Indoor cannabis cultivation in the US uses more energy than all outdoor agriculture in the country combined. This generates a large and growing emissions footprint that often goes unrecognised.
鈥淐onsumers are led to believe that this is 鈥榥ature鈥檚 medicine鈥� and that it鈥檚 鈥榞reen鈥� in every sense of the word,鈥� says at Energy Associates, a consultancy in California. 鈥淭here鈥檚 lots of greenwashing.鈥�
More than 60 per cent of the 24,000 tonnes of cannabis grown each year in the US is cultivated in indoor farms that rely on large arrays of lights as well as heating and cooling systems. Those controlled conditions enable the production of more potent flowers and for crops to be grown in more places with more security 鈥� or secrecy. But they come with a large environmental cost.
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Mills used data on both the legal and illegal US cannabis industry to estimate the total energy use and emissions generated by these indoor plant factories. He found they use around 596 petajoules per year. That鈥檚 a 鈥渞emarkable鈥� amount of energy, equivalent to about a third of current energy demand from US data centres, says Mills.
Generating that electricity, as well as the carbon dioxide pumped into indoor operations to fertilise cannabis plants, produces emissions equivalent to 44 million tonnes of CO2 per year 鈥� about the same as 6 million homes. For the average daily cannabis user 鈥� more than 17 million of whom live in the US 鈥� that would mean cannabis accounts for half their personal CO2 footprint.
That large climate footprint has also grown as the industry has seen a rapid expansion with legalisation over the past decade, as well as incentives for indoor cultivation. These figures show that energy use has tripled and emissions have also nearly tripled since Mills conducted a in 2012.
鈥淚ndoor cannabis cultivation is ridiculously energy intensive, especially when you鈥檙e in cold climates,鈥� says at Colorado State University. He says the new figures are in line with .
Energy-efficiency measures could help a bit, but the emissions reductions would be marginal and the industry often opposes such changes, says Mills. Growing more cannabis outdoors would be far more effective, he says, with the potential to slash emissions by three-quarters.
at the National Cannabis Industry Association says one hindrance is regulations requiring certain states to grow cannabis indoors while outlawing commerce between states with suitable climates to grow outdoors.
Consumer preference for potent, indoor-grown plants is also an obstacle. 鈥淢y dream someday is that people will start making decisions based on environmental impacts and people will start asking 鈥榃here鈥檚 my cannabis coming from?鈥欌�� says Quinn.
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