s technology is getting the syngas–which doesn’t dissolve easily–to the bacteria, says Andy Aden, a research scientist at the National Renewable Energy Laboratory, in Golden, CO. A key question is whether specialized bioreactors for delivering the syngas can be cheap enough for the process to be practical, he says, or whether less expensive, conventional reactors can deliver the syngas effectively.