Canadians smoked a lot of weed last year. But Canada’s licensed pot growers had to destroy a lot of it, too: For every kilogram of legal cannabis consumed in Canada, nearly eight kilograms of cannabis plants and waste are composted, burned, or destroyed by Canadian pot growers.

In 2017, medical cannabis patients consumed somewhere in the ballpark of 52 tonnes of cannabis, 23 tonnes of it in its dried, smokable form and 28 tonnes of it in oil form. That's just a fraction of the 402 metric tonnes of cannabis and cannabis byproducts that Canadian LPs destroyed in 2017, according to documents obtained from Health Canada by VICE News through the access to information act.

The records refer to what Health Canada calls “destruction events,” which must be rigorously documented, and the product weighed, in order to comply with the department’s regulations. According to the documents — which, for privacy reasons, were released without the names of the producers responsible for each destruction — the destruction events range in size, from an entry of one gram destroyed at some point in July 2017 to an entry in which 12.2 million grams (12.2 tonnes) were destroyed in October.

The destruction records reflect the total weight of all cannabis products, including waste, trimmings, and dried cannabis flower that doesn’t pass quality assurance (or falls on the floor).

Sign up for the VICE News Canada Newsletter to get the best of our content delivered to your inbox daily.

It highlights the fact that growing cannabis is a very waste-heavy process. And with those numbers only expected to grow once Canada legalizes recreational marijuana next month, it raises the question: what happens to all that waste?

Currently, nothing; it just gets destroyed.

Destroying cannabis is no small task for a cannabis company; for obvious reasons, it’s not as simple as throwing it all in a bonfire and setting it on fire. The Access to Cannabis for Medical Purposes Regulations (ACMPR) sets out how cannabis must be destroyed. Those regulations require rigorous documentation and record-keeping, ostensibly in order to keep cannabis from leaking out into the black market. Each destruction must be witnessed by at least two senior employees “who are qualified to witness the destruction,” and the method used must not “result in any person being exposed to cannabis smoke.” Growers can still incinerate it, but it must be done in an enclosed unit. (So no, you can’t use it to hotbox anything.)

"The only method ever prescribed in regulations is called the kitty litter method."

“The only method ever prescribed in regulations,” said Cam Battley, executive vice-president of Aurora Cannabis, “is called the kitty litter method,” referring to the Marihuana Medical Access Regulations (MMAR), the first iteration of the country’s medical cannabis system, which recommended blending any cannabis waste with water and then mix it with cat litter to mask the odour before throwing it out.

Battley told VICE News that the industry relies on a variety of methods to dispose of cannabis waste. “Everything from incineration, to shipping it or transporting it to municipal landfills, municipal compost facilities,” he said. “The whole idea is that you’re required to make it unusable.”

But there’s no specific prescription for what can be done with it; Health Canada just has to approve whatever plan you have for disposal. “We are restricted by Health Canada as to what we can do with the waste. The plant material itself has to be destroyed in a way that deactivates the cannabinoids,” said Terry Lake, vice-president of corporate social responsibility at the Quebec-based LP Hydropothecary.

Lake said that somewhere in the ballpark of three-quarters of all plant material has to be discarded in their growing operations. Since they can’t reuse it for anything it has virtually no value to the company, so they simply compost it and bury the composting. “It’s a great big flipping composter, and everything goes in there,” he said. “It’s really just taking the plant and returning it back to the earth.”

That leaves some room for new solutions. In December, Aurora Cannabis partnered with a company called Micron Waste to use Micron’s technology, which the company says is able to “convert organic waste into clean water that meets municipal effluent discharge standards.” That water can then be used to water future cannabis crops, or simply flushed down into the sewer system, said Karen Lauriston, director of communications with Micron Waste.

“Thus far the results have been excellent,” said Battley. Other methods, like composting, can take weeks to complete and come with costs, including transportation and security. Micron’s “digester” technology, on the other hand, takes between 24 to 48 hours to dispose of the cannabis. “Our intention is, once we validate this in cannabis, to install those digesters at all of our facilities in Canada and globally.” (The name of the cannabis digesting machine, by the way, is “The Cannavore.”)

Since producers are not required to distinguish between stalks, leaves, and dried flower in their accounting to Health Canada, there is no way to tell how much actual dried, smokeable weed is being destroyed. And producers aren’t in a hurry to make that information available; Canopy Growth, Aurora and Aphria, three of the biggest producers in Canada, all either declined to provide that information or did not respond to several requests for comment.

Nor is this information readily communicated to shareholders in most companies. Occasionally, however, companies do disclose it: in January 2018, Organigram told its shareholders that “late-stage biological assets that are disposed of and inventory that does not pass the company’s quality assurance standards are expensed to indirect production. For the three-month period ending November 30, 2017, $454,976 was expensed as indirect production.”

"The question is, is there a better use for the waste, the plant particularly? And I think: yeah."

A loosening of the rules on Health Canada’s part would open up new avenues for those parts of the plant that are wasted, said Lake. All of that waste could have some value, either in fibers (as hemp is used) or as the market opens up to a wider range of products and uses for cannabis, like beverages. “The question is, is there a better use for the waste, the plant particularly?” said Lake. “And I think: yeah.”

And as the production levels rise with the opening of the recreational market, there will be exponentially more cannabis waste. “The amount of waste produced is going to go up in an order of magnitude, so it would be really nice to have alternative uses,” said Lake.

What those alternative uses are, though, remains a bit of an open question. Because of rigorous Health Canada tracking — when the government says seed to sale tracking, they mean it, joked Lake — producers haven’t been able to toy around much with what cannabis waste could be used for.

“We don’t really know,” he said, “because no one has been able to do much work with this.”