advances in bio-fuels
Introduction to Bio-fuels
The first bio-fuel to be used mechanically was vegetable oil in the early 1900s. The diesel engine in use today was designed by Rudolf Diesel for use with peanut oil and today's bio-diesel is designed to be more compatible with such diesel engines. There are many types of bio-fuels and each has many applications. Biodiesel is one of the most popular types that is widely used in diesel engines. Bio-alcohols are another type of bio-fuel; the most common of bio-alcohol is methanol which is used as a vehicle fuel. Ethanol on the other hand is the most widely used bio-fuel. This is due to the fact that ethanol can be used as a substitute for gasoline in petrol engines. Finally, Bio-gas is another commonly used bio-fuel that is used in industry. This Paper will discuss all of the previous types of bio-fuels and all the advances that the mainstream energy companies have done to perfect those bio-fuels. Some of the bio-fuels that are currently being developed, such as cellulosic ethanol, will also be discussed.
Biodiesel is typically manufactured by a process called transesterification, which exchanges one ester alcohol group with another of vegetable oil or animal feedstock. Biodiesel is made of biomass such as vegetable oil from soybean, canola, etc. There are many applications of bio-diesel ranging from biodiesel powered trains to commercial boilers. The first step towards cleaner flying by the use of biodiesel was taken when a test flight from London to Heathrow was successful. Biodiesel is also used in the automotive industry to power vehicles, for instance Daimler Chrysler has intentions to use 20 percent biodiesel blends. One application of biodiesel that is currently being researched is its use in heating oil in boilers, but the components of the current boilers need to be modified to be compatible with the properties of biodiesel. The most interesting application of biodiesel is in trains, called “diesel trains,” which uses 80 percent biodiesel and only 20 percent petro diesel. Cellulosic ethanol produced from Lignocelluloses could be the future of fuel, as it produces 85 percent less carbon dioxide from production and reduces erosion.
Bio-alcohols are typically made from the fermentation of sugars and starches. A benefit of bio-alcohols is that when combined with petrol or diesel they tend not to produce as much carbon emissions. This makes bio-alcohols a renewable source of energy that can be made many times over without depleting the earth’s resources. There are three types of bio-alcohols; Methanol, Ethanol, and Butanol. Methanol has been used since World War II as a fuel substitute. It has a higher octane rating which results in higher engine efficiency. According to Robert Evans, Ethanol is not suitable for use in aircrafts because it has a low energy density, however, Ethanol can be used in spark-ignition marine engines. Butanol is manufactured as seen in the figure to the right. Around 350 million gallons per year iscurrently being used throughout the world. Butanol is mainly used as a solvent, and hopefully will be used as a fuel in the future due to its physical properties. Although there is much research that is needed in order to make bio-alcohols more compatible for daily use, it is the future’s next fuel source. This is due to it being environmentally friendly and it can be as good as petro-fuels. Currently more than 50 countries are researching bio-alcohols to make it more reliable.
Biogas is formed when biological materials ferment slowly over a period of 10 to 120 days depending on the ambient temperature. Fermentation of organic materials forms methane and carbon dioxide in the absence of oxygen when the pH level ranges from 6.5 to 7.5 at a constant temperature of 15C to 55C. Anaerobic fermentation of agricultural and organic waste, sludge digestion in tanks of sewage treatment plants, and organic residues in garbage piles can form a considerable amount of biogas. Also, harvesting this biogas enables us to reduce offensive smells and greenhouse gases.
Agricultural waste is collected in a primary pit and sterilized to remove harmful chemicals. The waste is then moved to a digester where the biogas produced is collected in a storage tank to provide a non-fluctuating flow of gas. This is then fed to a gas engine as the gas mixture produced in the digester consists of 50 to 70% methane. (CH4). This high concentration of methane makes biogas suitable for combustion in gas engines. The chemical energy is converted to mechanical energy in the gas engine. It is then converted to electrical energy using an alternator much like the type commonly found in automobiles that are used to recharge the vehicle’s electrical system.
