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Research & Development Horticulture, Legislation & policy

An Inconvenient Truth

Evan Mills has been writing about climate change for 40 years. He participated in the work of the Nobel-Prize-winning Intergovernmental Panel on Climate Change and is a former Senior Scientist at the US Department of Energy’s Lawrence Berkeley National Laboratory, where he is now an affiliate. His specialty? Energy analysis – specifically the efficiency of energy use as the number-one strategy for addressing climate change.

In 2012, he conducted a study that aimed to quantify a previously undocumented component of energy demand in the US – and to establish baseline impacts in terms of energy use, costs, and greenhouse-gas emissions in the cannabis industry. Mills observed, as is the case in many other areas of the economy, that many reversible inefficiencies are embedded in current practices. The ultimate area of inefficiency? Indoor cultivation.

Indoor facilities contain lighting as intense as that found in an operating room (500-times more than needed for reading), sixtimes the air-change rate of a biotech laboratory and 60-times that of a home. In short, it requires the electric power intensity of a data center. He writes that “large-scale industrialized and highly energy-intensive indoor cultivation of cannabis is driven by criminalization, pursuit of security, and the desire for greater process control and yields. The practice occurs across the United States and in many other countries.”

With the yearly greenhouse-gas pollution from the electricity, plus associated transportation fuels, equaling that of 3 million cars, its annual energy bill was close to $6 billion at the time of the original study. In his latest article for Medium (one of hundreds that Mills has written over the last decade), he calls indoor cultivation “an unaffordable luxury in a warming world.”

We spoke to him to find out what’s changed, what hasn’t, and why not.

How did you come to study indoor cultivation? 

About ten years ago, I was innocently shopping at a local nursery and noticed a row of 1000-watt lamps behind the counter, fans, ducting, CO2 canisters, the whole shebang. I started asking questions about the technology and standard practices. I built a spreadsheet model of facility energy use and... one thing led to another. The proprietor of that store, Scott Zeramby, had a healthy combination of conscience, knowledge, and curiosity and helped me understand the industry and real-world practices. He collaborated with me on our upcoming publication.

Have things gotten better or worse since the study you published in 2012?

Sadly, by most measures they have gotten far worse. There is actually little evidence of reductions in carbon-intensity (greenhouse-gas emissions per unit weight yield), despite the gradual introduction of LED lights, which people tend to regard as a panacea. I think there have been countervailing trends, such as increased illumination levels, more mechanization, more voluminous facilities, and wider aisles (requiring heating, cooling, and dehumidifying), and increased carbon dioxide injection. Meanwhile, there is far more indoor production in aggregate than previous years, so the total carbon footprint is no doubt growing. There was a lot of hope for misnamed “green” houses, but the reality is that they have incredibly energy-inefficient envelopes and still use a lot of artificial lighting, ventilation, and natural gas for heating, with the result that carbon intensity is only 25 percent lower than windowless warehouse facilities, according to published data.

Is your work being met differently now that climate breakdown is more visible? 

There has been a lot of discussion and appreciation of the work since the beginning – though that, of course, is a far cry from change in actual practices. That said, a number of growers have contacted me over the years saying they’ve shifted operations outdoors, in part due to what they learned from my publications. There was never any serious push-back on the work. It took High Times five years to raise some questions, and it was kind of embarrassing for them, since their points were mostly erroneous (some outrageously so) or were strawman arguments attempting to shift the conversation away from the industry.

They also aligned themselves with long-since-debunked misinformation from the fossil fuel industry. It was kind of like Big Tobacco saying cigarettes are healthy for you. They really missed an opportunity to take a constructive leadership posture on the issue. As I  wrote to them at the time, I have no bias against the cannabis industry, safe recreational use, or legitimate medical applications of its products, but do have a strong bias against excessive avoidable energy use and associated greenhouse gases, wherever they can be found.  Marijuana is hardly being singled out here. On the contrary, it has had a free ride for decades while all other energy uses have had to come into the 21st century.

Could you explain the concept of “embedded” energy use?

Few policymakers have the patience to really understand energy systems, and, increasingly, even fewer are willing to take an unpopular position of concern about cannabis cultivation practices.

There is a widespread practice of quantifying the energy and carbon embedded (sometimes people say “embodied”) in the making of stuff – for example, the packaging, transportation, and storage energy use associated with a quart of milk. For cannabis, this would include growing media, fertilizers, industrial CO2 for injection into the growing space, carbon content of failed crops, and equipment manufacture. As one example, the very popular mineral-wool growing media is made by essentially melting rock (often with coal). This is a one-and-done product, with no recycling or other re-use. In our new study, we estimate that a 100ksf indoor grow would use 85,000 to 200,000 cubic feet of mineral wool per year (which goes to landfill), bumping the overall carbon footprint by 5 percent to 11 percent, depending on your assumptions.

In their recent study, Jason Quinn, Hailey Summers and Evan Sproul analyzed the impact of the energy and carbon embodied in waste, transportation, injected CO2 and some agricultural inputs in some detail and found the inclusion of embedded energy to make a non-trivial contribution to the overall carbon footprint: it ranged almost 50 percent in milder climates to about 20 percent in more severe climates where relative energy use was greater.

There is also a parallel consideration of embedded water. Few people realize that it takes a lot of water to produce electricity. Those giant, iconic hourglass-shaped towers condense and cool a thermal power plant’s exit water so that it can be safely reintroduced to the environment (rivers and oceans). Even more water per unit of energy output is evaporated from behind hydroelectric dams. Water is also needed for the routine washing of solar arrays. When considering this “hidden” use, it turns out that it takes far more water to grow cannabis indoors than outdoors. This is yet another inconvenient truth about indoor cultivation.

