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Here, we take a look at the top issues related to cannabis cultivation: what top environmental problems still face the cannabis industry, how to reduce emissions in grow facilities, the different effects of various strains on carbon emissions, and how the government is finally helping the industry do a deeper dive into understanding these issues.
Presenting new environmental studies for a safer indoor grow operation.
How much does cannabis cultivation really affect the environment? And what should cultivators do about that?
Some cultivation facility builders believed that they already determined those factors in the design phase of their grow facility. The reality is that the myriad of environmental factors inside a grow operation is a crucial issue that the cannabis industry is still trying to manage (1).
There are also employee health considerations to consider as well. Workers inside indoor cannabis grow facilities need to know more about what they are facing in their work environment.
According to the Colorado Department of Public Health and Environment (CDPHE), the top occupational hazards of cannabis cultivation are biological (heat, molds, bacteria, fungus, and allergens), and chemicals to support crop production (carbon dioxide, carbon monoxide, volatile organic compounds, biogenic volatile organic compounds [BVOCs], fertilizers, and pesticides).
Cannabis emits BVOCs, which can alter the ozone by forming toxic air pollutants. That’s why emission controls and respiratory protection are essential for worker and public health.
This “Tech Innovations” column discusses what top environmental issues still face the cannabis industry, how they can help reduce emissions in their grow facility, the different effects of various strains on carbon emissions, and how the government is finally helping the industry do a deeper dive into understanding these issues.
Greenhouse gases (GHG) are gases that trap heat in the atmosphere (2). So, how much GHG is generated by a cannabis cultivation facility?
That was what Jason Quinn set out to discover. Quinn is the associate professor in mechanical engineering and director of the Sustainability Research Laboratory at Colorado State University in Fort Collins, Colorado. He is one of the authors who recently published a study into greenhouse gases for indoor cannabis grows in Colorado because the state is such a good place to find and study greenhouse gas emission data (3). Colorado grew more than 1.8 million pounds of legal cannabis in 2020 (4), with Denver, Pueblo, and El Paso growing the most number of plants in 2020—over half a million plants in Denver alone. Quinn’s study included the results of a recent survey that showed 41% of producers in North America indicated that their grow operations occur solely indoors.
It is well known that indoor cannabis cultivation requires significant energy input, reflected in high utility bills. However, many of these large energy loads, along with other material inputs required to cultivate indoor cannabis, have not yet been equated to GHG emissions.
Some quantifications of GHG emissions from indoor cannabis have been performed by equating emissions with electricity use from monthly bills. But that’s not enough.
According to Quinn’s study, this quantification approach omits additional GHG emissions from other energy sources, such as natural gas, upstream GHG emissions from the production and use of material inputs, and downstream GHG emissions from the handling of waste.
To help develop data on these sources and their effects, Quinn and his associates quantified the GHG emissions of commercial indoor cannabis production using life cycle assessment (LCA) methodology (a technique for assessing the environmental aspects associated with a product over its life cycle ), and expanded the scope to include geographic effects across the US.
An indoor cannabis cultivation model was developed by Quinn and his researchers to track the necessary energy and materials required to grow cannabis year-round in an indoor, warehouse-like environment. This environment maintains climate conditions as required for the cannabis plants, yielding a consistent product regardless of weather conditions.
The model calculates the necessary energy to maintain these indoor climate conditions by using a year’s worth of hourly weather data from more than 1000 locations in the US. (The researchers analyzed locations independent of current legal status, and represent hypothetical grow facilities in all 50 US states.)
The model then converts the required energy, supplied from electricity and natural gas, into GHG emissions through electrical grid emissions data from 26 regions in the US and life cycle inventory (LCI). Additionally, the model accounts for the upstream, or cradle-to-gate, GHG emissions from the production and transportation of material inputs such as water, fertilizers, fungicides, and bottled carbon dioxide (CO2) supplied for increased plant growth, as well as the downstream process of waste handled in a landfill.
The resulting cumulative GHG emissions for annual indoor cannabis cultivation across the US was represented as kilogram CO2e per kilogram of dried cannabis flower (kgCO2e kg–1). “Carbon dioxide equivalent” or “CO2e” is a term for describing different greenhouse gases in a common unit. For any quantity and type of greenhouse gas, CO2e signifies the amount of CO2 which would have the equivalent global warming impact (6).
Quinn explained that the primary conclusions of the study were that greenhouse gas intensity varies dramatically geographically across the US for two reasons. “If you have an indoor grow facility in San Diego, California compared to Fargo, North Dakota, the energy intensity of maintaining that comfortable cannabis growing environment is very different between those two locations just based on the heating, venting, and air-conditioning (HVAC) intensity associated with those two locations,” Quinn said. “The second thing is what I will call the cleanliness of the grid. So, the emissions intensity associated with the grids in different regions also has a major impact as well.”
