German Car Zone

Merc1 · 06-22-2007, 02:31 AM

Chasing Cheetahs With Clean Diesel

We've been in South Africa less than three hours and we find ourselves attaching a leather collar to an anesthetized cheetah. It's clear that this is not going to be your standard road test.

The world's fastest animal is an endangered species in this part of the world and the De Wildt Cheetah Tracker program is committed to ensuring its survival. This is a fascinating project, made more interesting by its choice of support vehicle.

The project is being used as a test for Sasol-Chevron's Gas-to-Liquid (GTL) technology. Each of the Mercedes-Benz M-Class sport-utilities is powered by diesel fuel made not from crude oil but instead from natural gas. GTL diesel technology like this could have major environmental significance, especially in the U.S.

What Is GTL Diesel?

GTL diesel relies on a ready supply of natural gas. In the first stage of production, natural gas and water combine in a reforming process to produce synthetic gas (syngas). The syngas is then put through the Fischer-Tropsch process to become syncrude. This syncrude can then be distilled like traditional crude oil to produce diesel.

GTL has been available commercially since 1993, when Shell opened a GTL plant in Malaysia, but production has only recently gained worldwide momentum. Last year, Sasol-Chevron opened a new $1 billion plant in Qatar that produces around 8 million barrels per year. In 2009, Sasol-Chevron will open a second $2.5 billion GTL facility in Nigeria, and Shell expects to open a plant in Qatar.

By 2015, it's estimated that GTL will account for around 4 percent of the world's diesel.

What Are the Benefits?

Although initial tests suggest that GTL is carbon-neutral over its lifecycle, it offers a number of other, more immediate environmental benefits.

For example, GTL diesel is virtually free of sulfur and aromatic compounds, so a diesel car running on GTL reduces particulate emissions by 25-40 percent. This kind of emissions performance could help diesel engines comply with even the most stringent U.S. emissions regulations without the need for expensive after-treatment processes, such as DaimlerChrysler's Bluetec.

For the enthusiast, GTL has additional benefits. It has a cetane rating (the diesel equivalent of octane) of over 70, compared to around 50 for conventional diesel. In theory, the higher cetane rating results in improved combustion efficiency, lower emissions and improved fuel consumption, not to mention more power.

This property is already being put to the test. In some European countries, GTL is already blended with conventional diesel to create premium Shell V-Power diesel. This blend represents 30 percent of the diesel formula used to power the Audi R10 diesel that won the 2006 24 Hours of Le Mans.

And the Downside?

Just as an engine needs to be modified to make the best use of high-octane gas, so it has to be optimized for GTL. "The performance benefits of GTL are maximized when it's used as a neat fuel," says Mark Schnell, Sasol-Chevron's global marketing director, "but the engines need to be tuned to take advantage of it."

Schnell also notes, "There's a chicken-and-egg situation. Manufacturers are unwilling to commit to developing new engines unless a market develops. In the short term at least, we are likely to see GTL used to boost the quality of oil-based diesel, rather than as a neat substitute."

It's also worth pointing out that GTL continues to rely on natural gas. This fossil fuel is underutilized in some countries such as Qatar, but the world's reserves of natural gas are thought to be no greater than those of oil. It is also possible to create syncrude from biomass products, but this is not thought to be a practical, high-volume solution.

Life on the Road

At first glance you'd be hard-pressed to tell the difference between GTL and water. While traditional diesel fuel is yellowy, GTL is clear. The 2,987cc inline-6 engines employed in the Mercedes-Benz ML 320 CDI sport-utes used by the De Wildt preservation project are unmodified, yet they are noticeably quieter when powered by GTL. The exhaust has a chlorinelike smell.

My traveling companion is Deon Cilliers, the De Wildt Wild Cheetah Project's conservation manager. He drives about 4,500 miles each month, covering more than 3 million hectares of South Africa's Northern bush on a mix of tarmac and dirt roads. Sasol is a South African company and its sponsorship of the project has benefits in public relations, but it is also a source of useful real-world data. "Every 2,500 kilometers, we send a sample of oil for laboratory tests," says Cilliers, "and DaimlerChrysler analyzes the impact of GTL on the engines."

Cilliers has an enviable job. South Africa is a troubled country with racial tensions and a sky-high murder rate, but it has natural beauty and is home to some of the world's most interesting wildlife. Cilliers' job is to protect the 600 cheetahs still left in the South African wild from trophy hunters and angry farmers.

He's based at the De Wildt Cheetah and Wildlife Centre. This is around two hours' drive from Johannesburg and is home to around 80 cheetahs that have been bred in captivity and are scheduled to be returned to the wild.

The GTL Diesel Future

In the short term, neat GTL is likely to be used only in specialized public-transport applications, where the environmental benefits of the fuel could prove critical. Sasol-Chevron has engaged in dialogue with the cities of Berlin, London, Singapore and Tokyo, as well as the eco-conscious state of California. Such transportation systems would almost certainly use their own supplies of GTL in dedicated fuel bunkers.

We're probably more likely to encounter GTL in blended form. For example, it's estimated that a 30 percent GTL blend could help diesel engines pass even California's stringent emissions regulations.

In the long term, GTL won't replace oil-based diesel or gasoline, but it will be an important ingredient in a menu of different fuel options. "It's important to remember that conventional fuels will be here for a long time to come," says Schnell. As a means of improving performance, lowering emissions and reducing global reliance on OPEC countries, GTL has much to offer.

Finally, with a little help from the South African cheetah, every U.S. state might be able to sample the modern, high-performance diesels enjoyed by the rest of the world.

Chasing Cheetahs With Clean Diesel -- Inside Line

M

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