In 2019, the Colorado Department of Public Health and Environment's Air Pollution Control Division (APCD) conducted an air emissions field sampling study at four commercial cannabis cultivation facilities. Measurements of ambient biogenic volatile organic compounds (VOC) concentrations were collected from various growing stages of cannabis (vegetative and flowering) and during post-harvest activities (drying and trimming). This data was then used to determine room-specific biogenic VOC emission rates for three of the facilities from the vegetative stage of the life cycle through post-harvest activities.
This study shows that the magnitude of biogenic VOC emissions within a cannabis cultivation facility varies widely, with the highest emission rates of up to 7.18E-1 kg/hr found during mechanical trimming and up to 2.33E-1 kg/hr in the drying rooms. These were up to an order of magnitude higher than emission rates found in the cultivation rooms. For example, Facility A vegetative room had an emissions rate of 1.46E-2 kg/hr. Normalized by the amount of biomass present, the drying rooms had the highest VOC emissions rates, with a maximum rate of 1.6E-3 kg/hr/kg biomass. The flowering room rates were found to be up to 3.25E-4 kg/hr/kg biomass, and drying rooms up to 1.16E-3 kg/hr/kg biomass. When normalized by plant count, emission rates in the flower rooms ranged from 8.11E-6 to 3.62E-4 kg/hr/plant. The dominant monoterpenes from sampling were β-myrcene, terpinolene, and D-limonene.
The results of the study suggest that the variability in emission rates across cannabis production will create a challenge in establishing a generalized emission factor for all facilities, the researchers say. "Across the industry, cannabis cultivation conditions and strategies can vary widely, impacting the amount and type of VOC emissions. Minimizing uncertainties for VOC emission from cannabis facilities requires site-specific information on air exchange rates, plant counts, cannabis strains, biomass, and if hand or mechanical processing is used."
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Study on VOC emission