Not so green: how the weed industry is a glutton for fossil fuels

https://www.theguardian.com/society/2017/jun/20/cannabis-climate-change-fossil-fuels

Oliver Milman in Denver
@olliemilman
Tuesday 20 June 2017

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He now owns three cannabis-growing facilities, all housed in what were shuttered Denver warehouses. The second largest, a windowless blockhouse that holds around 500 cannabis plants, throbs with energy.

Large 1,000-watt lamps bathe the plants in a blueish hue during the vegetative phase, when the plants are gaining mass, while a fizzing yellow light scorches the vegetation as it enters its flowering phase, producing the buds of weed that are trimmed, cured and sold for around $1,400 a pound. (It used to be much more, before a stampede of growers saturated the local market).

“We are consuming a lot of energy compared to what we would with LED lights,” said Isenbergh, who pays at least $4,000 a month for electricity. “We tried LED but we couldn’t get the right yield from the plants. And this is a weight game. The LEDs just don’t have the horsepower.”

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And with around half of all US states now allowing cannabis for various uses, hothoused cultivation is increasingly a concern for governors and mayors promising to fill a Donald Trump-sized hole in emissions reductions.

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Evan Mills, a senior scientist at the University of California, was one of the first researchers to quantify how energy hungry the nascent industry is, estimating in 2011 that indoor cannabis cultivation represents 1% of total electricity use across the US, a figure backed up by a New Frontier study last year.

Lighting can comprise up to half of a cannabis grower’s energy use, with the desire to create a round-the-clock version of natural growing conditions requiring hugely powerful high pressure sodium (HPS) lights. These lights are on a par with those found in hospital operating rooms, throwing out around 500 times the illumination recommended for reading.

As a result, producing just a couple of pounds of weed can have the same environmental toll as driving across America seven times. Cannabis may still invoke thoughts of small-time, hippyish pursuits but the actual energy impact of indoor growers is on a par with humming data centers, Mills’s study found.

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Denver’s electricity use has been edging up at a rate of more than 1% a year, with nearly half of that increase due to marijuana-growing facilities, the city has said. While just a small percentage of Denver’s electricity is used by cannabis operations, they are far more energy intensive on a per-square-foot basis than most other types of businesses. This demand, in turn, drives fossil fuel use, because Colorado gets the majority of its energy from coal-fired power plants.

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In order to calibrate conditions to reap multiple harvests a year, growers have to bake the plants in light while cranking the air conditioning to ensure rooms stay at a finely balanced temperature. A dehumidifier is used to prevent mold, carbon dioxide is pumped in to bolster growth and fans mimic the presence of a breeze. Irrigation systems are often hoses plugged into the plants, leading to tubs of water. The goal is healthy, weighty buds.

All of this uses a lot of energy and LEDs, despite saving a lot of power, have been deemed by many growers to be less effective and more expensive than HPS lights.

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Still, LEDs aren’t in themselves a perfect answer. Because marijuana generally takes longer to mature under LEDs, it can result in not much energy being saved. And large greenhouses such as Strawberry Fields’ two-acre facility in Pueblo County still need supplemental lamp light alongside natural sunshine.

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