Key Points
- Researchers at the University of British Columbia measured emissions of 22 terpenes from indoor cannabis facilities using gas chromatography coupled with flame ionization detection (GC-FID) and found large variability in emission rates (up to 1500%) depending on activity and lighting, with peak emissions during bud extraction (trimming).
- Dispersion modeling of β-myrcene, a key cannabis terpene, showed that even average emissions can exceed odor thresholds in many scenarios, highlighting the potential for significant odor episodes and secondary air pollution.
- Due to facility-specific factors such as emission controls, strain types, and environmental conditions, researchers caution against broad generalizations of their data and emphasize the need for robust environmental policies tailored to evolving industry practices.
Researchers at the University of British Columbia (Vancouver, Canada) aimed to quantify terpene emissions from indoor cannabis operations in the Lower Fraser Valley, British Columbia, Canada—a region already affected by odorous sources and peak ozone concentrations in the summer due to imbalance of volatile organic compounds (VOC) and nitrogen oxides (NOx) emissions. An automated gas chromatography coupled with flame ionization detection (GC-FID) sampling and processing protocol was established to measure concentrations of 22 key cannabis terpenes in eight rooms of an indoor cultivation facility and six rooms of a processing and extraction facility. A paper based on their research was published in Environmental Science: Processes & Impacts (1).
Terpenes are naturally occurring chemical compounds found in plants and some animals. These compounds are responsible for the aromas, flavors, and even colors associated with various types of vegetation. These compounds are what make certain cannabis plants smell or taste differently from others and may work with the plant’s cannabinoids and other compounds to produce medicinal effects (2).
As new jurisdictions legalize cannabis use and commercialization for medical and recreational purposes (3), interest has increased among researchers and regulators about potential occupational and environmental impacts of the increased number and size of cannabis production facilities (4), such as greenhouse gases emissions (5), land cover change and resources use (6), the depletion of natural systems (7), and quality of the air (8).
The Lower Fraser Valley comprises the districts of Metro Vancouver and the southwestern portion of the Fraser Valley Regional District. Prospective participating facilities were asked to complete a questionnaire addressing their cultivation practices, facility management, and air emissions control technologies. Two facilities (named CCF for Cannabis Cultivation Facility and CPF for Cannabis Processing Facility) were selected for this study, based on their market influence, type of operation, and their capacity to participate in logistical planning for sampling. Concentrations of 22 terpenes for eight rooms of the CCF and six rooms of the CPF were measured using gas chromatography coupled with flame ionization detection (GC-FID) (1).
Emission rates were found to vary widely, ranging from 1.05 × 10−3 to 3.09 × 10−1 kg h−1, with the highest emissions occurring during extraction of the cannabis buds (also referred to as trimming). The researchers observed substantial temporal variability; individual terpene concentrations fluctuated by up to 1500% depending on activity type and lighting conditions. Pearson correlation analysis revealed non-linear relationships between the individual terpenes and total emissions, which the researchers believe suggests shifts in chemical composition during peak emissions. For the assessment of odor implications, screening dispersion modeling for β-myrcene, a terpene considered a tracer of cannabis emissions, was conducted. Of the 7560 dispersion scenarios evaluated, 88 exceeded the odor threshold under average emissions, increasing to 241 scenarios during peak trimming emissions (1).
