The Star Tribune editorial "Stick with Minnesota's biodiesel mandate" (Aug. 6) applauded a recent decision by state officials to double the current biodiesel blending mandate to 20 percent (B20) for half the year — from April through September — making Minnesota the only state in the country, and one of the few places in the world, to dictate biodiesel blending at such a high level.

As a member of the Minnesota Biodiesel Task Force and a producer of both diesel fuel and biodiesel, I have concerns about the practicality of increasing the mandate to such unprecedented levels.

Biodiesel is a very capable fuel, but it has limitations. Although it's improving, most high-level biodiesel blends do not perform well in cold weather. Even with its sophisticated quality-control program and heated storage, Metro Transit has reported engine filters clogging at biodiesel blends as low as 2.5 percent when temperatures drop below 35 degrees. At B20, clogging has been reported at fuel temperatures as warm as 50 degrees, leading Metro Transit to caution against requiring the use of B20 during transitional months such as April, when temperatures tend to range widely from day to day and vary dramatically across the state.

While B20 is a sound consumer choice under the right conditions, the fact remains that not all diesel engine manufacturers cover higher blends in their engine warranties. Forcing consumers to purchase B20 could void warranties for some Minnesotans who own light-duty diesel vehicles.

The B20 mandate also presents a number of practical challenges. Very few of the fuel loading terminals that serve Minnesota are expected to have the necessary tanks and blending infrastructure in place to accommodate B20. Unlike Minnesota's previous transitions from B2 to B5 and B10, the jump to B20 presents a problem with both the physical size of the current tanks and the blending equipment needed to deliver the appropriate biodiesel volumes. It's a math problem that cannot be solved without a significant investment in new infrastructure. Absent this investment, Minnesota could see more product outages during peak demand, longer wait times for loading and delivery of fuel, and higher costs for trucking.

Finally, increasing the mandate so far beyond what any other state requires ignores the role that the regional marketplace and the federal government play in influencing the cost and use of biodiesel. Today, biodiesel (B100) typically costs $1.75 to $2 per gallon more than diesel fuel and, at times, the difference has exceeded $3 per gallon. Traditionally, these costs are either passed on to consumers or partly absorbed by taxpayers. By mandating B20, the state is forcing consumers to purchase the fuel regardless of cost, making Minnesota susceptible to sudden market variations or potential changes in federal law that could result in dramatically higher biodiesel prices at the pump.

The Star Tribune Editorial Board and others who support doubling Minnesota's biodiesel mandate dismiss these concerns out of a belief that the risk is worth the reward and more is always better.

However, the benefits of mandating biodiesel have never been validated. Claims that the B20 mandate will increase soybean values for farmers and promote in-state biodiesel production lack merit when you compare Minnesota with states that do not mandate the use of biodiesel. Many of these states produce more biodiesel than Minnesota and their farmers earn more for growing soybeans.

Biodiesel is an excellent product under the right conditions, but those conditions matter. The law requiring B20 was passed nearly a decade ago with the best intentions. But without some reforms, its implementation next year could harm consumers and undermine confidence in the fuels people depend on.

Brett Webb is director of commercial development for Flint Hills Resources of Wichita, Kan., which operates the Pine Bend refinery in Rosemount.