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Alternative fuels: Using biodiesel in off-highway engines

As researchers look for the fuels of the future — alternatives that are both better for the environment and reduce dependence on petroleum products — they’re finding answers in the past.

“Biofuels, which are produced from plant oils, have been around since the 1800s,” says Anton Zimmermann of Caterpillar’s engine research division in Europe. “Dr. Rudolf Diesel actually invented the diesel engine to run on a variety of fuels — including vegetable oil.”

When Diesel showed his engine at the World Exhibition in Paris in 1900, it was running on 100 percent peanut oil. The fuel source switched to petroleum because at that time it was cheap and available. Today, researchers are taking another look at biofuels.

Zimmermann, a 6 Sigma Black Belt, focuses on liquid biofuels and how they can successfully be used in Caterpillar diesel engines. Caterpillar has been researching First Generation biofuels since the mid-1990s. Research also has begun into next-generation biomass-to-liquid fuels (BTL), which use the whole plant matter instead of just extracting the plant oil.

“We’re looking at our fuel systems, making sure they meet current and future regulations — and that they will also be compatible with biodiesel,” says Zimmermann.

Why biodiesel?

Zimmermann cites three key drivers to the production of biodiesel that will influence the legislation and targets set by governments, as well as the types of fuels that will become commercially available:

Meeting standards

Europe is leading the way in setting targets for the reduction of carbon emissions and the use of biofuels and other renewable fuels for transport. The 2005 target was a 2.5 percent substitution of diesel and petroleum with biofuels; the 2010 target is a 5.75 percent substitution. In North America, the United States and Canada targeted a 5 percent displacement by 2010. The United States also has called for doubling the use of renewable fuels.

Impact on machines

First Generation biodiesel runs in any unmodified diesel engine. Caterpillar customers — including many in the mining industry — are using blended biofuels on sites around the world. “Our position right now is that the Caterpillar C7 and bigger engines can use 30 percent biodiesel quite happily,” Zimmermann says. “Some customers have found a cost benefit of using it at 100 percent, but there are issues beyond a 30 percent blend that engines right now are not designed for.”

Potential issues must be managed by the customer through the use of good quality fuel and fuel handling. Fuel management is essential to avoid oxidation, biodegradation and microbial growth. Biodiesel must conform to EN14214 or ASTM D6751 specifications.

“You must be very strict about the quality of fuel,” Zimmermann says. “Without fuel standards, we can’t know what the engine will experience.”

Biodiesel’s lower energy content may affect performance, but Zimmermann says research to date shows that the loss of power is negligible. “In a field trial that was part of a 6 Sigma project in Germany, we monitored a wheel loader using 100 percent biodiesel in a low-load situation,” says Zimmermann. “The operator couldn’t tell a difference. So it’s really application-specific. And even then it’s an 8 to 10 percent reduction in power.”

“Again, the main thing to be aware of is fuel quality,” he says. “You must make sure to use high quality fuels that conform to standards and are accredited.”

What's ahead?

While the peak potential for worldwide use of First Generation biofuels is about 5 percent, research into Second Generation biofuels (biomass to liquid) increases that potential to 30 percent, Zimmermann says.

Next-generation fuels use a method called the Fischer-Tropsch process to turn the whole plant matter into a liquid fuel. “These fuels are very good for combustion and emissions — with no drawbacks,” he says. “And they should require no changes to our engines.”

Zimmermann doesn’t expect BTL fuels to be available until at least 2015. “Right now, no one is doing BTL commercially because it is very expensive,” says Zimmermann. “We need a supply chain to exist. Economies of scale are important because the capital investment to build a suitable facility is very high. The process will need a site the size of a traditional oil refinery.”

Through its Perkins Engines Company, Caterpillar has partnered with the Carbon Trust to link its diesel engine research with next-generation biofuels. The Carbon Trust is an independent UK government funded body that works with UK businesses and the public sector to cut carbon emissions and develop commercial low-carbon technologies.

Caterpillar is working to ensure that its new advanced combustion strategies — designed to reduce emissions — are compatible with the promising BTL fuels.

“This project is linking research into advanced diesel combustion and the next generation of biofuels so that the ideal BTL fuel for this combustion process can be determined.” Zimmermann says.

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