Whoa — Growing Weed Indoors Results In High GHG Emissions

By Amy Lupica, ODP Staff Writer

Marijuana is now legal in 15 states and counting, and medical marijuana is now legal in 34 states. It’s big business — 2020 sales broke records, surpassing an estimated $15 billion. But new research from Colorado State University, a state that pulled in over $387 million in marijuana taxes in 2020, found that marijuana farming isn’t just producing revenue, it’s producing dangerous levels of greenhouse gasses as well. In states like Colorado, GHG emissions from marijuana production have even surpassed that of coal mining.   Why? Because growing it inside, which is mandatory, is energy-intensive.  

Why This Matters: The American Civil Liberties Union has called on governments to fully legalize cannabis and ensure that new legal markets make room for those who have been disenfranchised by marijuana laws in the past. But according to this new study, those markets are becoming some of the most polluting in their states, and that pollution greatly impacts people of color. To ensure that legalization promotes civil rights, protects public health, and fights climate change, marijuana production must be sustainable. 

High Emissions

“The emissions that come from growing 1 ounce, depending on where it’s grown in the US, is about the same as burning 7 to 16 gallons of gasoline,” said Hailey Summers, who worked on the study. Emissions vary widely by state, but approximately 2.3 to 5.2 tons of carbon dioxide equivalent (CO2e) are produced per kilogram of dried flower. Estimated emissions from Colorado grow operations totaled 2.6 megatons of CO2e compared to just 1.6 megatons from the state’s coal mining industry.

Why the high emissions? In the U.S. most cannabis is grown indoors. About 40% of America’s emissions come from powering, heating, and cooling buildings, and the heat lamps and climate control systems used in indoor growing operations consume electricity at extremely high rates. This isn’t always the fault of the growers; some states have legally mandated that cannabis plants be grown indoors to prevent theft. Additionally, illegal grow operations that (obviously) don’t follow regulations, can be even more highly emitting. Illegal growing “frequently involves on-site diesel generators, which are often less efficient and more polluting per kilowatt-hour than grid-purchased electricity,” explained researcher Evan Mills.

High Hopes

The CSU team says there are many ways that growers can reduce their indoor operation’s carbon footprint. Switching lamps to LED bulbs and retrofitting climate control systems are good places to start, but outdoor farms will do the most to reduce emissions. Greenhouses and natural sunlight are much more affordable than indoor infrastructure, but team member Jason Quinn pointed out that affordability isn’t a prime motivator for many of these operations. “One of the challenges associated with this is that the profit margins are so huge that you don’t have to be making super energy-conscious decisions,” he said. If grow operations make these changes, the CSU team estimated that Colorado alone could save 2.1 megatons of CO2e, representing 1.3 percent of the state’s total emissions.

Legalizing marijuana is crucial to racial justice in the United States. Between 2010 and 2018, there were more than six million marijuana-related arrests, most for possession. Black individuals are more likely to be arrested than white individuals in every single state, including those that have legalized marijuana.

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