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Nuances in Parsing Cannabis Cultivation Energy Use: Comment on "Cannabis and the Environment: What Science Tells Us and What We Still Need to Know"

  • Lawrence Berkeley National Laboratory (Retiree Affiliate)

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The scientific literature has begun to shed much-needed light on the complex environmental impacts of cannabis cultivation. Among the pathways—land cover change, water use, pesticide use, energy use, air pollution, and water pollution—energy use may prove to be the most significant, particularly where climate change is of concern. However, some estimates of energy use and greenhouse-gas emissions suffer from critical analytical errors that bias estimates in a downward direction. Among these are narrowed boundary conditions that exclude non-electric energy consumption, off-grid electricity, transportation energy, and less-efficient small-scale or black-market operations. Indoor cultivation presents one of the more complex energy analysis challenges, involving a combination of many end uses and bio-chemical factors at the core of any meaningful definition of "energy efficiency". Comprehensive analyses must also include a diversity of pre- and post-cultivation energy uses. These include energy embodied in inputs such as single-use growing media, fertilizer, water supply and treatment; post-cultivation drying, processing, extractions, and preparations; refrigerated storage; retail operations; and transportation. Other accounting considerations include energy embodied in failed and interdicted crops or those destroyed due to unacceptable lab-test results. Estimates based on field data--particularly using samples of convenience--can be biased in either direction if they do not reflect actual market conditions driven by local climate, strain choice, or production processes and their associated efficiencies. Greenhouse-gas emissions can be further underestimated if geographically varying electricity carbon emissions factors are not properly weighted, manufactured CO2 used to enhance plant growth is not counted, and particularly carbon-intensive black-market operations are excluded. While it has been stipulated that energy efficiencies have likely improved over time, major transformations in the industry (and increasing cannabis production) could be driving energy use either up or down, but most likely upward. It is thus critical to track efficiencies as well as aggregate demand metrics that can trend in opposite directions.
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Arecent Global Perspective by Wartenberg et al. in
Environmental Science &Technology Letters sheds much-
needed light on the complex environmental impacts of
cannabis cultivation.
Among the pathways identied by their
ambitious reviewland cover change, water use, pesticide use,
energy use, air pollution, and water pollutionenergy use may
prove to be the most signicant. Cannabis factory farming
involves energy-intensive lighting, space conditioning, dehu-
midication, articial CO2fertilization, water reclamation, and
other processes to boost yields while maintaining year-round
tropical indoor conditions irrespective of the outdoor climate.
The authors do a service by bringing further attention to the
role of energy in indoor cultivation, as the literature focuses
largely on outdoor practices.
The Global Perspective exemplies the accounting and
methodological complexities in cannabis energy analysis. The
authors suggest that my estimate (Mills
) of 20 TWh-y (1012
Wh-y) electricity consumption for legal and illicit indoor
cannabis cultivation in the U.S. may not be plausible, equating
it to the 1.7 quads (1015 BTU) site energy use for all U.S.
However, the energy equivalent of 20 TWh is only
0.068 quads (4% of U.S. agriculture).
The authors inadvertently cite a grey literature estimate of
national energy use for indoor cannabis cultivation (New
Frontier Data
) as 4.2 MWh-y (106Wh-y), lower than Mills
by more than six orders of magnitude. However, the source
document reports 4.2 million MWh-y (1012 Wh-y), admittedly
a peculiar phrasing of units. The authors also restate that
sources estimated greenhouse gas emissions only for legal
cultivation, one-quarter of the total presented therein. The
remaining factor-of-three dierence between these two
estimates is non-trivial and merits examination.
models energy intensity ((kWh/gram of nished
ower produced)), while the New Frontier Data study
limited eld measurements. Both studies extrapolate intensities
to estimate national energy demand and emissions. Impor-
tantly, the studiesboundary conditions and ndings are not
directly comparable, notably that o-grid and transportation
energy are not counted in the New Frontier Data study,
also excluded direct fossil-fuel use within the facilities and did
not explicitly include small-scale operations which may be
more energy intensive than larger professionally operated
Greenhouse gas emissions dier even more, as the New
Frontier Data study
excluded manufactured CO2used to
enhance plant growth, transportation energy, and o-grid
electricity typically produced by inecient diesel generators.
The New Frontier Data study
also utilized a proprietary,
nonrandomized, self-reported sample of cultivation sites
heavily representative of milder climates with cleaner grids
(California and Oregon). While various data are presented for
81 benchmark sites, only 24 (from seven states) yielded the
intensity metric underlying their national estimate. The sample
also likely represented atypical adoption of eciency features
(e.g., 20% of the sites had LED lighting, which was rarely
deemed cost eective at the time
). Lastly, the manner and
extent to which strain choice (a signicant factor),
drying, cold storage, and particularly carbon-intensive black-
market operations were addressed is not documented.
