The cannabis industry is set to grow — So is its environmental impact

Growing cannabis outdoors has significantly lower carbon emissions.

The $32 billion cannabis industry in the US is expected to expand after being on the ballot in four US states on Tuesday. That includes what would be a major market in Florida, where billionaire Ken Griffin has been outspent by the cannabis industry.

But expanding recreational cannabis use will amplify weed production’s disproportionate environmental footprint. That will make it more urgent than ever for growers to lower their emissions and land and water use, and for retailers to rethink packaging to be more environmentally friendly.

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Greenhouse gas emissions

North Dakota and South Dakota are voting on recreational marijuana ballot measures. They can look north to Canada, which legalized it in 2018 and has an industry expected to reach $4.7 billion this year. There, cold northern winters have meant that cannabis is largely grown indoors.

The heating and lighting needed mean a kilogram (2.2 pounds) of dry cannabis flower grown indoors can produce 1,500 to 4,000 kilograms of carbon dioxide equivalent, said Benjamin Goldstein, head of the University of Michigan’s Sustainable Urban-Rural Futures Lab. In comparison, he said, a kilogram of lettuce only emits one to two kilograms.

Electric heating is a lower-carbon alternative — especially in locations with large amounts of renewable energy on the grid — but hasn’t seen a large uptake due to the higher cost. Going electric would triple the cost of a greenhouse in Quebec during the winter, said Vincent Desaulniers Brousseau, an agricultural researcher who has studied the Canadian weed industry.

In the US, some places where marijuana is legal are working to increase renewables use in cannabis production. Boulder, Colorado, requires cultivators to offset their electricity usage by installing renewable energy on-site or paying into an offset fund for carbon reduction that goes toward expanding access to solar energy in the county. The city raised around $400,000 a year from the offset fund, as of 2021.

Growing cannabis outdoors has significantly lower carbon emissions. But with the drug illegal under federal law, “we cannot have interstate commerce, which means that you are not able to grow cannabis in the sunny, perfect outdoor climates and then ship it around to other states that are less conducive to outdoor growing,” said Aaron Smith, chief executive officer of the National Cannabis Industry Association, which represents over 450 businesses.

Water and land use

While indoor growing is six to 10 times more carbon-intensive than outdoor growing, it can use less than half the amount of water by using recirculation techniques.

Cannabis is primarily grown outdoors in warmer regions like Northern California’s Emerald Triangle, the largest cannabis-producing region in the US. These areas are also prone to drought, and growing weed can add to water stress.

“The way that it was traditionally cultivated used a lot of water,” said Jackee Riccio, executive director and co-founder of the nonprofit Cannabis for Conservation. The number of growers has strained the region’s water supplies, she added.

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Riccio’s organization works with over 350 cannabis farms in Northern California to make the cannabis industry more sustainable. She said farmers have been working to be more drought-resilient by conserving water through improving irrigation systems’ efficiency and installing rain catchment systems.

Farms are also trying to improve biodiversity by installing bat and bird boxes to get the native species to nest on their properties. “When you invite those species back onto your farm and they’re catching insects, they’re also producing guano, which is going to enrich your soil,” Riccio said.

Plastic packaging

Laws in Canada and the US around cannabis packaging can also lead to large amounts of plastic waste not always accepted by regional recycling programs. It can take 70 grams of plastic to package just 3.5 grams of dried cannabis, according to a 2020 McGill University research study. Smith said packaging can be safe without being excessive, but governments need to rewrite regulations — or, in the case of states that are just starting to legalize, to write packaging rules that have sustainability concerns in mind.

“We’re definitely not going to move away from these impacts we’re seeing at the moment” without government intervention, Desaulniers Brousseau said.

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