Thursday, March 10, 2011

Butanol Biofuel

A team of chemical engineers at the University of Arkansas has developed a method for converting common algae into butanol, a renewable fuel that can be used in existing combustion engines.

Butanol has several significant advantages over ethanol, the current primary additive in petrol (gasoline). Butanol releases more energy per unit mass and can be mixed in higher concentrations than ethanol. It is less corrosive than ethanol and can be shipped through existing pipelines. These attributes are in addition to the advantages gleaned from butanol's source. Unlike corn, algae are not in demand by the food industry. Furthermore, it can be grown virtually anywhere and thus does not require large tracts of valuable farmland.

The team grows algae on "raceways," which are long troughs made out of screens or carpet, usually 2 feet wide and ranging from 5-feet to 80-feet long, depending on the scale of the operation. Algae survive on nitrogen, phosphorus, carbon dioxide and natural sunlight, so the researchers grow algae by running nitrogen- and phosphorus-rich creek water over the surface of the troughs. Excess nitrogen and phosphorus in natural waters is sometimes referred to as "dead zones" because these elements in excess can kill fish and plants.
They enhance this algal growth by delivering high concentrations of carbon dioxide through hollow fiber membranes that look like long strands of spaghetti.

The researchers harvest the algae every five to eight days by vacuuming or scraping it off the screens. After waiting for it to dry, they crush and grind the algae into a fine powder as the means to extract carbohydrates from the plant cells. Carbohydrates are made of sugars and starches. They treat the carbohydrates with acid and then heat them to break apart the starches and convert them into simple, natural sugars. They then begin a unique, two-step fermentation process in which organisms turn the sugars into the organic acids butanoic acid( butyric acid), lactic acid and ethanoic acid (acetic acid).

The second stage of the fermentation process focuses on butanoic acid (butyric acid) and its conversion into butanol. The researchers use a unique process called electrodeionization which involves the use of a special membrane that rapidly and efficiently separates the acids during the application of electrical charges.

University of Arkansas, Fayetteville (2011, March 2). Algae converted to butanol; Fuel can be used in automobiles. ScienceDaily. Retrieved March 11, 2011, from­ /releases/2011/03/110301200638.htm

Further Reading
Elements and Compounds
Alkanols (alcohols)
Functional Groups
Carbon Cycle

Study Questions
  1. Draw a table with the headings elements and compounds. Place each element and compound mentioned in the article above into the table.
  2. Give the formula for each of the following:
    • butanol
    • ethanol
    • nitrogen gas
    • carbon dioxide gas
    • butanoic acid
  3. Describe what is meant when a Chemist uses the term carbohydrate.
  4. What is the difference between a sugar and a starch?
  5. Give 3 examples of compounds that are carbohydrates.
  6. Write an equation to represent the process by which algae produce glucose from carbon dioxide and water.
  7. Write an equation to represent the fermentation of glucose into ethanol.
  8. What are the advantages of using butanol as an additive to petrol (gasoline) rather than ethanol?

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