Why is growing pot so bad for the climate?
In his 2022 budget proposal, President Joe Biden included a rider first introduced by Republican Maryland Rep. Andy Harris that would block D.C.s ability to legalize and tax recreational marijuana, even after the citys residents voted to legalize possession back in 2014. While the budget provision is plainly at odds with Bidens support of D.C. statehood and autonomy, its also the latest example of Bidens conservative views on marijuanaviews that could have major consequences for the climate crisis. Advertisement  Currently, because marijuana is not legal at the federal level, cannabis growers are not allowed to ship their products over state lines, as Emily Atkin explains in a recent edition of her newsletter, Heated, aptly titled Bidens anti-weed budget is anti-climate. Rolling Stone dubs weed a climate villain, as cannabis sold in any state where its legal must be grown in-state. Because not every state boasts the year-round warm climate that cannabis thrives in, the vast majority of cannabis is grown indoors in large facilities. And there are other reasons indoor growing is thriving, as Evan Mills pointed out in a recent Slate piece, from misconceptions about the potency of cannabis grown indoors to budtenders who tend to toss outdoor-grown product onto the bottom shelf. Mills argues that the only way to make cannabis truly green is to grow it outside. Advertisement  Advertisement  Advertisement  A study by researchers at Colorado State University published in March has been cited again and again in the discussion over weed, regulations, and the environment. In the study, researchers calculated the energy costs of growing weed indoors in a thousand locations across the U.S. and found not only that indoor weed-growing is a major contributor to greenhouse gas emissions, but also that the environmental impacts vary by state (in Colorado, cannabis emissions outpaced coal). Slate spoke to Hailey Summers, the first author on the study and a Ph.D. candidate at Colorado State University, to learn more about marijuanas climate impacts and the federal governments role in the problem. This conversation has been condensed and edited for clarity. Hailey Summers: Right now, we actually have an extension project thats looking at other crops and how they might compare, but if I had to speculate, I think that most indoor agriculture will have high emissions, mostly from the lights and the environment controls needed to maintain certain indoor climates to make the plants happy. I think that theres also some things about cannabis that might make it have a little bit higher emissions, like the added carbon dioxide that cannabis growers are putting into the room. They are putting in bottled CO2, or theyre burning natural gas on-site to basically get CO2 in the room. That increases your rate of photosynthesis and makes your plants grow bigger and faster, so you can get more flower faster. Some other indoor cropping systems are doing that, but most crops cant afford to because the commodity just isnt as valuable economically, so they cant pay for all those added operational expenses. Just the CO2 accounts for between 11 and 25 percent of the total emissions for all the locations across the U.S. that we ran. It can be up to a quarter of your total emissions in any one location. And thats a conservative estimate. We only accounted for the emissions associated with actually bottling the CO2, and to transport and use that CO2 in the building. We didnt account for, say, if growers are putting in a molecule of CO2, and its not taken up by the plants, but then its released through the ventilation systems to the environment. Advertisement  In your study, you found that its more carbon-intensive to grow cannabis in some places over others, even when comparing indoor facilities. Advertisement  Theres two primary considerations that we figured out when it comes to geographic location. The first is grid mix and the second is weather. With grid mix, essentially, if youre pulling electricity in California versus New York versus Texas, the emissions per kilowatt-hour of electricity thats coming out of the wall will be different in each location based on what the utility providers are using to generate electricity in the region. So California has a lot of solar. Solar doesnt emit that many emissions compared to coal when youre actually generating electricity, so California has a pretty clean grid. If you were locating your facility in Texas or Colorado, we have a lot of coal and natural gas, and so those energy sources lead to a lot higher emissions when youre generating electricity. Advertisement  Weather comes into play because the plants need access to fresh air from the outside. The heating, ventilation, and air conditioning system uses a constant supply of fresh outside air, and then it just changes it to meet what the plants want to be comfortable at. When that heating, ventilation, and air conditioning equipment is modifying outside air, it needs more energy to modify it if theres extreme weather events. If youre always growing in Michigan and its really cold half the year, but the plants want to be at 75 degrees inside, its going to take more energy in Michigan to constantly meet and change that outside air to meet the comfortable inside air. Advertisement  We did back-of-the-envelope, precursory estimates of what emissions outdoors would be. If you strip away everything thats purely associated with indoor growing, your emissions drop by 80 percent. But it hasnt been studied to the level that I studied indoor growing. So the next step of research is really to understand the emissions from greenhouse and outdoor with quantitative numbers. I think one thing that could happen is having the industry adopt how our food is grown in the U.S. We have central locations for a lot of crops, and then its just transported across the U.S. Right now, you cant do that with cannabis. You cant grow in one state and cross state lines and sell in another. Even if youre growing indoors, if you could just locate those indoor facilities in places that are better suited, whether thats with clean grid mixes or weather that doesnt need to be as modified, and then ship it to states that dont have the suitable climate or clean emissions from their grid, the trucking emissions are very, very small relative to the differences [in emissions that come from] just relocating the facility. I think federal legalization can help that become a reality. Im also hopeful that more funding will become available for people that want to research this. Right now, theres no federal money allocated for cannabis research because its illicit.