How this UK-based firm is growing a more sustainable cannabis

Growing cannabis indoors uses a lot of energy, obviously resulting in higher emissions.

But some companies are trying to combat that like U.K.-based cultivator Glass Pharms. It claims to be the world's first firm to grow cannabis indoors in a carbon-neutral way. It actually says it goes one better, and produces in a carbon-negative way — without buying carbon credits that would usually offset emissions.

The company's greenhouse facility in the south of England gets all its power from an anaerobic digestion plant, which is fed on waste food that would normally go to landfill and release methane as it breaks down, CEO James Duckenfield explained to CNBC on a video call.

Carbon dioxide has been used as a unit of reference by the Intergovernmental Panel on Climate Change when gauging the global warming potential (GWP) of other greenhouse gases. In the case of methane, it has been estimated to have 28 times the global warming potential of CO2 over a 100-year timeframe.

Taking that equivalent measure of methane emissions into account is what makes Glass Pharms' process carbon negative, said Duckenfield.

Instead, the biogas created in the anaerobic digestion plant is converted into electricity, which also generates waste heat. That is then used to heat and cool Glass Pharms' greenhouse.

"When we get the energy we're really efficient with it," Duckenfield said.

In addition, he said that air is flowed through the plants vertically, instead of using horizontal fans that are normally seen in greenhouses. This creates a convection current that helps air move around the greenhouse and disrupts any microclimates that can lead to mold, he explained.

The facility's water supply is also harvested from the rain that lands on its roof, which is then treated and even recycled after use.

This means Glass Pharms' greenhouse facility does not take any electricity from the energy grid, nor does it rely on mains water.

These efficiencies are particularly beneficial to a business operating in this area. Duckenfield highlighted that the greenhouse cannabis industry is typically "very energy intensive" given the amount of light and water needed, as well as humidity control.

An indoor cannabis cultivation site with 500 plants that operates throughout the year can potentially consume between 1.6 million and 2 million liters of water a year, according to an analysis from the European Monitoring Centre for Drugs and Drug Addiction and Europol.

The analysis also pointed to research that showed around 6,000 kilowatt hours of energy is needed to produce 1kg of indoor herbal cannabis, which in Europe, is estimated to translate to releasing 1,374kg of CO2 into the atmosphere. In context, the estimated carbon footprint of a single joint of indoor-grown herbal cannabis is equivalent to driving a plug-in hybrid electric car nearly 3 miles.

Duckenfield said his passion for environmental issues started long before he became CEO of Glass Pharms.

"I trained as a chemist and then ended up in technology and I'm just loving coming back to things that are very close to my heart … I use my chemistry, I can now build a business that's truly environmentally responsible," he said.

Glass Pharms, which was set up in 2020, was granted the first U.K. commercial license to supply high-THC cannabis flower to lawful pharmaceutical companies by the Home Office the following year. The company finished building its greenhouse cultivation facility in 2023, completing 14 harvests last year.

Medical use of cannabis was legalized in the U.K. in 2018. This gave specialist doctors the option to prescribe unlicensed cannabis-based medicinal products.

The majority of cannabis-based products for medical use (CBPMs) are unlicensed in the U.K., meaning they have not yet been assessed for safety and efficacy by the country's regulatory agency and have not been granted marketing authorization.

A 2019 report from the Health and Social Care Committee highlighted that there were still gaps in research on medicinal cannabis, partly due to the fact that before the changes in 2018 restrictions made it more difficult to carry out the "robust clinical trials necessary to test efficacy and safety."

In fact, National Health Service England said in a publication in 2023 that many doctors and their professional bodies continued to be "concerned about the limited evidence on the long-term safety and efficacy of these products, which are mainly unlicensed." 

It added that "further evidence of benefits and harms are required before prescribing can become more widespread."

Data released in January 2023 by the U.K.'s NHS Business Services Authority showed that 89,239 unlicensed cannabis-based medicines were prescribed privately in England between November 2018 and July 2022. By comparison, fewer than five of these unlicensed medicines had been prescribed through the NHS.

A YouGov survey conducted in 2022, commissioned by medical cannabis clinic Sapphire Medical Clinics (now Curaleaf Clinic), estimated that around 1.8 million people in the U.K. self-medicated with illegal cannabis products to alleviate symptoms associated with chronic physical and mental health conditions.

Duckenfield said that the U.K. was "lagging behind" some other countries in which cannabis was seen as a more mainstream medicine.

He said that this was despite the fact that a leader in the space, GW Pharmaceuticals, had come out of the U.K. Jazz Pharmaceuticals bought GW Pharmaceuticals in 2021 for $7.2 billion.

"As a country, we ought to be fostering the medical cannabis industry and encouraging it to grow which requires the government really to be vocally standing behind it," Duckenfield said.