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The carbon footprint of indoor Cannabis production
Evan Mills
Energy Associates, Box 1688, Mendocino, CA 95460, United States
article info
Article history:
Received 7 September 2011
Accepted 10 March 2012
Available online 17 April 2012
Keywords:
Energy
Buildings
Horticulture
abstract
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 4600 kg
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.
&2012 Elsevier Ltd. All rights reserved.
1. Introduction
On occasion, previously unrecognized spheres of energy use
come to light. Important historical examples include the perva-
sive air leakage from ductwork in homes, the bourgeoning energy
intensity of computer datacenters, and the electricity ‘‘leaking’’
from billions of small power supplies and other equipment.
Intensive periods of investigation, technology R&D, and policy
development gradually ensue in the wake of these discoveries.
The emergent industry of indoor Cannabis production appears to
have joined this list.
1
This article presents a model of the modern-day production
process – based on public-domain sources – and provides first-
order national scoping estimates of the energy use, costs, and
greenhouse-gas emissions associated with this activity in the
United States. The practice is common in other countries but a
global assessment is beyond the scope of this report.
2. Scale of activity
The large-scale industrialized and highly energy-intensive
indoor cultivation of Cannabis is a relatively new phenomenon,
driven by criminalization, pursuit of security, pest and disease
management, and the desire for greater process control and yields
(U.S. Department of Justice, 2011a; World Drug Report, 2009). The
practice occurs across the United States (Hudson, 2003;Gettman,
2006). The 415,000 indoor plants eradicated by authorities in
2009 (and 10.3 million including outdoor plantations) (U.S.
Department of Justice, 2011a, b) presumably represent only a
small fraction of total production.
Cannabis cultivation is today legal in 15 states plus the District
of Columbia, although it is not federally sanctioned (Peplow,
2005). It is estimated that 24.8 million Americans are eligible to
receive a doctor’s recommendation to purchase or cultivate
Cannabis under existing state laws, and approximately 730,000
currently do so (See Change Strategy, 2011). In California alone,
400,000 individuals are currently authorized to cultivate Cannabis
for personal medical use, or sale for the same purpose to 2100
dispensaries (Harvey, 2009). Approximately 28.5 million people
in the United States are repeat consumers, representing 11%
of the population over the age of 12 (U.S. Office of National
Drug Control Policy, 2011).
Cultivation is also substantial in Canada. An estimated 17,500
‘‘grow’’ operations in British Columbia (typically located in residen-
tial buildings) are equivalent to 1% of all dwelling units Province-
wide, with an annual market value of $7 billion (Easton, 2004).
Official estimates of total U.S. Cannabis production varied from
10,000 to 24,000 metric ton per year as of 2001, making it the
nation’s largest crop by value at that time (Hudson, 2003;
Gettman, 2006). A recent study estimated national production
at far higher levels (69,000 metric ton) (HIDTA, 2010). Even at the
Contents lists available at SciVerse ScienceDirect
journal homepage: www.elsevier.com/locate/enpol
Energy Policy
0301-4215/$ - see front matter &2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.enpol.2012.03.023
E-mail address: evanmills1@gmail.com
1
This article substantively updates and extends the analysis described in
Mills (2011).
Energy Policy 46 (2012) 58–67
lower end of this range (chosen as the basis of this analysis), the
level of activity is formidable and increasing with the demand for
Cannabis.
No systematic efforts have previously been made to estimate
the aggregate energy use of these activities.
3. Methods and uncertainties
This analysis is based on a model of typical Cannabis produc-
tion, and the associated energy use for cultivation and transporta-
tion based on market data and first-principals buildings energy
end-use modeling techniques. Data sources include equipment
manufacturer data, trade media, the open literature, and inter-
views with horticultural equipment vendors. All assumptions
used in the analysis are presented in Appendix A. The resulting
normalized (per-kilogram) energy intensity is driven by the
effects of indoor-environmental conditions, production processes,
and equipment efficiencies.
Considerable energy use is also associated with transportation,
both for workers and for large numbers of small-quantities trans-
ported and then redistributed over long distances before final sale.
This analysis reflects typical practices, and is thus intended as
a ‘‘central estimate’’. While processes that use less energy on a
per-unit-yield basis are possible, much more energy-intensive
scenarios also occur. Certain strategies for lowering energy inputs
(e.g., reduced illumination levels) can result in lower yields, and
thus not necessarily reduce the ultimate energy-intensity per unit
weight. Only those strategies that improve equipment and pro-
cess energy efficiency, while not correspondingly attenuating
yields would reduce energy intensity.
Due to the proprietary and often illicit nature of Cannabis
cultivation, data are intrinsically uncertain. Key uncertainties are
total production and the indoor fraction thereof, and the corre-
sponding scaling up of relatively well-understood intensities of
energy use per unit of production to state or national levels could
result in 50% higher or lower aggregate results. Greenhouse-gas
emissions estimates are in turn sensitive to the assumed mix of
on- and off-grid power production technologies and fuels, as off-
grid production (almost universally done with diesel generators)
can – depending on the prevailing fuel mix in the grid – have
substantially higher emissions per kilowatt-hour than grid power.
Final energy costs are a direct function of the aforementioned
factors, combined with electricity tariffs, which vary widely
geographically and among customer classes. The assumptions
about vehicle energy use are likely conservative, given the longer-
range transportation associated with interstate distribution.
Some localities (very cold and very hot climates) will see much
larger shares of production indoors, and have higher space-
conditioning energy demands than the typical conditions
assumed here. More in-depth analyses could explore the varia-
tions introduced by geography and climate, alternate technology
configurations, and production techniques.
4. Energy implications
Accelerated electricity demand growth has been observed in
areas reputed to have extensive indoor Cannabis cultivation. For
example, following the legalization of cultivation for medical
purposes (Phillips, 1998;Roth, 2005;Clapper et al., 2010)in
California in 1996, Humboldt County experienced a 50% rise in
per-capita residential electricity use compared to other parts of
the state (Lehman and Johnstone, 2010).
