Whether it's grown indoors, outdoors, or in a greenhouse, the modern cannabis industry has a negative environmental impact. In a rush to legalize, the industry as a whole has failed to consider the environmental ramifications of commercialization.
A review from a research team at the Department of Environmental Science, University of California, has attempted to compile what we know (and what we don't) about cannabis' dirty little secret.
Their summary, “Cannabis and the Environment: What Science Tells Us and What We Still Need to Know,” relied on available peer-reviewed research to explore exactly what sort of environmental impact commercial cannabis production has on water, energy, and other valuable resources.
A cannabis plant consumes six gallons of water per day for the duration of its lifespan. In rural areas, like Humboldt County, California, one study estimated this might account for 11,000 cubic meters of water diverted to cannabis per year.
While this number represents only 0.0002% of the total crop irrigation in the area, many experts believe most of this water comes from surface water diversions. In dry years, this may mean completely 'dewatering' an area to feed the plants.
Other surveys have suggested that in Northern California, a majority of growers rely on groundwater. Evidence from smaller studies indicates that during peak cannabis production season, there is a measurable decrease in groundwater levels. Some estimates report that cannabis irrigation pulls nearly two percent of monthly streamflow.
The University of California authors conclude that “in the absence of regulation, cannabis irrigation could significantly exacerbate water stresses in drought-prone regions.”
Most people assume the majority of the industry's environmental impact comes from its energy consumption. Indoor and mixed-lighting facilities rely wholly or in part on grow lights, HVAC systems, and other environmental controls, all of which are substantial burdens on the local electrical grid.
Electricity Plans estimates that cannabis consumes 2,000 to 3,000 kilowatt-hours (kWh) of energy for every pound of indoor flower produced. Multiplied by every pound produced in every facility, that translates into massive energy consumption.
The report from the University of California could find only one peer-reviewed paper on the subject, dating back to 2012. In the rapid evolution of the cannabis industry, these numbers are embarrassingly outdated. However, this older study estimated that illegal and legal cultivation in the US had an electricity-use footprint of 20 TWh annually.
Given today's expanding legalization movement, there is an urgent need to reassess the energy consumption in cannabis' new industrial landscape. Many monstrous indoor cultivation facilities cover millions of square feet, requiring lighting, humidity, and temperature control. The more we know about the impact of these facilities, the better the industry can adopt sustainable technologies.
Carbon Footprint & Emissions
Cannabis also has an emissions problem. According to Aster Farms' recent 2020 Sustainability report, which examined its own environmental impact, the average pound of indoor-grown flower accounts for 1,000 kg of CO2 emissions. The industry average for a single joint is 1.5 kg of CO2. When compared with a gallon of gasoline that emits 9 kg of CO2, the environmental impact of a single joint is shocking.
The same older study from 2012 estimated that the annual carbon emissions from legal and illegal cultivation accounted for 15 million metric tons of CO2. As another shocking comparison, that would be the equivalent to the energy consumption of the entire US agricultural sector. Nearly a decade later, it's safe to assume we are now working with an exponentially larger footprint from the cannabis sector.
Unfortunately, CO2 isn't the only emission coming from the cannabis sector. The plants are chock full of potent and volatile compounds, like terpenes, prone to disperse into the air. While terpenes are often a sought-after component within a more extensive strain profile, some studies suggest they could negatively impact the ozone layer.
One preliminary study “predicted increases in hourly ozone concentrations, indicating that concentrated indoor cannabis cultivation could influence ozone pollution.” This is an area requiring more controlled research.
Cannabis' True Environmental Impact Largely Unknown
The research included within this comprehensive examination by the University of California team is notably limited in scope. The authors admit that most of the available information is outdated, specific to Northern California, and/or based on case studies.
Yet, even this preliminary research paints a dire picture. Considering the rapid expansion of the commercial cannabis sector, one can only assume a growing impact on the environment.