|  |
|
Bio-Fuels
Leslie Shama
Agricultural & Biological Risk Assessment
Montana State University
lshama@montana.edu |  |
What are Bio-fuels?
With the spike in oil prices in 2005, much attention has turned to the utilization of alternative fuels. A popular alternative fuel source is bio-fuel. Bio-fuel is a broad term that encompasses both bio-diesel and ethanol. It is a fuel not derived from fossils, but is instead derived from one of two sources: agricultural crops such as corn, soybean, and sugar cane, or biomass resources such as agricultural, wood, animal, and municipal wastes and residues. Bio-fuel is a renewable source of fuel used as liquid fuels for transportation, but it also can be used for direct combustion for electricity production. Bio-diesel is different from ethanol because it is made from the oils of plants, mainly soybean, sunflower and waste vegetable oil. It contains no petroleum, is free of sulfur and aromatics, and can be blended at any level with petroleum diesel, usually called bio-diesel blend.
Ethanol production
The chemical process of turning cellulose and starch into dimethyl ether (ethanol) first requires breaking the chemicals into single sugar molecules. Both cellulose and starch are a polysaccharide or string of many individual sugar molecules (monomers) attached together in a plant. The sugars, once they are broken down, are fermented into ethanol. The ethanol then needs to be distilled before it is ready for automobiles (Moreira 2005). Currently, researchers are working on engineering an organism that will break down the cellulose and ferment the sugars in one step. This will reduce the cost of producing ethanol and make the process feasible for quicker scale-up. After the ethanol is produced, it is blended with petroleum-based fuel that can be pumped directly into the gas tank of our current vehicle models depending on the ethanol/petroleum blend. All cars can run on E10, which is 10 percent ethanol and 90 percent petroleum, but cars need to be altered to run efficiently on a blend any higher than E10 (for example E20, E85). Cars cannot tolerate high concentrations of ethanol because ethanol has higher oxygen content than petroleum-based fuel and cars need to be able to detect this with a fuel sensor. Many of the other car parts exposed to ethanol also need to be modified because it is an alcohol and it can disrupt the parts. To make a vehicle that can tolerate the high ethanol concentrations, it may cost the manufacturer about 100 dollars more than making a non-flexible fuel vehicle (Des Garennes 2005).
Environmental benefits…..or are they?
The popularity of bio-fuels is increasing because of the many benefits, especially in a world that is becoming more environmentally conscious and pressured by the instability of oil supplies and prices.
Crops used for the production of bio-fuel take in carbon dioxide from the atmosphere and some argue that this offsets the greenhouse gases released when the fuel is burned. Replacing petroleum with bio-fuel has the potential of reducing air pollution, including emissions of fine particulates and carbon monoxide. Greenhouse gas emissions from vehicles are reduced when vehicles run on any blend of ethanol or bio-diesel. Powering vehicles with a blend of 10% ethanol can potentially reduce greenhouse gas emissions by 10 grams of carbon dioxide for every kilometer driven (Iogen Corporation 2006).
Another benefit is that rural economies may have the chance to sustain themselves and possibly grow because the process of making bio-fuels creates jobs and may raise farm incomes. Bio-fuel can be produced locally and at the same time is a renewable fuel, giving opportunities to diversify energy sources and lower the dependence on foreign oil. The benefits are numerous, but will only make the biggest difference in the environment if bio-fuels become a main energy source. The largest obstacle to this is land availability, therefore land efficiency or maximizing energy yield per acre is an essential aspect when considering bio-fuels as a main energy source. The impact of biotechnology is making this latter point less of a challenge with advances in crop yield productivity.
|
Bio-fuel Facts
Corn, sugarbeets, and sugarcane are the main crops for ethanol production and soybean is the main crop for biodiesel.
About 1.3 billion tons of biomass = 130 billion gallons of ethanol.
"Ethanol blended fuels reduced CO2 equivalent GHG (green house gas) emissions by approximately 7.03 million tons in 2004, equal to removing the annual GHG emissions of 1.04 million cars from the road."
