Cellulose, the basic component of plants, is easily converted to sugar. Sugar can then be converted to ethyl alcohol. This whole process is known as hydrolysis and has been used for hundreds of years.
A new process, enzymatic hydrolysis , is under research and development and will produce greater yields with fewer waste products. To make this more economically viable there are other technological developments under way such as novel harvesting methods, better crop management, separation-process improvements, improved enzymes, genetic engineering advances and pretreatments.
Lignin, the natural glue that holds vegetable material together, must be removed for the production of ethanol from cellulose. The DOE, Department of Energy, has been working on a process to directly convert ligno-cellulose to ethanol without removing the lignin first. Microorganisms are being developed at the Oak Ridge National Laboratory in Tennesse to speed up the conversion of cellulose and hemicellulose to sugars, which can then be converted to alcohol. The DOE hopes to reduce the cost of ethanol from biomass to just 83 cents to $1.33 per gallon by the year 2005. This would be far cheaper than gasoline and might reduce or keep gasoline prices stable.
Ethanol is used as a clean burning fuel and can be a petroleum additive. Currently, industrial plants have increased ethanol production to 60 gallons per ton at a cost of $1.50 to $2 per gallon. In 1993 alone, the U.S. produced 1.1 billion gallons of ethanol. With increasing technologies and the DOE's predictions ethanol will be a competitive fuel.
When compared to ethanol production, the biodiesel process requires no distiller's license, less water and energy, and produces a high-protein meal as a byproduct.
For the replacement of diesel comparisons of biodiesel are made in DI [direct injection] and IDI [indirect injection] engines. The problems with using vegetable oils to fuel direct-injection engines included start-up problems in cold weather and fouled injector tips in the engines after sustained operation. Technical aids can help with the starting problems, but the fouled injector tips are a result of high viscosity. Carbon builds up in the injector holes, interfering with the spray pattern of the fuel and affecting the combustion. Engine power declines and exhuast smoke and engine misfiring increase. The cause of this is oils that are high in unsaturated fats. They contain molecular structures called triglycerides, which are made up of glycerol (one of many alcohols) and fatty acids. Fatty acids without the glycerides are more valuable as fuel oil. A process called esterification involves the transformation of the large, branched triglyceride molecules of bio-oils and fats into smaller, straight-chain molecules, resembling the size of molecules in diesel fuel. The oil can then be filtered and preprocessed to remove free fatty acids. Then it is mixed with methanol and a catalyst, usually sodium or potassium hydroxide, and the esters and glycerols can be separated easily and purified.
The viscosities of vegetable-oil esters are similar to those of diesel fuel, but esterification increases the cost by 50%. Esters are an organic solvent so the widespread ester-fuel specifications will be needed for large-scale use. Esters also form crystals at cold temperatures but engine issues amd problems are worth solving for using vegetable oil esters as a fuel.
In the long run using these oils can reduce the need for diesel and the mass production of agriculture for bio-diesel and ethanol will only help the environment.
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