Aside from sporadic news reports (Anderson, 2010;Quinones,
2010), policymakers and consumers possess little information on
the energy implications of this practice. A few prior studies
tangentially mentioning energy use associated with Cannabis
production used cursory methods and under-estimate energy
use significantly (Plecas et al., 2010 and Caulkins, 2010).
Driving the large energy requirements of indoor production
facilities are lighting levels matching those found in hospital
operating rooms (500-times greater than recommended for read-
ing) and 30 hourly air changes (6-times the rate in high-tech
laboratories, and 60-times the rate in a modern home). Resulting
power densities are on the order of 2000 W/m
2
, which is on a par
with that of modern datacenters. Indoor carbon dioxide (CO
2
)
levels are often raised to 4-times natural levels in order to boost
plant growth. However, by shortening the growth cycle, this
practice may reduce final energy intensity.
Specific energy uses include high-intensity lighting, dehumi-
dification to remove water vapor and avoid mold formation, space
heating or cooling during non-illuminated periods and drying,
pre-heating of irrigation water, generation of carbon dioxide by
burning fossil fuel, and ventilation and air-conditioning to remove
waste heat. Substantial energy inefficiencies arise from air clean-
ing, noise and odor suppression, and inefficient electric generators
used to avoid conspicuous utility bills. So-called ‘‘grow houses’’ –
residential buildings converted for Cannabis production – can
contain 50,000 to 100,000 W of installed lighting power (Brady,
2004). Much larger facilities are also used.
Based on the model developed in this article, approximately
13,000 kW/h/year of electricity is required to operate a standard
production module (a 1.2 1.2 2.4 m (4 48 ft) chamber). Each
module yields approximately 0.5 kg (1 pound) of final product
per cycle, with four or five production cycles conducted per year.
A single grow house can contain 10 to 100 such modules.
To estimate national electricity use, these normalized values
are applied to the lower end of the range of the aforementioned
estimated production (10,000 t per year), with one-third of the
activity takes place under indoor conditions. This indicates
electricity use of about 20 TW/h/year nationally (including off-
grid production). This is equivalent to that of 2 million average
U.S. homes, corresponding to approximately 1% of national
electricity consumption —or the output of 7 large electric power
plants (Koomey et al., 2010). This energy, plus associated fuel uses
(discussed below), is valued at $6 billion annually, with asso-
ciated emissions of 15 million metric ton of CO
2
—equivalent to
that of 3 million average American cars (Fig. 1 and Tables 1–3.)
Fuel is used for several purposes, in addition to electricity. The
carbon dioxide injected into grow rooms to increase yields is
produced industrially (Overcash et al., 2007) or by burning propane
or natural gas within the grow room contributes about 1–2% to the
carbon footprint and represents a yearly U.S. expenditure of $0.1
billion. Vehicle use associated with production and distribution
contributes about 15% of total emissions, and represents a yearly
expenditure of $1 billion. Off-grid diesel- and gasoline-fueled
electric generators have per-kilowatt-hour emissions burdens that
are 3- and 4-times those of average grid electricity in California. It
requires 70 gallon of diesel fuel to produce one indoor Cannabis
plant (or the equivalent yield per unit area), or 140 gallon with
smaller, less-efficient gasoline generators.
In California, the top-producing state, indoor cultivation is
responsible for about 3% of all electricity use, or 9% of household
use.
2
This corresponds to the electricity use of 1 million average
California homes, greenhouse-gas emissions equal to those from
1 million average cars, and energy expenditures of $3 billion per
2
This is somewhat higher than estimates previously made for British
Columbia, specifically, 2% of total Provincial electricity use or 6% of residential
use (Garis, 2008;Bellett, 2010).
E. Mills / Energy Policy 46 (2012) 58–67 59
year. Due to higher electricity prices and cleaner fuels used to
make electricity, California incurs 50% of national energy costs but
contributes only 25% of national CO
2
emissions from indoor
Cannabis cultivation.
From the perspective of individual consumers, a single Cannabis
cigarette represents 1.5 kg (3 pounds) of CO
2
emissions, an amount
equal to driving a 44 mpg hybrid car 22 mile or running a 100-watt
light bulb for 25 h, assuming average U.S. electricity emissions. The
electricity requirement for one single production module equals that
of an average U.S. home and twice that of an average California
home. The added electricity use is equivalent to running about 30
refrigerators.
From the perspective of a producer, the national-average
annual energy costs are approximately $5500 per module or
$2500 per kilogram of finished product. This can represent half
the wholesale value of the finished product (and a substantially
lower portion at retail), depending on local conditions. For
average U.S. conditions, producing one kilogram of processed
Cannabis results in 4600 kg of CO
2
emissions to the atmosphere
(and 50% more when off-grid diesel power generation is used), a
very significant carbon footprint. The emissions associated with
one kilogram of processed Cannabis are equivalent to those of
driving across country 11 times in a 44-mpg car.
These results reflect typical production methods. Much more
energy-intensive methods occur, e.g., rooms using 100% recircu-
lated air with simultaneous heating and cooling, hydroponics,
or energy end uses not counted here such as well-water pumps
and water purification systems. Minimal information and con-
sideration of energy use, coupled with adaptations for security
and privacy (off-grid generation, no daylighting, odor and noise
control) lead to particularly inefficient configurations and corre-
spondingly elevated energy use and greenhouse-gas emissions.
The embodied energy of inputs such as soil, fertilizer, water,
equipment, building materials, refinement, and retailing is not
estimated here and should be considered in future assessments.
The energy use for producing outdoor-grown Cannabis (approxi-
mately two-thirds of all production) is also not estimated here.
Mechanically
ventilated light fixture
Ballast
High-intensity lamps
Motorized lamp
rails
Heater Water purifier
CO2
generator Pump
Submersible
water heater
Vehicles
Dehumidifier
In-line duct fan,
coupled to lights
Oscillating fan Room fan
Chiller
Controllers
Powered
carbon filter
Ozone
generator
Fig. 1. Carbon footprint of indoor Cannabis production.
Table 1
Carbon footprint of indoor Cannabis production, by end use (average U.S
conditions).
Energy intensity
(kW/h/kg yield)
Emissions factor (kgCO
2
emissions/kg yield)
Lighting 2283 1520 33%
Ventilation &
dehumid.
