Wednesday, December 3, 2008

What's Next in the Evolution of Biofuel Production?



With the recent rise in oil prices, along with growing concern about global warming caused by carbon dioxide emissions, biofuels have been gaining popularity. Biofuel are derived from organic materials and can be produced from many carbon feedstocks, especially photosynthetic plants. Globally, biofuels are most commonly used to power vehicles and heat homes and stoves. (Image to left: vegetable oil is a source used for biofuel (1).)

First-generation biofuels are made from starch, sugar, vegetable oil and animal fats. Ethanol, the most common biofuel used worldwide, is produced by fermenting sugars derived from wheat, corn and other sugars and starches from which alcoholic beverages can be made from. (Image to right: Corn is commonly used in the production of ethanol (2).) Ethanol is produced by microbial fermentation of the sugar. Starch can be economically converted to sugars for fermentation. However, cellulosic ethanol, where the cellulose part of a plant is broken down via enzymes to sugars and converted to ethanol, is also utilized but is economically less viable. For the ethanol to be usable as a fuel, water must be removed and most of the water is removed by distillation. Then dehydration occurs to remove the rest of the water from the ethanol/water mixture (3).

Ethanol is most commonly used to power automobiles, though it may be used to power other vehicles, such as farm tractors and airplanes. Ethanol consumption in an engine is approximately 50% higher than for gasoline since the energy per unit volume of ethanol is 34% lower than gasoline (4). However, the higher compression ratios in an ethanol-only engine allow for increased power output and better fuel economy (5). When ethanol-only vehicles evolve to be practical, the fuel efficiency of such engines should be equal or greater than current gasoline engines. However, since the energy content by volume of ethanol fuel is less than gasoline, more ethanol fuel would still be required to produce the same amount of energy (6). In spite of that, the ethanol-only vehicle wastes less energy, yielding the same or higher mileage which not only helps to improve fuel economy but also reduces atmospheric pollution (3). (Image to above: The Saab BioPower Hybrid has been named "the world's first fossil free hybrid vehicle" (6).)

There are costs and benefits to producing ethanol from sources of biomass such as corn or cellulose. Corn ethanol is the most common type of ethanol in the United States. Ethanol is produced from corn as a biomass through industrial fermentation and is primarily used as an alternative to gasoline and petroleum. Corn ethanol production occurs through two corn processing methods: dry and wet corn milling. Dry milling involves liquefying the corn starch and using a second enzyme to convert the liquefied starch to sugars; the sugars are then fermented by yeast into ethanol and carbon dioxide. Wet milling operations separate the fibre, germ, and protein from the starch before it is fermented into ethanol (7). (Image to left: plant where corn ethanol is produced (8).)

Cellulosic ethanol is a type of biofuel produced from lignocellulose, a structural material that comprises much of the mass of plants. Production of ethanol from lignocellulose has the advantage of abundant raw material compared to sources like corn and cane sugars. The drawback to it is that it requires a greater amount of processing to make the sugar for the microorganisms that are typically used to produce ethanol by fermentation. However, one of the benefits of cellulosic ethanol is that it reduces greenhouse gas emissions over gasoline (3).

A new fungus, Gliocladium roseum (Picture to left: G. roseum growing on a petri dish. (9)), has been discovered that could potentially be a new source of biofuel. Gliocladium roseum lives inside the Ulmo tree in the Patagonian rainforest and possesses the metabolic processes to produce a variety of hydrocarbons that are similar to those of petroleum derived diesel. The fungus utilizes cellulose to produce diesel compounds, which makes it a better source of biofuel than other sources since cellulose is the most abundant carbon compound in most plants. The fuel that it produces has been termed “myco-diesel.” “Although the fungus makes less myco-diesel when it feeds on cellulose compared to sugars, new developments in fermentation technology and genetic manipulation could help improve the yield for the future” (9). The genes of the fungus itself may lead to helpful new advances in the biofuel production.

Sources
1. http://www.chrismadden.co.uk
2. http://www.worldcommunitycookbook.org/season/guide/photos/corn.jpg
3. http://en.wikipedia.org/wiki/Biofuel
4. http://www.eere.energy.gov
5. http://courses.washington.edu/me341/oct22v2.htm
6. http://www.hybridcars.com/
7. https://www.smithbarney.com/features/ethanol050106.html
8. www.minnpost.com
9. Britt, Robert Roy. "Newfound fungus makes better biofuel ." MSNBC. 04 November2008. MSNBC. 20 Nov 2008 .
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