Medical marijuana, 4/20 and Earth Day: How green is your green?

Get your marijuana-infused celebrating done on 4/20 tomorrow, since two days later, on Earth Day, there apparently won't be much to light up about.

According to new research, indoor marijuana cultivation -- i.e., the kind that accounts for the vast majority of medical marijuana sold in Colorado -- accounts for a mind-blowing 1 percent of the country's electricity use.

That's enough power to fuel two million typical U.S. homes -- and produces the same amount of greenhouse gases as three million cars.

This information comes from "Energy Up in Smoke," an independent study conducted by Evan Mills, a researcher at the Department of Energy's Lawrence Berkeley National Laboratory in California. The research, conducted independently of the DOE lab, focused on the electrical demands of modern indoor grow facilities, which, according to Mills, suck up as much power as a computer datacenter and require an air-exchange rate six times that of a typical biotech lab.

As it turns out, the demands of all those grow lights and circulation fans add up: Indoor pot cultivation consumes $5 billion in energy costs each year. In California, the top producing state, indoor grows account for 3 percent of all electricity use and 8 percent of home electricity use. (While Mills doesn't single out Colorado in his study, it's reasonable to guess the number-two producing state's stats aren't too far behind.) That power generation, along with the emissions from transporting all that pot, equal a hefty amount of pollution. A single joint, concludes Mills, costs two pounds of carbon dioxide emissions to produce, the same amount as running a 100-watt bulb for seventeen hours.

Some illicit indoor growers aren't dependent on regular power supplies at all -- but that doesn't make their production methods any more green. Mills notes that off-the-grid grows demand seventy gallons of diesel fuel to grow a single pot plant, and that's using the most efficient gas generators possible. Outdoor grows have markedly less of an environmental impact, but they aren't necessarily earth-friendly. According to the USDA Forest Service, unlawful marijuana cultivation consumed thousands of acres of public lands, contaminating creeks and watersheds with pesticides and fertilizers, a practice that has skyrocketed in national forests over the past few years.

Mills is quick to point out on his website that he's not trying to suggest marijuana is inherently bad for the environment. He's just arguing that, as part of marijuana's struggle for legitimacy, it's high time for growers to think green about how they're growing their green. "If improved practices applicable to commercial agricultural greenhouses are any indication, the energy use for indoor cannabis production can be reduced dramatically," he writes. "Cost-effective efficiency improvements of 75 percent are conceivable, which would yield energy savings of about $25,000 a year for a generic ten-module growing room."

Results like that could keep people celebrating from 4/20 right on through Earth Day.

More from our Marijuana archive: "THC blood test: Pot critic William Breathes nearly 3 times over proposed limit when sober."

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Joel Warner is a former staff writer for Westword and International Business Times. He's also written for WIRED, Men's Journal, Men's Health, Bloomberg Businessweek, Popular Science, Slate, Grantland and many other publications. He's co-author of the 2014 book The Humor Code: A Global Search for What Makes Things Funny, published by Simon & Schuster.
Contact: Joel Warner