Wartenberg et al.
caution about the unavailability of
accurate energy-use data from individual cultivators. Fortu-
nately, such information is increasingly found in the
which supports model validation, as are
market-level data,
which support estimates of
aggregate energy demand. While they note an absence of
data on cultivation area and planting densities, these are not
inputs to either studys methodology.
While others arrive at similar or higher measured energy
and shares of total regional electricity de-
as in Mills
, the authors note that energy eciencies
likely improved during the six-year interval between the two
studies. That said, during this period, there were major
transformations in the industry (and increasing cannabis
) that could have driven energy use either up
(e.g., larger facility volumes) or down (e.g., more greenhouses,
which average 25% lower energy intensity
). One data set
indicates a trend toward larger facilities, which could elevate
energy intensities. It is thus critical to track eciencies as well
as aggregate demand metrics that can trend in opposite
directions. Meanwhile, a recent and exhaustive peer-reviewed,
model-based assessment
identies a carbon-intensity range
bracketing the value in Mills
, and demonstrates the strong
inuence of climate and electric generation mix on carbon
emissions. The New Frontier Data study
is a signicant
outlier (Figure 1) among the other studies in terms of its very
high yield density (grams/m2-y, twice the average of a large
Received: January 26, 2021
Accepted: May 4, 2021
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) and correspondingly low energy intensity (one
quarter to one seventh that of other studies
Many pre- and post-cultivation energy uses must also be
quantied. These include energy embodied in inputs such as
growing media, fertilizer, water supply and treatment;
postcultivation processing, extractions, and preparations;
refrigerated storage; retail operations; and transportation.
Other energy-accounting considerations include energy
embodied in failed and interdicted (black-market) crops or
those destroyed due to unacceptable lab-test results.
Energy use in this industry is a largely unattended issue
among policymakers.
Yet, at energy intensities of 6 kWh/
indoor cannabis cultivation is 500 times more energy
intensive than aluminum smelting,
and energy per unit oor
area is 50100 times that of homes and oces.
et al.
outline traditional policy recommendations, including
performance standards, incentives for energy eciency, and
data disclosure. While such measures yield large savings in
other contexts, a confounding factor exists in the case of indoor
cannabis. Consider one planned 55-acre [22 ha] windowless
industrial park in the California desert which includes a
dedicated natural-gas power plant that could power 90,000
all-electric homes.
To instead employ solar
electricity would require photovoltaic arrays spanning 25
times the roof area, or roughly 1400 acres [567 ha], far more
than outdoor cultivation would require for the same yield. This
draws into question the potential for sustainabile indoor
cannabis cultivation, where best practicespromise only to
optimize the suboptimal. Meanwhile, the alternativevirtually
zero-energy outdoor cultivation, which would require only
0.01% of U.S. agricultural lands
to meet current demand
receives no nancial or policy inducements and indeed is
banned in many jurisdictions, rendering it at a competitive
disadvantage to indoor practices eligible for market-distorting
subsidies (utility rebates)
to nance costly measures like
LED lighting.
Notably, some indirect nonenergy impacts identied by
Wartenberg et al.
may prove as or more severe for indoor than
outdoor cultivation. These include land use (energy extraction,
infrastructure), water use (evaporation during electricity
generation), water pollution (hydroponic systems shunting
pollutants into wastewater treatment systems), indoor/outdoor
air pollution (VOC emissions in urban air basins), and solid
waste production (soil and articial growing media landlled
after each cropping cycle at intervals as short as 40 days,
while frequently replaced high-pressure sodium and metal-
halide grow lights contain mercury).
In sum, indoor cannabis production is a particularly complex
and fast-growing driver of energy demand and greenhouse gas
emissions and yet is far less studied than other comparable uses
of energy. In particular, despite the passage of a quarter century
since cannabis was rst legalized for medical use, U.S. energy
and environmental agencies have conducted no known
technical or policy research on associated energy impacts.
Even leading states have only recently begun considering it.
There remains a pressing need for more analysis, particularly
given that legalization of indoor cannabis cultivation by the
incoming Biden Administration would directly undermine its
ambitious climate goals.
Evan Mills
Complete contact information is available at:
The author declares no competing nancial interest.
