Cellulose ethanol, more commonly known as cellulosic ethanol, is ethanol that is made from the portions of plants not generally eaten, at least by humans. This type of ethanol commonly uses items such as wood and grass. While mass producing ethanol fuel at a profit from such sources is still a developing industry, it does hold some potential as a possible source, according to some companies looking into the issue.
The main advantage of cellulose ethanol is that it would be made from crops that do not have to be replanted after harvests. The most common material currently used to make ethanol in the United States is corn. The only way to use the corn is to harvest it, meaning there is only one crop per year, or perhaps two at some lower latitudes. Using crops such as switchgrass, considered a prime candidate for cellulose ethanol production, would allow an almost continuous harvest.
Another advantage of cellulose ethanol is that it would bypass the entire food versus fuel debate. One of the criticisms of corn ethanol, and even sugar ethanol to some extent, is that it takes away the potential of using such sources for food. Some believe it is a moral issue to use food stock for fuel, when people are going hungry around the world. Others say that corn is already used for multiple purposes, such as for feeding livestock, thus eliminating some of those criticisms.
Making cellulose ethanol would also reduce the amount of fossil fuels needed to grow the crops responsible for traditional sources of ethanol. Some debate has even centered on whether there is actually a net energy gain in producing ethanol this way. Moreover, cellulose ethanol does not need as much human intervention in order to get the raw materials.
Currently, there are some problems that must be overcome before cellulose ethanol can achieve full-scale, and widespread production. These include finding a way to extract as much energy as possible from the product, and retrofitting existing facilities to produce ethanol from such materials. These will involve a significant amount of capital investment by companies seeking to use this production. While all will take time to complete, they are not impossible tasks.
There are a couple of prototype plants in the United States that are processing cellulose ethanol for fuel. These plants may serve as models for others, but more work still needs to be done before this source makes a significant impact on the industry. In some cases, ethanol plants used for corn may be able to be retrofitted so that they will be able to make ethanol from either corn or cellulose materials.