Now that it is legal in many areas, marijuana is often cultivated in controlled conditions, such as greenhouses, increasingly at the corporate scale. In such conditions, light, water, and growth-enhancing substances from exogenous sources can be supplied at optimized levels. Artificial lighting replaces sunlight; at least one study more than a decade ago estimated that the cultivation of cannabis indoors accounted for 1% of electricity use in the United States. Marijuana is now big business.
Per kilogram of finished product, the cultivation of marijuana in the United States emits up to 5.2 kg of carbon dioxide (or its equivalents), compared to wheat (0.52), corn (0.47) and onions (0.17). A kilogram of cannabis has the climate impact of a pork roast (5.8). Greenhouse growth of marijuana exceeds the carbon dioxide emissions of tomatoes (2.2) and lettuce (3.7) grown in similar conditions. Most of the energy used to grow marijuana indoors stems from electricity for high-intensity growth lights. Often substantial irrigation is required as well.
Like it or not, marijuana is here to stay, so it would behoove us to minimize its environmental impact, especially its carbon footprint on the climate. There is much to say in favor of its traditional cultivation outdoors, with modest soil supplements to enhance growth.
With every toke you take, you warm the climate. If you care about the planet, stay at home and eat onions.
Clune, S., E. Crossin and K. Verghese. 2012. Systematic review of greenhouse gas emissions for different fresh food categories. Journal of Cleaner Production 140: 766-783.
Mills, E. 2012. The carbon footprint of indoor cannabis production. Energy Policy 46: 58-67
Shrestha, P. and 7 others. 2020. Life-cycle assessment of wheat production, and wheat-based crop rotations. Journal of Environmental Quality 49: doi: 10.1002/jeq2.20158
Summers, H.M., E. Sproul and J.C. Quinn. 2021. The greenhouse gas emissions of indoor cannabis production in the United States. Nature Sustainability 4: 644-650.
3 thoughts on “Cannabis”
I also find it interesting that concern over the environmental impact of growing cannabis extends beyond CO2 in certain places. For example, the volatile organic compounds released by growing cannabis and hemp extraction may enhance levels of tropospheric ozone in Denver’s ozone non-attainment area (Wang et al. 2019 Atmos. Chem. Phys., 19, 13973–13987, https://doi.org/10.5194/acp-19-13973-2019).
This led me down a terrible rat hole, but let’s look at the CO2 content of alcohol. A kg of corn will yield 0.33 kg of pure ethanol, which apparently equals 1.05 L of 80 proof vodka (40% by volume, EtOH and water shrinks 4% on mixing). This does not count the the CO2 released to ferment the corn and distill the alcohol, the CO2 cost of the bottle, or conversely the residual food value of the non-fermentable corn.
Sorry, I suspect a 100 g of cannabis will last the average consumer a lot longer time than 1 kg of booze.
By my very rough calculation, producing 1 liter of bourbon (~ 1 kg) releases about 1/10 of the carbon dioxide than producing 1 kg of marijuana, but a kilo of marijuana would certainly last longer in normal use for a daily high after work. But, of course, I wasn’t doing that comparison in the blog.
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