He said that a lot of the grow facilities use a higher concentration of CO2 in the room. “The big issue here is the number of air exchanges that the cannabis industry uses in order to maintain a mold-free environment,” said Quinn. “They’re in a situation where the revenue they can make enables them to not require optimization of the facility in terms of energy. And so, they’re putting in rich CO2 but they’re doing massive air exchanges, like more air exchanges then most hospitals. That CO2 is just being pushed out.”
Are any indoor cultivation facilities trying to do anything about these emissions? Quinn said that there are certain retailers and growers who are trying to make a name for themselves in this area. “As a part of this study, I found out that there was a grow facility in Colorado that is 100% hydro-power,” he said. “They reached out to me to say, ‘Hey, listen, we’re hydropower. So therefore, our emissions are much lower.’ That’s a true story, because that dramatically impacts the overall emissions associated with that specific grow facility.”
The study also noted that geographic variations of GHG are most noticeable in Colorado, where the mountainous locations of Leadville, Aspen, Gunnison, and Alamosa lead to significantly more GHG emissions than locations on the plains of Pueblo, Trinidad, or Denver. For example, the practice of growing cannabis in Leadville leads to 19% more GHG emissions than in Pueblo.
Grow operations could consider moving to other areas of the state and operate with lower GHG emissions. For example, the savings in GHG emissions from moving indoor cultivation to Pueblo and away from Leadville are likely to be much greater than the GHG emissions of transporting the final product to retail locations in Leadville.
A study about cannabis cultivation facilities and air quality impact in Colorado (7) first noted that terpenoids are highly reactive compounds with atmospheric lifetimes ranging from seconds to hours. They are primarily biogenic in origin (emissions that come from natural sources ), and their reactions alter the atmospheric oxidizing capacity, resulting in a range of low volatility products that can partition into the aerosol phase and, depending on the concentration of nitrogen oxides, lead to the formation of ozone.
Various studies have found that ozone concentrations in Denver are volatile organic compound (VOC)-sensitive, meaning that an increase in volatile organic compound concentrations will increase ozone production. When combined with VOCs and sunlight, nitrogen oxides help form ground-level ozone, a major component of smog (9). Ozone can cause or exacerbate chronic lung diseases like asthma, chronic obstructive pulmonary disease, or emphysema, especially among vulnerable populations like children and the elderly, for whom it may prove deadly. Researchers attributed 254,000 premature deaths to ozone pollution in 2015.
The location of cannabis indoor grow facilities in a VOC-sensitive region in Denver suggests a potential emission source that may impact regional air quality.
William Vizuete, a former professor in Department of Environmental Sciences & Engineering at the University of North Carolina, and a chemical engineer by training, co-authored that air quality and cannabis study (10). He noted that there were few assessments to date on the environmental impacts of the production of cannabis, especially about the possible BVOCs emitted from the growing of cannabis, and its impact on indoor and outdoor air quality.
Vizuete watched as the legalized cannabis market came to Denver in 2014, and warehouse space was being snapped up because growers were regulated to have a secure perimeter around their grow. Growing indoors was the best way to achieve that requirement, he explained.
Many warehouses in Denver are built near transportation hubs or zones, such as the intersection of I-70 and I-25 in downtown Denver. “Ozone requires both VOCs and nitrogen oxides (11), which are coming from car and truck engine combustion,” said Vizuete, “Cities have lots of nitrogen oxide because there are lots of cars and industry. The bulk of VOCs come from cars. But if you’re in Atlanta, Georgia, there’s also a huge amount of VOCs that come from trees.”
What’s interesting about Denver is that it’s high desert and doesn’t have a huge input of VOCs from trees. “What they did was build all these grow plants right where the highest concentration of nitrogen oxide was,” Vizuete said. “If this was any other industry, like a gas station or power plant, I could go to the EPA and look up the emission factor and know exactly what emissions it produces for every mile driven. I can build an inventory for the entire industry. And then I can input that into my model and see if it makes a difference for ozone.”
He eventually published some of the first studies about emission factors for cannabis, such as the cannabis emissions research project for Santa Barbara County, California that he designed and oversaw (12).
One of the most surprising things he heard from a colleague is that he’s never seen a plant like the cannabis plant as far as emissions. “There are a wide variety of types of VOCs that come off the plant,” he said he found out from his colleague. “The amount varies by lifecycle, whether it’s young or old, whether it’s indoor or outdoor. And what’s surprising is that it varies pretty significantly by strain.”
If you look at Colorado’s 600-plus strains, Vizuete said, every single one of them is different as far as what they emit, when they emit it, and how much they emit. “That was really, really surprising,” he said. “The second thing that was really surprising is that it’s very difficult to build an emission inventory if you don’t know what plants they are, how many of them there are, and what strain they are. That information is actually very difficult to get from the state. So, there’s a lot of uncertainty in building these inventories for the state.”
There is also an interest in mitigating smell from cannabis grows, as more and more growers must address smell complaints (13) by the communities where their grow operations are located.
