Greenhouse gas emissions from the legal cannabis industry in the United States climbed so quickly in recent years they now equal that of about 10 million cars, according to a study into the energy and emissions of cannabis production. A switch from indoor to outdoor grows, however, could lessen that environmental impact by lowering emissions as much as 76%. That’s according to Northern California-based researcher Evan Mills, who has spent years building a model of the legal cannabis industry’s energy inputs and emissions outputs. He concludes, energy use by the sector is “on par with that of all other crop production” and the cannabis industry represents 1% of “total national emissions from all sectors of the economy”.
Compared to other industries, the study continues, “direct, on-site use of fuels and electricity by the cannabis industry is four times that of domestic use by the US pharmaceutical industry and beverage and tobacco manufacturing. Energy use is a third of what is used by data centres nationally” it adds, “and 1.5 times that of cryptocurrency mining”. Mills’ lifecycle analysis includes not just cultivation itself, but transportation, retail and waste disposal. “Cannabis has become the most energy and carbon-intensive crop” the author wrote, “as cultivation has shifted from open fields to indoors, covering an area of ∼5 million square metres in the US”. That physical footprint, he noted, is “greater than that dedicated to artificially lit food production and floriculture across the country”.
Mills’ report asserts that about 90% of cannabis-related emissions come from indoor grows, which are far more energy intensive than outdoor cultivation. “Indoor cultivation can also yield worse outcomes for indoor and outdoor air quality, power grids, waste production, water use, energy costs, worker safety and environmental justice. Emissions have risen substantially despite widespread state-level legalisation efforts, which suggests that relying on market forces alone is not a viable climate strategy for this industry” the report says. “More targeted policy initiatives are needed to manage emissions, and the greatest potential lies in guiding the industry toward a much larger share of open-field cultivation”.
Additional policy shifts that could reduce emissions include increased home growing of cannabis, wider use of greenhouses by cultivators, use of more energy efficient varieties of the plant, implementation of on-site solar and other updates. “Key upward pressures include rising demand for cannabis, changes in industry structure, reversion of legal producers to the illicit market (where electricity sources can be dirtier and less efficient) in response to what are perceived as overzealous regulations and a trend toward derivative products that embody added processing energy” the report says.
Currently, cultivation is trending the wrong direction. “Large-scale legal indoor cultivation is increasingly concentrated in environmentally overburdened urban areas” it says. The study comes on the heels of separate research last year finding, “outdoor cannabis agriculture can be 50 times less carbon-emitting than indoor production”. Authors of that report noted while a handful of studies have examined indoor production, “very little is known about the impact of outdoor cannabis agriculture”. “Dissemination of this knowledge is of utmost importance for producers, consumers and government officials in nations that have either legalised or will legalise cannabis production” they wrote.
A 2023 report from the International Coalition on Drug Policy Reform and Environmental Justice drew attention to the negative impacts of unregulated drug production in areas like the Amazon Rainforest and the jungles of Southeast Asia. Attempts to protect those critical ecosystems, the report warned, “will fail as long as those committed to environmental protection neglect to recognise and grapple with, the elephant in the room”, namely, “the global system of criminalised drug prohibition, popularly known as the ‘war on drugs’”.
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