Studies Show Fuel Efficiency Comparable to Full Diesel in Heavy-Duty Vehicles with B10 and B20 Blends

22 August 2008

With about 200,000 miles left to go in the two-year Two Million Mile Haul over-the-road B20 biodiesel demonstration (earlier post), data collected from each truck’s electronic data recorder are showing fuel efficiency for the B20 blend comparable to that of petroleum diesel. The partners in the project announced the results to-date during the Great American Truck Show in Dallas, Texas.

Separately, a study by Purdue University for the Indianapolis, Indiana transit agency IndyGo found that switching to a B10 (10% biodiesel) blend in the IndyGo bus fleet had no impact on total fuel economy.

Conventional No. 2 diesel has a lower heating value of 128,450 Btu/gal, while the value for B100 biodiesel is 119,550 Btu/gal, according to US Department of Energy figures. A B20 blend from these blendstocks would offer a heating value of approximately 127,259 Btu/gal—a 1.4% difference. (National Biodiesel Board figures vary slightly, showing a 1.7% difference between B20 and No. 2 diesel.)

“In recent months, we have learned that driver variability makes more difference in fuel efficiency than biodiesel utilization does,” said Dr. Don Heck, coordinator of biotechnology and biofuels programs at Iowa Central Community College in Fort Dodge, Iowa, where Two Million Mile Haul test data is analyzed.

These findings map to a recently published study by the National Renewable Energy Lab and the National Biodiesel Board, showing only a 1.7% decrease in fuel economy in buses running B20 compared to ultra-low sulfur diesel. (Earlier post.)

In addition to fuel efficiency data, the Two Million Mile Haul aims to demonstrate operability of a B20 blend year-round in cold weather situations. Although both the petroleum and B20 groups experienced some fuel filter plugging in zero degree Fahrenheit weather, the B20 trucks did not experience any considerable challenges because test partners implemented proper handling and storage measures, according to the partners.

The two-year study is sponsored by the Iowa Soybean Association, Iowa Central Community College, Decker Truck Line Inc., Caterpillar Inc., the National Biodiesel Board, Renewable Energy Group and the US Department of Agriculture. The study is believed to be the first comprehensive, publicly documented demonstration of B20 in over-the-road trucks.

The study, which began in the fall of 2006, consists of two groups of 10 Decker Truck Line Inc. semi-tractors running with flatbed trailers on matched routes to either Minneapolis or Chicago. The control group uses 100% No. 2 petroleum diesel. The B20 test group uses a blend of 20% biodiesel from Renewable Energy Group and 80% No. 2 petroleum diesel.

IndyGo B10. The IndyGo fuel economy report, prepared by Dr. Gregory Shaver, an assistant professor of mechanical engineering, with doctoral student Dave Snyder and undergraduate Chris Satkoski, compared bus operations in April 2006 and April 2007 to determine the impact of switching from standard diesel fuel to B10. IndyGo switched its entire fleet to B10 in 2007.

Officials wanted to know the impacts of switching to B10 and whether it would be advisable to replace B10 with B20.

In our assessment, we would recommend going to B20. We also saw a significant benefit to using the diesel-electric hybrid buses, so we would recommend increasing the number of hybrids in the fleet. The best bang for your buck might be running B20 in hybrid buses, depending on the initial cost of hybrids compared to standard buses.

—Gregory Shaver

The researchers found that the 280-bus fleet’s two diesel-electric hybrid buses increased miles per gallon by 30% compared with the conventional buses. Going from B0 to B10 had virtually no overall effect on mile-per-gallon fuel economy in the fleet. IndyGo buses consumed about 1.8 million gallons of fuel in 2007.

The report indicated that one anticipated negative environmental impact to burning B10 fuel is a modest increase—from 1% to 3%—in NO_x emissions.

It is a concern, and it’s one of the things we are working on in our research team for blends higher than 20 percent.

—Gregory Shaver

Among Shaver’s research projects at Purdue are studies on low temperature combustion (LTC) and the clean and efficient combustion of alternative diesel fuels via closed-loop control.