Thursday, June 19, 2008
Although thermochemical and biochemical methods for the production of ethanol are the most practical and widely used methods to produce ethanol and cellulosic ethanol, electrochemical methods are another option. Thermochemical methods pertain mainly to burning the cellulose in a controlled fashion to produce a gas stream. This is usually combined with a biochemical catalyst (most likely a bacterium), where the gas stream is converted into ethanol. This combination of thermochemical and biochemical methods are what GM and Coskata are backing in their hopes to pioneer efficient ethanol production from cellulose.
However, Mitsubishi and RedOx Biofuels have agreed to work together on an electrochemical approach to producing ethanol from cellulosic feedstocks. With gas prices soaring and the price of corn skyrocketing due to the flooding in the Midwest, there has been an even greater push towards the creation and implementation of an efficient process to produce cellulosic ethanol. Electrochemical methods, such as those used by Mitsubishi, uses electricity and acid/base hydrolysis to break the bonds in cellulosic ethanol so that the sugars can be accessible to the bacteria that can convert them into ethanol.
The problem with Mitsubishi's method is that unless they develop a way to use electricity in a highly efficient manner to break the bonds in cellulose I can almost guarantee to you that the process will use more energy than it produces. Thermochemical methods have the potential of working because the burning process can be self-sustaining once the material begins to burn (requiring only a portion of the feedstock to continue the process). So my reasoning is that although Mitsubishi is trying something new, it doesn't seem like they will be able to get very far with this process. Their proposed target is only 800 liters of ethanol produced next year, which is pitifully small even for a pilot-plant.
The facts are that fuel molecules, such as ethanol and certain furfural compounds that can mimic gasoline can be produced using electrochemical methods. The problem is that they can only produce a small amount of product and it takes an immense amount of energy using current procedures to make the process work. If nothing else works, these methods would be fine.... but I think we can do much better.
Here is a schematic diagram of what Mitsubishi envisions for their process: