Energy

About synthetic fuels

Synthetic fuels are derived from fossil fuel deposits other than petroleum including coal, gas and oil shale.

A range of processes are available or in development to produce liquid fuels that can be 'dropped in' to replace fuels conventionally obtained by refining oil. These processes include coal-to-liquids (CTL), gas-to-liquids (GTL) and shale-to-liquids (STL) technologies.

CTL

Coal-to-liquids (CTL) is the production of fuels and petroleum products using coal as feedstock.

There are two broad streams of CTL technology:

• direct liquefaction—which involves either carbonisation or hydrogenation processes and converts the coal directly into a syncrude without the need for an intermediate stage.

• indirect liquefaction—in this process, coal is subjected to intense heat and pressure to create a syngas which is treated to remove impurities and unwanted compounds such as mercury and sulphur. The syngas is then converted to syncrude in the same way as a GTL process. Syncrude produced by this method is essentially identical to that produced through GTL processes and can therefore be further refined or blended in the same way.

Underground coal gasification involves combusting coal in situ which produces a syngas without the need for a specialised plant.

GTL

Gas-to-liquids (GTL) technology enables the conversion of natural gas into high-value liquid fuels (including methanol, dimethyl ether (DME), and middle distillates), specialty chemicals and waxes.

GTL production involves the initial conversion of natural gas into synthesis gas (syngas) which is a mixture of hydrogen and carbon monoxide. The syngas is then converted into synthetic crude (syncrude). A common method of syngas conversion is the Fischer-Tropsch process which has existed since the 1920s. The resultant syncrude can then be further refined in its own right or used as a refinery blendstock.

Of the various GTL products, the focus of recent Australian proposals has been the production of GTL middle distillate (diesel and jet fuel). Fuels produced by a GTL process are ultra clean with low emissions of particulates, oxides of nitrogen and sulphur, and hydrocarbons. GTL offers a value added pathway to commercialisation of Australia's large, undeveloped gas reserves.

Shale to liquids

Oil shale (also known as kerogen) is rock that was developed long ago from the deposition of organic sediments occurring in ancient lake environments. Over time, with pressure and high temperature, the mixture of organic-rich sediments was transformed into oil shales.

Shale oil is the common name for oil produced from this rock, but fuels produced from this product could also be described as shale-to-liquids.

More information

For more information about synthetic fuels email TransportFuels@ret.gov.au.