Why are policymakers so reluctant to address the cannabis carbon bomb?  

It’s an enigma, but my theories are that it is a combination of ignorance, being co-opted, and political inconvenience. Few policymakers have the patience to really understand energy systems, and, increasingly, even fewer are willing to take an unpopular position of concern about cannabis cultivation practices. I think people are wooed and/or wowed by all the bling of indoor cultivation. (The indoor industry unashamedly uses women in bathing suits to sell lighting equipment and such…) The industry is much better organized and moneyed than the sungrowers, and has a more aggressive and sophisticated lobbying presence.

I think there is also a problem with local government, which is hungry for the sales-tax revenue, and the only way to get that is to keep cannabis cultivation within the city limits – which of course generally necessitates indoor cultivation because of land prices and odor-control considerations. And energy companies (often referred to as “20-percent partners” by growers who pay that proportion of their revenues for electricity) want the increased revenue, even though in other quarters they talk a good line about promoting climate solutions. I’ve even been (quite) disappointed with my own colleagues who are so exuberant about energy efficiency that they can’t see that doing this in the particular case of cannabis is only optimizing the suboptimal. Meanwhile, environmental groups probably feel they would be in a bind by coming out against (indoor) cannabis, which many of their subscribers imbibe in and identify with in the increasingly blurred association with cannabis, nature, and green values.

Can you speak more about the conflation between these things? At what point did cannabis and environmentalism diverge?

Cannabis was more or less synonymous with the social and intellectual movements of the 1960s: mind expansion,  interconnected, the earth and its resources are finite and need to be stewarded rather than squandered. Of course, some (perhaps many) cannabis cultivators and users likely still hold those good values, but there was a divergence first when cultivation moved indoors (requiring intensive energy use) and later as the industry became “big business.”

As is the case for almost all big businesses, profits and the game of skirting regulation often come before other goals. Though this is gradually improving, progress is slow and cannabis producers have not appeared in the vanguard.

It’s important to say that, in parallel with this, many outdoor growers came to flaunt environmental values as well (illegal water diversions, use of illegal rodenticides, and unpermitted road construction, for example). As is the case for almost all big businesses, profits and the game of skirting regulation often come before other goals. Though this is gradually improving through the environmental, social, and governance (ESG) movement, progress is slow and cannabis producers have not appeared in the vanguard. Most of the attention to sustainability among indoor producers does not get far beyond green-washing, with energy improvements limited to those that enhance profits and solar panels on the roof that look great but only meet a few percent of total energy needs.

So, who should be leading the charge: producers, investors, retailers, consumers, or policymakers?

All of the above.

Is there any other change that comes close to switching to outdoor growing in terms of environmental gains?  

I’m afraid there is no viable alternative to outdoor cultivation. But the good news is that outdoor cultivation has helped people get high and healthy for 5,000 years. It’s like they say: if it ain’t broke, don’t fix it.

It would only take 0.01 percent of US farmland to meet all US cannabis needs outdoors. The only crop requiring less land today is birdseed.

I used to think that creating “net-zero” indoor facilities--with high efficiency and all energy provided by solar panels--was the way to go.  But, I later found that zeroing-out carbon emissions would require vastly more capital investment than this industry or its investors would tolerate.

To provide all electricity needs for a typical grow requires around twenty times the building’s land area in solar panel coverage.

To provide all electricity needs for a typical grow requires around twenty times the building’s land area in solar panel coverage, which is clearly a non-starter as well. I don’t see that waiting decades for the grid to be clean is appropriate either, as there are many, many other electric loads that have no outdoor alternative that need to be first in line. Also, there are impacts of centralized renewable energy production and transmission, so we need to always optimize and minimize energy demand first before producing energy, be it with coal plants or wind turbines.

Do you think you’ll see positive change in the cannabis industry within your lifetime?

I’m certainly hopeful, but there is no real indication that this is happening – or that the industry or policymakers are taking it seriously enough. Rather, we’re seeing a lot of green-washing by this industry and willful ignorance by policymakers (local, state, and national). On the rare occasion when an indoor grower contacts me and says, “Hey, we’re running our operation with no carbon emissions,” I congratulate them, ask for the data, and then never hear from them again.

What has to happen for industry to take greenhouse gas emissions more seriously?

In decades of work on climate policy, we have massive evidence that free markets don’t, on their own, properly value environmental costs. This is often because of market imperfections and distortions. Regulation is usually needed to resolve market failures.

As for the industry itself, I think there needs to be an effort to dispel the mythology about the inferiority of sungrown cannabis.

I think the only option for policymakers is to require that all cannabis cultivation occur outdoors (and, of course, follow sustainable practices). This makes it incumbent on them to remove disincentives (for example, subsidies to indoor growers for LED lights that just make unsubsidized sungrown less competitive)and barriers (for example, the interstate transport issue – growing indoors in Long Beach requires half the energy as growing in Anchorage). As for the industry itself, I think there needs to be an effort to dispel the mythology about the inferiority of sungrown cannabis. If best-practices are pursued, subsidies or favoritism to indoor cultivators stopped, and the tendency of indoor retailers to undermine the reputation of sungrown is curbed, the straight economics will ultimately show that outdoor can be the most profitable strategy.

You can find Evan Mills collective works here

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About the Author
Phoebe Harkin

Deputy Editor

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