It's a secret just how much oil
the US military uses, but estimates range from around 400,000 barrels a
day in peacetime - almost as much as Greece - to 800,000 barrels a day
at the height of the Iraq war.This puts a single nation's armed forces
near Australia as an oil consumer and among the top 25 countries in the world today.

Either way it is by far the world's largest single buyer of oil
and the last thing any admiral, general or under secretary of defence
has had to be been concerned about is whether there's gas in the tanks
or that the navy's carbon emissions are a bit extravagant.

But
there are signs of change. Every $10 rise in the price of oil costs the
gas-guzzling US air force around an extra $600m each year. Just keeping
one US soldier in Afghanistan with the world price of oil at $80 a
barrel now costs hundreds of dollars a day in fuel alone. And because
the US as a country imports more than $300bn worth of oil a year, fiscal
reality is dawning. The US military spent around $8bn in 2004 on fuel,
and probably twice that last year. Surging world fuel prices are likely
to put the brakes on the US oil war machine as much as political
opposition.

The military knows this. Earlier this year a Joint Operating Environment report
from the US joint forces command predicted that global surplus oil
production capacity could disappear within two years and there could be a
shortfall of nearly 10m barrels a day by 2015.

"Peak oil",
said the generals, would impact massively on the US and other
economies, and the US military would be compromised. Meanwhile Wesley
Clark, former supreme allied commander in Europe, has argued strongly that America's addiction to foreign oil is unsustainable and, by extension, the military's $20bn a year spend on oil and other energy must be reconsidered.

The military answer has been to obey former President Bush and look to home. The navy's decision to convert one ship to algae-based biofuel
echoes a US Air Force plan to create a massive synthetic-fuel industry
to provide the military with guaranteed, secure homegrown supplies. One
idea is to turn America's abundant supplies of coal and biofuel crops
into liquid fuel, just as the Nazis did in Germany when its oil supplies
were cut off during the second world war. Tests are now being conducted
and the first of 6,000 navy jets are expected to fly with it next year.

Coal-based synthetic fuels, and biofuels
- from both algae and crops such as corn - are now strong contenders to
replace the fuels that the military uses to power its tanks and jet
engines, says the Department of defence . But the search for more
affordable, cleaner-burning alternative fuels is not driven by
environmental concerns and there are massive drawbacks. Coal is not just
one of the world's prime drivers of man-made climate change, but also
air pollution and acid rain.