WASHINGTON -- The Environmental Protection Agency has warned producers of biodiesel they could be fined up to $32,500 a day if their fuel does not meet quality standards.

In a "guidance document" sent to producers and blenders last month, the EPA said it plans to increase enforcement to assure biodiesel producers are complying with quality and technical standards set by ASTM International.

EPA said that "any biodiesel that does not meet the version of ASTM D 6751 in effect at the time of registration will be considered an unregistered fuel subject to ... civil penalties of up to $32,500 per day, per violation."

For example, the ASTM (formerly American Society for Testing and Materials) standards set the flash point for biodiesel at 199.4 degrees Fahrenheit, and limits glycerin content to 0.24 percent of the total volume.

Jenna Higgins, a spokeswoman for the National Biodiesel Board, said the industry group worked with EPA on the guidance document, which was part of a larger industry outreach program to raise awareness about biodiesel quality.

The group also has "been working with state and federal agencies to request that they engage in fuel quality enforcement. That level of enforcement is something our own members - many of them fuel suppliers - asked us to do. That should give you an idea of how serious our industry is about quality," Higgins said.

There have been reports in recent months that a significant number of producers were failing to turn out biodiesel that meets the ASTM quality specifications.

Some in the trucking industry want the EPA to get tougher with biodiesel producers because of problems caused by off-spec biodiesel. The truckers want enforcement proceedings against producers and resellers that fail to meet the required quality specifications.

Higgins said the biodiesel board was supportive of increased enforcement and the use of fines. "We absolutely encourage fuel-quality enforcement, including fines if necessary," she said. "It would be to the detriment of our industry to wait for the market to sort out the bad actors."

In its advisory, EPA also said buyers should purchase biodiesel only from reputable dealers.

"Improperly processed biodiesel may contain unreacted or partially reacted oils or fats - measured by the total glycerin - which can cause the fuel to gel at higher than expected temperatures," the agency said.

With winter quickly approaching, colder temperatures can cause problems with poor-quality biodiesel. In fact, a lot of the biodiesel quality concerns are exacerbated in cold weather.

For example, one of the common problems experienced by biodiesel producers is the failure to remove glycerin from the finished product. In warmer weather, a higher glycerin concentration than what the spec allows may not immediately cause a clogged fuel filter. However, in colder weather, that same off-spec product could strand a vehicle.

Higgins noted that it is against the law to sell any fuel that does not meet an ASTM specification, and that biodiesel in blends of up 20 percent made with on-spec biodiesel, will perform all winter just like diesel, provided the fuel distributor has properly treated the blend for cold weather use.