Cardboard boxes and paper envelopes packed with marijuana, cocaine and other drugs line warehouse-style shelves at the State Highway Patrol's Ohio crime laboratory, where seizures large and small are stored for safekeeping for sometimes years until they're no longer needed as evidence.

Then comes a tricky task: How do you destroy it all?

Most often by incineration, but where and how varies, according to police spokesmen and officers who oversee evidence. Arranging evidence burns can be tricky because rules are different everywhere, allowing more leeway in some places than others.

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Police have used crematories, foundries, hospital incinerators or specialized businesses -- and even torched drugs in 55-gallon drums.

Troopers in Ohio used to destroy thousands of pounds of seized drugs -- for free -- at factories where they could be vaporized in molten steel. But the companies worried about it potentially affecting the quality of their product and producing emissions: the kind that create environmental concerns and the kind that could skew employee drug tests, said Capt. David Dicken, a director at the crime lab.

"If we're throwing 940 pounds of marijuana into the vat, you know, it flares up," he said.

To maintain a dedicated drug destroyer, the agency switched last year to a paid contract with a federally permitted company that handles hazardous materials.

Federal standards regulate waste incinerators that burn pharmaceuticals, but those used only for contraband are exempt from those rules, said Dina Pierce, a spokeswoman for the Ohio Environmental Protection Agency.

Various local environmental and safety rules can apply, creating a complicated regulatory picture for evidence-management officers sorting out what destruction methods are allowed, said Joseph Latta, an instructor and executive director at the Burbank, California-based nonprofit International Association for Property and Evidence Inc.

"During the class, we say, 'Here are the ways that we've heard of. Here are the legal ways. Here are some maybe unorthodox ways that we've had to do," Latta said.

U.S. Customs and Border Patrol, which seizes millions of pounds of illegal narcotics, pays contractors to destroy the drugs or turns them over to other agencies, such as the Drug Enforcement Agency, said Jaime Ruiz, a CBP spokesman.

DEA destroys marijuana at EPA-approved incinerators because those seizures are generally bulkier, and it burns other contraband drugs at its labs, said Special Agent Rich Isaacson, spokesman for the agency's Detroit division.

In California, where environmental regulations tend to be stricter, the legal option is usually limited to EPA-approved energy-plant incinerators that operate under emissions and security standards, Latta said. But reaching those sites could be impractical for smaller, more rural law enforcement agencies that take in lesser amounts of drugs, he said, acknowledging some "have probably taken shortcuts."

It can be a dilemma for officers who must either arrange for destruction or allow drug evidence to accumulate, which risks making the storage area a potential theft target, Latta said.

Other jurisdictions have more choices: State police in the Detroit area use a metal forging plant's high-temperature furnace, but smaller posts use burn barrels. Indiana State Police have similar options. Pennsylvania State Police handle drug destruction internally, such as with a small incinerator. New York State Police use an outside contractor they won't disclose.

In West Virginia, some authorities may use fire pits, state police Capt. Joe White said.

Drug destruction arrangements with steel facilities still work for some agencies, including Columbus, Ohio, police and the FBI's Cleveland division. Cincinnati police are using that option for the first time this year because the university facility they used in the past stopped providing the service, department spokeswoman Sgt. Julian Johnson said.

Especially when drug-destruction work is pro bono, police tend to be tight-lipped about details to protect security, the businesses involved and sometimes the arrangements themselves.

"The word gets out there that this facility does it, then 50 other agencies want to go there ... and that gets to be too much for that place to handle, and then you lose that place. And then you've got to go find another one," said Sgt. Jeff Yaney, who oversees evidence for Dayton, Ohio, police.

Yaney wouldn't divulge where the department destroys drugs. It used to take advantage of the incinerator that burned classified materials at nearby Wright-Patterson Air Force Base, but the base replaced it with a shredder rather than paying for changes to meet environmental rules a few years ago.

Representatives for two federally permitted hazardous waste incinerators in Ohio, Ross Environmental Services Inc. near Elyria and the patrol's vendor, Heritage Environmental Services in East Liverpool, said they provide a more controlled, secure destruction process with environmental protections and benefits not necessarily found at other types of facilities.

For that, though, agencies generally must pay. Heritage has destroyed about 10,000 pounds of drugs and paraphernalia since July for the patrol, at a cost of roughly $22,000, said Lt. Craig Cvetan, a patrol spokesman. The funding came from seized drug money, which is also used for drug enforcement and drug-abuse prevention programs.