Grass is Not So Green: Marijuana Has a Huge Carbon Footprint

The yearly greenhouse-gas pollution of the $40 billion per year marijuana industry is responsible for about 3% of all electricity use or 8% of household use. Indoor growers use high-intensity lights that are 500 times more powerful that a standard reading lamp. They also use several other high energy industrial practices.  The closest comparison for these massive, industrial-style grow facilities are data centers, which consume about two percent of the nation’s electric power.

by Tracey de Morsella, Green Economy Post

It turns out that grass (Marijuana) is not all that green, particularly if it is grown indoors.  Evan Mills, Ph. D, a longtime energy analyst at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, last week released his independent study that examined the carbon footprint of the indoor marijuana industry.

In his report, Energy Up in Smoke: The Carbon Footprint of Indoor Cannabis, Mills reports that indoor Marijuana production, considered the largest cash crop in the U.S., with an annual production value estimated at about $40 billion, uses 1% of the nation’s entire electricity consumption. This comes to energy expenditures of $5 billion per year.  This is due to the fact that Cannabis production has for the most part shifted indoors, were it is out-of-sight of law enforcement. This is particularly the case in California, which is the top producer among the 17 states to allow cultivation for medical purposes, where medical marijuana growers use high-intensity lights.  These lights are usually reserved for operating rooms that are 500 times more powerful that a standard reading lamp.

Also driving the large energy requirements are 30 hourly air changes (6 times the rate in high-tech laboratories, and 60 times the rate in a modern home). The closest comparison for these massive, industrial-style grow facilities are data centers, which consume about two percent of the nation’s electric power.

“The yearly greenhouse-gas pollution”, Mills wrote. “the practice is responsible for about 3% of all electricity use or 8% of household use.

Marijuana production has raised other environmental concerns. Each Marijuana plant said to need between 3 and 5 gallons of water per day to grow to fruition, which significantly raises its carbon footprint.  The Bay Citizen, a San Francisco publication, reported last year on the risk of pot being tainted with pesticides used by growers. Even though 17 states allow growing Marijuana for medical purposes, it is a controlled substance under federal law and U.S. regulatory agencies do not supervise how it is grown or monitor the pesticides used in its cultivation.  Mills also  notes that marijuana growers often raise indoor carbon dioxide levels to four-times natural levels to boost plant growth.

Broken down to the individual level, one Cannabis cigarette represents 2 pounds of CO2 emissions, an amount equal to running a 100-watt light bulb for 17 hours with average U.S. electricity.  It has the greenhouse gas impact of driving 15 miles in a 44-mile-per-gallon car.

Mills, a member of the U.N. Intergovernmental Panel on Climate Change, compiled his data from open literature and interviews with horticultural equipment retailers.  He conducted the study quantify a previously undocumented component of energy demand in the United States, to understand the underlying technical drivers, and to establish baseline impacts in terms of energy use, costs, and greenhouse-gas emissions.

Mills writes in his report that criminalization contributes to inefficient energy practices. Compared to electric grids, off-grid power production often produced more greenhouse-gas emissions, requiring 70 gallons of diesel fuel to produce one indoor Cannabis plant, or 140 gallons with smaller, less-efficient gasoline generators. He also describes how long driving distances and odor suppression measures take away from ventilation efficiencies. Mills also points out that the huge carbon footprint is caused by the lights, fans, and air filters need for indoor cultivation. Outdoor weed plantations do not have these types of energy use issues, and when managed correctly, do not have a significant environmental impact, but also suggests that there are solutions for indoor growers.

Mills observed that there are many reversible inefficiencies are embedded in current practices.  “If improved practices applicable to commercial agricultural greenhouses are any indication, the energy use for indoor cannabis production can be reduced dramatically,” he said. “Cost-effective efficiency improvements of 75 percent are conceivable, which would yield energy savings of about $25,000/year for a generic 10-module growing room,” he wrote.

Eric Wesoff, at GreentechEnterprise suggests pot cultivation’s carbon footprint could be reduced by replacing metal halide and high-pressure sodium lights with more energy-efficient solid-state LED lighting.  “This LED grow light site claims reductions in electricity usage of 40 percent to 75 percent compared MH or HPS lights. However, other sites in the indoor grow community have some reservations over the effectiveness of LEDs,” he wrote.

Mills provided the following recommendations for growers, communities, suppliers, utilities, regulators, and medical dispensaries:

• Growers should be applying science to understanding how to achieve necessary environmental conditions in a less energy-intensive manner.
• Energy providers, policymakers, and forecasters need to better account for this particular driver of energy demand, and thus more accurately evaluate the effects of unrelated programs and policies on the consumption of energy at the macro scale.
• Planning and building officials at the city, state, and federal level may choose to seek better understanding of the energy consequences of this activity in their localities.Some (Berkeley, Boulder, Fort Bragg) have already made steps in this direction.
• To support more responsible consumer decision-making, medical dispensaries should provide disclosure of product carbon content and other dimensions of environmental footprint.
• Growers should select better, commercially available equipment.
• Designers and manufacturers of the energy-using equipment can more precisely analyze and consider the issues from an engineering and market standpoint.
• Utilities have already begun to recognize legal producers, granting them lower (agricultural) tariffs in exchange for safety inspections.
• Equipment vendors should develop even more efficient equipment, and educating their customers.
• Consumers and the general public can be more informed about the carbon footprint associated with this practice and better consider the environmental consequences of their actions.
• Growers should reduce the use of off-grid power generators fired with fossil fuels.

Visit Mills’ web site to to read his  study.

© 2011, Tracey de Morsella. All rights reserved. Do not republish.

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