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Supplementary resource (1)

This review addresses knowledge gaps in cannabis cultivation facility (CCF) air emissions by synthesizing the peer-reviewed and gray literature. Focus areas include compounds emitted, air quality indoors and outdoors, odor assessment, and the potential health effects of emitted compounds. Studies suggest that β-myrcene is a tracer candidate for CCF biogenic volatile organic compounds (BVOCs). Furthermore, β-myrcene, d-limonene, terpinolene, and α-pinene are often reported in air samples collected in and around CCF facilities. The BVOC emission strength per dry weight of plant is higher than most conventional agriculture crops. Nevertheless, reported total CCF BVOC emissions are lower compared with VOCs from other industries. Common descriptors of odors coming from CCFs include "skunky", "herbal", and "pungent". However, there are few peer-reviewed studies addressing the odor impacts of CCFs outdoors. Atmospheric modeling has been limited to back trajectory models of tracers and ozone impact assessment. Health effects of CCFs are mostly related to odor annoyance or occupational hazards. We identify 16 opportunities for future studies, including an emissions database by strain and stage of life (growing cycle) and odor-related setback guidelines. Exploration and implementation of key suggestions presented in this work may help regulators and the industry reduce the environmental footprint of CCF facilities.
Full-text available
The legalization of cannabis has caused a substantial increase in commercial production, yet the magnitude of the industry’s environmental impact has not been fully quantified. A considerable amount of legal cannabis is cultivated indoors primarily for quality control and security. In this study we analysed the energy and materials required to grow cannabis indoors and quantified the corresponding greenhouse gas (GHG) emissions using life cycle assessment methodology for a cradle-to-gate system boundary. The analysis was performed across the United States, accounting for geographic variations in meteorological and electrical grid emissions data. The resulting life cycle GHG emissions range, based on location, from 2,283 to 5,184 kg CO2-equivalent per kg of dried flower. The life cycle GHG emissions are largely attributed to electricity production and natural gas consumption from indoor environmental controls, high-intensity grow lights and the supply of carbon dioxide for accelerated plant growth. The discussion focuses on the technological solutions and policy adaptation that can improve the environmental impact of commercial indoor cannabis production. As cannabis production becomes legalized and legitimized, its production will likely change and expand with attendant environmental impacts. This life cycle analysis of energy and material costs across the United States focuses on indoor cannabis growing operations.
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Riding the global waves of decriminalization, medical or recreational use of cannabis (Cannabis sativa spp.) is now legal in more than 50 countries and U.S. states. As governments regulate this formerly illegal crop, there is an urgent need to understand how cannabis may impact the environment. Due to the challenges of researching quasi-legal commodities, peer-reviewed studies documenting environmental impacts of cannabis are limited, slowing the development of policies and agricultural extension guidelines needed to minimize adverse environmental outcomes. Here we review peer-reviewed research on relationships between cannabis and environmental outcomes, and identify six documented impact pathways from cannabis cultivation (land-cover change, water use, pesticide use, energy use, and air pollution) and consumption (water pollution). On the basis of reviewed findings, we suggest policy directions for these pathways. We further highlight the need to formalize existing traditional and gray literature knowledge, expand research partnerships with cannabis cultivators, and ease research restrictions on cannabis. Finally, we discuss how science might contribute to minimize environmental risks and inform the development of regulations for a growing global cannabis industry.
Full-text available
Legalization of cannabis production has daylighted a unique and highly valuable crop in California agriculture. State and regulatory agencies must now address the ecological, social and agricultural effects of cannabis production, but little is known about how growers produce this crop. Using an online survey, we gathered information from growers in July 2018 on their production practices. According to responses from about 100 growers, most cannabis was produced outdoors or in greenhouses, relied primarily on groundwater and used biologically based inputs for pest management. Many farms employed seasonal workers paid at fixed piece rates. Regulatory compliance varied according to farm size. Beginning to document growing practices will help scientists formulate key environmental, social and agronomic questions and develop relevant research and extension programs to promote best management practices and minimize negative environmental impacts of production.
Full-text available
Until recently, the commercial production of Cannabis sativa was restricted to varieties that yielded high-quality fiber while producing low levels of the psychoactive cannabinoid tetrahydrocannabinol (THC). In the last few years, a number of jurisdictions have legalized the production of medical and/or recreational cannabis with higher levels of THC, and other jurisdictions seem poised to follow suit. Consequently, demand for industrial-scale production of high yield cannabis with consistent cannabinoid profiles is expected to increase. In this paper we highlight that currently, projected annual production of cannabis is based largely on facility size, not yield per square metre. This meta-analysis of cannabis yields reported in scientific literature aimed to identify the main factors contributing to cannabis yield per plant, per square metre and per W of lighting electricity. In line with previous research we found that variety, plant density, light intensity and fertilization influence cannabis yield and cannabinoid content; we also identified pot size, light type and duration of the flowering period as predictors of yield and THC accumulation. We provide insight into the critical role of light intensity, quality and photoperiod in determining cannabis yields, with particular focus on the potential for light-emitting diodes (LEDs) to improve growth and reduce energy requirements. We propose that the vast amount of genomics data currently available for cannabis can be used to better understand the effect of genotype on yield. Finally, we describe diversification that is likely to emerge in cannabis growing systems and examine the potential role of plant-growth promoting rhizobacteria (PGPR) for growth promotion, regulation of cannabinoid biosynthesis and biocontrol.
