Happy 420, everyone! Today is April 20, often known as the unofficial holiday when many people celebrate and enjoy their favorite leafy green, marijuana. Whether you partake or not, it’s worthwhile to learn more about America’s cannabis culture. As of 2021, most U.S. states have decriminalized marijuana in some form or another. In fact, as recently as March 31, New York joined the list of 14 other states that have decriminalized recreational marijuana use. With the marijuana industry expanding to new audiences, what do eco-conscious people need to know about this plant and its demands on the environment? From water usage to pollution, growing cannabis may have a larger footprint than you’d think.

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A green marijuana plant.

Water use

Like most plants, marijuana needs water to grow, perhaps even more so than other crops. As Andrea Michelson wrote for Smithsonian, “cannabis [is] a particularly thirsty plant,” one that has even led the California State Water Resources Control Board to establish guidelines for regulating the industry’s water use. While there are often limited studies on marijuana due to legal complications, we do have some information on the crop’s water demands.

For example, during the growing season in California, each plant needs nearly 22 liters of water a day. According to information from a JSTOR Daily article on “The Environmental Downside of Cannabis Cultivation,” this water usage can reach a total of “three billion liters per square kilometer of greenhouse-grown plants between June and October.” That’s a significant amount of resources, but the industry’s environmental impact doesn’t stop there.

An indoor marijuana growth operation with arrays of indoor lighting and planters.

Energy consumption

How does energy use factor into growing cannabis? Growing cannabis indoors requires a significant amount of energy. These indoor operations appeal to many growers because they can allow faster production, but that production requires electricity to power everything from high-intensity lighting to heating systems and dehumidifiers. Some research estimates that the energy consumed by the indoor grow industry accounts for 1% of the total annual electricity used in the U.S. While that number may seem small out of context, it is actually the equivalent to the amount of electricity needed to power 92,500 American homes for a year. As Smithsonian reports, “That’s 472 tons of electricity-related carbon—and the number is growing as the industry expands.”

Pollution and emissions

According to data from Grist, many “indoor growers plug into the grid, and about two-thirds of the electricity on the grid is generated by fossil fuels.” This means that every pound of marijuana produced creates about 1.95 metric tons of carbon dioxide, the equivalent of three cross-country trips in a 44 mpg hybrid car, or 2,095 pounds of coal burned. That’s a lot of CO2 — in fact, it’s the same amount of carbon sequestered by “1.6 acres of U.S. forests in a year.”

While Smithsonian agrees that “indoor cultivation comes with a massive carbon footprint,” carbon emissions aren’t the only concern. To understand more about emissions from cannabis growth, let’s look at what happened in Colorado after the state began allowing the sale of recreational cannabis in 2014.

As detailed in JSTOR Daily, emissions from over 600 licensed growers in Denver alone were enough to raise alarm over air pollution. William Vizuete, associate professor at the University of North Carolina’s Gillings School of Public Health, investigated this issue, and “his research showed that cannabis plants produce volatile organic compounds or VOCs that can produce harmful pollutants,” journalist Jodi Helmer reports in the article.

In Vizuete’s own words, “if plants produce VOCs, there is a high possibility that under certain conditions, cannabis cultivation could impact the ozone.” These VOCs not only spell trouble for the environment but for human health, too. In high enough concentrations, VOCs are linked to conditions such as nausea, liver damage and cancer.

But licensed growers aren’t the only ones involved in the marijuana industry, and illegal growth operations present their own issues. Among these issues is the use of “banned insecticides and other chemicals” that can devastate local wildlife and water supplies. Some areas have already seen the direct effects of this pollution. According to Grist, “a recent study suggested that more than 85 percent of Pacific fishers near grow sites in the Sierra Nevada range were exposed to poison, which accounted for about 10 percent of all deaths of the threatened species.” JSTOR Daily provides further evidence of harm to wildlife with the example of decimated Coho salmon and steelhead trout populations after growers diverted streams in Mendocino, California. All this information may cast a harsh light on the marijuana industry overall, but there are important perspectives to consider for improving its environmental footprint.

Two people farming marijuana outdoors.

Perspectives and solutions

Meaningful changes to the marijuana industry don’t have to be out of reach. As Grist explains, “There are plenty of climate-friendly fixes that would make a lot of sense if we wanted to green the weed industry, and many of them aren’t unique to pot.” These measures include cleaner energy to alleviate emissions and standards for energy efficiency within the industry. Speaking of standards, JSTOR Daily points out that decriminalizing marijuana at a federal level could help “set emissions standards.”

To further illustrate the importance of decriminalization, JSTOR Daily enlisted Van Butsic, co-director of the Cannabis Research Center at the University of California Berkeley. As Butsic explains, “There are lots of technologies that capture VOCs before they enter the atmosphere that are required in other industries like gas stations.” But, “before [emissions] standards can be set for cannabis, we need recognition of the issue and long-term data to develop regulatory statutes—and we’re a long way from that because federal prohibition has hindered research and we don’t have the science yet.”

While Jennifer Carah, a senior scientist in the water program at the Nature Conservancy of California, acknowledges that unlicensed growers polluting and diverting waterways may not go away completely, it’s worthwhile to “entice growers into the legal market, [where] their agricultural practices can be regulated like other agricultural crops, which will go a long way to addressing potential environmental impacts.”

Via Grist, Smithsonian and JSTOR Daily

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