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The Eco-Marathon is an annual competition sponsored by Shell, in which participants build special vehicles to achieve the highest possible fuel efficiency. The Eco-Marathon is held around the world with events in the UK, Finland, France, Holland, Japan, and the USA.
The events are entered by a range participants from enthusiastic amateurs to university teams and major motor manufacturers with a variety of designs. The only two motor manufacturers to have any success in the event have been Ford[1] and Honda.[citation needed]
A world record was set by a French team in 2003 called Microjoule with a performance of 10,277 miles per gallon (MPG) (3,638 km/L). The current record is 12,665 MPG (4,483 km/L), set in 2005 by the PAC-Car II.
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[edit] Cellulosic ethanol
Main article: Cellulosic ethanol
Sugars for ethanol fermentation can be obtained from cellulose.[22][23] Until recently, however, the cost of the cellulase enzymes capable of hydrolyzing cellulose has been prohibitive. The Canadian firm Iogen brought the first cellulose-based ethanol plant on-stream in 2004.[24] Its primary consumer so far has been the Canadian government, which, along with the United States Department of Energy, has invested heavily in the commercialization of cellulosic ethanol. Deployment of this technology could turn a number of cellulose-containing agricultural byproducts, such as corncobs, straw, and sawdust, into renewable energy resources. Other enzyme companies are developing genetically engineered fungi that produce large volumes of cellulase, xylanase, and hemicellulase enzymes. These would convert agricultural residues such as corn stover, wheat straw, and sugar cane bagasse and energy crops such as switchgrass into fermentable sugars.[25]
Cellulose-bearing materials typically also contain other polysaccharides, including hemicellulose. When hydrolyzed, hemicellulose decomposes into mostly five-carbon sugars such as xylose. S. cerevisiae, the yeast most commonly used for ethanol production, cannot metabolize xylose. Other yeasts and bacteria are under investigation to ferment xylose and other pentoses into ethanol.[26]
On January 14, 2008, General Motors announced a partnership with Coskata, Inc. The goal is to produce cellulosic ethanol cheaply, with an eventual goal of US$1 per U.S. gallon ($0.30/L) for the fuel. The partnership plans to begin producing the fuel in large quantity by the end of 2008. By 2011 a full-scale plant will come on line, capable of producing 50 to 100 million gallons of ethanol a year (200?400 ML/a).[27]
[edit] Prospective technologies
The anaerobic bacterium Clostridium ljungdahlii, recently discovered in commercial chicken wastes, can produce ethanol from single-carbon sources including synthesis gas, a mixture of carbon monoxide and hydrogen that can be generated from the partial combustion of either fossil fuels or biomass. Use of these bacteria to produce ethanol from synthesis gas has progressed to the pilot plant stage at the BRI Energy facility in Fayetteville, Arkansas.[28]
Another prospective technology is the closed-loop ethanol plant.[29] Ethanol produced from corn has a number of critics who suggest that it is primarily just recycled fossil fuels because of the energy required to grow the grain and convert it into ethanol. There is also the issue of competition with use of corn for food production. However, the closed-loop ethanol plant attempts to address this criticism. In a closed-loop plant, the energy for the distillation comes from fermented manure, produced from cattle that have been fed the by-products from the distillation. The leftover manure is then used to fertilize the soil used to grow the grain. Such a process is expected to have a much lower fossil fuel requirement.[30]
Though in an early stage of research, there is some development of alternative production methods that use feed stocks such as municipal waste or recycled products, rice hulls, sugarcane bagasse, small diameter trees, wood chips, and switchgrass.[31]
[edit] Testing
Near infrared spectrum of liquid ethanol.Breweries and biofuel plants employ two methods for measuring ethanol concentration. Infrared ethanol sensors measure the vibrational frequency of dissolved ethanol using the CH band at 2900 cm-1. This method uses a relatively inexpensive solid state sensor that compares the CH band with a reference band to calculate the ethanol content. The calculation makes use of the Beer-Lambert law. Alternatively, by measuring the density of the starting material and the density of the product, using a hydrometer, the change in specific gravity during fermentation indicates the alcohol content. This inexpensive and indirect method has a long history in the beer brewing industry.
