For cannabis cultivators looking to lessen the negative environmental impacts of growing weed, choosing to grow outdoors may be the answer.
A new study has found that growing outdoors can reduce carbon emissions, but critics say the study doesn’t take certain environmental challenges into consideration.
The study recently appeared in ACS Agricultural Science & Technology, a journal published by the American Chemical Society. The researchers set out to find new fertilizer regimes for outdoor grows that provide “optimal” yield with less input and to “quantify how this shifts greenhouse gas emissions, resource depletion (fossil and metal), terrestrial acidification, and the eutrophication potential.”
The study analyzed the environmental impacts of marijuana plants grown in Canada over three growing seasons. Researchers tracked supplies and equipment used and assessed environmental impacts in five areas: Global warming potential, the potential of excessive nutrient build-up in marine and freshwater, increased ground acidity, fossil fuel depletion and metal resource depletion.
During the study, the scientists found that growing weed outdoors could potentially produce 50 times less carbon than growing indoors. That’s because indoor grows require more energy to power heating, ventilation and air-conditioning (HVAC) systems. By removing those systems from the equation, producers can significantly reduce their carbon footprint — although they would have to sacrifice some of the control afforded from growing indoors.
The study also found areas where the already lower footprint of outdoor grows could be further reduced.
The researchers looked at different fertilizer formulas and rated their carbon footprints. Using this data, they were able to find a low-nitrogen, high-potassium formula known as L+ that had the lowest carbon footprint. And as luck would have it, they discovered that the formula would also increase THC production.
The scientists said they wanted to look at fertilizer effects on THC production because it’s an area of study that is severely lacking. By comparing various formulas, they found that in addition to having the smallest carbon footprint, L+ also helped plants produce over 30% more THC (15 percent compared to 10%) than its competitors, meaning that producers could comfortably transition from high-nitrogen fertilizers without having to worry about producing less potent flower.
The study also found that one of the largest contributors to carbon production involved in outdoor grows is the use of disposable pots and the fuel required to ship them. To mitigate this, the researchers suggest that cultivators utilize reusable pots.
The study only used a single cannabis strain, known as Candy Cane. The researchers said they chose this particular strain for its quick maturation rate in case of an early frost.