Muncipal waste contains about 150 to 250kg of organic carbon per ton. This organic carbon is biodegradable and converted into landfill gas in anaerobic conditions. It has a relatively high calorific value of about 5 kWh/m3N and can be effectively used to generate power. If this gas is continuously extracted under controlled conditions, a tremendous amount of energy can be harvested. Almost 40 to 50% of methane is present in this type of landfill gas. To harvest this gas, perforated tubes are drilled into the landfill body and connected to a pipe system. A blower sucks the gas away from the landfill and it is then later compressed, dried, and fed to a gas engine. This energy is converted to electrical energy and fed into the local power grid.
Sewage gas is harvested in much the same way. Sewage sludge is first dried and then pumped into a digester. The gas emitted from the digester typically contains about 50 to 60% methane. The gaseous emissions are then compressed and fed to a gasometer. This acts a fuel tank to the actual electrical energy generator unit. Enough energy is generated to power the sewage treatment plant itself.
Fisher Tropsch Synthesis Process
This process creates a variety of desirable products and undesirable byproducts. It converts synthesis gas, a mixture of carbon monoxide and hydrogen, into liquid hydrocarbons of different types. The primary purpose is to produce a synthetic petroleum substitute typically from coal, natural gas or biomass. This promising technology has the potential to reduce our dependence on foreign oil. This technology was patented in 1930 and was used in World War II by the Japanese and German forces. In fact, 6.5 million tons of synthetic fuel was produced by Nazi Germany everyday.
Shell in Malaysia produces low-sulfur diesel fuels using this process. A company named Sasol produces most of South Africa’s diesel fuel using FT technology.. In 2005, Pennsylvania governor Edward Rendell announced plans for an FT plant near Philadelphia to be built using licensed technology by Shell and Sasol. In 2006, Finnish paper and pulp manufacturer UPM announced its plans to produce biodiesel using FT Synthesis using waste biomass generated during the manufacture of its paper products.
The US Air Force has been actively developing this technology as well. A publicly traded US company, Syntroleum, has been working with the US Air Force to develop a synthetic jet fuel blend to help the Air Force minimize its dependence on imported petroleum. In 2006, a B-52 successfully completed a 7 hour flight powered by a 50/50 blend of conventional jet fuel and Syntroleum’s FT fuel.
There are many advantages in using bio-fuels such as reducing the amount of CO2 emissions and hence reducing global warming. The advantage of using butanol is improving our homeland security by disseminating fuel generation throughout biomass such as corn, and reducing our dependence on foreign oil resources. However bio-fuels also have many disadvantages that need to be addressed before they become publicly accepted. One main thing to consider is that it will take considerable amounts of biomass to produce Biodiesel at a global scale, which could deplete some nation’s food supply. Biodiesel must be treated carefully at all times. For example biodiesel doesn’t flow smoothly at cold temperatures, and so cannot be stored in tanks outside of homes. Also, this means that biodiesel cannot be transported in pipe lines but it has to be transported by trucks or rail, ref . Bio-ethanol also has its disadvantages because it could produce some negative effects on electric pumps by raising the level of internal wear. Biogas on the other hand is commercially unattractive due to its low value, but this means that it is economically attractive when compared to other bio-fuels.
Bio-fuels as the main source of energy worldwide must be accepted in order to have a better and cleaner future. This means that we need to take the necessary steps to improve our technology to be able to efficiently harness the enormous potential that bio-fuel could bring. We must also research and work hard to be able to eliminate the disadvantages that bio-fuels have and turn them into usable advantages. There are many new bio-fuels being developed such as the Fisher Tropsch biodiesel. Also, there will be bio-fuels to be invented in the future. I believe that bio-fuels will one day replace petro-fuels and hence our dependence on other countries.
6. Evans, Robert L. Fueling Our Future, the university of British Columbia,2007.