Converting biomass-derived sugar into ethanol fuel

Converting Sugar Into Fuel

Man's body is a machine and an extremely efficient one. This machine also requires fuel to keep it going just like other man-made machines. Plants take up carbon dioxide from the atmosphere, and convert it into carbohydrate or sugar in the presence of sunshine and water molecules. Variations of this basic process serve as the source of fuel for all life forms on this planet. Therefore, if sugar, one of the key ingredients of Mountain Dew, can provide energy to our body machine for its workings, it should be able to do the same for man-made machines as well. (Process to Turn Biomass Derived Sugar into Fuel) Scientists have been investigating this possibility for years so as to provide a cheaper, environmental friendly and non-polluting alternative to fossil fuels which are not just non-renewable but also pollute the earth's atmosphere. The shortage of petrol along with a surplus of sugar production since 1979 has also fuelled interest in the possibility of converting sugar into petrol. (Toussaint-Samat; Bell, 561); (Highfield, 5)

Discussion

Requirement of an alternative fuel source

One of the major challenges in reducing global warming is the hunt for an alternative fuel source that would not harm the environment. It is estimated that approximately 25% of the greenhouse gases emitted into the atmosphere as a result of human activities in the U.S. can be traced to transportation. President Obama has also emphasized that the country's $400 billion transportation fuel market must adopt a low-carbon standard. (Roosevelt, 5)

Research in the field of converting sugar into fuel

Now, ethanol has several drawbacks in that it becomes easily contaminated by absorbing water from the atmosphere, evaporates easily, requires a high energy consuming distillation process and has a low energy density. In 2006, a team of scientists led by Prof. James Dumesic at the University of Wisconsin-Madison reported the development of a new method of converting the sugar present in fruits or fructose into fuel. This process converts fructose into DMF or 2, 5- dimethylfuran. This liquid fuel possesses almost as much energy as petrol and 40% more energy than ethanol. This is a two-stage process wherein fructose is first converted to hydroxymethylfurfural -- HMF in water in the presence of a solvent with low-boiling-point with the aid of an acid catalyst. The HMF is extracted from water with the help of the solvent and by the addition of certain catalysts like copper-ruthenium catalyst which limits formation of impurities. The HMF is then converted to DMF and in the process removing from the compound two oxygen atoms thus lowering the boiling point. This makes it appropriate for its role as a fuel used for transportation. However, it will still be some years before such a product can be made commercially viable. As for efficiency, this liquid fuel will be as efficient as gasoline and more efficient than ethanol but the environmental impact is not likely to be less than gasoline. (Process to Turn Biomass Derived Sugar into Fuel); (Highfield, 6)

Another team of scientists led by Y.H. Percival Zhang, a biological systems engineering Assistant Professor at Virginia Tech., and assisted by other researchers at the University of Georgia and Oak Ridge National Laboratory, are working on the conversion of polysaccharides or sugary carbohydrates obtained from biomass to low-cost hydrogen which can be used to drive "hydrogen-powered fuel cell vehicles." Zhang and his coworkers are using synthetic biology techniques wherein a mixture of 13 synthetic enzymes, not found in nature are used to transform polysaccharides and water into hydrogen as and when required. As per laboratory tests conducted so far, it has been seen that these reactions take place at low temperatures and atmospheric pressure. It is estimated that the approximate energy output produced by one kg of polysaccharide containing starch will be equivalent to 0.38 gallons or 1.12 kg of gasoline. Therefore, a vehicle having a 12-gallon tank will be able to store 27 kg of starch and would give a range of over 300 miles. This fuel would not only be energy efficient but would also be clean, safe and environmentally friendly. It would not require any special infrastructure and the starch could also be sold through grocery stores in the future. A sugar-hydrogen fuel cell system's energy conversion efficiency is estimated to be 3 times higher than the efficiency provided by a sugar-ethanol-internal combustion engine. (Novel sugar-to-hydrogen technology promises transportation fuel independence)