[edit] Purification
Main article: Ethanol purification
Ethylene hydration or brewing produces an ethanol?water mixture. For most industrial and fuel uses, the ethanol must be purified. Fractional distillation can concentrate ethanol to 95.6% by weight (89.5 mole%). This mixture is an azeotrope with a boiling point of 78.1 °C, and cannot be further purified by distillation.
In one common industrial method to obtain absolute alcohol, a small quantity of benzene is added to rectified spirit and the mixture is then distilled. Absolute alcohol is obtained in the third fraction, which distills over at 78.3 °C (351.4 K).[11] Because a small amount of the benzene used remains in the solution, absolute alcohol produced by this method is not suitable for consumption, as benzene is carcinogenic.[32]
There is also an absolute alcohol production process by desiccation using glycerol. Alcohol produced by this method is known as spectroscopic alcohol ? so called because the absence of benzene makes it suitable as a solvent in spectroscopy.
Other methods for obtaining absolute ethanol include desiccation using adsorbents such as starch or zeolites, which adsorb water preferentially, as well as azeotropic distillation and extractive distillation.
[edit] Grades of ethanol
[edit] Denatured alcohol
Main article: Denatured alcohol
Pure ethanol and alcoholic beverages are heavily taxed, but ethanol has many uses that do not involve consumption by humans. To relieve the tax burden on these uses, most jurisdictions waive the tax when an agent has been added to the ethanol to render it unfit to drink. These include bittering agents such as denatonium benzoate and toxins such as methanol, naphtha, and pyridine. Products of this kind are called denatured alcohol.[33][34]
[edit] Absolute ethanol
Absolute or anhydrous alcohol generally refers to purified ethanol, containing no more than one percent water. Absolute alcohol not intended for human consumption often contains trace amounts of toxic benzene (used to remove water by azeotropic distillation). Generally this kind of ethanol is used as solvents for lab and industrial settings where water will disrupt a desired reaction.
Pure ethanol is classed as 200 proof in the USA, equivalent to 175 degrees proof in the UK system.
[edit] Use
[edit] As a fuel
Fuel type MJ/L MJ/kg Research
octane
number
Ethanol 23.5 31.1[35] 129
Methanol 17.9 19.9 123
Regular Gasoline 34.8 44.4[36] Min 91
Premium Gasoline Min 95
Aviation gasoline
(high octane gasoline, not Jet fuel) 33.5 46.8
Gasohol
(90% gasoline + 10% ethanol) 33.7 93/94
Autogas (LPG)
(60% Propane + 40% Butane) 26.8
Liquefied natural gas 25.3 ~55
Diesel 38.60 45.41 25
Volumetric energy density of some fuels compared with ethanol:[37]
Main article: Ethanol fuel
The largest single use of ethanol is as a motor fuel and fuel additive. The largest national fuel ethanol industries exist in Brazil (gasoline sold in Brazil contains at least 25% ethanol and anhydrous ethanol is also used as fuel in more than 90% of new cars sold in the country). The Brazilian production of ethanol is praised for the high carbon sequestration capabilities of the sugar cane plantations, thus making it a real option to combat climate change.[38]
Henry Ford designed the first mass-produced automobile, the famed Model T Ford, to run on pure anhydrous (ethanol) alcohol -- he said it was "the fuel of the future". Today, however, 100% pure ethanol is not approved as a motor vehicle fuel in the US. Added to gasoline, ethanol reduces ground-level ozone formation by lowering volatile organic compound and hydrocarbon emissions, decreasing carcinogenic benzene, and butadiene, emissions, and particulate matter emissions from gasoline combustion.[39]
Prior to the development of electronic fuel injection (EFI) and computerized engine management, the lower energy content of ethanol required that the engine carburetor be rejetted to permit a larger volume of fuel to mix with the intake air. EFI is able to actively compensate for varying fuel energy densities by monitoring the oxygen content of exhaust gases. However, a standard EFI gasoline engine can typically only tolerate up to 10% ethanol and 90% gasoline. Higher ethanol ratios require either larger-volume fuel injectors or an increase in fuel rail pressure to deliver the greater liquid volume needed to equal the energy content of pure gasoline.
