It's Cheaper to Grow Pot in Arizona in Greenhouses Than Indoors, But Is It Better?

You would be forgiven for not recognizing the nondescript brick warehouse in Phoenix’s Grand Avenue industrial district as the site of a high-tech agricultural facility.  

But as soon as you step inside, the smell of hundreds of marijuana plants is overwhelming. As you make your way through the small rooms that line the main hallway, you can hear the whoosh of ventilation fans and the gentle hum of huge artificial lights suspended above a lush green canopy of leaves. Reggae, old-school hip-hop, and pop-punk blare from a portable speaker as a crew of 30 or so workers trim, water, and inspect the all-female crop of cannabis plants casually known as “the ladies.” 

A relaxed grower, originally from Colorado, gleefully announces, “The plants respond to the type of music you play them.” 

The plants also respond to all the energy it takes to power an indoor grow facility like this one. That results in some pretty hefty electricity bills. 

So why grow pot indoors, particularly legal pot? Why not stick it in a field and rely on the strong Arizona sun? Arizona’s medical marijuana law and local ordinances stress the importance of security and discretion, making indoor growing an easy sell to regulators worried about public perception. But there’s another option: the greenhouse, a cross between indoor and outdoor growing that relies in large part on the sun. 

The energy savings associated with growing cannabis in greenhouses are undeniable, says Mark Steinmetz of Nature’s AZ Medicines. His company operates both indoor and greenhouse facilities. 

Steinmetz estimates that he can power his 14,000-square-foot indoor complex for $25,000 a month in the summer — the same amount it takes to power his two greenhouses, which cover more than 100,000 square feet. 

But in the cannabis cultivation business, “greenhouse” is a dirty word. Not only are there environmental factors to take into account, greenhouses have long produced inferior marijuana in a world where boutique cannabis is practically a given. 

“I even hate to say the word greenhouse. I kind of cringe a little bit every time I say it,” Steinmetz admits.

He and others are out to change that. 

The national legal marijuana market reached nearly $5.5 billion in revenue in 2015, and is expected to grow to $21.8 billion by 2020, according to a report by ArcView Market Research, a national cannabis investment group. 

But just how are these gardens of cannabis grown? Hard to say. National statistics on marijuana cultivation are largely unavailable. The DEA and FBI track plant destruction and seizures related to illegal cultivation as well as arrests for possession, manufacturing, and distribution of marijuana. But that sheds little light on legal marijuana markets.

In 2015, Arizona dispensaries grew and sold more than 19 tons of medical marijuana, according to the Arizona Department of Health Services. Arizona officials track weight, not price, but New Times estimates that in 2015, Arizona dispensaries were responsible for more than $215 million in revenue. Anecdotally, we know that the vast majority of this valuable crop is grown in energy-intensive indoor facilities like the Grand Avenue warehouse. 

And making that happen burns a lot of fuel. 

A landmark study in 2012 provides some of the best data on energy use in marijuana cultivation. Evan Mills, a senior scientist at the University of California, estimates that each marijuana cigarette or “joint” that reaches the hands of a consumer is equivalent to using a 100-watt lightbulb for 25 hours or driving almost 23 miles in a hybrid car.

Even more startling, according to Mills: “The indoor cultivation of marijuana uses $6 billion worth of electricity every year, which amounts to 1 percent of overall U.S. electricity.”

That was four years ago. Energy use stands to increase as states across the country move to legalize marijuana. Arizona will consider legalizing recreational use in November. 

If the medical marijuana cultivation industry in Arizona is any indication, indoor growing certainly dominates. 

According to the Arizona Department of Health Services, there are currently 99 state licensed dispensaries, 79 of which have approved cultivation permits. Tom Salow, a branch chief in the Division of Public Health Licensing Services with AZDHS, says his office doesn’t track such things — but he’s pretty sure that only three of Arizona’s sanctioned growers use greenhouses. 

Although marijuana has now been legal for medical purposes in Arizona for the last four years, you would be hard-pressed to notice much innovation in the industry. In buildings that more closely resemble fortresses than farms, master growers operate increasingly large facilities. Some are home to only a few plants, while others have thousands. Facilities can range in size from a few thousand square feet to 100 times that size. 

And around here, bigger is definitely better for dispensary owners. Unlike many other states with medical or recreational marijuana, Arizona has no limits on the number of plants a dispensary can cultivate.

As cultivation facilities increase in size, so too can the headaches caused by poor practices. Most growers are using the same practices that made them successful years ago with their first closet-, garage-, or basement-grown harvest. 

One of the biggest inefficiencies, currently, is the fact that these growers are forced to re-create the power of the sun using artificial lighting. 

But the greenhouse method is not without its challenges. Even the growers at Mark Steinmetz’s Nature’s AZ Medicines admit that it’s often easier to grow marijuana indoors. 

Because greenhouses are more open to the outdoors than traditional indoor cultivation facilities, they face unique problems. Constantly exchanging air by pushing out stale air and drawing in fresh air from the outdoors leaves greenhouses more susceptible to problems that don’t affect indoor facilities as often, including the ability of pests to enter, bringing in molds and mildews that are prevalent in nature; the inability to control the indoor climate; lack of interior rooms to contain infestations; and potentially inadequate lighting, depending on the location.

For these reasons, Jennifer Gote, a Phoenix-based marijuana cultivation consultant who works with dispensaries across the state, is still partial to indoor cultivation. 

“Indoor cultivation offers a lot more control,” she says. Gote believes that the ability to precisely control the environment can result in a better quality medicine. 

“There is absolutely a quality difference between indoor and greenhouse marijuana. Indoor is much higher quality.” 

She doesn’t dispute the energy savings — just the quality. 

“Greenhouse will always come in lower cost. But will the quality be there?” 

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