Full-text available
Cannabis agriculture is a multi-billion dollar industry in the United States that is changing rapidly with policy liberalization. Anecdotal observations fuel speculation about associated environmental impacts, and there is an urgent need for systematic empirical research. An example from Humboldt County California, a principal cannabis-producing region, involved digitizing 4428 grow sites in 60 watersheds with Google Earth imagery. Grows were clustered, suggesting disproportionate impacts in ecologically important locales. Sixty-eight percent of grows were >500 m from developed roads, suggesting risk of landscape fragmentation. Twenty-two percent were on steep slopes, suggesting risk of erosion, sedimentation, and landslides. Five percent were <100 m from threatened fish habitat, and the estimated 297 954 plants would consume an estimated 700 000 m3 of water, suggesting risk of stream impacts. The extent and magnitude of cannabis agriculture documented in our study demands that it be regulated and researched on par with conventional agriculture.
Full-text available
The liberalization of marijuana policies, including the legalization of medical and recreational marijuana, is sweeping the United States and other countries. Marijuana cultivation can have significant negative collateral effects on the environment that are often unknown or overlooked. Focusing on the state of California, where by some estimates 60%–70% of the marijuana consumed in the United States is grown, we argue that (a) the environmental harm caused by marijuana cultivation merits a direct policy response, (b) current approaches to governing the environmental effects are inadequate, and (c) neglecting discussion of the environmental impacts of cultivation when shaping future marijuana use and possession policies represents a missed opportunity to reduce, regulate, and mitigate environmental harm.
Full-text available
Lighting technologies for plant growth are improving rapidly, providing numerous options for supplemental lighting in greenhouses. Here we report the photosynthetic (400-700 nm) photon efficiency and photon distribution pattern of two double-ended HPS fixtures, five mogul-base HPS fixtures, ten LED fixtures, three ceramic metal halide fixtures, and two fluorescent fixtures. The two most efficient LED and the two most efficient double-ended HPS fixtures had nearly identical efficiencies at 1.66 to 1.70 micromoles per joule. These four fixtures represent a dramatic improvement over the 1.02 micromoles per joule efficiency of the mogul-base HPS fixtures that are in common use. The best ceramic metal halide and fluorescent fixtures had efficiencies of 1.46 and 0.95 micromoles per joule, respectively. We also calculated the initial capital cost of fixtures per photon delivered and determined that LED fixtures cost five to ten times more than HPS fixtures. The five-year electric plus fixture cost per mole of photons is thus 2.3 times higher for LED fixtures, due to high capital costs. Compared to electric costs, our analysis indicates that the long-term maintenance costs are small for both technologies. If widely spaced benches are a necessary part of a production system, the unique ability of LED fixtures to efficiently focus photons on specific areas can be used to improve the photon capture by plant canopies. Our analysis demonstrates, however, that the cost per photon delivered is higher in these systems, regardless of fixture category. The lowest lighting system costs are realized when an efficient fixture is coupled with effective canopy photon capture.
Full-text available
The emergent industry of indoor Cannabis production -- legal in some jurisdictions and illicit in others -- utilizes highly energy intensive processes to control environmental conditions during cultivation. This article estimates the energy consumption for this practice in the United States at 1% of national electricity use, or $6 billion each year. One average kilogram of final product is associated with 4600kg of carbon dioxide emissions to the atmosphere, or that of 3 million average U.S. cars when aggregated across all national production. The practice of indoor cultivation is driven by criminalization, pursuit of security, pest and disease management, and the desire for greater process control and yields. Energy analysts and policymakers have not previously addressed this use of energy. The unchecked growth of electricity demand in this sector confounds energy forecasts and obscures savings from energy efficiency programs and policies. While criminalization has contributed to the substantial energy intensity, legalization would not change the situation materially without ancillary efforts to manage energy use, provide consumer information via labeling, and other measures. Were product prices to fall as a result of legalization, indoor production using current practices could rapidly become non-viable.
Electrical Load Impacts of Indoor Commercial Cannabis Production; Northwest Power and Conservation Council Memorandum
  • M Jourabchi
Jourabchi, M. Electrical Load Impacts of Indoor Commercial Cannabis Production; Northwest Power and Conservation Council Memorandum: Portland, OR, 2014.