Let's Talk About Diesel

Diesel began with Rudolf Diesel who, after several false starts, successfully developed his compression ignition engine in the 1890s. Though Diesel himself died in mysterious circumstances in 1913, the new engine quickly replaced steam engines and gained a reputation for greater fuel efficiency than its rivals, as well as greater durability and a longer service life. 

These qualities quickly made it a favourite for heavy duty use; marine was an early technology adopter, followed by rail and the heavy goods sector of road transport. Durability and lower running costs also appealed to the construction and extraction sectors and, ultimately, diesel was used for electricity generation. Diesel received a further boost during the Second World War when it was recognised by the military as a less flammable drivetrain technology than petrol alternatives; a status which it retains to this day.

The limitations of diesel technology, particularly in terms of noise and performance when compared to petrol alternatives, meant that diesel took a far greater time to establish itself in the passenger vehicle market. However, European car manufacturers, most notably Mercedes-Benz, further developed diesel technology to be competitive in the passenger vehicle space and at the high end of the market, not simply in the pick-up, run around segment. Diesel technology for passenger vehicles received its final stamp of approval when European governments employed fiscal incentives to dieselize the passenger vehicle fleet. It was a concerted effort to reduce emissions, particularly CO2, by exploiting diesel’s greater fuel efficiency but this uncritical endorsement proved to be a double-edged sword.  

Just as the march of diesel seemed unstoppable, the technology suffered two serious reverses; air quality issues, where it was deemed to be a major cause of pollution, and the emissions testing scandal, which broke in 2015 when the United States Environmental Protection Agency issued a notice of violation of the Clean Air Act to the Volkswagen Group for emissions test-related irregularities. From being a transport fuel answer, in the eyes of many, diesel became a transport fuel problem, however, diesel technology is such an irreplaceable global workhorse that the challenge is how to make diesel cleaner. This challenge has been taken up by the global energy sector and has resulted in the development and provision of real commercial alternatives which are in the market and making a difference today. At the forefront of this revolution is paraffinic diesel made using the Gas to Liquids (GTL) process and one of the family of synthetic fuels.

The drawbacks of traditional crude-derived diesel, now often referred to as petro-diesel to distinguish it from the much cleaner paraffinic diesel alternative, were recognised by both the automotive sector and the fuel producers in the early 2000s. In Europe, they formed the Alliance for Synthetic Fuels in Europe (ASFE), which still exists. ASFE promotes the adoption of cleaner synthetic fuels as the next essential change in emissions reductions following the capture of most of the mechanical reduction opportunities. Unfortunately, the case for synthetic fuels achieved little traction at this time because the focus was entirely on CO2 reduction, where GTL is only a marginal (though positive) player. With the emphasis now shifting to air quality, regulatory focus has now broadened. The synthetic fuel sector has been fully vindicated in its original view that air quality matters, that it is a major public health issue and that it cannot be ignored. As the Euro VI fuel specifications and the International Maritime Organisation’s IMO2020 sulphur reductions programme demonstrate, regulation now reflects this reality too.

What gives GTL paraffinic diesel its unique edge in this environment is the combination of its chemical qualities and its versatility which meets the requirements of regulators and consumers alike.

The two primary characteristics of GTL paraffinic diesel are a zero-sulphur content and a very high cetane value (in excess of 70 compared to the traditional 48 -52 of petro-diesel). The zero-sulphur quality is a function of the production process which requires the removal of sulphur from the natural gas feedstock in order to protect the catalyst. Consequently, GTL effortlessly improves on the sulphur profile of Ultra Low Sulphur Diesel (ULSD), which is generally fifteen parts per million or less. GTL offers substantial emissions reductions of sulphur dioxide (SO2) and Particulate Matter (PM), making it a contender in premium markets with stringent emissions standards. Further, the zero-sulphur quality gives the refiner an easy option to instantly blend fuels with higher sulphur content down to the required compliance values without having to retrofit a refinery. It is a quick, easy and cost-effective way to achieve an instant fuel quality improvement win and access markets which would remain closed to any fuel which failed to meet the required standard.  

The high cetane value builds on GTL’s zero-sulphur qualities and delivers an emissions win for the environment and a performance win for the consumer. Essentially the high cetane level allows for a more complete burn which considerably reduces emissions of Particulate Matter and unburned Hydrocarbons (HC). Hydrocarbons and Particulate Matter (also known as ‘Black Smoke’) are two of the most significant contributors to poor air quality. Research carried out by DaimlerChrysler (as was) in 2003 recorded reductions of almost 90% and 40% respectively when comparing neat GTL with a standard Euro diesel (Environmental Excellence - Effect of GTL Diesel Fuels on Emissions and Engine Performance, Daimler 2003). Even when used as a blendstock, GTL’s high cetane value enhances the quality of the blend and achieves emissions reductions that are disproportionate to the GTL component of the blend. For example, the Daimler study also tested a 50:50 GTL/Eurodiesel blend which still managed to deliver approximately three quarters of the emissions reductions in Particulate Matter achieved by the neat fuel.  

Global GTL production is not currently sufficient to sustain such an exercise, however, were the world to theoretically switch entirely to GTL paraffinic diesel, large scale emissions reductions would be delivered literally overnight. Further, such a move would not face any technical obstacles since GTL paraffinic diesel can be used in existing diesel engines and can be distributed using existing distribution systems. Though not yet global, GTL paraffinic diesel is available in neat form in some parts of the world, most notably the United Kingdom. It is a fleet-fueling option for environmentally aware operators looking to reduce their emissions footprint, particularly in the London area, and to build both their business and their reputation by doing so. Neat GTL users also enjoy the performance advantages of a premium, high-performance fuel, which include prolonged lubricant life and less build-up of residues in the engine. This, in turn, reduces engine wear. There is also noticeably less smoke and less noise and, in the event of a spill, bio-degradable paraffinic diesel is far more benign than traditional petro-diesel, including being less of a slip hazard. A valuable quality in any environment, this is an invaluable quality in sensitive marine environments where GTL is likely to figure prominently in the future.

The global fuel slate is changing and it is now clear that the future will be a mix of multiple fuel solutions, each tailored to specific demands imposed by geography, application and user requirements. Because of its versatility and diversity, diesel technology will be part of that mix but the diesel emissions profile of the past has no place in the present, much less the future. The development of high performance, low emission premium compression ignition fuels like GTL has a critical role to play in making diesel technology fit for purpose in the twenty first century. 

The future of energy is about smart technology making cleaner fuel, a description which fits GTL paraffinic diesel exactly. Over a century after Rudolf Diesel’s death, GTL is making his creation work in the modern era.