Energy-intensive indoor pot growth has become a sizable source of greenhouse gas emissions, but there are ways to lessen the environmental burden, new research finds.
Driving the news: The paper in Nature Sustainability provides a full and granular "lifecycle" accounting of the many ways indoor growth produces carbon emissions.
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Why it matters: This cultivation is rising thanks to states including California, Colorado, Massachusetts and others legalizing recreational sales.
"This industry is developing and expanding very quickly without consideration for the environment," Colorado State University researchers said in a summary at The Conversation.
The findings can inform policymaking in states with legal weed or ones considering it, they said.
How it works: The biggest source of emissions is energy needed for sophisticated indoor air management to grow specialized crops at the right temperature and humidity.
Other big ones include electricity needed for high-intensity grow lights, use of CO2 to enhance plant growth, and transportation of various supplies.
The intrigue: The authors find lots of regional variation in modeled emissions as they explored the natural gas and electricity needed for cultivation.
That's due to differing climates and regional differences in how much clean energy is used for power production.
"Areas such as the Mountain West and Midwestern United States are especially intensive for growing cannabis indoors," they find.
Of note: The regional data in the paper's modeling does not reflect the legal status of pot in the different areas.
Threat level: Comparing indoor cultivation to other industrial sectors in Colorado helps provide a sense of scale.
Colorado State associate professor Jason Quinn said it creates about 2.6 million metric tons of CO2-equivalent annually.
"This is similar to coal mining and waste management sectors that are 1.8 and 4.2 million metric tons of CO2-equivalent annually," the paper's co-author told Axios.
"We've estimated that indoor cannabis is responsible for about 1.7% of the state's annual greenhouse gas emissions," he said.
Quick take: None of this is a civilizational threat! But rising sources of emissions are important at a time when scientists warn that steep emissions cuts are needed.
What's next: Changes to growing practices can reduce emissions, the paper notes, including...
Making decisions based on geography and better engineering of indoor farms.
Moving to greenhouses or outdoor growing, which can vastly curb emissions but can also bring their own environmental and security problems.
The chart above provides a sense of the big regional variations in estimated emissions from indoor cannabis growth.
This doesn't show the small amounts of CO2 sequestered during the growing process.
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