As the legal cannabis industry grows, so does its carbon footprint. In order to grow cannabis plants indoors, cultivators must resort to using powerful high-pressure sodium lights, similar to the ones used in hospital operating rooms. These lights produce about 500 times as much illumination as a typical reading light, and consume an enormous amount of electricity. It is estimated that growing a couple of pounds of weed indoors has the same environmental impact as driving across the country seven times.
Some cultivators have tried to turn to more energy-efficient technology like LED lights, but found that their plants did not grow as well. Paul Isenbergh, owner of three cannabis grow-ops in Denver, said that his grows are “consuming a lot of energy compared to what we would with LED lights. 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.”
According to University of California senior scientist Evan Mills, indoor cannabis grows use around 1% of the country's total electricity. In Denver, the city's electricity use has been growing by over 1% every year, and nearly half of that increase is from cannabis cultivators. Because Colorado gets most of its energy from coal, an increase in electricity usage means an increase in fossil fuel use and greenhouse gas emissions.
Amy Andrle, co-owner of L'Eagle dispensary and grow-op, has found a partial solution by using LEDs for the vegetative growing areas, and restricting HPS use for the flowering rooms. This decision has saved them around $1,800 a month in electricity bills. “The cannabis industry is often pigeonholed as being very heavy users of resources,” she said. “It’s true we do have those needs but we are being evaluated against agriculture that’s been around for hundreds of years. No-one could really do the research on lighting or other technology until we could step into the light with legalization, the innovation since then has been astounding.”
Mills pointed out that because marijuana grows are federally illegal, they are not subject to federal policies or programs on energy conservation. “The sad irony is that legalization is probably the only avenue for solving the problem, if only policymakers would confront it. Until then, some of the nation’s hard-earned progress towards climate change solutions is on the chopping block as regulators continue to ignore this industry’s mushrooming carbon footprint.”