BiofuelsBiofuels are biologically derived fuels. One of the most common biofuels is ethanol which is primarily developed from cornstarch though this method has inherent limitations. One promising alternative method for producing bioethanol is by using cellulose, which turns out to be the most abundant biological substance on earth.
There are many benefits to using cellulose in the production of ethanol. Perhaps the biggest benefit is the fact that plants (in which cellulose functions to provide structure and support) are abundant and renewable. In fact, it is likely that an industry for the farming and harvesting of cellulose rich plants will emerge. In addition to their abundance and renewability, plants can be farmed in a wide variety of environments and locations which allows for the decentralization of energy production. Small, decentralized biofuel producing factories with very small footprints can be “taken to the source” thus removing some of the need for and cost of transportation. Bioethanol also has the distinct advantage over fossil fuels of being carbon neutral, and thus not releasing emissions that contribute significantly to global warming.
Unfortunately, the current process for converting cellulose into ethanol is slow and inefficient. Because of this, the cost of ethanol is still not cost-competitive, although several cars now support partial ethanol fuel. The big challenge going forward is to develop efficient systems for the mass production of cellulosic bioethanol.
The current process of making ethanol out of cellulose involves three main steps:
1. Thermochemical treatment of biological material to make them more amenable to enzymatic breakdown.
2. Applications of enzymes to break down biological material into a mixture of simple sugars
3. The use of bacteria in the process of fermentation to convert the sugars from step 2 into ethanol.
Step 1 turns out to be one of the main obstacles to the efficient production of bioethanol. Step 1 is necessary because of the natural biological function of cellulose: to provide rigid structure to plants. Because of this natural biological function, naturally occurring cellulose is difficult to break down and ferment into ethanol. Efficient production in the future might result from biologically engineered plants whose cellulose is more amenable to enzymatic breakdown. Another strategy for avoiding the first time consuming step is to start the process with biomass that is already in sugar form.
While cellulose provides the most promising method for mass ethanol production, there are also techniques being developed for the employment of biowaste. One of the benefits of using biowaste over cellulose is that it does not require as much pre-treatment for the breakdown of the energy source. This is because a great deal of biowaste (discarded food) is already amenable to quick enzymatic breakdown. Another benefit of using biowaste is that there is a natural mapping between locations that need high quantities of energy and locations that produce high quantities of biowaste. Contrast this with the fact that plants are more abundant in locations with less energy needs, and less abundant in areas with high energy needs.
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