SAINT PAUL, Minn. — Freezing cold temperatures in Minnesota have suspended a small part of the state’s leading anti-global warming initiative until April.

The state will not be enforcing its 5 percent biodiesel requirement as of Jan. 15 due to a freezing spell in the Great Lakes region, but only ULSD1 is affected — that’s a blend of 5 percent biodiesel and pure kerosene.

The more common ULSD2, which blends biodiesel with regular diesel and kerosene, is not affected by the ban.

"The biodiesel and petroleum industries have been monitoring reports of very rare instances of filter clogging of storage tanks containing 5 percent biodiesel and pure kerosene (ULSD No. 1)," says the Minnesota Biodiesel Council (MBC). "These rare reports in Minnesota are occurring in extremely cold temperatures and only in tank dispensing filters with certain types of kerosene and some types biodiesel."

The Minnesota Department of Commerce decided to temporarily suspend the ULSD1 rule based on requests from the MBC and the Minnesota Petroleum Marketers Association.

The concern is that extremely cold temperatures causes gelling of biodiesel, which could lead to clogged filters, especially in older truck engines.

Samples of diesel fuel and filters have been collected statewide and are being tested to help confirm the cause of recently reported problems. The majority of refiners, terminals and users have reportedly not experienced any significant trouble.

Minnesota was the first state to introduce a biodiesel mandate. It raised the biodiesel mixture from B2 to B5 last May. Some officials are calling for a B20 rule — 2 percent hikes over the next eight years — by 2018. 

A handful of other states, as well as some Canadian provinces, like B.C. and Manitoba, have since implemented B2 or B5 standards.

Meanwhile, the U.S. biodiesel tax credit expired at the end of December, leaving biodiesel producers, truckstops and truckers who use the fuel uncertain over what prices will be in the future.