Biodiesel is the only alternative fuel in the US to complete EPA Tier I Health Effects Testing under section 211(b) of the Clean Air Act, which provide the most thorough inventory of environmental and human health effects attributes that current technology will allow.
|
Plant efficiency is important when considering the input/output ratios of energy. Corn for example is one of the least efficient sources of ethanol. Sugar beets and sugarcane produce double the ethanol yield per acre compared to corn. The energy input to make ethanol from corn (growing, transporting, and distilling) uses almost as much energy contained in the ethanol itself. Sugarcane yields eight times as much energy that is needed to produce ethanol compared to corn. Unfortunately, with growing fuel demands in tropical countries like Brazil, fuel demand translates into increased sugarcane production, meaning a demand for more fields, resulting in reductions in rainforest area (Murray 2005).
Debate over benefits
Some would argue that ethanol production from biomass requires the consumption of more fossil fuel-derived energy than it saves. David Pimentel from Cornell University says that ethanol production from corn consumes 29 percent more energy than it returns as fuel (Pimentel and Patzek 2005). When farming corn there is the use of plows, combines, and other farm machinery and petroleum-based fuels power them all. There are alternative arguments to this such as using the bio-fuels as a source of energy for powering the plants producing bio-fuels, which will reduce the use of fossil fuels. The balancing of energy consumption, meaning the growing, the harvesting and the production of fuel, is just one debate of the pros and cons of bio-fuels. Others have argued that energy balance is not the main concern for energy security, but supplementing the capacity needed to support growing fuel demands is more important. The oil fields are not running dry yet, but the oil is increasingly more difficult to reach and pump out and the demand is growing every year. If the oil suppliers can keep up with the demand, the world can remain dependent on oil, but if the demand is not met, the world needs an alternative.
Another debate is the amount of land use and fertilizer and pesticide consumption to support the development of crops for bio-fuel production. Replacing the U.S. fuel supply with corn ethanol would require at least 60 percent of the nation's available cropland. Using plant waste or cellulosic biomass would decrease the use of crops such as corn and decrease the amount of cropland needed to produce enough bio-fuel (Moreira 2005). There are locations in the U.S. more suited for producing crops for fuel, but these same locations also support food crops. An alternative for corn production to produce bio-fuels is the production of sugar beets. They have a higher energy output than input and could reduce the amount of land that is needed to produce fuel.
Why hasn't the world caught on?
The use of bio-fuels and constructing cars that are compatible with the fuel is a topic that has continued for more than a century. In 1900, Rudolf Diesel showed an engine at the World Exhibition in Paris that ran on peanut oil and since the 1930's bio-diesel has been in small-scale use in Paris. In the 1920's Henry Ford was an enthusiast for crop-based ethanol. In 1973, Brazil built cars adapted to burn pure ethanol until the 1980's when oil prices began to plummet and sugar prices soared. Because of this, many of the cars used for ethanol use were no longer being built (The Economist 2005). The drop in oil prices in the 1980's not only made it unnecessary for biomass-derived ethanol production, but it increased the price of producing bio-fuels.
Perhaps, beyond the oil price/bio-fuel price competition the largest reason why this technology has not caught on is the lack of a focused national effort to make it happen. Research on bio-fuels ceased, or at least slowed down, and the consequence of the hiatus devastated the progress because knowledge was inherently lost (Lee 2004).
The guarantee from car manufacturers to the purchaser is an issue if that guarantee is invalidated when the owner decides to fill up with bio-fuel. A few car companies are setting limitations on the percentage of bio-fuel they will guarantee on your car. For example, Volkswagen has extended its guarantee on their diesel-engine cars, which are now available in the U.S. On January 8th 2006, Volkswagen, Shell, and Iogen (Bio-fuel company in Canada), signed an agreement to conduct a study into the economic feasibility of producing cellulose ethanol in Germany. This is the first time an automotive manufacturer, an oil company, and a technology company have collaborated to advance the possibility of using clean fuel (Iogen Company 2005).
One positive aspect that might increase bio-fuel use is that by June 2006, diesel is going to be required to eliminate sulfur. Sulfur in the fuel makes the fuel "slippery", but by adding bio-diesel, the "slipperiness" can be regained.
 |
