Minnesota began requiring all diesel fuel in the state to contain 10% biodiesel on July 1, becoming the first state to mandate sales of the B-10 blend.

The state is dialing down the requirement during winter months, when fueling stations sell diesel with 5% of biodiesel. Previously, the state required diesel fuel to contain at least 5% biodiesel and 2% during the winter.

One of the fleets affected by this change, the state's Department of Natural Resources, isn't worried about the mandate. Dave Schiller, fleet, safety and materials handler, manages approximately 600 on-road diesel vehicles and about the same number of off-road vehicles.

"We've been experimenting with B-20 and other blends for some years and like the added lubricity from the bio portion," Schiller said. "We also like that there is no degrade in fuel economy."

When biodiesel made its debut in Minnesota nearly a decade ago, poor-quality fuel led to clogged fuel filters, angry drivers, and emergency waivers of the new law. However, the biodiesel industry says the quality problem has long been solved, and Schiller agrees.

"The quality of the biodiesel component has really improved with the ASTM specification, and we don't anticipate problems from going to a B-10 blend," he said. "We don't expect any performance or maintenance issues with this change, but we will watch our filters more closely for a while."

Schiller expects the biodiesel mandate to help the fleet financially in the long run. While biodiesel prices fluctuate and will continue to do so, he said this past spring, the biofuel has been cheaper than diesel.

Kevin Schlangen, CPFP, CAFM, CEM, fleet manager at Dakota County in Minnesota said the county fleet began using B-10 this month on 125 of its units -- about 33% of its powered fleet. Schlangen said the price in comparison to the B-5 the fleet previously used varies by a cent or two, and he has not seen any repair or mainteance issues with B-10.

Originally, state lawmakers wanted all diesel fuel to contain 10% biodiesel by 2012 and 20% by 2015, but inadequate blending infrastructure pushed back the deadline. A B-20 mandate is still on the books for 2018.

U.S. biodiesel is most often made from soybean oil, and Minnesota ranks third in soybean production in the nation. According to the Minnesota Department of Agriculture, the state has three biodiesel plants with a combined production capacity of approximately 63 million gallons.

Sixteen other states now have mandates or tax incentives to blend biodiesel with petroleum-based diesel, according to the National Biodiesel Board. Illinois offers a tax break to blend biodiesel at 11% or more, but only Minnesota mandates that high of a blend.

*Updated 7/10/14 with Kevin Schlangen's comments.