1848 1231 27%
Air conditioning 1284 855 19%
Space heat 304 202 4%
CO
2
injected to
increase foliage
93 82 2%
Water handling 173 115 2%
Drying 90 60 1%
Vehicles 546 12%
Total 6074 4612 100%
Note: The calculations are based on U.S.-average carbon burdens of 0.666 kg/kW/h.
‘‘CO
2
injected to increase foliage’’ represents combustion fuel to make on-site CO
2
.
Assumes 15% of electricity is produced in off-grid generators.
E. Mills / Energy Policy 46 (2012) 58–6760
If improved practices applicable to commercial agricultural
greenhouses are any indication, such large amounts of energy are
not required for indoor Cannabis production.
3
The application of
cost-effective, commercially-available efficiency improvements to
the prototypical facility modeled in this article could reduce
energy intensities by at least 75% compared to the typical-
efficiency baseline. Such savings would be valued at approxi-
mately $40,000/year for a generic 10-module operation (at
California energy prices and $10,000/year at U.S. average prices)
(Fig. 2(a)–(b). These estimated energy use reductions reflect
practices that are commonplace in other contexts such as more
efficient components and controls (lights, fans, space-condition-
ing), use of daylight, optimized air-handling systems, and reloca-
tion of heat-producing equipment out of the cultivation room.
Moreover, strain choice alone results in a factor-of-two difference
in yields per unit of energy input (Arnold, 2011).
5. Energy intensities in context
Policymakers and other interested parties will rightfully seek
to put these energy indicators in context with other activities in
the economy.
One can readily identify other energy end-use activities with
far greater impacts than that of Cannabis production. For example,
automobiles are responsible for about 33% of U.S. greenhouse-gas
emissions (USDOE, 2009), which is100-times as much as those
produced by indoor Cannabis production (0.3%). The approxi-
mately 20 TW/h/year estimated for indoor Cannabis production
is about one/third that of U.S. data centers (US EPA, 2007a,
2007b), or one-seventh that of U.S. household refrigerators
(USDOE, 2008). These shares would be much higher in states
where Cannabis cultivation is concentrated (e.g., one half that of
refrigerators in California (Brown and Koomey, 2002)).
On the other hand, this level of energy use is high in compari-
sion to that used for other indoor cultivation practices, primarily
owing to the lack of daylighting. For comparison, the energy
intensity of Belgian greenhouses is estimated at approximately
1000 MJ/m
2
(De Cock and Van Lierde, No date), or about 1% that
estimated here for indoor Cannabis production.
Table 2
Equivalencies.
Indoor Cannabis production consumesy3% of California’s total
electricity, and
9% of California’s
household electricity
1% of total U.S.
electricity,
and
2% of U.S.
household
electricity
U.S. Cannabis production & distribution
energy costsy
$6 Billion, and results in the
emissions of
15 Million tonnes per
year of greenhouse
gas emissions (CO
2
)
Equal to the
emissions of
3million
average cars
U.S. electricity use for Cannabis
production is equivalent to that ofy
1.7 Million average U.S.
homes
or 7 Average U.S. power
plants
California Cannabis production and
distribution energy costs...
$3 Billion, and results in the
emissions of
4Million tonnes per
year of greenhouse
gas emissions (CO
2
)
Equal to the
emissions of
1Million
average cars
California electricity use for Cannabis
production is equivalent to that ofy
1Million average California
homes
A typical 4 48-ft production module,
accomodating four plants at a time,
consumes as much electricity asy
1Average U.S. homes, or 2Average California
homes
or 29 Average new
refrigerators
Every 1 kilogram of Cannabis produced
using national-average grid power
results in the emissions ofy
4.3 Tonnes of CO
2
Equiva-
lent to
7Cross-country trips
in a 5.3 l/100 km
(44 mp g) car
Every 1 kg of Cannabis produced using a
prorated mix of grid and off-grid
generators results in the emissions
ofy
4.6 Tonnes of CO
2
Equiva-
lent to
8Cross-country trips
in a 5.3 l/100 km
(44 mp g) car
Every 1 kg of Cannabis produced using
off-grid generators results in the
emissions ofy
6.6 Tonnes of CO
2
Equiva-
lent to
11 Cross-country trips
in a 5.3 l/100 km
(44 mp g) car
Transportation (wholesaleþretail)
consumesy
226 Liters of gasoline per kg or $1 Billion dollars
annually, and
546 Kilograms of
CO
2
per
kilogram of
final product
One Cannabis cigarette is like drivingy37 km in a 5.3 l/100 km
(44 mpg) car
Emitting
about
2kg of CO
2
, which is
equivalent to
operating a 100-watt
light bulb for
25 Hours
Of the total wholesale pricey49% Is for energy (at average
U.S. prices)
3
See, e.g., this University of Michigan resource: http://www.hrt.msu.edu/
energy/Default.htm
E. Mills / Energy Policy 46 (2012) 58–67 61
Energy intensities can also be compared to those of other
sectors and activities.
Pharmaceuticals —Energy represents 1% of the value of
U.S. pharmaceutical shipments (Galitsky et al., 2008) versus
50% of the value of Cannabis wholesale prices. The U.S.
‘‘Pharma’’ sector uses $1 billion/year of energy; Indoor Canna-
bis uses $6 billion.
Other industries —Defining ‘‘efficiency’’ as how much energy is
required to generate economic value, Cannabis comes out the
highest of all 21 industries (measured at the three-digit SIC
level). At 20 MJ per thousand dollars of shipment value
(wholesale price), Cannabis is followed next by paper (14),
nonmetallic mineral products (10), primary metals (8),
petroleum and coal products (6), and then chemicals (5)
(Fig. 3). However, energy intensities are on a par with Cannabis
in various subsectors (e.g., grain milling, wood products, rubber)
and exceed those of Cannabis in others (e.g., pulp mills).
Alcohol —The energy used to produce one marijuana cigarette
would also produce 18 pints of beer (Galitsky et al., 2003).
Other building types —Cannabis production requires 8-times
as much energy per square foot as a typical U.S. commercial
building (4x that of a hospital and 20x that of a building for
religious worship), and 18-times that of an average U.S. home
(Fig. 4).
