An ‘Inconvenient Truth’ About Indoor Growing

By Hilary Corrigan
Jul 17, 2020
Source: Unsplash

Indoor growing’s extraordinary energy use and “mushrooming carbon footprint” is not justifiable, according to a recent report. Instead, it proposes growing cannabis outdoors.

“The continuation of indoor cultivation does not appear to be defensible on energy and environmental grounds,” according to the report, “Energy Use by the Indoor Cannabis Industry: Inconvenient Truths for Producers, Consumers, and Policymakers.”

“We have to look at the carbon footprint,” the report’s co-author, Evan Mills, said in an interview. An energy and environmental systems analyst and retired Lawrence Berkeley National Laboratory senior scientist, Mills compiled the report and released it with co-author and cannabis industry consultant Scott Zeramby. It appears as a chapter in a forthcoming book, “The Routledge Handbook of Interdisciplinary Cannabis Research.” (Routledge is an academic book publisher.)

It calls for more research, transparency and disclosure on energy use. The report also calls for the elimination of subsidies that result in more energy use. Giving indoor growers lower electricity prices or incentives for new equipment, it notes, disadvantages outdoor growers.

Mills said his years of research on the issue have shown him that there’s “no rational justification for indoor cultivation.” And that renewable energy and efficient light bulbs won’t make up for it.

“You can’t kind of engineer your way out of this,” he said. “There’s an alternative, which is growing it outside.”

‘Uncomfortable truth’

Mills, a vegetable gardener, became interested in cannabis growing about 10 years ago after noticing portable air conditioners, fans, dehumidifiers, lights, turkey bags and other odd items at a nursery.

“It’s uncomfortable,” he said of the report’s findings. “It’s a very inconvenient truth.”

Sam Milton, founder and principal at Maine-based consulting firm Climate Resources Group, said the report “shines a light” on the issue. It shows there’s massive opportunity for the industry to improve its energy use. It also highlights a need for more energy data, reporting and analysis. Indoor growing is “perhaps less than ideal from an energy perspective. But that’s where we are,” Milton said.

“Elegant, Sustainable, Ethical”

Mills’ earlier research found that nationwide indoor growing sucks up 20B kilowatt-hours of electricity annually. This corresponds to 15M metric tonnes of carbon dioxide and energy expenditures totaling $6 billion.

That’s more than four times the energy used by the country’s pharmaceutical industry. Windowless-warehouse cannabis production facilities need 26 times as much electricity per square foot as a typical U.S. commercial building, and 11 times that of a hospital.

The energy needed to produce a 1-gram joint creates 10 pounds of carbon dioxide pollution, the equivalent of running 10 10-watt LED light bulbs or one 100-watt incandescent bulb for 76 hours. A small grow with 10 lights consumes about as much electricity as 10 average U.S. homes. Indoor operations that inject industrially-manufactured carbon dioxide and run HVAC and lighting equipment can require as much energy as a data center. It calls cannabis “decades behind” in energy efficiency.

The new report calls outdoor cultivation the “most technologically elegant, sustainable, ethical, and economically viable approach” to minimize cannabis’ energy and environmental impacts. Legalization—while necessary to address energy issues— has the potential to make the problem worse, the report says. For instance it can encourage the rapid scale-up of indoor facilities.

Policy-makers, the report says, rarely evaluate the impact of indoor cultivation’s high energy use. It calls this one of the industry’s least explored policy questions. Questions like taxes, zoning and child safety issues often overshadow the environment, it says.

“Windowless cannabis factory farms constantly battle local weather conditions to maintain round-the-clock tropical temperatures and pump out acres of electric light brighter than the summer sun, day or night,” the report states. “Such industrialized cannabis cultivation facilities—whether in Fairbanks or Phoenix—must simulate and maintain artificially cloudless tropical environments while suppressing humidity year-round.” 

The report singles out the permissive regulatory environment in California’s Coachella Valley. The lack of caps on facility size, among other policies, have helped make the scorching desert region a major production hub. There, large-scale indoor cultivation takes place in a climate  that needs more air conditioning and ventilation than areas “more naturally suited for cultivation.”

Not enough renewables, data

Mills’ report discounts the perception that indoor growers “need only ‘go solar.’” A facility would need a solar array many times larger than its roof, the report says. Although the Coachella Valley is a major producer of wind energy, cannabis grows will soon eclipse the entire output of all 40 wind projects in the area. 

The report also finds consumers largely unaware of the energy and environmental impacts of indoor cultivation. The “ethical purchasing” movement—in which consumers choose sustainable products—has barely emerged in cannabis. And environmental organizations “have conspicuously sidestepped the issue,” possibly because they fear stigmatization.

The report also mentions other areas that need more policy attention. Those include water. The “massive amounts” of water evaporated from dams and cooling towers while producing electricity for indoor cultivation “vastly exceeds” the water needs of outdoor grows.

Another hurdle to reducing cannabis’ energy use is the ban on interstate commerce. That would allow facilities to be consolidated and make transport more efficient. “Were the nation’s supply of cannabis grown in climatically benign locations, energy use would be vastly reduced,” the report says.

To Mills, that just makes sense. “We don’t grow pineapples in North Dakota. We grow them in Hawaii” and export them, he said.

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