ORLANDO, Fla. –Biodiesel certainly sounds like a cleaner fuel. Who could argue against the idea of replacing “black gold” with an option made from “amber waves of grain”?

As clean as it sounds, however, biodiesel still presents a number of challenges for those who want to use it. Higher concentrations of this plant-matter-turned-power-supply happen to flow poorly in cold weather. And there is also a lack of standards governing the way any of the fuel is made.

“There’s too many feedstocks out there,” says Mark Louzon, chief engineer at Volvo Powertrain.

Most biodiesel is made with a fatty acid methyl ester, which can be found in a variety of material including soybeans, rapeseed, palm oil and canola. But one of the biggest problems is that each type of plant matter will generate a fuel with different performance properties, speakers said during a meeting of the Technology and Maintenance Council.

When compared to some of its counterparts, a formula made with palm oil is more likely to crystallize in cold weather, explained Tom Weyenberg of Lubrizol, which makes fuel additives. A fuel made from soybeans will flow better in cold weather, but its poor “oxidative stability” can leave a lacquer inside an engine’s injectors.

“A manufacturer can swing his plant from soybeans to tallow if the price of soybeans goes higher,” he added. Buyers will probably have no way of knowing which of the commodities was used.

The concentrations of the fuel can also make a big difference in the way the biodiesel performs. At the extreme end of the offerings, a B100 mixture -signifying that it is 100% biodiesel -contains 11% less energy than the same volume of ultra low-sulfur diesel (ULSD). The cloud point and cold filter plugging point will also rise along with any increase in the amount of biofuel.

“Flow improvers” may be able to address the latter challenge in mixtures up to a concentration of B10, but there are limitations in mixtures that are more concentrated than that, Weyenberg says.

Of course, any fuel requires additives. Today’s ULSD includes “lubricity improvers” to reclaim some of the lubricating properties that are lost when sulfur is removed from traditional diesel. A “conductivity improver” is also needed to ensure that static electricity is not a safety issue at fueling terminals. But Louzon warns fleets against selecting their own additives to address the different challenges.

“It’s really important that it’s done at the refineries or your fuel terminal, but not in your tanks,” he says.

Meanwhile, there are also challenges relating to the tanks that hold the fuel. Biodiesel may act as a great detergent, but that means it can also attract the water bottoms in a fuel tank, depositing all of these nasty contaminants into a fuel filter.

“You have the possibility of having three things that microbes like most: fuel, water and heat,” Weyenberg adds, referring to the conditions in some heated storage tanks. “The hygiene of the fuel storage system now becomes more important.”

“It has a short shelf life when compared to the diesel you’re used to,” Louzon adds, noting how a supply of B20 might last as little as six months.

Regardless, there is only so much biodiesel to go around in the short term. The 1.7 billion litres that were generated in 2007 still represents a mere 0.7% of the overall diesel supply in the US, Weyenberg says. “Nearly half of what was used as B100 and exported to Europe.”

He suggests that the future of such fuels will probably be found in the form of a “synthetic” diesel created with products including chicken fat, beaks and feet. (Tyson and ConocoPhillips have teamed up in a deal to produce this mixture). Unlike the biodiesel of today, it is almost identical to traditional diesel, and it is produced right at the refinery level, he says.

“In a decade, these might go from the research stage into the pilot stage.”

The research into potential standards also continues. Engine manufacturers are in the midst of creating tests for B20 fuels, to determine the fuel’s impact on piston deposits, valve train wear and piston cylinder wear. The ASTM has set standards of its own (see the article on the following page for details).

This continuing focus -and the political will behind it -suggests that biodiesel will live on as an alternative fuel supply for years to come. •