6. Outdoor cultivation
Shifting cultivation outdoors can nearly eliminate energy use
for the cultivation process. Many such operations, however, require
water pumping as well as energy-assisted drying techniques.
Moreover, vehicle transport during production and distribution
remains part of the process, more so than for indoor operations.
A common perception is that the potency of Cannabis pro-
duced indoors exceeds that of that produced outdoors, leading
Table 3
Energy indicators (average U.S. conditions).
per cycle, per
production
module
per year, per
production
module
Energy use
Connected load 3,225 (watts/module)
Power density 2,169 (watts/m
2
)
Elect 2756 12,898 (kW/h/module)
Fuel to make CO
2
0.3 1.6 (GJ)
Transportation fuel 27 127 (Gallons
On-grid results
Energy cost 846 3,961 $/module
Energy cost 1,866 $/kg
Fraction of wholesale price 47%
CO
2
emissions 1936 9,058 kg
CO
2
emissions 4,267 kg/kg
Off-grid results (diesel)
Energy cost 1183 5,536 $/module
Energy cost 2,608 $/kg
Fraction of wholesale price 65%
CO
2
emissions 2982 13,953 kg
CO
2
emissions 6,574 kgCO
2
/kg
Blended on/off grid results
Energy cost 897 4,197 $/module
Energy cost 1,977 $/kg
Fraction of wholesale price 49%
CO
2
emissions 2093 9,792 kg
CO
2
emissions 4,613 kgCO
2
/kg
Of which, indoor CO
2
production
9 42 kgCO
2
Of which, vehicle use
Fuel use
During production 79 Liters/kg
Distribution 147 Liters/kg
Cost
During production 77 $/kg
Distribution 143 $/kg
Emissions
During production 191 kgCO
2
/kg
Distribution 355 kgCO
2
/kg
0
1000
2000
3000
4000
5000
6000
7000
8000
Worst Average Improved
Carbon Footprint (kgCO2/kg finished Cannabis)
Vehicles
Drying
Water handling
CO2 injected to increase foliage
Space heat
Air conditioning
Ventilation & Dehumid.
Lighting
54%
12%
41%
34%
8%
0
500
1000
1500
2000
2500
3000
Worst Average Improved
Electricity Cost ($/kg finsihed Cannabis)
California residential
65% (energy cost as % of wholesale value)
electricity price
US residential
electricity price
Fig. 2. Carbon footprint and energy cost for three levels of efficiency. (a) Indoor
cannabis: carbon footprint. (b) Indoor cannabis: electricity cost. Assumes a
wholesale price of $4400/kg. Wholesale prices are highly variable and poorly
documented.
Fig. 3. Comparative energy intensities, by sector (2006).
E. Mills / Energy Policy 46 (2012) 58–6762
consumers to demand Cannabis produced indoors. Federal sources
(National Drug Intelligence Center, 2005) as well as independent
testing laboratories (Kovner, 2011) actually find similar potencies
when best practices are used.
Illegal clearing of land is common for multi-acre plantations, and,
depending on the vegetation type, can accordingly mobilize green-
house-gas emissions. Standing forests (a worst-case scenario) hold
from 125 to 1500 t of CO
2
per hectare, depending on tree species,
age, and location (National Council for Air and Soil Improvement,
2010). For biomass carbon inventories of 750 t/ha and typical yields
(5000 kg/ha) (UNODC, 2009), associated biomass-related CO
2
emis-
sions would be on the order of 150 kg CO
2
/kg Cannabis (for only one
harvest per location), or 3% of that associated with indoor produc-
tion. These sites typically host on the order of 10,000 plants,
although the number can go much higher (Mallery, 2011). When
mismanaged, the practice of outdoor cultivation imposes multiple
environmental impacts aside from energy use. These include defor-
estation; destruction of wetlands, runoff of soil, pesticides, insecti-
cides, rodenticides, and human waste; abandoned solid waste; and
unpermitted impounding and withdrawals of surface water
(Mallery, 2011;Revelle, 2009). These practices can compromise
water quality, fisheries, and other ecosystem services.
7. Policy considerations
Current indoor Cannabis production and distribution practices
result in prodigious energy use, costs, and unchecked greenhouse-
gas pollution. While various uncertainties exist in the analysis,
the overarching qualitative conclusions are robust. More in-depth
analysis and greater transparency of the energy impacts of this
practice could improve decision-making by policymakers and
consumers alike.
There is little, if any, indication that public policymakers have
incorporated energy and environmental considerations into their
deliberations on Cannabis production and use. There are addi-
tional adverse impacts of the practice that merit attention,
including elevated moisture levels associated with indoor cultiva-
tion that can cause extensive damage to buildings,
4
as well as
electrical fires caused by wiring out of compliance with safety
codes (Garis, 2008). Power theft is common, transferring those
energy costs to the general public (Plecas et al., 2010). As noted
above, simply shifting production outdoors can invoke new
environmental impacts if not done properly.
Energy analysts have also not previously addressed the issue.
Aside from the attention that any energy use of this magnitude
normally receives, the hidden growth of electricity demand
in this sector confounds energy forecasts and obscures
savings from energy efficiency programs and policies. For exam-
ple, Auffhammer and Aroonruengsawat (2010) identified a
Fig. 4. Comparative energy intensities, by U.S. building type (2003).
Table A1
Configuration, environmental conditions, set-points.
