4/20, Canna4Climate, and Earth Day

Source: Richard T on Unsplash

Some may be surprised to learn that the celebration of Earth Day is closely connected to cannabis culture. Still, the proximity of National Cannabis Day and Earth Day is more than a happy accident. The introduction of marijuana into mainstream American culture was piloted by the same student groups that brought conservationism to national attention. In fact, the first Earth Day celebrated on April 22, 1970, preceded the first celebration of 4/20 by less than a year. Recently, cannabis enthusiasts have begun a movement that weds the two green celebrations through Canna4Climate Day, taking place on April 21.

The Cannabis sativa plant is a champion of the eco-friendly movement in its own right, consuming far more carbon dioxide and producing more oxygen than most other plants. However, the current circumstances under which cannabis is grown have reversed the plant’s climate positive effects. Recent studies have shown that the budding cannabis industry is a major source of greenhouse gas emissions across the country.

Cannabis and Climate Change: The Data

As a young industry with legal standing in only seventeen states, little research has been done on the environmental effects of cannabis cultivation. The existing data goes back only a few years, but already it offers a clear look at the harmful side effects of the burgeoning cannabis sector. With an average growth rate of 16% per year, it's more important than ever to understand the environmental impact of the cannabis industry.

In 2020 marijuana sales made up 2.7% of Colorado’s tax revenue, but there are equal negative consequences with all the crop's financial benefits. According to the Centennial State’s Department of Public Health and Environment, data from the same year showed that the weed industry in Colorado was responsible for 1.3% of its total carbon emissions, contributing to a larger part of the state’s environmental footprint than coal mining.

Colorado’s marijuana industry is a leader in the United States’ cannabis-related carbon emissions, owing in large part to the region’s weather extremes and the state’s reliance on coal and fossil fuels. Like California, states with coal-free energy grids have far lower marijuana-related carbon emission rates. Longbeach, CA, has the lowest greenhouse gas emissions (GHG) of all cannabis production sites in the United States, producing about 143 pounds of carbon dioxide per ounce of dried cannabis, while Kaneohe Bay, HI produces the most at 324 pounds per ounce. Researchers based out of Colorado State University conducted a survey of data collected by the US Department of Energy and the US Environmental Protection Agency. In general, greenhouse gas emissions are lowest at growing facilities on the Atlantic and Pacific coasts. However, the industry’s net emissions remain a large problem everywhere and will only continue to worsen as legalization spreads.

Greenhouse Gas emissions per kg of dried cannabis Source:Jason Quinn

What’s Changed in Marijuana Farming?

Cannabis, in one form or another, has been grown in the United States for centuries, so it can seem strange that the plant has developed such a large environmental footprint in recent years. This is due, in part, to the requirements unique to modern marijuana farming. Chief among these is the need to grow cannabis indoors, a condition that significantly increases the plant’s energy bill. Industrial hemp has long been grown in the Southeast and Midwestern regions of the United States. Still, as the plant became more profitable and quality concerns heightened, outdoor farming ceased to be a viable option for growers looking to create the best possible product.

The Case Against Inner Growth

In a sector as profitable as the cannabis market, it’s no wonder that extreme steps are taken and high prices are paid to keep weed crops safe and healthy. Indoor greenhouses allow growers to protect their plants from bad weather, insects, and even thieves. Growing facilities allow for year-round cultivation, meaning more profits for cannabis businesses. These greenhouses, however, have enormous energy costs.

Although cannabis is a hearty plant that can grow in a number of different climates, they flourish in warm, arid environments, resulting in higher energy costs for colder states, like Colorado. Maintaining an ideal growing environment – not too hot, not too cold – requires facilities to run heaters and air conditioners all year long.

The lights used in indoor greenhouses are also major sources of carbon emissions. To maximize growth, most facilities use powerful but energy-inefficient lights called high output fluorescents (HOs), with high-pressure sodium lights (HPS) also very popular. However, it’s uncommon for indoor greenhouses to use only one type of lighting. Most use a combination of HOs and HPS lights over the course of a plant’s growing process, because each stage, from initial propagation to the flowering of the crop, has unique lighting needs.

A large part of the carbon emissions of growing facilities is a result of a process meant to expedite plant growth. Growers often pump extra carbon dioxide (CO2) into greenhouses in order to increase the plants’ rate of photosynthesis. On its own, photosynthesis is a way in which CO2 is removed from the atmosphere and recycled to make oxygen and glucose, a sugar that plants use to grow. But much of the CO2 that planters artificially fill their greenhouses with is released back into the environment, constituting between 11 and 25% of these facilities’ emissions. Oxygen too, must be removed from indoor greenhouses at risk of the cannabis crop succumbing to toxic oxygenation. The task of regulating oxygen and carbon dioxide levels is relegated to enormous ventilation and filtration systems. This equipment also treats all the air that enters the facility, correcting its temperature and moisture levels. This process often happens dozens of times per day, with many facilities “replacing” their air once every hour.

Finding Sustainable Solutions

Little is known about the environmental impact of cannabis after it has left the greenhouse. Researchers have not yet studied cannabis-related emissions beyond the scope of indoor growing facilities, meaning the environmental impact of storing and processing weed is yet unknown. More studies are needed to form a complete picture of the industry’s ecological toll. Still, by unveiling the harmful consequences of indoor greenhouses, the existing research has allowed producers to better understand how to solve this part of the problem.

Researchers from Colorado State University recommended that growers make the switch from energy inefficient HO and HPS lights to the more eco-friendly LED bulb. Retrofitting the climate control systems and investing in high-efficiency HVAC equipment could also make an enormous difference in the energy requirements of cannabis facilities. Outdoor greenhouses would also drastically reduce carbon emissions, but some scientists argue that this practice would only generate new problems, such as pesticide run-off and deforestation.

The Importance of Marijuana Legalization

Though the large environmental footprint of the cannabis industry may give some would-be supporters of marijuana legalization efforts pause, legal cultivation poses a much smaller risk to the environment than illegal operations. According to Evan Mills, a retired senior scientist from the Lawrence Berkeley National Laboratory, “The energy profile of black-market production is distinctly different in that it frequently involves on-site diesel generators, which are often less efficient and more polluting per kilowatt-hour than grid-purchased electricity.” Illegal production sites are also more likely to use old buildings as the base of their indoor greenhouses, which are less energy-efficient than newer facilities subject to regulation. Most importantly, the recent legality of cannabis has allowed it to become the subject of research and scientific scrutiny.

Due to legalization, scientists are able to fill in the gaps in our understanding of our own net emissions. Pointing to cannabis as a source of greenhouse gasses offers us an opportunity to fix the problem. By studying the industry, researchers are learning how to improve it. Evidence suggests that CO2 emissions per kilogram of dried flower have already decreased since the correlation between marijuana farming and greenhouse gasses was first studied. Cannabis is a rapidly growing sector in the American economy and with all rapid expansions comes growing pains. But growth is also an opportunity for evolution.

As we move from 4/20 to Earth Day, it’s important for cannabis enthusiasts everywhere to support those industry leaders to whom the planet is of the utmost importance and recommend going green.