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Wednesday, July 18, 2018

Australian energy exports

Japan intends to establish a "hydrogen pipeline" to replace its existing imports of energy from Australia and elsewhere.
Hydrogen is the key to energy security and the fight against global warming

To speed up the development of a "hydrogen pipeline" for Japan, Australia may be able to adapt existing energy infrastructure for the purpose.

Hydrogen produced by renewable energy creates a number of challenges for special-purpose overland transport and shipping. An interim processing strategy can skip over these challenges and re-use existing infrastructure, saving time and money. A little chemistry explains how this can work...

When hydrogen is combined with carbon dioxide to form methane and water, the energy content in the methane is about the same as the energy that was present in just the hydrogen:

CO2 + 4H2 → CH4 + 2H2O

In the above reaction half of the hydrogen combines with oxygen from the carbon dioxide to form water. The other half of the hydrogen combines with the carbon from the carbon dioxide to form methane. This is known as the "Sabatier reaction". It is used commercially by Audi to create "e-gas" for its Compressed Natural Gas vehicles.

Natural gas is essentially methane with smaller amounts of other gases such as carbon monoxide and ethane. Methane made from hydrogen can be transported through natural gas pipelines and shipped as LNG - liquefied natural gas - from Australia to Japan using existing LNG terminals and LNG tankers.

When methane is combined with water to form hydrogen and carbon dioxide, the energy content in the hydrogen is about the same as the energy that was present in just the methane:

CH4 + 2H2O → 4H2 + CO2

In the above reaction oxygen from the water combines with carbon from the methane to form carbon dioxide. All the hydrogen that was part of both the methane and water is separated. This is known as "Steam Methane Reforming". It is widely used in industry to manufacture hydrogen from natural gas.

The carbon dioxide produced in the above reaction may be liquefied in Japan and returned to Australia on the empty LNG ships that delivered the methane.

This allows the carbon dioxide to be re-used indefinitely in Australia to convert hydrogen to methane for shipping to Japan using existing natural gas pipelines, LNG terminals and tankers.