https://orcid.org/0000-0003-4992-6501
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ABSTRACT
In 2019, an air emissions field sampling study was conducted by the Colorado Department of Public Health and Environment’s Air Pollution Control Division (APCD) 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). These data were 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. These data suggest that the variability in emission rates across cannabis production will create a challenge in establishing a generalized emission factor for all facilities. 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.
Implications: This study found that the magnitude of biogenic VOC emissions within a cannabis cultivation varies widely throughout rooms found in the facility, with the highest emissions found during post-harvest activities (i.e. trimming) and the lowest rates in the vegetative room. These data suggest that the large emission sources of VOCs are found post-harvest and emission inventories based solely on cultivation emissions will underestimate total biogenic VOC emissions from indoor cannabis cultivation facilities. The dominant measured terpenes throughout all facilities from cultivation to post harvest were: β-myrcene, terpinolene, and D-limonene.
Acronym glossary
| AER | = | air exchange rate |
| APCD | = | Air Pollution Control Division |
| BER | = | basal emission rate |
| CDPHE | = | Colorado Department of Public Health and Environment |
| DRI | = | Desert Research Institute |
| GC | = | gas chromatograph |
| hr | = | hour |
| HVAC | = | heating, ventilation, and air conditioning |
| kg | = | kilogram |
| lb | = | pound |
| m | = | meter |
| min | = | minute |
| ml | = | milliliter |
| MDL | = | minimum detection limit |
| MST | = | Mountain Standard Time |
| ng | = | nanograms |
| O3 | = | ozone |
| [OH]− | = | hydroxyl radical |
| PID | = | photoionization detector |
| PM | = | particulate matter |
| ppm | = | parts per million |
| ppb | = | parts per billion |
| ppbv | = | parts per billion by volume |
| µg | = | microgram |
| µg/m3 | = | micrometers per cubic meter |
| VOC | = | volatile organic compound |
Acknowledgment
The authors want to acknowledge the time and efforts of the cooperating volunteer cannabis cultivation facilities throughout this study. The authors also thank Sara Heald, Kristen Good, and Daniel Bon of CDPHE, Chi-tsan Wang of the University of North Carolina, Chiranjivi Bhattarai, Irina Lebedeva, and Vera Samburova of Desert Research Institute, Christine Wiedinmyer of the University of Colorado in Boulder, Micheal Wolf of Washoe County Air Quality, and Joe Southwell of Spokane Regional Clean Air Agency for their scientific inputs that helped inform this study and publication. The authors also thank CDPHE management staff for their ongoing support of this study. Specifically, Garry Kaufman and Leah Martland. Thanks to the 2018 CDPHE Innovation Grant for funding for this study. Thanks to the University of North Carolina - Chapel Hill for cost-sharing the publication fees with CDPHE.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data availability statement
The authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials besides the PID data that is available on request from CDPHE as it is multiple very large files. Contact the corresponding author, Kaitlin Urso, to request PID data.
Disclaimer
This document has been reviewed and approved for publication by all contributing authors.
Supplementary material
Supplemental data for this article can be accessed online at https://doi.org/10.1080/10962247.2023.2175741
Additional information
Funding
Notes on contributors
Kaitlin Urso
Kaitlin Urso is an environmental consultant with the Colorado Department of Public Health and Environment specializing with in helping small businesses reduce their environmental impacts and comply with regulations. Kaitlin was the lead author and project engagement manager for this study on indoor cannabis air emissions and for the “Terpene exhaust emissions and impact ozone modeling from cannabis plants at commercial indoor cultivation facilities in Colorado” study that took place simultaneously at the same cultivation facilities (Urso et al. Citation2022). She has 12 years of technical environmental experience and a mechanical engineering degree from the University of Colorado, Boulder. Kaitlin's work has been featured in Wall Street Journal, Forbes, CNN, NPR, Science Magazine, and countless other media and industry publications.
William Vizuete
William Vizuete is a Professor in the Department of Environmental Sciences and Engineering at the University of North Carolina at Chapel Hill. For the last 17 years he has been tackling the public health problems related to air pollution. In his research, he focuses on understanding how the atmosphere can change the formation processes of ozone and PM, and its connection to human health. Through his research Dr. Vizuete has increased our scientific knowledge in these areas and produced new insights through air quality models, field studies, laboratory experiments, and the development of a novel in vitro technology. Dr. Vizuete contributed to the concept of the paper, the analysis of data, writing the manuscript, producing tables, and overall editing.
Ryan Moravec
Ryan Moravec graduated from University of North Carolina at Chapel Hill in May 2022 with a Masters of Science in Environmental Engineering. His research explored the impacts of ozone induced oxidation of skin surface lipids. Ryan assisted in the modeling of this publication by calculating the emission rates of biogenic VOC and the chemical reaction analysis.
Andrey Khlystov
Andrey Khlystov is a Research Professor and the Director of the Organic Analytical Laboratory at the Desert Research Institute (DRI) with more than 30 years of experience in various aspects of air pollution research. For this study, Andrey led the laboratory analysis of collected samples. He has designed, organized, and directed several medium to large scale laboratory and field studies funded by the National Institutes of Health, the National Science Foundation, the EPA, and several other federal and non-governmental sponsors.
Alicia Frazier
Alicia Frazier is a physical scientist with the Colorado Department of Public Health and Environment’s Air Pollution Control Division. She specializes in planning and performing a variety of air toxics sampling activities. Alicia designed and implemented the sampling process for this study on indoor cannabis air emissions. She has over 20 years of environmental sampling experience, and a M.S. in Astrophysical, Planetary and Atmospheric Science from the University of Colorado.
Glenn Morrison
Glenn Morrison is a professor of Environmental Science & Engineering at the University of North Carolina and has been studying indoor and outdoor air pollution and human exposure for 30 years. He received his PhD from Berkeley, and his research has primarily been related to indoor physics and chemistry. He has a particular expertise in interfacial chemistry, having also worked as a chemical engineer on heterogeneous catalysis. This research has included ozone-surface chemistry, acid-base chemistry and its role in sorption to indoor surfaces, methamphetamine contamination in buildings, aerosol-SVOC modeling and field measurements of reactive oxygen species in homes. From 2014-2016 he was the President of the International Society of Indoor Air Quality and Climate (ISIAQ). Glenn Morrison contributed to the modeling and sensitivity analysis for this study, specifically focused on indoor chemistry and its influence on estimated emission rates.