Today, more than 20% of the Brazilian fleet of cars on the streets[40] are able to use 100% ethanol as fuel, which includes ethanol-only engines and flex-fuel engines. Flex-fuel engines in Brazil are able to work with all ethanol, all gasoline or any mixture of both. In the US flex-fuel vehicles can run on 0% to 85% ethanol (15% gasoline) since higher ethanol blends are not yet allowed. Brazil supports this population of ethanol-burning automobiles with large national infrastructure that produces ethanol from domestically grown sugar cane. Sugar cane not only has a greater concentration of sucrose than corn (by about 30%), but is also much easier to extract. The bagasse generated by the process is not wasted, but is utilized in power plants as a surprisingly efficient fuel to produce electricity.
World production of ethanol in 2006 was 51 gigalitres (13,000,000,000 US gal), with 69% of the world supply coming from Brazil and the United States.[41]
The United States fuel ethanol industry is based largely on corn. According to the Renewable Fuels Association, as of October 30, 2007, 131 grain ethanol bio-refineries in the United States have the capacity to produce 7.0 billion US gallons (26 GL) of ethanol per year. An additional 72 construction projects underway (in the U.S.) can add 6.4 billion gallons of new capacity in the next 18 months. Over time, it is believed that a material portion of the ~150 billion gallon per year market for gasoline will begin to be replaced with fuel ethanol.[42]
The Energy Policy Act of 2005 requires that 4 billion gallons of "renewable fuel" be used in 2006 and this requirement will grow to a yearly production of 7.5 billion gallons by 2012.[43]
A Ford Taurus "fueled by clean burning ethanol" owned by New York City.In the United States, ethanol is most commonly blended with gasoline as a 10% ethanol blend nicknamed "gasohol". This blend is widely sold throughout the U.S. Midwest, and in cities required by the 1990 Clean Air Act to oxygenate their gasoline during the winter.
[edit] Controversy
Further information: Food vs fuel
It is disputed whether ethanol as an automotive fuel results in a net energy gain or loss. As reported in "The Energy Balance of Corn Ethanol: an Update,"[44] the energy returned on energy invested (EROEI) for ethanol made from corn in the U.S. is 1.34 (it yields 34% more energy than it takes to produce it). Input energy includes natural gas based fertilizers, farm equipment, transformation from corn or other materials, and transportation. However, other researchers report that the production of ethanol consumes more energy than it yields.[45][46] In comparison, sugar cane ethanol EROEI is at around 8 (it yields 8 joules for each joule used to produce it).[citation needed] Recent research suggests that cellulosic crops such as switchgrass provide a much better net energy production than corn, producing over five times as much energy as the total used to produce the crop and convert it to fuel.[47] If this research is confirmed, cellulosic crops will most likely displace corn as the main fuel crop for producing bioethanol.
Michael Grunwald reports that one person could be fed 365 days "on the corn needed to fill an ethanol-fueled SUV".[48] He further reports that though "hyped as an eco-friendly fuel, ethanol increases global warming, destroys forests and inflates food prices." Environmentalists, livestock farmers, and opponents of subsidies say that increased ethanol production won't meet energy goals and may damage the environment, while at the same time causing worldwide food prices to soar. Some of the controversial subsidies in the past have included more than $10 billion to Archer-Daniels-Midland since 1980.[49][neutrality disputed] Critics also speculate that as ethanol is more widely used, changing irrigation practices could greatly increase pressure on water resources. In October 2007, 28 environmental groups decried the Renewable Fuels Standard (RFS), a legislative effort intended to increase ethanol production, and said that the measure will "lead to substantial environmental damage and a system of biofuels production that will not benefit family farmers...will not promote sustainable agriculture and will not mitigate global climate change."[50][51]
Recent articles have also blamed subsidized ethanol production for the nearly 200% increase in milk prices since 2004,[52] although that is disputed by some[citation needed]. Ethanol production uses the starch portion of corn, but the leftover protein can be used to create a high-nutrient, low-cost animal feed.[53]
In 2007 the United Nations' independent expert on the right to food, called for a five-year moratorium on biofuel production from food crops, to allow time for development of non-food sources. He called recent increases in food costs because of fuel production, such as the quadrupling of world corn price in one year, a growing "catastrophe" for the poor.[54] In February 2007, riots occurred in Mexico because of the skyrocketing price of tortillas. Ethanol has been credited as the reason for this increase in food prices [1]. The demand for corn has had a rippling effect on many corn-based products, like tortillas. The effects of ethanol and the increasing cost of food have also been felt in Pakistan, Indonesia, and Egypt [2].
