permaculture

["Lawrence F. London, Jr." <lfl@intrex.net>]

<http://news.yahoo.com/s/afp/energyenvironment;_ylt=AlCWz8a48ZyBBk4QMzYnwM5hr7sF>
Fructose biofuel spells sweeter news for shift out of oil

PARIS (AFP) - Chemists in the United States say they have broken new ground 
in biofuels, transforming plant sugar into a
liquid fuel that packs 40-percent more energy than ethanol and appears to 
have fewer of its drawbacks.

Ethanol (ethyl alcohol) is currently the only car fuel made in large 
quantities from biomass, under fast-expanding
initiatives to wean industrialised economies from dirty, costly oil.

Biomass sources such as corn, sugarcane and other plants are rich in 
potential energy, in the form of large chains of
carbohydrates.

In their plant form, these long sugary molecules comprise six carbon atoms 
and six oxygen atoms.

But car engines like a leaner form of carbohydrate molecule -- one with 
between five and 15 carbon atoms and with very
little oxygen.

Most ethanol facilities harness biology, using enzymes to break down starch 
and cellulose to glucose, which is then
fermented by a common yeast, Saccharomyces cerevisiae, to produce ethanol and 
carbon dioxide.

But the process takes days and the fuel still has relatively high levels of 
oxygen, which reduces its energy density,
makes it evaporate readily and leaves it liable to water contamination by 
absorbing atmospheric humidity.

Distillation is needed to separate the fuel from water, and this process is 
energy-intensive.

Biofuel engineers at the University of Wisconsin at Madison believe they have 
found the answer in a process that results
in 2,5-demethylfuran, or DMF, which volume for volume delivers 40 percent 
more energy than ethanol.

In addition, it is not soluble in water and is stable in storage.

Under the process, reported on Thursday in the British journal Nature, 
enzymes rearrange the plant carbohydrates into a
highly oxygenated sugar, fructose.

The next step is to turn the fructose into an intermediate chemical, 
hydroxymethylfurfural, or HMF, by using an acid
catalyst and a solvent with a low boiling point. This expels three oxygen 
atoms.

Under the final phase, the HMF is converted to DMF by exposing it to a 
copper-ruthenium catalyst that kicks out two more
oxygen atoms and converts the gas to a liquid at a lower temperature, thus 
making it easier to use as a general fuel for
transport.

More research is needed before the technology can be commercialised, 
according to lead researcher James Dumesic, a
professor of chemical and biological engineering, who has previously won 
plaudits for work on HMF.

"There are some challenges that we need to address, but this work shows that 
we can produce a liquid transportation fuel
from biomass that has energy density comparable to petrol," he says.

Biofuels are touted as a green alternative to traffic fuels derived from oil 
and gas.

Both biofuels and fossil fuels emit carbon dioxide (CO2), the principal 
greenhouse gas blamed for climate change.

The carbon emitted by fossil fuels is pumped out of the earth, where it has 
been stored for millions of years, and so it
adds to atmospheric pollution.

But in biofuels, plants suck CO2 out of the atmosphere in order to grow, and 
this carbon is returned when the fuel is
burned.

The process is renewable and environmentally-friendlier than fossils but not 
completely clean. Energy has to be used to
harvest and process the biomass, and this makes biofuels carbon-positive, not 
carbon-neutral.

Another growing concern against biomass is the environmental impact of 
converting land, especially in Amazonia, to
growing fuel crops. In addition, the rush to biofuels is having an impact on 
some food prices, as cornfields are given
over to ethanol production.