It is even doing research into hydrogen energy, which some see as a way, first, to turn fossil fuels into clean energy and ultimately as a means to replace petroleum.

"One of the most urgent tasks before applied science is the development of some portable source of power to replace petroleum - a most undesirable fuel from a political point of view"

In 1986 textiles replaced petroleum as China's largest single export item.

His campaign centred on the need to find alternative energy sources, to replace forestry products and petroleum.

It was aimed at reducing utility prices in the Russian Far East by replacing more expensive coal and petroleum at the regional power and heating plants with cheaper natural gas.

"It's up to us to develop materials and chemistries that will lead to a battery that will truly begin to replace petroleum as the principal source of fuel."

Studies show that, on paper, algal-based biofuels could completely replace petroleum as an energy source.

Because the transport sector uses the energy from petroleum very inefficiently, replacing petroleum with electricity for mobile energy will not require very large investments over many years.

Indeed, the study published by the National Academy of Sciences found that neither ethanol nor biodiesel can replace much petroleum without having an impact on food supply.

And coal could serve new uses: replacing petroleum in making chemicals, for example, or even fueling vehicles.