NATURE: Plant-to-oil equations point up unsustainable profligacy
- Calculations illustrate fossil-fuel crisis: Plant-to-oil equations point
up unsustainable profligacy.Calculations illustrate fossil-fuel crisis
Plant-to-oil equations point up unsustainable profligacy. 29 October 2003
If you burned a litre of petrol on the way to work this morning, consider
this: it took 23.5 tonnes of ancient, buried plants to produce. That's
the equivalent of 16,200 square meters of wheat, roots and stalks
included. So says new research that aims to raise awareness about the
need to change our energy-consumption habits. The long, slow process that
converts plant matter into oil is extremely inefficient, says ecologist
Jeff Dukes of Carnegie Institution of Washington, Stanford, who did the
calculations. Less than one part in 10,000 of the organic matter becomes
"So much carbon is lost back to the atmosphere through decomposition,
it's only the residues that are turned into fossil fuels," says Dukes. He
warns that less than a tenth of the carbon in plants buried in peat bogs
was turned into coal1.
In 1997, he points out, we burned fossil fuels equivalent to more than
400 times the amount of plant matter produced on Earth in the same year.
Despite these inefficiencies, fossil fuels created over the past 500
million years have given us a relatively inexpensive fuel source for the
past 250 years. "It is fantastic stored free energy from the past, but
it's not sustainable," Dukes says. Modern ways to convert biomass into
fuels such as ethanol are far more efficient. But it would still take
nearly a quarter of all the plants on Earth to replace the fuel used in
1997. That's 50% more than humans already remove or pave over each year,
says Dukes. "Hopefully we'll use more wind and solar power," he suggests.
It's a valid point, says geologist Sandra Neuzil of the US Geological
Survey in Reston, Virginia, who studies peat decomposition. But she is
cautious about the many unknowns in such equations, saying: "When you
start multiplying uncertainties the numbers start to become meaningless."
Dukes acknowledges that his calculations have a large degree of
uncertainty, but believes he has captured the essence of the process.
"I'm hoping that it will make people think," he says.
Dukes, J. S. Burning buried sunshine: Human consumption of ancient solar
energy. Climatic Change, published online, (2002). |Homepage|
� Nature News Service / Macmillan Magazines Ltd 2003
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