But the rendering industry has been trying to lock down the growing market, driven by demand for biodiesel, from freeloaders. Many restaurants now have contracts with collection companies to sell their grease for about $300 per container.

As companies have invested more time and money in lobbying efforts, the police have started to take notice. Randall C. Stuewe, chairman and chief executive of Darling International, the largest publicly traded rendering company in the United States, said it had recorded 100 arrests in 2011.

California has a taken a lead in the crackdown on grease theft. In October, the state’s Department of Food and Agriculture began a program with local police departments to target areas most often hit. As of early December, the police had caught and cited five people suspected of grease theft, and they will probably pay fines. They will announce full results from the pilot program soon and expand it to other parts of the state, Mr. Hepper said.

Turning arrests into convictions with punishments large enough to deter future theft is rare, in part because of how hard it can be to determine not just the value of the stolen grease, but also how much was stolen and from where. The thieves typically strike at multiple restaurants on one night, carting away the grease in tanker trucks or barrels in the back of a van.

Out of frustration, larger companies like Darling have started hiring lawyers to press civil charges against pilferers in a bid to recoup losses. “The reception in municipal court is very uneven,” said Steven T. Singer, a lawyer in New Jersey hired by Darling. “You’re reliant upon the prosecutors, so you got to get them to understand the seriousness of this, as well as the judge.”

In the past couple of years, Darling, which has about 2,000 trucks that pick up grease at sites in 42 states, has filed two civil lawsuits against companies accused of taking its grease, and has received close to $60,000 in damages.