NREL researchers find ways to break through biodiesel blending barriers

In Colorado, barriers that are currently preventing the use of greater percentages of biomass-based diesel fuel blended into petroleum diesel have been identified, along with strategies to overcome them, according to researchers at the National Renewable Energy Laboratory (NREL).

The bio-derived diesel fuel in use today is blended into petroleum diesel at a relatively low percentage, typically from 5% to 20%. An NREL team investigated the performance of much higher blends of biodiesel into both renewable diesel and petroleum diesel. They specifically examined blends of 20%, 40%, 60%, and 80%. A switch to using higher percentages of biomass-based diesel fuels would reduce the amount of greenhouse gasses emitted by the transportation sector.

The researchers examined biodiesel produced from soybean oil, which is the most common feedstock used in the United States to make the fuel. They pointed out that a detailed understanding about the properties of biodiesel blended at levels above 20% is lacking.

At less than 50%, the differences do not pose much of a challenge. 

Challenges with biodiesel blends greater than 50% can be mitigated, however. For example, diesel fuels must be reformulated in winter months to ensure that the cloud point—the temperature where wax begins to form—is below the expected ambient temperature. Wax can cause fuel filter clogging such that the engine cannot operate. Biodiesel cloud point can be as low as 20°F but for soy biodiesel is around 32°F, making the use of 100% biodiesel problematic in areas with colder winters.