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As Marijuana Industry Explodes, Some Shift Focus to Water Conservation

No one yet knows how big the legalized recreational marijuana business will become. But as it grows, water consumption is sure to become a concern in the arid West. Brandy Keen gives one industry leader’s point of view.

Written by Matt Weiser Published on Read time Approx. 7 minutes
An organic indoor marijuana growing operation in Pueblo, Colo., photographed in 2016.Photo by Jeffrey Rotman, Biosphoto, via AFP

Marijuana is becoming big business around the West as more states legalize the plant’s cultivation for recreational purposes. California’s entry into the field, which becomes official on January 1, is certain to bring an explosion of cannabis-related commerce simply because of the size of its market.

All this poses a vital question: How much will marijuana tax the West’s water supplies?

No one knows the answer to that yet, but some in the industry are already working diligently to slash marijuana’s water footprint. Marijuana is known to be a thirsty crop, but much of that depends on how it’s grown.

To get a feel for this landscape, Water Deeply recently interviewed Brandy Keen, co-founder and senior technical adviser at Surna. The company, based in Boulder, Colorado, makes and distributes water-efficient indoor cultivation equipment and serves as a consultant to growers who want to manage their resource consumption and expenses.

Keen got into the business when she and her husband, an epileptic, discovered that marijuana helped manage his seizures and eliminated his need for conventional medication. In September, Keen was a featured speaker on water and energy conservation at the Cannabis World Congress and Business Expo, held in Los Angeles.

Brandy Keen, co-founder and senior technical adviser of Surna Inc., which makes and distributes water-efficient indoor cannabis cultivation equipment and also serves as a consultant to growers. (Photo courtesy Surna, Inc.)

Water Deeply: How much water does marijuana use?

Brandy Keen: It’s pretty water-intensive. It uses a lot of water in comparison to other crops. But what’s really interesting is that cannabis is grown in a controlled environment far more often than agricultural food crops. And when you cultivate in a controlled environment, you can dramatically reduce waste [such as] runoff associated with growing in fields, for instance.

In California, a lot of folks are still growing their marijuana plants outside, but they’re growing them in pots in an effort to conserve water. But they may still have a bunch of evaporation out of their pots that the plants aren’t actually using. We can reduce that with cannabis through creative irrigation and reducing the amount of evaporation by not overwatering. That compares to a hydroponic system, where I irrigate and then store that water, and it’s not evaporating.

But the most interesting thing you can do is use reclaimed condensate. No plant consumes water. Plants borrow water. They use water as a delivery mechanism for nutrients, then they transpire that water back out into the space. So when you grow in an open-air greenhouse or outdoors, all the water your plant transpires is evaporated. It just ends up back in the atmosphere.

When I grow in a controlled environment where I dehumidify that space, now I can actually recapture all that condensate. That’s water I gave my plant, and I can just condense it back out of the air and reuse it. It’s basically like you’re producing distilled water. You just add more nutrients to it and give it right back to the plant. I can actually make this a net-zero water consumption process.

Water Deeply: How common is the use of reclaimed condensate?

Keen: It’s increasingly common. In some areas reclaimed water is accepted for some kinds of agricultural use, but not accepted for cannabis yet, for whatever reason. Denver right now is actually looking at its regulations, and it looks like they’re going to change it so the city of Denver will allow you to use reclaimed condensate.

Water Deeply: What does it involve mechanically?

Keen: In a controlled growing environment, you have condensate piping from cooling and dehumidifying systems already. You already are putting in the piping that puts that condensate down the drain or outside. So I just build a tank to hold it instead. It’s not any more expensive from an infrastructure standpoint, except for the cost of the tank. Then you need a filtration system for the condensate, which is going to be a couple thousand dollars.

Water Deeply: Presumably there’s a saving on the water bill as well.

Keen: Oh yes. If I can reduce my water consumption – even if it’s just by half – that’s a big deal. Keep in mind, most cultivation facilities incorporate some kind of reverse osmosis system on their municipal water supply anyway. And they do that because in order to accurately measure the nutrients I’m adding back into the water, I’ve got to start with low concentrations in the water. Reverse osmosis produces some parts clean water and some parts of extremely dirty water as a waste product. That means for every gallon I save through reclaimed condensate, I’m actually saving two gallons. And as that one gallon is continually reused, it eventually saves me six gallons of municipal supply.