Production parameters
Growing module 1.5 m
2
(excl.
walking area)
Number of modules in a room 10
Area of room 22 m
2
Cycle duration 78 days
Production continuous throughout
the year
4.7 cycles
Illumination Leaf phase Flowering
phase
Illuminance 25 klux 100 klux
Lamp type Metal halide High-pressure
sodium
Watts/lamp 600 1000
Ballast losses (mix of magnetic &
digital)
13% 0.13
Lamps per growing module 1 1
Hours/day 18 12
Days/cycle 18 60
Daylighting None none
Ventilation
Ducted luminaires with ‘‘sealed’’
lighting compartment
150 CFM/1000 W
of light (free
flow)
Room ventilation (supply and
exhaust fans)
30 ACH
Filtration Charcoal filters on
exhaust; HEPA on
supply
Oscilating fans: per module, while
lights on
1
Water
Application 151 liters/room-
day
Heating Electric submersible
heaters
Space conditioning
Indoor setpoint —day 28 C
Indoor setpoint —night 20 C
AC efficiency 10 SEER
Dehumidification 7x24 hours
CO
2
production —target
concentration (mostly natural gas
combustion in space)
1500 ppm
Electric space heating When lights off to
maintain indoor
setpoint
Target indoor humidity conditions 40–50%
Fraction of lighting system heat
production removed by
luminaire ventilation
30%
Ballast location Inside conditioned
space
Drying
Space conditioning, oscillating fans,
maintaining 50% RH, 70–80F
7 Days
Electricity supply
grid 85%
grid-independent generation (mix
of diesel, propane, and gasoline)
15%
4
For observations from the building inspectors community, see http://www.
nachi.org/marijuana-grow-operations.htm
E. Mills / Energy Policy 46 (2012) 58–67 63
statistically significant, but unexplained, increase in the growth
rate for residential electricity in California during the years when
indoor Cannabis production grew as an industry (since the mid-
1990s).
Table A2
Assumptions and conversion factors.
Service levels
Illuminance
n
25–100 1000 lux
Airchange rates
n
30 Changes per hour
Operations
Cycle duration
nn
78 Days
Cycles/year
nn
4.7 Continuous
production
Airflow
nn
96 Cubic feet per
minute, per module
Lighting
Leafing phase
Lighting on-time
n
18 hrs/day
Duration
n
18 days/cycle
Flowering phase
Lighting on-time
n
12 hrs/day
Duration
n
60 days/cycle
Drying
Hours/day
n
24 hrs
Duration
n
7 days/cycle
Equipment
Average air-conditioning age 5 Years
Air conditioner efficiency [Standards
increased to SEER 13 on 1/23/2006]
10 SEER
Fraction of lighting system heat production
removed by luminaire ventilation
0.3
Diesel generator efficiency
n
27% 55 kW
Propane generator efficiency
n
25% 27 kW
Gasoline generator efficiency
n
15% 5.5 kW
Fraction of total prod’n with generators
n
15%
Transportation: Production phase (10
modules)
25 Miles roundtrip
Daily service (1 vehicle) 78 Trips/cycle. Assume
20% live on site
Biweekly service (2 vehicles) 11.1 Trips/cycle
Harvest (2 vehicles) 10 Trips/cycle
Total vehicle miles
nn
2089 Vehicle miles/cycle
Transportation: Distribution
Amount transported wholesale 5 kg per trip
Mileage (roundtrip) 1208 km/cycle
Retail (0.25oz 5 miles roundtrip) 5668 Vehicle-km/cycle
Total
nn
6876 Vehicle-km/cycle
Fuel economy, typical car [a] 10.7 l/100 km
Annual emissions, typical car [a] 5195 kgCO
2
0 kgCO
2
/mile
Annual emissions, 44-mpg car
nn
2,598 kgCO
2
0.208 kgCO
2
/mile
Cross-country U.S. mileage 4493 km
Fuels
Propane [b] 25 MJ/liter
Diesel [b] 38 MJ/liter
Gasoline [b] 34 MJ/liter
Electric generation mix
n
Grid 85% share
Diesel generators 8% share
Propane generators 5% share
Gasoline generators 2% share
Emissions factors
Grid electricity —U.S. [c] 0.609 kgCO
2
/kW/h
Grid electricity —CA [c] 0.384 kgCO
2
/kW/h
Grid electricity —non-CA U.S. [c] 0.648 kgCO
2
/kW/h
Diesel generator
nn
0.922 kgCO
2
/kW/h
Propane generator
nn
0.877 kgCO
2
/kW/h
Gasoline generator
nn
1.533 kgCO
2
/kW/h
Blended generator mix
nn
0.989 kgCO
2
/kW/h
Blended on/off-grid generation —CA
nn
0.475 kgCO
2
/kW/h
Blended on/off-grid generation —U.S.
nn
0.666 kgCO
2
/kW/h
Propane combustion 63.1 kgCO
2
/MBTU
Prices
Electricity price —grid
(California —PG&E) [d]
0.390 per kW/h (Tier 5)
Electricity price —grid (U.S.) [e] 0.247 per kW/h
Electricity price —off-grid
nn
0.390 per kW/h
Electricity price —blended on/off —CA
nn
0.390 per kW/h
Electricity price —blended on/off —U.S.
nn
0.268 per kW/h
Propane price [f] 0.58 $/liter
Gasoline price —U.S. average [f] 0.97 $/liter
Diesel price —U.S. average [f] 1.05 $/liter
Table A2 (continued )
Wholesale price of Cannabis [g] 4,000 $/kg
Production
Plants per production module
n
4
Net production per production module [h] 0.5 kg/cycle
U.S. production (2011) [i] 10,000 metric tonnes/y
California production (2011) [i] 3,902 metric tonnes/y
Fraction produced indoors [i] 33%
U.S. indoor production modules
nn
1,570,399
Calif indoor production modules
nn
612,741
Cigarettes per kg
nn
3,000
Other
Average new U.S. refrigerator 450 kW/h/year
173 kgCO
2
/year (U.S.
average)
Electricity use of a typical U.S. home —2009
[j]
11,646 kW/h/year
Electricity use of a typical California home —
2009 [k]
6,961 kW/h/year
Notes:
n
Trade and product literature; interviews with equipment vendors.
nn
Calculated from other values.
Notes for Table A2.
[a]. U.S. Environmental Protection Agency., 2011.
[b]. Energy conversion factors, U.S. Department of Energy, http://www.eia.doe.gov/
energyexplained/index.cfm?page=about_energy_units, [Accessed February 5, 2011].
[c]. United States: (USDOE 2011); California (Marnay et al., 2002).
[d]. Average prices paid in California and other states with inverted-block tariffs are
very high because virtually all consumption is in the most expensive tiers. Here the
PG&E residential tariff as of 1/1/11, Tier 5 is used as a proxy for California http://
www.pge.com/tariffs/ResElecCurrent.xls, (Accessed February 5, 2011). In practice a
wide mix of tariffs apply, and in some states no tier structure is in place, or the
proportionality of price to volume is nominal.
