Fuel from fuel: converting biodiesel waste into ethanol

Environmental Expert.com
Source: European Commission, Environment DG
Published: Sept. 12, 2008

Researchers have discovered that under the correct conditions, glycerol, a major by-product of biodiesel production, can be turned into ethanol by harmless strains of the bacterium Escherichia coli. Furthermore, yields of ethanol obtained from this method are higher than those obtained from conventional means of production.

As society looks for alternative sources of energy to replace the use of fossil fuels, the production of renewable fuels such as biodiesel has significantly increased. However, biodiesel production creates large amounts of glycerol, a by-product of the conversion process from vegetable oil to fuel. Nearly one kilogram of glycerol is created for every ten kilograms of biodiesel produced. Although refined glycerol is used extensively by the chemical industry in the manufacture of cosmetics, drugs and food products, there remains a surplus of glycerol which some biodiesel manufacturers must pay to have removed.

Ethanol is produced by using bacteria to ferment glycerol. Although widely used in the biotechnology industry, researchers had previously thought that the bacterium E. coli was unable to ferment glycerol, because the bacterium did not produce a vital chemical, 1,3-propanediol, (1,3-PDO) required during the process. However, this research has identified mechanisms which overcome this barrier and enable E. coli to convert glycerol into ethanol. Yields of ethanol produced in this way are greater than yields produced by the standard means of ethanol production, which converts plant sugars from crops such as corn into fuel. Furthermore, production costs are lower using this method.

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