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Does smoking cannabis fuel the climate crisis?

by Emma Batha | @emmabatha | Thomson Reuters Foundation
Friday, 9 April 2021 12:51 GMT

A customer lights a joint at Lowell Farms, America's first official Cannabis Cafe offering farm-to-table dining and smoking of cannabis in West Hollywood, California, October 1, 2019. REUTERS/Mike Blake

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Colorado State University study says rapidly expanding indoor marijuana cultivation is a growing source of planet-heating emissions

By Emma Batha

LONDON, March 9 (Thomson Reuters Foundation) - Is a beer, a cup of coffee or a spliff more damaging for the climate? If the cannabis is cultivated indoors on a commercial scale, the answer is probably the joint.

That's the finding of researchers at Colorado State University who say booming indoor marijuana production in the United States is a major and growing source of greenhouse gas emissions that cause global warming.

The $13.6 billion industry has nearly quadrupled since 2012 when Washington and Colorado became the first states to open the doors to recreational use.

But policymakers and consumers have largely ignored the environmental cost of energy-hungry indoor cultivation, the researchers said in a study.

Nearly a third of U.S. states allow recreational use, while medical cannabis is legal in about two-thirds.

In Colorado, indoor cultivation accounts for an estimated 1.7% of the state's annual greenhouse gas emissions - similar to that for coal mining, the study's co-author Jason Quinn told the Thomson Reuters Foundation on Tuesday.

Large contributors include the heating, ventilation and air conditioning needed to maintain the right conditions for the plants, high-intensity grow lights and the use of supplemental carbon dioxide to boost growth.

Preliminary research suggests the level of planet-heating emissions per 0.1 grams of pot - about a third of a joint - was likely to be far greater than for a glass of beer, wine or spirits, a coffee or cigarette, the authors said.

"We were very surprised at how high the impact is," added Quinn, director of the university's Sustainability Research Laboratory.

"There's a real opportunity here to reduce that impact. Consumers can start asking, 'Is your cannabis produced indoors or outside?'."

Moving to greenhouse or outdoor cultivation could cut emissions by 42% and 96% respectively, said the study published in Nature Sustainability.

The research revealed a large variation in emissions across the country, and within some states, with indoor cultivation in milder climates requiring less heating or air conditioning to maintain favourable temperatures and humidity.

Producing 1 ounce (28g) of dried cannabis in eastern O'ahu in Hawaii was roughly equal to burning 16 gallons (60 litres) of gasoline, creating more than twice the emissions from growing the same amount in southern California, the authors said.

They suggested states that had already legalised cultivation should steer indoor production towards regions with more optimal climates, while states legalising cultivation in the future should consider avoiding indoor production.

However, they said switching production outdoors could create security concerns and make it harder for growers to produce multiple harvests a year and ensure consistency.

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(Reporting by Emma Batha @emmabatha; Editing by Helen Popper and Katy Migiro. Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, which covers the lives of people around the world who struggle to live freely or fairly. Visit http://news.trust.org)

Our Standards: The Thomson Reuters Trust Principles.

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