Higher blends of biodiesel fuel could cut transportation emissions

Obstacles which are at present stopping the usage of larger percentages of biomass-based diesel gasoline blended into petroleum diesel have been recognized, together with methods to beat them, based on researchers on the Nationwide Renewable Power Laboratory (NREL).

The bio-derived diesel gasoline in use at the moment is mixed into petroleum diesel at a comparatively low share, sometimes from 5% to twenty%. An NREL group investigated the efficiency of a lot greater blends of biodiesel into each renewable diesel and petroleum diesel. They particularly examined blends of 20%, 40%, 60%, and 80%.

A change to utilizing greater percentages of biomass-based diesel fuels would scale back the quantity of greenhouse gases emitted by the transportation sector. Biodiesel is an oxygenate comprised of fat, oils, and greases. Renewable diesel is comprised of the identical feedstocks however processed to be a hydrocarbon chemically much like petroleum diesel.

“It’s amazing to me, but there are thousands of papers published every year on biodiesel, and almost nobody looks at blends over 20%,” mentioned NREL Senior Analysis Fellow Robert McCormick, corresponding creator of the newly printed analysis paper titled “Properties That Potentially Limit High-Level Blends of Biomass-Based Diesel Fuel,” which is printed within the journal Power & Fuels.

“This research addresses a major data gap regarding biodiesel blends, both because it looks at high-level blends and because it looks at blends with renewable diesel as well as petroleum diesel. Biodiesel blends with renewable diesel are 100% renewable.”

The paper was coauthored by researchers Gina Fioroni, Nimal Naser, and Jon Luecke, all additionally from NREL.

The researchers examined biodiesel produced from soybean oil, which is the most typical feedstock utilized in america to make gasoline. They identified {that a} detailed understanding of the properties of biodiesel blended at ranges above 20% is missing.

Heavy-duty long-haul vans and off-road gear, marine transport, and commercial aircraft are anticipated to proceed requiring liquid fuels at the same time as electrification of smaller automobiles ramps up. These fuels might want to yield low-net greenhouse gasoline emissions—reminiscent of biodiesel and renewable diesel—and be suitable with current engines. The usage of biodiesel and renewable diesel is forecast to cut back transportation-related greenhouse gasoline emissions from 40% to 86% in comparison with petroleum diesel, relying upon the feedstock used.

McCormick mentioned with a biodiesel blend larger than about 50%, “you start to have property differences with petroleum that could be problematic.” At lower than 50%, the variations don’t pose a lot of a problem.

Challenges with biodiesel blends larger than 50% might be mitigated, nonetheless. For instance, diesel fuels should be reformulated in winter months to make sure that the cloud level—the temperature the place wax begins to type—is under the anticipated ambient temperature.

Wax could cause gasoline filter clogging such that the engine can’t function. Biodiesel cloud level might be as little as 20°F, however for soy, the biodiesel cloud level is round 32°F, making the usage of 100% biodiesel problematic in areas with colder winters.

“This issue can be managed by reducing the blend level or by blending the biodiesel into different hydrocarbon blendstocks with a lower cloud point during the winter months—as is commonly done today for B20 (a blend of 20% biodiesel and 80% petroleum diesel),” McCormick mentioned. “A similar strategy could be used to mitigate the high boiling point of biodiesel, which is near the top of the diesel boiling range.”

A hydrocarbon blendstock with a decrease boiling level, reminiscent of kerosene, may very well be used for biodiesel blends over 50%, assuaging challenges in chilly beginning the engine, accumulation of gasoline within the engine lubricant, and doubtlessly failure of emission management catalysts to “light-off” or obtain excessive sufficient temperature.

The analysis additionally examined different gasoline properties reminiscent of density, oxidation stability, and water content to find out whether or not these would possibly restrict the mixing of biodiesel. Oxidation stability, for instance, could also be lowered as extra biodiesel is mixed, however the issue might be overcome through the use of greater ranges of antioxidant components.

Vital future analysis is required to handle the challenges of excessive degree biodiesel blends, significantly on how they affect diesel engine emission management programs. The NREL paper serves as a analysis street map for addressing these challenges.