Terpene exhaust emissions and impact ozone modeling from cannabis plants at commercial indoor cultivation facilities in Colorado

In 2019, an air emission field sampling study was conducted by the Colorado Department of Public Health and Environment (CDPHE) Air Pollution Control Division (APCD) at three commercial cannabis cultivation facilities. The goal of the study was to quantify biogenic-terpene volatile organic compound (VOC) emissions from growing cannabis at cultivation facility exhaust points to estimate a VOC emission rate by a top-down approach. The resulting VOC emission rates were then used in combination with 2019 commercial cannabis cultivation facility biomass production volumes (harvest weight) and cultivation locations from the Colorado Department of Revenue’s Marijuana Enforcement Division (MED) to model the potential ozone and PM_2.5 formation impacts of the cannabis industry in the Denver Metro North Front Range (DM/NFR) Ozone Nonattainment Area (NAA). Despite cannabis cultivation facilities’ high nuisance odors, this study found the biogenic VOC emission rate from the sampled indoor facilities to be low (2.13 lbs to 11.12 lbs of VOC/ton of cannabis harvested), even at large production facilities. The dominant terpenes from this sampling study present in most samples were β-caryophyllene, D-limonene, terpinolene, α-pinene, β-pinene, and β-myrcene, respectively, by concentration. Interestingly, the cannabis emissions exhaust profile lacked isoprene, a terpene commonly emitted from other plants that is highly reactive and has great potential to contribute to ozone formation (Sharkey et al. 2008). The low biogenic VOC emission rate and the lack of isoprene from the cannabis cultivation facilities sampled resulted in a very low to negligible impact on both ozone formation (0.005–0.009% increase in ozone from cannabis cultivation) and PM_2.5 formation (largest maximum 24-hr PM_2.5 difference of 0.009 µg/m³) in the DM/NFR NAA. <i>Implications</i>: This study concluded that even though cannabis cultivation facilities can have overwhelming nuisance odor impacts, based on samples collected and production rates they actually have a low VOC emission rate (2.13 to 11.12 lbs of VOC/ton of cannabis harvested), even at large high-volume production facilities. Additionally, the dominant VOC emissions from samples collected at the three cannabis cultivation facilities were β-caryophyllene, D-limonene, terpinolene, α-pinene, β-pinene, and β-myrcene. The low biogenic VOC emission rate and the lack of isoprene from the cannabis cultivation facilities sampled resulted in a very low to negligible impact on both ozone formation (0.005%–0.009% increase in ozone from cannabis cultivation) and PM_2.5 formation (largest maximum 24-hr PM_2.5 difference of 0.009 µg/m³) in the DM/NFR NAA.

2019年，科罗拉多州公共卫生与环境部（Colorado Department of Public Health and Environment, CDPHE）下属空气污染控制部（Air Pollution Control Division, APCD）在三家商业大麻种植设施开展了空气排放现场采样研究。本研究旨在量化大麻种植过程中，设施排气口处释放的生物源萜类挥发性有机化合物（biogenic-terpene volatile organic compound, VOC）排放量，通过自上而下法估算VOC排放速率。随后，将所得VOC排放速率与科罗拉多州税务局大麻执法部（Marijuana Enforcement Division, MED）提供的2019年商业大麻种植设施生物量产量（收获重量）及种植区位数据相结合，对丹佛都会区北前陆（Denver Metro North Front Range, DM/NFR）臭氧不达标区（Ozone Nonattainment Area, NAA）内大麻产业可能造成的臭氧与细颗粒物（PM₂.₅）生成影响进行建模分析。尽管大麻种植设施常伴随强烈的扰民气味，但本研究发现，即便在大规模生产设施中，本次采样的室内种植设施的生物源VOC排放速率仍较低（2.13磅至11.12磅VOC/吨收获大麻）。按浓度由高到低排序，多数采样样本中占主导的萜类化合物依次为β-石竹烯（β-caryophyllene）、D-柠檬烯（D-limonene）、萜品油烯（terpinolene）、α-蒎烯（α-pinene）、β-蒎烯（β-pinene）及β-月桂烯（β-myrcene）。值得注意的是，大麻排放的尾气组分特征中未检测到异戊二烯（isoprene）——这是一种常见于其他植物的高反应性萜类化合物，极易促进臭氧生成（Sharkey et al. 2008）。本次采样的大麻种植设施所呈现的低生物源VOC排放速率与无异戊二烯排放的特征，使其对DM/NFR臭氧不达标区内的臭氧生成（大麻种植导致臭氧浓度提升0.005%至0.009%）与PM₂.₅生成（最大24小时PM₂.₅浓度差为0.009 μg/m³）的影响极低，甚至可忽略不计。研究启示：本研究结论指出，尽管大麻种植设施可能带来严重的扰民气味问题，但基于采样数据与生产速率测算，即便在大规模高产能生产设施中，其VOC排放速率仍较低（2.13磅至11.12磅VOC/吨收获大麻）。此外，三家大麻种植设施的采样样本中占主导的VOC排放物依次为β-石竹烯、D-柠檬烯、萜品油烯、α-蒎烯、β-蒎烯及β-月桂烯。前述低生物源VOC排放速率与无异戊二烯排放的特征，同样使得该产业对DM/NFR臭氧不达标区内的臭氧生成（0.005%至0.009%的臭氧浓度增幅）与PM₂.₅生成（最大24小时PM₂.₅浓度差为0.009 μg/m³）的影响极低且可忽略。