Vizuete formed a company to continue his research into VOCs after wrapping up his university studies, and “bring science to the wild west of this industry.”
His company was the very first to identify and confirm, with both gas chromatographs and with a nose test, what created the cannabis smell. “I had a hypothesis that there’s no way that this smell from the plant, this skunky smell, is a terpene, which is the conventional wisdom of the industry,” he said. “I know the chemistry that forms that skunky smell for beer in bottles and I know the molecules that it generates. The hypothesis I had was that the cannabis plant is producing those same kind of molecules but are emitting it directly, and are not having to occur via chemistry in a beer bottle.”
Since there is the ability to measure every molecule that’s coming off a cannabis plant, he said, he believed that those molecules could be found. “Sure enough, we found those in the sulfur, and sulfur smells. Just a variety of VOCs, the amount and type and variety of styles varies by strain, and accounts for some of the differences in strength and odor.”
If a cultivation operator knows what the molecule is, there is a test standard available, and they can design their carbon sequestration, the air exchange—basically everything can be designed around that molecule.
“As far as smell mitigation, what we suggest is a combination of a couple of things and it always depends on where you are,” Vizuete said. “We would recommend that you measure and know exactly how much your plants are breathing out, like how many of these gas molecules are breathing out. Then we can size the mitigation to take just enough to capture what they’re breathing out. Not to take too much because then you’re over-designing and you’re wasting energy. You’re drying out your plants. Knowing the amount of gas molecules that are coming off and knowing which molecules to look for helps us in designing and sizing our (mitigation) controls.”
Vizuete hopes to continue his research understanding the consequences to the air quality by cannabis cultivation, but bumps up against limits that are imposed by the US government. For example, he said that, when he looked up the emission factors for cannabis, there’s “absolutely zero” literature that told him anything about any gases. Getting a study done to find those gas measurements was problematic because it’s cannabis. No federal facility or academic institution that relies on government grants would allow him or other researchers to touch it.
Researchers have needed expanded legal access to modern cannabis strains for research on cannabis and cannabis-derived products for more than 50 years. Vizuete and other researchers are always frustrated by the lack of access to cannabis for their work, and, when they finally do get federally-approved cannabis from a legal grow operation in the US, the quality is so poor that it becomes problematic to do the kind of new and advanced tests that the industry needs.
That is finally changing... slowly but surely.
The Drug Enforcement Administration (DEA) just authorized another legal grow operation—their 7th—since announcing that they would make more legal grows available in 2021 (there has been only one DEA-legal grow facility since 1968 ).
That newly licensed facility, Maridose (15), a biopharmaceutical research and product development company focused on cannabis and cannabis-derived products operating out of Brunswick Landing, Maine, was notified by the DEA of its selection in late August after the company spent 5 years working with the DEA.
The criteria for the selection by the DEA was a bit confusing, according to Richard Shain, founder of Maridose. “The way they phrased it was if you’ve been involved in the state cannabis markets, even if it’s legal within the states, the DEA would look unfavorably on the application,” he said. “They didn’t say they would refuse it. Then the next criteria was that they were looking for people that had experience within the industry. That kind of goes against each other.”
The DEA is not going to issue an unlimited supply of licenses, but are limited just to what was needed to supply the needs of the research community.
The way it works is each manufacturer can provide their own strains to the Maridose grow facility. But Maridose has also licensed all the intellectual property from Tikun Olam (16), Israel’s largest medical cannabis provider, providing Maridose with a bank of some of the most researched strains in the world. “So, we have access to all of these strains and research, and we’re going to make those available to the DEA researchers,” Shain said.
Because Maridose is a DEA-licensed manufacturer, the company can only sell to DEA researchers. “As of a year or so ago, that number was a little more than 600 licensed researchers. So, when you look last year at the total quota for the entire research, DEA researchers got 3.2 million grams. That’s not a lot in the scheme of things when you look at sales out there to dispensary. You really don’t need a lot of land to satisfy how much you can grow.”
Their grow operation right now is inside Brunswick Landing, which is an old naval base with its own airport that was decommissioned years ago. “Right now, we haven’t built our larger facility. Our facility now is inside the building. But from a security standpoint, there is phenomenal security.” He said that he wanted to keep the size of the grow confidential for now.
The DEA-approved researchers can research only the dry plant and the extracts. Only DEA-approved manufacturers can grow the live plants. “For example, if the Dana Farber Cancer Institute has run a study and they want to try a different combination of active ingredients and a different strain, they can’t grow it. One of the manufacturers has to grow it. We plan on doing that and having that be something that we made as something of value for our customers.”
David Hodes has written for many cannabis publications, and organized or moderated sessions at national and international cannabis trade shows. He was voted the 2018 Journalist of the Year by Americans for Safe Access, the world’s largest medical cannabis advocacy organization.
D. Hodes, Cannabis Science and Technology® Vol. 5(8), 16-20 (2022).