But energy is the big cost component right now. Water is a pretty small consideration. It just doesn’t cost that much to get water. If water was as expensive as energy – well, then we’d be having a different conversation today. That being said, it’s so cheap and so easy to reclaim condensate, and drop my water consumption 70 to 80 percent, there’s absolutely no reason not to do it.

Small marijuana plants are viewed at The Growing Kitchen in Lafayette, Colo., in October 2014. The Growing Kitchen is set in an old scientific research facility near Boulder, Colo., 30 minutes from Denver, and is licensed for medical and recreational marijuana. (Photo by Ivan Couronne, AFP)

Water Deeply: What factors affect marijuana’s water consumption?

Keen: What we see most commonly is actually a calculation based on how much light density is in the space. So the type of light the cultivator selects and the intensity of that light is what drives the transpiration from the plant. And how quickly it’s transpiring tells you how much more [water] it needs to uptake.

We like to drive as much transpiration as possible because that means we’re getting as much yield from the plant as we can. But water and nutrient consumption and photosynthesis are all really closely interrelated. So every time I change one of those things, they all change. If I switch to a lower-intensity bulb, I’m going to be adjusting other things to get my plant to consume as much water as it can.

We typically see watering ranges of somewhere between 3 and 5 gallons [11-19 liters] per day per kW of light – not per plant – in the building. And generally speaking, in a growing operation you have between 0.6 kW and 1 kW for every 25 square ft [2 square meters] of plant canopy.

Water Deeply: What else can be done to reduce water consumption?

Keen: People are doing things like reducing the evaporation of water outside of what your plant is transpiring: not having open tubs of water laying around, covering your pots so that water that would be evaporating out of the pot is contained so your plant can actually drink it.

That has the added benefit of helping you control your environment. Humidity is a huge problem in cultivation facilities. When I’ve got a bunch of water evaporating in a room, now I’m using a whole bunch of energy to dehumidify water that’s not even being used by my plants.

Water Deeply: Are growers interested in saving water?

Keen: Absolutely. We have a multi-pronged reason for doing this. One is obviously the cost of cultivation. Everyone’s always going to be looking at the competition and how to cultivate at a lower price point. Is the cost of water their biggest consideration? No. Overall, water is pretty inexpensive. But it’s still a consideration. So that’s one driver.

The other is, as I like to put it, the ability to do good and do well. We all understand we have to be stewards of this planet. Anything we can do to reduce the resource intensive cultivation of anything, we should be doing it. It takes energy to move that water and treat it. So I think the industry in general wants to do better, wants to be more efficient, wants to do these things that are better for our planet. Whether it’s out of complete altruism, whether it’s out of a marketing competitiveness to say, “We’re a water-wise business,” or whether it’s simple mathematics around how I can make this less expensive to do.

Water Deeply: Do marijuana consumers care how much water their weed uses?

Keen: I don’t think so. But I think in certain markets, they’re going to be really receptive to the marketing component. If the grower can say “We are focusing on energy conservation and water conservation,” I think there are certain buyers who would be influenced by that. Folks in more progressive markets, like California, or areas where brownouts and droughts are really common, people are a lot more focused on this kind of thing than they would be in states like Texas, where climate change doesn’t exist. I’m from Texas, by the way, so I can say that.

So, certainly I think it will start to matter to the consumer. But it’s the industry itself that has to start talking about it.

Water Deeply: What’s the growth potential of this industry?

Keen: The sky is the limit. California and Canada are a huge focus for our company because of the marketing potential there. There are estimates that California alone is going to triple the size of the regulated cannabis market just by itself. So it’s game-changing for the industry.

And it’s a really positive thing, too, that we’re regulating it. Because now we can actually get this information out there [about saving water]. Historically, the industry has had all these underground facilities, and everybody was kind of guessing at what they were doing, because nobody knew where they were, nobody was regulating pesticide use or water consumptive activities.

But I’ve already seen, in some of the cities down in the desert, where they’ve actually had to tell people, “we can’t provide you that many acre-feet of water because the city just can’t even get that much water.” If we go in and reclaim all our condensate, and suddenly that’s 70 percent less water – well, guess what? Suddenly we can build there. If we can figure out a way to make sure we are using water mindfully – well, then we’ve got a completely different opportunity there.

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