The Coskata process that GM is promoting can use a wide range of different feedstocks to produce ethanol. Materials ranging from agricultural waste to purpose grown crops that can be raised on marginal lands (switchgrass being the most widely known example of this) to waste materials such as old tires and even municipal waste streams can all be used as the raw materials that can be turned into ethanol with very little to zero landfill waste.
The Coskata process is fundamentally a biological reaction that takes place inside a specialized reactor (which is simply a vessel to contain the microbes and keep them in an environment where they are happy to live and produce ethanol). Anaerobic bacteria are fed carbon monoxide and hydrogen (known as syngas), which are produced by gasification, which can be done a number of different ways, depending on the feedstock material.
The reactor for this process is a sealed plastic tube filled with millions of filaments on which the bacteria live. Having bacteria living on the filaments provides an enormous amount of surface area for them to live on in a very concentrated volume. The syngas is passed through the reactor, and bacteria feed on the carbon monoxide and hydrogen and produce ethanol.
Other methods for ethanol production typically use enzymatic reaction to break down materials which are then fermented and turned into alcohols by microorganisms. Coskata's process uses gasification to directly convert raw materials into syngas (which is mostly carbon monoxide and hydrogen gas). This makes Coskata's process more efficient than vat-type bio-processes, and leads to less waste produced.
The process of plasma gasification which we wrote about last year is another one of the potential front-end methods that could be used, particularly in conjunction with more variable sources of raw materials such as municipal or factory waste streams. (In fact, this is one area GM and Coskata have talked about working together; expect to see a waste gasification/ethanol production plant at a GM manufacturing plant in the near future as a pilot demonstration of the process working with a highly variable source of raw materials and contributing to a zero landfill waste production facility.)
Coskata has taken pains to note that they are NOT using genetically modified organisms (GMOs) in this process, and that the microbes they are using are not pathogenic. In fact, because these bacteria are anaerobic, if there was a breakdown and they were released into the atmosphere, they would quickly die off, just as we would if we wandered into a roomful of carbon monoxide. One part of Coskata's research has been to identify suitable strains of bacteria that work well in their process and then selectively breed them to produce "thoroughbred" strains that work better.
Coskata's process is also significantly less taxing on water resources. While other current methods of ethanol production take 3 to 4 gallons of water for each gallon of fuel produced, the Coskata process needs less than a gallon of water per gallon of fuel.
Note: GM paid for my travel to attend a background briefing about this program.
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