[e]. State-level residential prices, weighted by Cannabis production (from Gettman.
2006) with actual tariffs and U.S. Energy Information Administration, ‘‘Average
Retail Price of Electricity to Ultimate Customers by End-Use Sector, by State’’, http://
www.eia.doe.gov/electricity/epm/table5_6_a.html, (Accessed February 7, 2011)
[f]. U.S. Energy Information Administration, Gasoline and Diesel Fuel Update (as of
2/14/2011) – see http://www.eia.gov/oog/info/gdu/gasdiesel.asp Propane prices –
http://www.eia.gov/dnav/pet/pet_pri_prop_a_EPLLPA_PTA_dpgal_m.htm, (Accessed
April 3, 2011).
[g]. Montgomery, 2010.
[h]. Toonen et al., 2006); Plecas et al., 2010.
[i]. Total Production: The lower value of 10,000 t per year is conservatively retained.
Were this base adjusted to 2011 values using 10.9%/year net increase in number of
consumers between 2007 and 2009 per U.S. Department of Health and Human
Services (2010), the result would be approximately 17 million tonnes of total
production annually (indoor and outdoor). Indoor Share of Total Production:The
three-fold changes in potency over the past two decades, reported by federal
sources, are attributed at least in part to the shift towards indoor cultivation See
http://www.justice.gov/ndic/pubs37/37035/national.htm and (Hudson, 2003). A
weighted-average potency of 10% THC (U.S. Office of Drug Control Policy, 2010)
reconciled with assumed 7.5% potency for outdoor production and 15% for indoor
production implies 33.3%::67.7% indoor::outdoor production shares. For reference,
as of 2008, 6% of eradicated plants were from indoor operations, which are more
difficult to detect than outdoor operations. A 33% indoor share, combined with per-
plant yields from Table 2, would correspond to a 4% eradication success rate for the
levels reported (415,000 indoor plants eradicated in 2009) by the U.S. Drug
Enforcement Agency (http://www.justice.gov/dea/programs/marijuana.htm).
Assuming 400,000 members of medical Cannabis dispensaries in California (each
of which is permitted to cultivate), and 50% of these producing in the generic 10-
module room assumed in this analysis, output would slightly exceed this study’s
estimate of total statewide production. In practice, the vast majority of indoor
production is no doubt conducted outside of the medical marijuana system.
[j]. Total U.S. electricity sales: U.S. energyinformation administration, ‘‘retail sales of
electricity to ultimate customers: Total by end-use sector’’ http://www.eia.gov/
cneaf/electricity/epm/table5_1.html, (Accessed March 5, 201 1)
[k]. California Energy Commission, 2009;2011.
E. Mills / Energy Policy 46 (2012) 58–6764
Table A3
Energy model.
ELECTRICITY Energy
type
Penetration Rating
(Watts or %)
Number of
448-ft
production
modules served
Input energy per
module
Units Hours/day
(leaf phase)
Hours/day
(flower
phase)
Days/cycle (leaf
phase)
Days/cycle
(flower phase)
kW/h/cycle kW/h/year per
production
module
Light
Lamps (HPS) elect 100% 1,000 1 1,000 W 12 60 720 3,369
Ballasts (losses) elect 100% 13% 1 130 W 12 60 94 438
Lamps (MH) elect 100% 600 1 600 W 18 18 194 910
Ballast (losses) elect 100% 0 1 78 W 18 18 25 118
Motorized rail motion elect 5% 6 1 0.3 W 18 12 18 60 0 1
Controllers elect 50% 10 10 1 W 24 24 18 60 2 9
Ventilation and moisture control
Luminare fans (sealed from conditioned
space)
elect 100% 454 10 45 W 18 12 18 60 47 222
Main room fans —supply elect 100% 242 8 30 W 18 12 18 60 31 145
Main room fans —exhaust elect 100% 242 8 30 W 18 12 18 60 31 145
Circulating fans (18’’) elect 100% 130 1 130 W 24 24 18 60 242 1,134
Dehumidification elect 100% 1,035 4 259 W 24 24 18 60 484 2,267
Controllers elect 50% 10 10 1 W 24 24 18 60 2 9
Spaceheat or cooling
Resistance heat or AC [when lights off] 90% 1,850 10 167 W 6 12 18 60 138 645
Carbon dioxide Injected to Increase foliage
Parasitic electricity elect 50% 100 10 5 W 18 12 18 60 5 24
AC (see below) elect 100%
In-line heater elect 5% 115 10 0.6 W 18 12 18 60 1 3
Dehumidification (10% adder) elect 100% 104 0 26 W 18 12 18 60 27 126
Monitor/control elect 100% 50 10 5 W 24 24 18 60 9 44
Other
Irrigation water temperature control elect 50% 300 10 15 W 18 12 18 60 19 89
Recirculating carbon filter [sealed room] elect 20% 1,438 10 29 W 24 24 18 60 54 252
UV sterilization Elect 90% 23 10 2.1 W 24 24 18 60 4 18
Irrigation pumping elect 100% 100 10 10 W 2 2 18 60 2 7
Fumigation elect 25% 20 10 1 W 24 24 18 60 1 4
Drying
Dehumidification elect 75% 1,035 10 78 W 24 7 13 61
Circulating fans elect 100% 130 5 26 W 24 7 4 20
Heating elect 75% 1,850 10 139 W 24 7 23 109
Electricity subtotal elect 2,174 10,171
Air-conditioning 10 420 W 583 2,726
Lighting loads 10 W 259 1,212
Loads that can be remoted elect 100% 1,277 10 W 239 1,119
Loads that can’t be remoted elect 100% 452 10 W 85 396
CO2-production heat removal elect 45% 1,118 17 W 18 12 18 60 ——
Electricity Total elect 3,225 W 2,756 12,898
FUEL Units Technology
Mix
Rating
(BTU/h)
Number of
448-ft
production
modules served
Input energy per
module
Hours/day
(leaf phase)
Hours/day
(flower
phase)
Days/cycle (leaf
phase)
Days/cycle
(flower phase)
GJ or
kgCO
2
/cycle
GJ or kgCO
2
/
year
On-site CO
2
production
Energy use propane 45% 11,176 17 707 kJ/h 18 12 18 60 0.3 1.5
CO2 production –4emissions kg/CO
2
20 93
Externally produced Industrial CO
2
5% 1 0.003 liters
CO
2
/hr
18 12 18 60 0.6 2.7
Weighted-average on-site/purchased kgCO
2
210
E. Mills / Energy Policy 46 (2012) 58–67 65
For Cannabis producers, energy-related production costs have
historically been acceptable given low energy prices and high
product value. As energy prices have risen and wholesale com-
modity prices fallen, high energy costs (now 50% on average of
wholesale value) are becoming untenable. Were product prices to
fall as a result of legalization, indoor production could rapidly
become unviable.