Oil has historically had a much higher EROEI than corn produced ethanol, according to some[citation needed]. However, oil must be refined into gasoline before it can be used for automobile fuel. Refining, as well as exploration and drilling, consumes energy. The difference between the energy in the fuel (output energy) and the energy needed to produce it (input energy) is often expressed as a percent of the input energy and called net energy gain (or loss). Several studies released in 2002 estimated that the net energy gain for corn ethanol is between 21 and 34 percent. The net energy loss for MTBE is about 33 percent. When added to gasoline, ethanol can replace MTBE as an anti-knock agent without poisoning drinking water as MTBE does. In Brazil, where the broadest and longest ethanol producing experiment took place, improvements in agricultural practices and ethanol production improvements led to an increase in ethanol net energy gain from 300% to over 800% in recent years.[citation needed] Consuming known oil reserves is increasing oil exploration and drilling energy consumption which is reducing oil EROEI (and energy balance) further.[55]
Opponents claim that corn ethanol production does not result in a net energy gain or that the consequences of large scale ethanol production to the food industry and environment offset any potential gains from ethanol. It has been estimated that "if every bushel of U.S. corn, wheat, rice and soybean were used to produce ethanol, it would only cover about 4% of U.S. energy needs on a net basis."[56] Many of the issues raised could likely be fixed by techniques now in development that produce ethanol from agricultural waste, such as paper waste, switchgrass, and other materials, but EIA Forecasts Significant Shortfall in Cellulosic Biofuel Production Compared to Target Set by Renewable Fuel Standard.[57]
Proponents cite the potential gains to the U.S. economy both from domestic fuel production and increased demand for corn. Optimistic calculations project that the United States is capable of producing enough ethanol to completely replace gasoline consumption.[citation needed] In comparison, Brazil's ethanol consumption today covers more than 50% of all energy used by vehicles in that country.
In the United States, preferential regulatory and tax treatment of ethanol automotive fuels introduces complexities beyond its energy economics alone. North American automakers have in 2006 and 2007 promoted a blend of 85% ethanol and 15% gasoline, marketed as E85, and their flex-fuel vehicles, e.g. GM's "Live Green, Go Yellow" campaign.[58] The apparent motivation is the nature of U.S. Corporate Average Fuel Economy (CAFE) standards, which give an effective 54% fuel efficiency bonus to vehicles capable of running on 85% alcohol blends over vehicles not adapted to run on 85% alcohol blends.[59] In addition to this auto manufacturer-driven impetus for 85% alcohol blends, the United States Environmental Protection Agency had authority to mandate that minimum proportions of oxygenates be added to automotive gasoline on regional and seasonal bases from 1992 until 2006 in an attempt to reduce air pollution, in particular ground-level ozone and smog.[60] In the United States, incidents of methyl tert(iary)-butyl ether (MTBE) groundwater contamination have been recorded in the majority of the 50 states,[61] and the State of California's ban on the use of MTBE as a gasoline additive has further driven the more widespread use of ethanol as the most common fuel oxygenate.[62]
A February 7, 2008 Associated Press article stated, "The widespread use of ethanol from corn could result in nearly twice the greenhouse gas emissions as the gasoline it would replace because of expected land-use changes, researchers concluded Thursday. The study challenges the rush to biofuels as a response to global warming."[63]
One acre of land can yield about 7,110 pounds (3,225 kg) of corn, which can be processed into 328 gallons (1240.61 liters) of ethanol. That is about 26.1 pounds (11.84 kg) of corn per gallon.
[edit] Ethanol Fuel Cells
Main article: Direct-ethanol fuel cell
Ethanol may be used as a fuel to power Direct-ethanol fuel cells (DEFC) in order to produce electricity and the by-products of water (H20) and carbon dioxide (CO2).[64] Platinum is commonly used as an anode in such fuel cells in order to achieve a power density that is comparable to competing technologies. Until recently the high price of platinum has been cost prohibitive. A company called Acta Nanotech has created platinum free nanostructured anodes using more common and therefore less expensive metals.[65] A vehicle using a DEFC and non-platinum nanostructured anodes was used in the Shell Eco-Marathon 2007 by a team from Offenburg Germany which achieved an efficiency of 2716 kilometers per liter (6388 miles per gallon).[66]
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