Cellulosic Ethanol

 For a long time the American public has been concerned with the idea of alternative energy. For a biosystems engineer it is one of our main topics. The idea of taking agriculture byproducts and turning it in to ethanol is not a new idea, but with POET’s Project Liberty cellulosic ethanol plant scheduled to come online in early 2014 I thought it might be interesting to take a look at this form of bio-energy and its ins and outs.

Materials

For cellulosic bio-fuel you need to cellulose naturally. Luckily cellulose is easy to come by because it is the structure for most plants. This means that the material that can be used for this bio fuel can be almost anything, wood chips, corn cobs, switch grass, etc. The processes I would like to focus on uses primarily

corn stover. Corn stover is basically the residue of a corn farmer harvest, meaning the leftover bits. It includes things like corn cobs, leaves, and husk; it is this matter is what companies, like POET intends to convert to fuel. A farmer would come in after harvesting the kernels and bale the stover, wait for it to dry to a certain level and then ship it off to a processing plant.

Process

The process of turning plant matter into fuel takes several steps. The first step is breaking down the complex molecule into simple sugars. This step is called hydrolysis, where enzymes make this break down

happen. After hydrolysis we are left with sugar and some remaining matter that then have to be separated. The sugar portion then has to fermented and distilled to produce alcohol that can be further concentrated to almost pure ethanol. This process is in contrast to the traditional production of corn ethanol because corn already consists of simple sugars and so hydrolysis (the breakdown of molecules) is not necessary.

Advantages

The advantages of using cellulosic ethanol over corn ethanol have a lot to do with the process behind it. Both approaches return the same product, ethanol which is great but there are some environmental and economic advantages to the use of cellulosic. First it has been said that corn ethanol can reduce green house gas emission by 13% where cellulose ethanol is a net 88% reduction in comparison to traditional fossil fuels. Economically speaking, the building of cellulose ethanol plants and the hiring of management etc. would add quite a few jobs and it looks pretty good for the corn farmers in the area too. Because this process uses a crop farmers waste, the proprietor is essentially make money off of their garbage. Not a bad gig, not to mention that the corn on corn acres used to produce corn stover can increase yield and can result in darker soil leading to faster germination of plants. Lastly there is the hope that this ethanol could reduce Americans dependence on foreign oil.

Disadvantages

Unfortunately they are some disadvantage to our cellulosic ethanol dream. The first is merely that the

technology is so there are very few commercial production plants and it is fairly costly to build a new facility.

Because of this cost and the fact that there is a cheaper alternative (gasoline) most cellulose ethanol projects

need to be government incentivized and without much private funding projects could fall though. Also, the ethanol produced has a reduce MPG meaning more trips to the gas station. Ethanol also absorbs water which means its shelf life is shorter that traditional fuel and transport is more difficult. Lastly the cost of enzymes needed to break down the cellulose can be costly.

In conclusion I believe that cellulosic ethanol has its advantages and disadvantages just like any other fuel in the world. I am not going to sit here and tell you that it is the solution to our fuel and environmental problems, but I do believe that it is a step in the right direction. At the very least I think it is pretty incredible that this technology can turn waste into energy.

Sources: http://greenthefuture.com/CELLETHANOL_PROSCONS.html; http://poetdsm.com/biomass;