Indoor weed farms are a hotboxing the planet

As more states legalize the herb, its commercial production is increasing. These growing operations can not only attract customers, but also raise the temperature of the planet.

A new study published Monday in Nature Sustainability aims to quantify the climate impact of indoor cannabis cultivation across the country. The authors, who are researchers at Colorado State University, wanted to know how greenhouse gas-intensive these operations would be if they were implemented anywhere in the country.

“Policymakers and consumers do not pay much attention to the environmental impacts of the cannabis industry”, Jason Quinn, an associate professor of theirechanicalEngineering Department at Colorado State University and lead author of the study, wrote in an email. “There are little to no emissions regulations for growing cannabis indoors. Consumers also ignore the environmental effect. This industry is growing and developing very quickly regardless of the environment. “

Many cannabis growers prefer growing indoors outside because it offers better control over plant habitats and more safety. But these indoor operations come at a cost to the climate, as they require heating, ventilation, and air conditioning to maintain ideal temperature and humidity levels and high-intensity grow lights that stay on 24 hours a day. 24. They also often pump in a steady supply of carbon dioxide to speed up plant growth and increase profits.

To determine how carbon intensive the weed crop is, the team of researchers developed a model to track the energy and materials used for the type of indoor warehouse-style cultivation operation that 41% of American producers use. The model was designed to mimic a typical real warehouse, complete with HVAC, grow lights, pesticides and fungicides, water applied by drip irrigation “at an average rate of 3.8 liters per plant per day”, and more again.

Since temperatures and humidity across the United States vary widely, the authors’ model calculated the energy required to maintain these indoor climatic conditions using a year of hourly weather data from more than 1,000 locations across. the country. Using data on emissions from the electricity grid across the country, the model then showed the greenhouse gas emissions that all the energy required would produce. In addition, the model took into account emissions “upstream” from the production and transport of water, fertilizers, fungicides and carbon dioxide bottles to grow houses, and also tracked pollution. by greenhouse gases “downstream” of all the waste that these operations send to landfills.

In total, the authors found that the cumulative greenhouse gas emissions created by one of these indoor grow stores were between 5,033 pounds (2,283 kilograms) and 11,428 pounds (5,184 kilograms) of carbon equivalent for each 2.2 pounds (1 kilogram) of dried flower. . In other words, the eighth of the weed you buy (legally, of course) has a carbon footprint of up to 41 pounds (19 kilograms).

The authors say that doesn’t have to ruin your buzz, however. We don’t need to give up growing weed. We just need to start moving the industry towards more outdoor growing activities.

“If indoor cannabis cultivation were to be fully converted to outdoor production, these preliminary estimates show that the state of Colorado, for example, would see a reduction of more than 1.3% in annual production in the state. [greenhouse gas] emissions, ”says the study. This means Colorado alone would see a reduction of 2.3 million tonnes of carbon equivalent each year, which the study found is about the same as emissions from the entire mining sector. of state coal.

The results of the study suggest that 80% of greenhouse gas emissions created by growing cannabis are caused by “practices directly related to indoor growing methods, in particular controlling the indoor environment, High intensity grow lights and carbon dioxide input for increased plant growth. . Yes, growing outdoors still requires materials and equipment to ship, and always results in trash being sent to landfills – issues we should continue to work on. But it is much less energy intensive, the authors found.

Of course, outdoor cultivation may not be possible in all parts of the country. Thus, in the States, the authors also identified places where growing indoors is comparatively less energy intensive. In Colorado, for example, “the practice of growing cannabis in Leadville results in 19% more GHG emissions than in Pueblo,” because the former tends to be cooler. In climates where outdoor growing might work, policymakers should take steps to usher in the transition. This includes changing bylaws and zoning codes to allow more of these operations outside.

But all of this is just a first step, say the authors. Much more research needs to be done on how to make this growing industry more sustainable.