Another success in the path of fulfilling the U.S. Department of Energy's vision of implementing a hydrogen-based economy has been achieved by Prof. Thomas Wood at the chemical engineering department in Texas A&M University in 2008. Thomas Wood has been working with E. coli, bacteria that usually cause food poisoning. He has succeeded in genetically modifying a particular strain of these bacteria so that it releases around 140 times the amount of hydrogen than it would have normally produced in a natural process. Wood's method consists of selectively knocking out six specific genes from the DNA of E. coli so that it is virtually transformed into a minute hydrogen-releasing factory fueled by sugar. This process can build up on current advances in extracting sugar or sugar-like molecule from various plant sources like corn. This process is less energy-intensive as it does not require any electricity or heating. One problem that exists with this kind of fuel is its transportation as building new pipelines would not just be cumbersome but it would be dangerous to transport large amounts of hydrogen. (Novel sugar-to-hydrogen technology promises transportation fuel independence); (E.coli a future source of energy?)

However, just like the earlier invention, Wood also believes in producing "hydrogen on-site" instead of transporting it since spilling sugar during transportation would not be as catastrophic as leaking of hydrogen could be. This sugar-converted fuel is also years away from commercial exploitation but nonetheless, is an important stepping stone towards production of alternate renewable energy source. (Novel sugar-to-hydrogen technology promises transportation fuel independence); (E.coli a future source of energy?) Research work is also going on to develop other kinds of microorganisms that can convert sugar more efficiently, like being able to digest the C5 sugars apart from easily digestible C6 sugars and transforming them into synthesis gas containing carbon monoxide and hydrogen, H2, or into several intermediate chemical products like propane diol, succinic acid, or lactic acid. (Centi; Santen, 48)

Some researchers have even developed fuel cell batteries that are powered by any type of sugar ranging from soft drinks to the sap obtained from trees. Such biodegradable batteries have the ability to last 3 to 4 times longer than the lithium ion batteries in use today. It is not just the average consumer who is interested in these products but the military is also extremely interested in using such sugar-powered batteries. The portability of such devices would be appropriate for the extreme mobility required in the battlefield. It would also be suitable in emergency situations when access to electricity and other vital gasoline supply lines are cut off. Using any kind of sugar source available in the vicinity would be enough to charge up the batteries. (Fuel cell batteries that run on sugar) The energy needs of the U.S. Armed Forces are extremely high and the Department of Defense requires a constant supply of fuel for its military jets. Therefore, as per the instructions of the U.S. Congress, DOD and DARPA have also evinced interest in alternative fuel sources like ethanol derived from sugar. (Bio-fuels for the U.S. Military)

Conclusion

Rising crude oil prices, environmental concerns, and gradual depletion of non-renewable energy sources have fueled interest in the research and development of alternative fuels which can prove to be clean, efficient, less energy-intensive, sourced from renewable materials and environmentally friendly. Brazil has already paved the way for a shift away from a gasoline-dependent fuel to a more sugar-derived ethanol dependent fuel. However, ethanol has its share of limitations and scientists are actively working on producing other kinds of energy-efficient fuel from sugar derived from biomass. Various degrees of success have been achieved by several teams working towards this goal.

Some researchers have targeted living cells like bacteria who consume sugar, producing enormous amounts of hydrogen that can be used to power hydrogen fuel cell-based vehicles whereas others are working on converting sugar present in fruits to produce DMF, a liquid fuel which has proved to be more efficient than ethanol and as efficient as gasoline. These kinds of innovations may pave the way for an entirely new kind of fuel for the future and may reduce dependence on a few oil-producing countries of the world. This might mean more independence and economic progress for the Third World countries as well. On the whole, progress in the field of developing new fuels from sugars and other biomass derivatives has been steady and the day might not be far off when instead of queuing up at the petrol pumps, consumers may be seen queuing up at grocery stores to fill up their vehicles.