One of these natural hydrogen fields is already known to exist in North America, and extends from Canada to Kansas.

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THE world’s energy problems could be over after the discovery of vast quantities of hydrogen gas, widely regarded as the most promising alternative to today’s dwindling stocks of fossil fuels, in the Earth’s crust.

The find by scientists has stunned energy experts, who believe that it could provide virtually limitless supplies of clean fuel for cars, homes and industry.

Governments across the world are urgently seeking ways of switching from conventional energy sources such as coal, gas and nuclear power to cleaner, safer alternatives. Energy specialists estimate that oil production will start to decline within the next 10 to 15 years, as the economically viable reserves start to run out.

Hydrogen gas has been hailed as the ultimate clean fuel, as it produces only water when burned. Until now, however, moves to switch to a “hydrogen economy” have been dogged by the cost of making the gas. The two most common ways – extraction from natural gas and sea water – are expensive and create environmental problems.

Now scientists at Nasa, the American space agency, have found that the Earth’s crust is a vast natural reservoir of hydrogen which has become trapped in ancient rocks.

The team made its discovery while trying to explain how bacteria live many miles below the Earth’s surface. Such bugs have no access to sunlight, forcing them to rely on another source of energy for life. Scientists suspected that hydrogen was the source.

According to Professor Friedemann Freund and colleagues at Nasa’s Ames Research Centre, in California, the gas is produced when water molecules trapped inside molten rock break down to release hydrogen. “In the top 20km of the Earth’s crust, the conditions are right to produce a nearly inexhaustible supply of hydrogen,” said Prof Freund.

Studies by the team of common rock types such as granite and olivine have revealed extraordinarily high levels of trapped hydrogen. Prof Freund told The Telegraph that his team had “tantalising evidence” that as much as 1,000 litres of hydrogen may be trapped in each cubic metre of rock.

Although formidable engineering problems remain to be overcome in abstracting the gas, the sheer volume of the Earth’s crust means that such a high concentration would solve the world’s energy problems.

“Everyone thinks of gas and oil as the main sources, and it’s very difficult to get anyone to take alternatives seriously,” said Dr David Elliott, the professor of technology policy at the Open University. “The possibility of vast reserves of hydrogen in the Earth’s crust could change that mindset.”

The daily energy needs of the UK road vehicle fleet could be supplied by the hydrogen trapped in a cubic mile or so of rock.

“The key factor is whether the energy in the mined hydrogen would ever outweigh the energy required to extract it,” he said.

Prof Freund believes that the extraction and crushing of rock to extract the trapped hydrogen is likely to be prohibitively expensive. The reaction which creates the gas takes place at depths far below those involved in oil extraction, which are typically about two miles down.

The most promising source of the hydrogen may be geological “traps” similar to those now drilled for natural gas. Prof Freund said: “One of these natural hydrogen fields is already known to exist in North America, and extends from Canada to Kansas.”