For legally sanctioned operations, the application of energy
performance standards, efficiency incentives and education,
coupled with the enforcement of appropriate construction codes
could lay a foundation for public-private partnerships to reduce
undesirable impacts of indoor Cannabis cultivation.
5
There are
early indications of efforts to address this.
6
Were such operations
to receive some form of independent certification and product
labeling, environmental impacts could be made visible to other-
wise unaware consumers.
Acknowledgment
Two anonymous reviewers provided useful comments
that improved the paper. Scott Zeramby offered particularly
valuable insights into technology characteristics, equipment con-
figurations, and market factors that influence energy utilization in
this context and reviewed earlier drafts of the report.
Appendix A
See Tables A1–A3.
References
Auffhammer, M., Aroonruengsawat A., 2010. Uncertainty over Population, Prices,
or Climate? Identifying the Drivers of California’s Future Residential Electricity
Demand. Energy Institute at Haas (UC Berkeley) Working Paper, August.
Anderson, G., 2010. Grow Houses Gobble Energy. Press Democrat, July 25.See
/http://www.pressdemocrat.com/article/20100725/ARTICLES/100729664S.
Arnold, J., 2011. Investigation of Relationship between Cannabis Plant Strain and
Mass Yield of Flower Buds. Humboldt State University Proposal.
Barnes, B., 2010. Boulder Requires Medical Pot Growers to Go Green. NewsFirst5.com,
Colorado Springs and Pueblo. May 19 /www.newsfirst5.com/y/boulder-requires-
medical-pot-growers-to-go-green1/S, (accessed June 4, 2011).
Bellett, G., 2010. Pot growers stealing $100 million in electricity: B.C. Hydro
studies found 500 Gigawatt hours stolen each year. Alberni Valley Times.
October 8.
Brady, P., 2004. BC’s million dollar grow shows. Cannabis Culture. /http://www.
cannabisculture.com/articles/3268.htmlS, (accessed June 4, 2011).
Brown, R.E., Koomey, J.G., 2002. Electricity use in California: past trends and
present usage patterns. Lawrence Berkeley National Laboratory Report No
47992. /http://enduse.lbl.gov/info/LBNL-47992.pdfS.
California Energy Commission, 2009. California energy demand: 2010–2020 —
adopted forecast. Report CEC-200-2009-012-CMF), December 2009 (includes
self-generation).
California Energy Commission, 2011. Energy almanac. /http://energyalmanac.ca.
gov/electricity/us_per_capita_electricity.htmlS, (accessed February 19, 2011).
Caulkins, P., 2010. Estimated cost of production for Legalized Cannabis. RAND
Working Paper, WR-764-RC. July. Although the study over-estimates the hours
of lighting required, it under-estimates the electrical demand and applies
energy prices that fall far short of the inclining marginal-cost tariff structures
applicable in many states, particularly California.
Central Valley High Intensity Drug Trafficking Area (HIDTA), 2010. Marijuana
Production in California. 8 pp.
Clapper, J.R., et al., 2010. Anandamide suppresses pain initiation through a
peripheral endocannabinoid mechanism, Nature Neuroscience, 13, 1265–
1270, doi:10.1038/nn.2632 /http://www.nature.com/neuro/journal/v13/n10/
full/nn.2632.htmlS.
De Cock, L., Van Lierde, D. No Date. Monitoring Energy Consumption in Belgian
Glasshouse Horticulture. Ministry of Small Enterprises, Trades and Agriculture.
Center of Agricultural Economics, Brussels.
Easton, S.T., 2004. Marijuana Growth in British Columbia. Simon Frasier University,
78 pp.
Galitsky, C.S.-C. Chang, E. Worrell, Masanet, E., 2008. Energy efficiency improvement
and cost saving opportunities for the pharmaceutical industry: an ENERGY STAR
guide for energy and plant managers, Lawrence Berkeley National Laboratory
Report 62806. /http://ies.lbl.gov/iespubs/62806.pdfS.
Galitsky, C.N. Martin, E. Worrell, Lehman, B., 2003. Energy efficiency improvement
and cost saving opportunities for breweries: an ENERGY STAR guide for energy
and plant managers, Lawrence Berkeley National Laboratory Report No. 50934.
/www.energystar.gov/ia/business/industry/LBNL-50934.pdfS.
Garis, L., 2008. Eliminating Residential Hazards Associated with Marijuana Grow
Operations and The Regulation of Hydroponics Equipment, British Columbia’s
Public Safety Electrical Fire and Safety Initiative, Fire Chiefs Association of
British Columbia, 108pp.
Gettman, J., 2006. Marijuana Production in the United States, 29pp. /http://www.
drugscience.org/Archive/bcr2/app2.htmlS.
Harvey, M., 2009. California dreaming of full marijuana legalisation. The Sunday
Times, (September). /http://business.timesonline.co.uk/tol/business/indus
try_sectors/health/article6851523.eceS.
Hudson, R., 2003. Marijuana Availability in The United States and its Associated
Territories. Federal Research Division, Library of Congress. Washington, D.C.
(December). 129pp.
Koomey, J., et al. 2010. Defining a standard metric for electricity savings.
Environmental Research Letters, 5, http://dx.doi.org/10.1088/1748-9326/5/1/
014017.
