Insatiable demand for cannabis has created a huge carbon footprint

It’s no secret that the $ 13 billion US cannabis industry is big business. Less obvious is the environmental tax that this thriving business is demanding, in the form of greenhouse gas emissions through commercial, mostly indoor production.

A new study by researchers at Colorado State University provides the most detailed accounting to date of the industry’s carbon footprint, an amount about which there is only a limited understanding. What is clear, however, is that consumer demand for cannabis is insatiable and shows no signs of stopping as more states report legalization.

The study, published in Nature sustainability, was led by graduate student Hailey Summers, whose advisor, Jason Quinn, is an associate professor in the Department of Mechanical Engineering. Summers, Quinn and Evan Sproul, a mechanical engineering scientist, conducted a life cycle assessment of indoor cannabis operations in the US, analyzing the energy and materials needed to grow the product, and the corresponding greenhouse gas emissions.

They found that greenhouse gas emissions from cannabis production were largely attributed to electricity production and natural gas consumption through indoor environmental controls, high-intensity greenhouse lights and carbon dioxide supplies for accelerated plant growth.

“We knew the emissions would be large, but because they had not been fully quantified before, we identified them as a large space for research opportunities,” Summers said. “We just wanted to run with it.”

The CSU group’s efforts are to update previous work by researchers from the Lawrence Berkeley National Laboratory, which quantified small-scale growth operations in California and preceded the cascade of state-by-state legalization since Colorado was first legalized is in 2012. To date, 36 states have legalized. medical use of cannabis, and 15 legalized recreational use.

Mapping of variable emissions

The CSU team suspected that there would be great volatility in emissions, depending on where the product is grown, due to the climate as well as the release of electrical grid. Their recently published work contains the potential distribution of large rural distribution areas of large commercial warehouses for the cultivation of marijuana, and it models emissions for different growth areas in the country. The results include a map showing relative emissions across the US, as defined as emissions per kilogram of cannabis flower. They also developed a GIS map that allows users to enter a country name and find local exhaust gas estimates.

Their research shows that U.S. indoor marijuana cultivation emits greenhouse gases during the life cycle between 2,283 and 5,184 kilograms of carbon dioxide per kilogram of dried flower. Compare that to the release of electricity consumption in the growth of cannabis outdoors and greenhouse, which are 22.7 and 326.6 kilograms of carbon dioxide, respectively, according to the New Frontier Data 2018 Cannabis Energy Report. The number of outdoor and greenhouse gases only takes into account electricity, while CSU researchers estimate more comprehensively, but the comparison still highlights the enormously larger footprint of indoor greenhouse operations.

The researchers were surprised to discover that heating, ventilation and air conditioning systems had the greatest energy needs, with numbers varying depending on the local climate – whether it was in Florida, which requires excessive dehumidification, or Colorado, where the heating more important.

The high energy consumption of cannabis is partly due to the regulation of the product, Quinn said. In Colorado, many growth operations must be near store windows, and this has caused an explosion of energy-hungry indoor warehouses in urban areas like Denver. According to a report by the Department of Public Health and the Environment in Denver, the use of electricity by cannabis cultivation and other products grew from 1% to 4% of Denver’s total electricity consumption between 2013 and 2018.

The team is looking for more funding to continue their modeling work, hoping to expand it to a comparison between indoor and potential outdoor growth activities. Ultimately, they want to help the industry address environmental concerns, while legal cannabis is still relatively new in the US

“We want to try to improve the environmental impact before it is built into the way we do business,” Sproul said.