Companies that tout their product as “ecofriendly” or “green” will have to back up some of their claims, with updated guidelines from the Federal Trade Commission.

The FTC cautioned marketers not to make unqualified general environmental benefit claims because “it is highly unlikely that marketers can substantiate” them.

The green guidelines leave several gray areas, however, with no specific rules for claims of “natural” and “sustainable” products, according to the FTC, because it lacked “sufficient evidence on which to base general guidance.”

As for organic claims, the FTC said the U.S. Department of Agriculture’s National Organic Program has specific rules.

The FTC considered hundred of comments before issuing the rules. Among those many comments, Los Angeles, Calif.-based Paramount Farms asked the FTC to allow companies flexibility in making consumer claims about the use of renewable energy resources. Paramount’s 1.1-megawatt solar energy system at a pistachio processing plant went online in June 2007.

In updating the “Green Guides,” first issued in 1992, the FTC advises marketers not to make an unqualified claims of degradeability for solid waste products unless they can prove that the entire product will completely break down within a year after being thrown away. Rules on claims of products being compostable, recyclable and having recycled content were updated, and new sections include certifications and seals of approval, carbon offsets, “free-of” claims, non-toxic claims, “made with renewable energy” claims, and made with renewable materials claims.

With more companies telling their stories about sustainability to consumers, produce marketers should pay attention to the Green Guides, said Kathy Means, vice president of government relations and public affairs for the Produce Marketing Association, Newark, Del.

“Guidance from the government is one thing, but losing consumer confidence because of unsubstantiated consumer claims is far worse,” she said. “I would hope and expect that folks in our industry are making only substantiated claims that are understandable and relevant to consumers.”

The FTC also cautions marketers not to use environmental certifications or seals that don’t clearly convey the basis for the certification. A full list of eco-labels is available online.

The guides describe the types of environmental claims the FTC might find deceptive. The agency can act on deceptive claims, including banning deceptive advertising and fines if those orders are violated.