Could Synthetic Diesel From Coal be Viable?

Arguably, the fuel with some of the most apparent environmental promise is diesel – but not diesel as we know it.

One of the biggest challenges facing many alternative fuels is not their technological development. It is the fact that their mainstream use would require the reinvention of delivery infrastructure required to get the fuel from point of manufacture to the vehicles.

Hydrogen is a prime example. An efficient delivery system for it has get to be contrived, and will require substantial investment if it is. Every service station on Planet Earth will need an extreme makeover … and current engine technology – plus the vehicles that embody it – will be obsolete.

A smoother segue to greener pastures would be to produce fuels compatible with today’s infrastructure and vehicles, using sustainably sourced materials.

It’s happening now. Synthetic diesel is being manufactured using the carbon and hydrogen in ‘biomass’ (see below).

Choren Industries ( in partnership with DaimlerChrysler and Volkswagen have developed SunDiesel, which has not even a whiff of fossilised anything about it. Choren is a pioneer in synthesising hydrocarbons from biomass – without the pesky several-million-year wait (or impurities) Mother Nature prefers. Choren’s process, called BtL, or ‘biomass-to-liquid’, converts biomass into synthetic diesel in a two-stages. First, the biomass is reduced to a simple ‘synthesis gas’ – a mixture of hydrogen and carbon-monoxide. Then, in a tongue-twisting operation called Fischer-Tropsch Synthesis, synthesis gas is converted to synthetic SunDiesel.

It’s important to remember synthetic diesel is completely different to biodiesel, which is produced from rapeseed oil and requires engine mods before it can be used. SunDiesel, in comparison, is able to be used without modification in modern production diesel engines. It’s the same as conventional diesel – only better.

SunDiesel has advantages beyond carbon-neutrality. Its properties can be more precisely engineered than fuels produced at crude-oil refineries. In fact they can be tailored precisely to minimise emissions, which virtually eliminates particulate emissions, sulphur and oxides of nitrogen.

Particles from fossil-based diesel is a particularly touchy subject. The particles in question are invisible, measuring between less than 2.5 microns (millionths of a metre). These penetrate deeply into the lungs and are thought to be “strongly associated with adverse health effects”, according to the Medical Journal of Australia. The World Health Organisation says “diesel engine emissions contribute disproportionately to the very-small-particle fraction of urban air pollution”.

SunDiesel could easily prove a boon to health in the developed world. In a prototype 103kW SunDiesel-powered Volkswagen Golf, carbon-monoxide emissions dropped 23 per cent, hydrocarbon emissions fell 34 per cent, oxides of nitrogen fell 68 per cent and particulates were cut by a staggering 90 per cent, all compared with conventional diesel. A lifecycle assessment of SunDiesel commissioned in part by Volkswagen found similar dramatic emissions reductions across all stages of the SunDiesel process from raw material extraction to ultimate use.

In its Sustainable Development Progress Report, the German Government said: “In the medium to long term, a new generation of biofuels produced synthetically from biomass exhibits the greatest potential because […] high-quality diesel can be produced from any kind of biomass – such as waste, plant or wood.”

The current production cost (not the pump price) of SunDiesel is around AUD $1.17 per litre, which means cleaner, greener SunDiesel could be coming soon to a bowser near you. Choren Industries is currently building the world’s first commercial BtL plant in Freidberg, Saxony. If completed on schedule it will pump out 15,000 tones of BtL fuel annually from the end of this year, with the company targeting 1 million tonnes annual production in Germany alone, with international markets currently under consideration.



  • In countries like Spain and France, 60 per cent of all new cars sold are currently diesels. The average for Europe is about 50 per cent. In Australia in the 12 months to March 2007, diesels made up just four per cent of private passenger car sales, but that represented a growth of 143 per cent on the previous 12 months.
  • Modern diesels produce 100 per cent more torque, 60 per cent less noise, 90 per cent lower emissions and 30 per cent greater economy, compared with an equivalent 1988-spec diesel engine. The improvement is down to hi-tech engine management, piezo-electric injectors and a ‘common’ fuel rail running at pressures as high as 1800 atmospheres.
  • The diesel you buy at the pump today is, like petrol, a product derived from the refining of crude oil. Most people are aware that petrol is, notionally, a chemical called octane. And most propeller-heads know that octane is comprised of eight carbon atoms and 18 hydrogen atoms. Petrol is, in fact, a cocktail of hydrocarbons that approximates the behaviour of the chemical we know as octane.
  • Diesel is heavier than petrol, containing an average of 12 carbon atoms and 26 hydrogens. That makes it boil at a higher temperature, which is how they separate it from petrol, kerosene, bitumen and all the other petrochemical ‘fractions’ jumbled up in crude oil.
  • Most people have heard of ‘octane number’ or ‘octane rating’, which is an indicator of how easily petrol burns explosively rather than in a controlled manner. Diesel has a similar rating, called a ‘cetane’ rating.
  • On January 1, 2006, stringent new ‘Euro 4’ fuel quality standards came into force here. The sulphur content of Australian diesel dropped by an incredible 90 per cent, from 500 parts per million to just 50 parts per million. Many diesel cars previously available in Europe (which adopted this fuel standard earlier) became compatible with the Australian market overnight.




Almost anything will do – wood, forestry waste, quick agricultural crops like straw, corn … anything green, basically. Even waste products like paper can be used. Choren industries says the main player here, long-term will be the agribusiness sector. The company estimates that the European Union, for example, could currently grow sufficient biomass for the production of 70 million tonnes of synthetic fuel annually without compromising its food production. So, in other words, biomass production could well open up substantial new agricultural markets, making farmers a significant force in the 21st Century energy equation.



Synthetic diesel is not new. It’s already produced around the world by a gas-to-liquid (GtL) conversion process that captures natural gas (formerly ‘flared’ on oil platforms because it was considered a waste product). Industrial-scale GtL has been performed since 1993, and today Shell operates the largest GtL plant in the world in Malaysia, which produces 6.5 million tonnes annually. Oil companies Chevron and Sasol are currently building a GtL plant in Nigeria designed to produce 1.5 million tonnes per annum.

As promising as GtL seems, however, like fossil-based diesel it is sustainably hamstrung by its inability to achieve carbon-neutrality. You need to keep sucking on crude oil to make it.


fuelJohn CadoganComment