By Paul Mason
BBC Newsnight business correspondent
Demand for oil is soaring, and with it the price - currently $46 a barrel.
The SiGen hydrogen car: Still some way to go
Discoveries of new reserves are getting thinner and the cost of production is rising, especially in the older fields.
Some believe we are reaching the beginning of the end of the oil epoch. But, they say, hydrogen cars could offer a route out of the problem.
Hydrogen technology is not new but the millions of research dollars spent in recent years may finally realise the potential, some experts believe.
"It's not a question of oil running out," says environmental campaigner George Monbiot.
"There will always be dregs stuck in the ground. But if demand exceeds supply as costs of extraction rise, we will see a very serious price crunch."
In the year 2000, total demand for oil was 3,604 million tonnes, according to the International Energy Agency.
In the richest countries, transport accounts for the biggest share, with industry and power generation dominant among the other uses.
In the developing world, there are fewer cars, so oil for transport is less important. But by 2030, the picture will have changed.
World demand will be 5,769 million tonnes, and, while the rich countries will be using an even bigger proportion for transport, the poorer countries' oil profile will look like ours does now. And it is all because of humanity's love affair with the motor car.
Cars driven by hydrogen-powered fuel cells are the much trumpeted solution.
Fuel cells turn the chemical energy stored in the hydrogen into electrical energy which drives the car. There are now several test vehicles working the open roads.
The SiGen mini I looked at recently drove like a cross between a dodgem and a Robin Reliant - but then it was just a cheap model converted to prove the concept.
The company behind the car is run by former North Sea oilmen who have seen the writing on the wall.
"Looking at field data, it was clear we were facing very serious problems with hydrocarbon production," says David McGrath, SiGen's managing director.
"There might be oil in the ground but we're not going to be able to produce it fast enough to meet demand. Something has to give. We saw hydrogen fuel-cell technology as an opportunity to displace fossil hydrocarbons - albeit very slowly, but progressively."
"The future is hydrogen"
Until the late 1990s, the big car companies dismissed the idea of fuel-cell engines. They do not anymore.
"Ford and other manufacturers agree the future is hydrogen," says Pete Pethers, director of Ford's vehicle environmental engineering department. "It's not a question of what the fuel is in the future; it's a question of the pace of change.
"We have to address the infrastructure issues; our customers have to be able to purchase this fuel to refuel their vehicles. And we also have to address the very fundamental concern of accessing this hydrogen from renewable sources, such as solar and wind.
Until the late 1990s, the big car companies dismissed the idea of fuel-cell engines
"The next phase of the Ford programme in 2007 will be to put greater quantities of these vehicles out into the market place to prove our technology, to prove there are no durability issues. If you are looking at when you could buy a fuel-cell car, you're looking at the 2010-12 timescale."
Although at the users' end hydrogen may appear abundant (it is in the H20 of seawater) and clean (zero emissions), at the producers' end, things are not so straightforward.
What is the most efficient and cleanest way to split the water? Should we use nuclear and renewable sources, such as wind and waves, to isolate the hydrogen? Or should we take the hydrogen out of fossil fuels? The hydrogen lobby cannot agree.
Last year, on the eve of the invasion of Iraq, President Bush announced a $1.2bn research programme into hydrogen fuel technology. Labelled the Freedom Car, the Bush plan sees 90% of the hydrogen coming from fossil fuels, with the other 10% from nuclear.
Sustainable energy is dismissed as too expensive. The men who put together the SiGen vehicle think otherwise.
"If we were to exploit renewable energy resources around the UK - the UK has the highest level of renewable energy concentration in the whole of Europe - we could dramatically decrease our dependence on import of fossil hydrocarbons; and have a big impact on environment and on the balance of payments," believes David McGrath.
If we really are approaching the end of the oil age, the biggest problem facing the transition is the existing infrastructure - the pipelines and petrol stations worth an estimated six trillion dollars.
Writing this off would require an economic revolution much bigger than the one Henry Ford started.
"Energy transitions take a long time," says Dr David Hart, from the department of environmental science and technology at Imperial College London.
"It's clear to see from the longevity of a Routemaster bus, for example, that once something is put in place that works well, it's difficult to change it.
"So, hydrogen transition is more a 50-year solution to the end state. That doesn't mean that somewhere along the road, in 10-15 years from now, we won't have a significant amount of energy that can be used from hydrogen.
"What we are likely to see is a much more decentralised system of energy production and distribution. At the moment, energy is produced centrally and is transported over very long distances over very large infrastructures.
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"We are likely to become personally much more involved in energy in the future. We are likely to have things attached to our vehicles and our houses to cushion us as we move away from these large, centralised schemes."
But to start the transition to a hydrogen economy, it is not enough to put public funds into researching the technology, believe campaigners.
"There has to be a clear policy signal given to consumers and companies alike. Governments would have to say, "the oil age is coming to an end and we're going to create the policy framework to make it profitable to build the new infrastructure".
"If the economy is going into recession, if the oil price keeps rising - the time to invest in all this is now," argues George Monbiot.
"But political pressure for the investment in the re-engineering of our cities and infrastructure, it isn't there yet. People don't riot for austerity; they riot because they want more, not less. We have to riot for less."