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Spoonful of sugar makes biofuel greener
12 November 2005
From New Scientist Print Edition.
Zeeya Merali

Take a vat of vegetable oil and add a scorched sugar lump. It might not catch on as the latest cocktail, but the mixture could speed up the widespread production and use of biodiesel in vehicles.

Converting vegetable oils to fuel requires a catalyst. Most existing catalysts are derived from petrochemicals, but using them defeats the environmentally friendly object of biofuels. Liquid sulphuric acid is an alternative, but it is expensive and wasteful because it is hard to remove after the conversion. Now a team led by Masakazu Toda at the Tokyo Institute of Technology in Japan has developed a cheap, renewable catalyst from glucose.

The Tokyo chemists heated glucose and sucrose in a chamber without oxygen to remove some of the oxygen and hydrogen atoms. Then the charred remains were treated with sulphuric acid, which sticks to the sugars in place of the hydrogen and oxygen. This creates a solid, insoluble catalyst that can easily be added and removed from the fuel (Nature, vol 438, p 178). "The advantage is similar to using tea bags instead of tea leaves," says Peter Licence, a specialist in catalytic chemistry at the University of Nottingham in the UK.

As the raw materials are glucose and sucrose, the sugar catalyst should be cheap. It is also more than twice as efficient as its solid competitors, although it is not as effective as a liquid catalyst because the molecules aren't as free to make contact with the oil.

"The sugar catalyst sings on many chords of green chemistry," says Licence. "It helps produce a renewable fuel and is itself made from renewable food stocks." But Licence also points out that producing the sugars in the first place and heating them to make the catalyst takes a lot of energy and uses petrochemical fuels, which reduces the catalyst's environmentally friendly credentials.

However, Licence believes that the benefits outweigh the disadvantages. "Overall this could make biodiesel generation easier - and people will use biodiesel as it becomes more readily available. We already see that in California." More than 600 filling stations across the US now sell biodiesel alongside gasoline, according to the US National Biodiesel Board.

From issue 2525 of New Scientist magazine, 12 November 2005, page 32

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