Improving Operability in Cold Temperatures

Updated: Feb 2

The latest edition of the Biodiesel Handling and Use Guide is a valuable resource for those who blend, distribute or use biodiesel.

Winter comes with plenty of transportation challenges, from frozen roads and frigid temperatures to blizzards that can shut down cities. While we can’t prevent frosty weather, we have proven solutions to ensure cleaner fuels keep engines performing when the temperature drops.

All diesel fuels, including biodiesel, can freeze or gel if temperatures drop low enough. If this happens, it can lead to various operational issues, including clogged fuel filters, fuel-system damage and reduced engine performance. The ability of the fuel to flow and perform adequately in low-temperature conditions is called cold-flow operability, and understanding it is vital to keeping your fuel flowing properly.

These challenges are regularly studied by institutions such as the National Renewable Energy Laboratory and others, with support from Clean Fuels Alliance America, the national trade association representing biodiesel, renewable diesel and sustainable aviation fuel (SAF). NREL and Clean Fuels work to support and publish research that is useful to users, fleets, blenders, distributors and others who handle and use biodiesel and biodiesel blends.

NREL’s latest edition of the Biodiesel Handling and Use Guide is just such a publication. The guide serves as a background and resource for those who blend, distribute and/or use biodiesel and biodiesel blends. It provides essential information on biodiesel’s proper and safe use in compression-ignition engines, home heating-oil systems, boilers and more.

The guide outlines important low-temperature performance metrics for handling and blending biodiesel, including cloud point, cold filter plugging point (CFPP) and pour point.

The cloud point is the highest temperature at which wax begins to form and small, solid crystals can first be observed, giving the fuel a cloudy appearance. This is important because solidified waxes can clog filters and negatively impact engine performance.

CFPP, another critical metric, measures the lowest temperature at which diesel fuel will freely flow through a standardized filtration device when cooled under certain conditions. Winter operability of diesel fuel, including biodiesel, is often benchmarked by CFPP testing.

And finally, pour point is the lowest temperature at which fuels can be poured or pumped. The pour point is an indicator for distributors to determine if the fuel can be pumped, especially if temperatures are unsuitable for diesel engines.

If you’re facing challenges related to cold-flow operability, here are a few helpful tips to ensure a sustainable and smooth transition for using biodiesel in the winter months.

Store vehicles or equipment in an enclosed area, such as a barn or garage, during the winter months to protect the fuels in diesel engines from the cold. If equipment and fuel must be stored outside, keep the fuel clean and dry. This will help keep the fuel tank warm and improve engine start up. Most fuel blends containing 20 percent biodiesel (B20) can be stored underground without additional consideration because underground-storage temperatures are normally above 45 degrees Fahrenheit.

Blend biodiesel with No. 1-grade diesel, which has better cold-flow properties. By blending with increased volumes and percentages of No. 1 diesel, or kerosene, the finished fuel blend will achieve improved cold-weather performance while promoting renewable fuel use.

Use specialized fuel additives to prevent gelling and wax crystallization at low temperatures. Clariant, the leading provider of cold-flow additives for middle-distillate fuels, is in the final development stages of an additive that will provide the same operability that you can expect from a winterized diesel fuel, even for blends up to B50. Not all cold-flow fuel additives work equally as well in all fuels. Tests should be performed to find the additive that works best with your fuel and at the correct dosage.

If you are in a colder region, practice seasonal blending, adjusting the biodiesel-blend ratio according to the temperature. Minnesota, the first state to adopt a biodiesel mandate, requires blends of 20 percent biodiesel in the summer months and reduces the standard to 5 percent in the winter and early spring.

Biodiesel has a long track record of successfully lowering emissions in all climates. Though cold-flow operability is not without its challenges, following NREL guidelines will ensure that biodiesel remains a viable and effective alternative-fuel source for decarbonizing on- and off-road transportation sectors. Following the Biodiesel Handling and Use Guide is an effective way to maintain your carbon-reduction plans in colder weather.

In addition, the upcoming Clean Fuels Conference in Fort Worth, Texas, Feb. 5-8 will host experts on many of the pressing issues surrounding biodiesel, renewable diesel and SAF. More information is available at CleanFuelsConference.org.