We urgently need to develop alternative fuel sources that reduce our dependence on foreign oil. The only other imperative that competes with this urgency is the emergency of global warming. A few alternative fuels are serious contenders for alleviating the fossil fuel crisis including ethanol, natural gas, propane, hydrogen, and biodiesel. We are in dire need of other alternative fuel developments and discoveries.
Cellulosic Ethanol
Ethanol has been used as fuel in the United States since at least 1908. Touted as a potential aid to the fossil fuel dilemma, cellulosic ethanol is the only alternative energy source that could be produced in enough volume to make a dent in gas usage. Cellulosic ethanol, the biofuel that differs from corn-based ethanol in that it can be made from pretty much any organic matter, is simple to make and has as its source an inexhaustible resource - municipal waste. Cellulose (C6H10O5)n is a long-chain polymer forming the primary structural component of green plants. Cellulose ethanol exhibits a net energy content three times higher than corn ethanol and emits a low net level of greenhouse gases.
Cellulosic ethanol showed greenhouse gas emission reductions of about 80% compared to fossil fuels. Research is being funded in an effort to make us free from non-domestic fuel by more efficient synthesis of domestically produced biofuel. Resources of biomass that can be converted to cellulosic ethanol in many instances are negative cost feedstock. They are more expensive to dispose of than to process into fuel.
A bacterial culture digests organic matter and produces ethanol as a byproduct, at a fourth the retail cost of a gallon of gas. Entrepreneurs are using their venture capital to build processing plants that will become operational in the next 18 to 24 months. Cellulosic ethanol is on the radar screen of big business and can be a substantial help relieving our gasoline crisis.
The Cellulose Fermentation Process
In biomass, Glucose C6 sugar is bound to cellulose, and Xylose (C5) is locked in hemicellulose. Since normal yeast can't ferment Xylose, genetically engineered E. coli bacteria is used in an alternate reaction path to turn almost all the Xylose into ethanol. The cellulose in Fermentable Biomass is broken into Xylose sugar (gray bar). Then the Xylose is separated from the remaining cellulose (blue bar). The Xylose is fermented with E. coli (top yellow), and the cellulose it broken down into normal glucose (red) which is fermented the normal way (bottom yellow). Finally all the ethanol is distilled (the water and lignin byproducts removed). The lignin is burned in the the still's boilers. Lignin forms the woody cell walls of plants and the "cement" between them.
Natural Gas
Natural gas offers several advantages short term in that the product, its pipelines, storage, and dispensing stations are already in the infrastructure for mass transit worldwide. There are over 1,300 natural gas vehicle (NGV) fueling stations in the U.S. - over half are available for public use. Low emissions. With a cost approximately one third less than gasoline, natural gas vehicles most economically run fleet vehicles. NGVs are most practical for fleets because fleets generally operate a number of vehicles that are centrally maintained and fueled, and travel more miles daily than the average personal use vehicle.
Examples
* taxi cabs * transit buses * school buses * airport shuttles * over-the-road trucks * refuse haulers * delivery vehicles * forklifts
Propane
Another popular alternative fuel choice for vehicles is propane (LPG) with an infrastructure of pipelines, processing facilities, and storage already in service. Propane is produced as a by-product crude oil refining. With about 200,000 propane vehicles in the United States and about 9 million worldwide, stepping up consumption of this fuel over gasoline could limit emissions and global warming.
Biodiesel
Autos powered by recycled vegetable oil from restaurants and fast-food joints is an idea that is under some serious scrutiny by environmental groups. Although this alternative fuel may be cheap and clean, there simply isn't enough of it to make a big dent in our gas consumption.
The conversion to cooking oil is easy and inexpensive. It costs about $800 to convert a car using a diesel engine to run on vegetable oil. What is needed is an extra fuel tank which contains a heating element inside. The oil needs to be kept hot to burn. Also needed are fuel lines up to the engine, filters, valves, and toggle switches so the driver can choose between running on vegetable oil or on conventional diesel fuel.
On the downside are the facts that no infrastructure is currently in place to make the cooking oil fuel available commercially. One currently needs to make arrangements with local restaurants to obtain the oil, often given freely. One must also filter the cooking oil for solids left over from the frying process. With limited cooking oil resources available, there is little likelihood that commerce will be motivated to develop the necessary widespread infrastructure to make the fuel more readily available. Vegetable oil fuel for autos may gain at the grass roots level, and may eventually become more widespread, especially if fuel prices increase.
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