By Gregg Hennigan (for REG)
The frigid temperatures much of the U.S. and Canada are experiencing serve as a reminder of one of the more persistent myths about biodiesel: it does not perform well in the cold.
That’s simply not true. Science has proven it, and so have fleets everywhere. From New England to the Rocky Mountains and up into Canada, fleets run their diesel vehicles on biodiesel blends all year.
“With high-quality biodiesel, there’s almost no effect on cold weather operations with blends of 5% and below,” says Dave Slade, Executive Director, Biofuel Technology and Services at Renewable Energy Group, Inc. (REG), a leading biodiesel producer and supplier based in Ames, Iowa. “And even in the heart of winter, many fleets use up to a 20% blend. Biodiesel can gel in very cold temperatures, but the same is true of petroleum diesel.”
Proper additive use, storage and blending methods will help fuel marketers and fleets keep their operations running smoothly in the cold. The payoff is potentially significant. Not only does biodiesel often make good financial sense to marketers and fleets, its low emissions help organizations meet both their own and their customers’ environmental goals—an important issue as the sustainability trend continues to grow.
Cold Flow Facts
First, here’s a quick review of some cold flow basics, which apply to petroleum diesel and biodiesel:
- Cloud point: Temperature at which wax crystals first appear in the fuel
- Cold filter plugging point (CFPP): Indicator of cold weather operability
- Pour point: Lowest temperature that fuel continues to flow
Cold flow properties vary based on several factors, including the source of the crude oil, the feedstocks used to produce the biodiesel, the quality of the fuel, geography and more. Pure biodiesel, or B100, freezes at a higher temperature than most No. 2 Ultra-Low-Sulfur Diesel (ULSD), and untreated B20 usually freezes 2 – 10 degrees Fahrenheit (°F) faster, according to the National Biodiesel Board (NBB).
“What’s important to remember is that blends up to B20 can be used successfully in cold weather with winter additives,” Slade mentions. “Fuel marketers and fleets that operate in cold weather are already well versed in using winter additives with petroleum diesel.”
Slade offers these tips for using additives with biodiesel blended fuel:
- Use quality winter additives designed for biodiesel blends. Additives used in straight petrodiesel may not be the right solution.
- Use in-line blending to ensure the best mix.
- Keep the bulk fuel warmer than the additive’s handling temperature. Otherwise, the fuel can chill the additive and prevent good mixing.
- Introduce the additive while the fuel is in motion and at a temperature high enough to ensure both the additive and the fuel flow easily. The minimum handling temperature should be provided by the additive manufacturer. If the additive is denser than the fuel, add it to the top of the tank. If it’s less dense, add it to the bottom of the tank.
Many cold flow improver (CFI) additives are viscous, so it’s important for them to be warm enough that they mix well.
“If this does not happen, the CFI can concentrate in one part of the tank and cause issues,” Slade advises.
To test an additive’s effectiveness, place a small additized fuel sample in a refrigerator for one day. If particles or residue develop, make a new sample with more additive and try again. If the additive shows no effect at a level of 1 ounce per 3 gallons, consider switching additives.
It’s important to know the cold weather specifications of both your base diesel fuel and biodiesel before blending. For biodiesel, that should include the monoglyceride content, cold soak filtration test time and cloud point. A respectable supplier will provide a Certificate of Analysis that includes the product’s properties. That certificate isn’t always available with petroleum diesel from a terminal, but blenders should know the cloud point and/or CFPP of the diesel.
When it comes to the actual blending, try to blend the biodiesel and petroleum diesel at least 10°F above their respective cloud points. Also, the warmer the biodiesel, the better it will blend, with 70°F or above being ideal.
“If you are blending warm biodiesel into petrodiesel, that’s a good time to also mix in the additive,” Slade says. “The biodiesel will help the additive disperse throughout the fuel.”
The cloud point of the biodiesel blend will determine the storage temperature of the fuel. For blends up to B20, heated and insulated tanks are not typically needed except in extremely cold climates. It is recommended that B100/B99 be stored in heated and insulated tanks.
Extra precaution is needed in extreme cold. Above-ground storage and handling systems—including pipes, tanks and pumping equipment—should be protected with insulation, agitation, heating systems or other measures if temperatures regularly fall below the cloud point.
A good rule of thumb is to store biodiesel blended fuel at least 10°F warmer than its cloud point. This is less critical for tanks used consistently, or ones that can be recirculated or heated.
Many fuel marketers and fleets are aware of distillation because of its use in oil refineries. The purification process is relatively new to the biodiesel industry, and distilled biodiesel is already generating a lot of interest because of its many benefits. These include the end product’s purity and low carbon intensity score, but perhaps the biggest advantage of distilled biodiesel is its cold weather performance.
Compared to the traditional method for purifying biodiesel, distillation does a better job of removing minor components that cause filter-plugging issues. This gives distilled biodiesel advanced cold weather properties. Even at a higher cloud point, distilled biodiesel can outperform undistilled low-cloud biodiesel in cold weather.
“We’ve also found that, with the superior removal of minor components, distilled biodiesel offers a little more flexibility on additives and can be stored closer to the fuel’s cloud point—about 5°F warmer compared with 10°F for undistilled biodiesel,” Slade comments.
Fleet Uses B20 All Year
So, what does cold weather biodiesel use look like in the real world? G&D Integrated is an Illinois-based for-hire carrier and third-party logistics provider. It has a fleet of over 400 vehicles travelling up to 26 million miles a year.
G&D Integrated started using biodiesel blends several years ago, thoroughly testing the fuel and finding it had no negative effect on performance. In fact, the increased lubricity helped with engine functionality, and the lower emissions emitted by biodiesel helped with their sustainability goals. G&D Integrated enjoys those benefits all year round, even during the Midwest’s freezing winter months.
The key, according to Vince Buonassi, the company’s Group Manager of Transportation Programs, is getting high-quality fuel, understanding cloud points and blending it properly.
“We ran on a B20 blend throughout all of last year, and we didn’t have any engine issues,” says Buonassi. “We didn’t have one clogged filter. We didn’t have any gelling.”