What does butane have to do with recreational marijuana? And why does the 319-page law that made Minnesota the 23rd state to legalize marijuana ban the home extraction of cannabis concentrates using butane and other “volatile solvents” such as propane and hexane?

With pun fully intended, it is there to try to head off an explosive issue relating to how some people and businesses might produce THC concentrates, such as hash oil, that greatly increase the potency.

If done improperly or without adequate equipment, using solvents like butane to draw THC from marijuana buds can lead to massive explosions if a spark sets off the evaporated solvents. Other recreational states have seen an increase, though hardly an epidemic, of such explosions and fires during the production of what is also called Butane Honey Oil.

A 2020 explosion in Los Angeles injured 11 firefighters who suffered burns and lung damage from inhaling superheated gasses. A former mayor of Bellevue, Washington, was killed from injuries suffered while fleeing an apartment building set ablaze by a butane-related explosion. An article in Firehouse.com, described the dangers that are exacerbated by delayed explosions of butane canisters after firefighters have begun battling the fires.

“Butane hash lab explosions can have devastating effects,” the website posted. “These explosions can cause significant structural damage and cause serious injuries to hash oil manufacturers, innocent bystanders and firefighters.”

Drafters and proponents of House File 100 were aware of these problems in other states and attempted to address them, if not totally prevent them, through the bill language. In addition to banning home extraction of cannabis concentrate, the law includes health and safety rules for licensed processing businesses.

A manufacturer of cannabis concentrates, hemp concentrates and artificially derived cannabinoids must get a special endorsement from state cannabis regulators. Applicants must describe the methods of extraction and any volatile chemicals used. The methods must be approved by the state.

In addition, manufacturers must have a third-party analysis conducted on their plans and equipment, including “all electrical, gas, fire suppression and exhaust systems.”

And among the pieces of data about licensees explicitly made public in the new law are “data describing whether volatile chemicals will be used in any methods of extraction or concentration.”

“The whole goal has been to regulate and keep it safe and deal with the harms caused by this product and the business activities around it,” said Ryan Winkler, the chair of MN is Ready and the prime sponsor of the 2021 precursor to this year’s legalization bill.

Leili Fatehi, a legalization advocate and partner in the cannabis public affairs firm Blunt Strategies, said drafters were aware of the issues in other states. Safety from accidents as well as keeping users safe from residual compounds were the goals.

“Those input ingredients can explode and the solvents can be caustic,” she said. “People will be able to make hash oil, there’s just going to have to be safety plans and they will have to demonstrate what they’re doing with those inputs.”

But as with some other aspects of the new law, such as the way it legalized public smoking and vaping of marijuana, what isn’t stated in the bill language can be as telling as what is. By banning the use of volatile solvents for concentrating THC, the bill nudged home practitioners to safer methods to reach the same end.

“The residual solvents that are left behind when you use some of these volatiles can be harmful,” said Bryant Jones, a plant scientist and cannabis horticulture consultant who helped draft the bill. “For the most part, things like butane — other than the fact that they’re explosive when they come out of the can — basically leave behind carbon dioxide and water. Pretty inert.” Other types of volatile solvents, such as those that end in “ENE,” can leave behind solvents that are “pretty much bad for you.”

The law doesn’t mean home-growers can’t concentrate their marijuana into higher-potency products.

“We did that in an effort to get people to focus on the old-school methods of preparing cannabis concentrates,” Jones said. “What we’re hoping for is a revival of the old-school hashshishin, where you just use cold water and ice and agitate your cannabis. There are no solvents and no chemicals used and you can make your own.”

There is also a method called rosin pressing that uses heat and pressure. Equipment for both are available to order online, including via Amazon for a few hundred dollars.

“Those methods are extremely inert. There are no explosive chemicals. Nothing that can hurt you,” Jones said. “We did it to, by process of elimination, say, ‘Here are the only two methods you can use at home.’”

Cannabis concentrates limit

While off-reservation retail sales of marijuana are still 18 months away, the new law allows home growing of marijuana. Those 21 and older can grow up to eight plants, but the law says that only four can be flowering at a time and no one can possess more than 2 pounds of dried leaf at a time. But they also can possess 8 grams or less of “cannabis concentrates,” defined in the law as “the extracts or resins of a cannabis plant or cannabis flower that are refined to increase the presence of targeted cannabinoids.”

In public, people 21 and older can possess 2 ounces of flower and 8 grams of concentrate. So there is some incentive for people with too much production from at-home plants to convert some to concentrates. But Jones said processing should be an option but not a necessity for home growers.

“Those numbers were meticulously chosen,” Jones said of the possession limits. “With the number of plants that we allow and the poundage, people should come under that in their annual harvest. It shouldn’t be too much of an issue. Between that and concentration methods, I think people will be pretty satisfied.”

HF 100 envisioned licensed labs offering services to home growers to take a customer’s marijuana and process it into hashish or hash oil or other products, perhaps akin to a hunter who takes a deer to a butcher to process it. But such labs, like all other licenses created by the law, will not be in business until early 2025.

As Jones notes, not all extraction methods use butane or similar chemicals. There are safer methods using CO2, ethanol, isopropyl alcohol and even near-freezing water. Even using volatile solvents, though illegal for unlicensed home labs, can be made safer with equipment using sealed systems and vacuum extraction of the vapors.

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They’re called volatile solvents because they’re volatile — that is, they easily vaporize into a gas. And being heavier than air, they pool invisibly near the floor. Those vapors can then ignite with a spark, even static from shoes on a rug. If it happens in a relatively contained space, the ignition can cause an explosion and fire and lead to additional explosions if unused butane containers overheat and explode.

Butane hash oil is made by spraying volatile solvents onto the plant’s buds to pull the THC from marijuana. Once the solvent has evaporated, the resulting substance can contain THC levels of 80% or higher, much higher than the 12% to 20% of the natural plant. But Jones said similar THC concentration levels can be achieved with safer methods.

“Depending on the cannabis it can be as low as 65% or hovering around 85 to 90% in some cases,” Jones said.