Kovner, G., 2011. North coast: pot growing power grab. Press Democrat. /http://
www.pressdemocrat.com/article/20110428/ARTICLES/110429371?Title=Report-
Growing-pot-indoors-leaves-big-carbon-footprint&tc=arS.
Lehman, P., Johnstone, P., 2010. The climate-killers inside. North Coast Journal,
March 11.
Mallery, M., 2011. Marijuana national forest: encroachment on California public
lands for Cannabis cultivation. Berkeley Undergraduate Journal 23 (2), 1–49
/http://escholarship.org/uc/our_buj?volume=23;issue=2S.
Marnay, C., Fisher, D., Murtishaw, S., Phadke, A., Price, L., Sathaye, J., 2002.
Estimating carbon dioxide emissions factors for the California electric power
sector. Lawrence Berkeley National Laboratory Report No. 49945. /http://
industrial-energy.lbl.gov/node/148S(accessed February 5, 2011).
Mills, E., 2011. Energy up in smoke: the carbon footprint of indoor Cannabis
production. Energy Associates Report. April 5, 14 pp.
Montgomery, M., 2010. Plummeting marijuana prices create a panic in Calif.
/http://www.npr.org/templates/story/story.php?storyId=126806429S.
National Drug Intelligence Center, 2005. Illegal and Unauthorized Activities on
Public Lands.
Overcash, Y., Li, E.Griffing, Rice, G., 2007. A life cycle inventory of carbon dioxide as
a solvent and additive for industry and in products. Journal of Chemical
Technology and Biotechnology 82, 1023–1038.
Peplow, M., 2005. Marijuana: the dope. Nature doi:10.1038/news050606-6,
/http://www.nature.com/news/2005/050607/full/news050606-6.htmlS.
Phillips, H., 1998. Of pain and pot plants. Nature. http://dx.doi.org/10.1038/
news981001-2.
Plecas, D.J., Diplock, L., Garis, B., Carlisle, P., Neal, Landry, S., 2010. Journal of
Criminal Justice Research 1 (2), 1–12.
Quinones, S., 2010. Indoor pot makes cash, but isn’t green. SFGate, /http://www.
sfgate.com/cgi-bin/article.cgi?f=/c/a/2010/10/21/BAPO1FU9MS.DTLS.
Revelle, T., 2009. Environmental impacts of pot growth. 2009. Ukiah Daily Journal.
(posted at /http://www.cannabisnews.org/united-states-cannabis-news/
environmental-impacts-of-pot-growth/).
Roth, M.D., 2005. Pharmacology: marijuana and your heart. Nature http://dx.doi.
org/10.1038/434708a /http://www.nature.com/nature/journal/v434/n7034/
full/434708a.htmlS.
See Change Strategy, 2011. The State of the Medical Marijuana Markets 2011.
http://medicalmarijuanamarkets.com/S.
National Council for Air and Soil Improvement, 2010. GCOLE: Carbon On Line
Estimator. /http://www.ncasi2.org/GCOLE/gcole.shtmlS, (accessed Sepember 9,
2010).
Toonen, M., Ribot, S., Thissen, J., 2006. Yield of illicit indoor Cannabis cultivation in
the Netherlands. Journal of Forensic Science 15 (5), 1050–1054 /http://www.
ncbi.nlm.nih.gov/pubmed/17018080S.
U.S. Department of Energy, Buildings Energy Data Book, 2008. Residential Energy
End-Use Splits, by Fuel Type, Table 2.1.5 /http://buildingsdatabook.eren.doe.
gov/docs/xls_pdf/2.1.5.xlsxS.
U.S. Department of Energy, 2009. ‘‘Report DOE/EIA-0573(2009), Table 3.
U.S. Department of Energy, 2011. Voluntary Reporting of Greenhouse Gases
Program /http://www.eia.doe.gov/oiaf/1605/ee-factors.htmlS, (accessed Feb-
ruary 7, 2011).
U.S. Department of Health and Human Services, 2010. 2009 National Survey on
Drug Use and Health. /http://oas.samhsa.gov/nsduhLatest.htmS.
U.S. Department of Justice, 2011a. Domestic Cannabis Eradication and Suppression
Program. /http://www.justice.gov/dea/programs/marijuana.htmS, (accessed
June 5, 2011).
U.S. Department of Justice, 2011b. National Drug Threat Assessment: 2010
/http://www.justice.gov/ndic/pubs38/38661/marijuana.htm#MarijuanaS,
(accessed June 5, 2011).
5
The City of Fort Bragg, CA, has implemented elements of this in TITLE 9 –
Public Peace, Safety, & Morals, Chapter 9.34. http://city.fortbragg.com/pages/searchRe
sults.lasso?-token.editChoice=9.0.0&SearchType=MCsuperSearch&CurrentAction=
viewResult#9.32.0
6
For example, the City of Boulder, Colorado, requires medical Cannabis
producers to offset their greenhouse-gas emissions (Barnes, 2010).
E. Mills / Energy Policy 46 (2012) 58–6766
US EPA, 2007a. Report to Congress on Server and Data Center Energy Efficiency:
Public Law 109-431. Washington, DC: U.S. Environmental Protection Agency,
ENERGY STAR Program. August 2.
U.S. Environmental Protection Agency, 2007b. Report to Congress on Server and
Data Center Energy Efficiency Public Law 109-431 133 pp.
U.S. Environmental Protection Agency, 2011. Emission Facts: Average Annual
Emissions and Fuel Consumption for Passenger Cars and Light Trucks. /http://
www.epa.gov/oms/consumer/f00013.htmS. (accessed February 5, 2011).
U.S. Office of National Drug Control Policy, 2011. Marijuana Facts and Figures.
/http://www.whitehousedrugpolicy.gov/drugfact/marijuana/marijuana_ff.
html#extentofuseS, (accessed June 5, 2011).
UNODC, 2009. World Drug Report: 2009. United Nations Office on Drugs and
Crime, p. 97. /http://www.unodc.org/unodc/en/data-and-analysis/WDR-2009.
htmlSFor U.S. conditions, indoor yields per unit area are estimated as up to
15-times greater than outdoor yields.
E. Mills / Energy Policy 46 (2012) 58–67 67
