*Carl Martel, Canadian cannabis scientist, has mapped hundreds of uses for hemp, including energy storage. Photo courtesy Advanced Botanical and Biomass Institute*

By Sarah Derouin

Integrating hemp into building products is a boon to the environment. But what if hemp could be used to push sustainability even further?

In June, the Hemp Home Expo held an international online conference about all topics related to hemp-building. The 2021 Expo featured education about the hemp building industry, and networking with architects, engineers, builders, innovators and investors. A series of talks were available for attendees, and the educational sessions were hosted by Ramon Granados, a building engineer, and founder/CEO of Hemp Engineering Pty Ltd, Australia.

Carl Martel, a cannabis researcher and founder of Advanced Botanical and Biomass Research Institute (ABBRI) was one of the featured lecturers. ABBRI is a research and innovation firm that looks to nature for inspiration in new sustainable and environmentally-friendly products. Industrial hemp is a big player in their innovations, and Martel said that’s by design.

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“One of the key things about hemp is that you can really do everything with this [plant],” he noted, adding that you can create anything with the plant, from clothing to cosmetics, food and building products. “That’s why I’m a big proponent of whole-plant utilization.”

Hemp is a jack-of-all-trades plant, but cannabis still has a negative connotation. Many people equate cannabis with smoking marijuana, but Martel wants to change that mindset. “I try to say to people, ‘When I go to a supermarket and I look at a potato, the first thing that comes to mind isn’t vodka— it’s chips or French fries,’” he said. Instead of imagining a drug, he wants people to associate cannabis with food, products, and industry.

Part of that mindset change is to recognize hemp as a multi-use plant. Martel wants to use hemp in its entirety—hemp seeds can be food or oil, while the biomass can be turned into industrial products. It’s this left over, carbon-rich plant material that has him thinking outside the box.

In his Expo talk, Martel highlighted new research that takes the carbon in hemp and turns it into a way to store energy. He said his inspiration began by observing trees. Martell called trees an efficient energy machine—the leaves absorb carbon dioxide from the air, process the carbon and turn it into life-sustaining energy. What if this same idea could be used in human-made products?

He looked at some hempcrete and wondered if it might behave like a tree—efficiently moving carbon as energy. He played around with some hemp biochar and lime, creating a conductive hempcrete. Using some salt water and metal, he hooked up electrodes to the hempcrete and powered a light.

“This got me thinking,” he remarked. “Can we store energy in walls?”

The idea for a Building Integrated Energy Storage (BIES) system was born. Martel coated a brick with the conductive hempcrete and calculated that one brick might store a small amount of energy: about 1 Watt hour per liter. In comparison, a traditional lead acid battery can store about 40 Watt hours per liter.

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While one brick seems woefully underpowered, remember that thousands of bricks line the wall of a building. “If you think about the surface area of a building, you get thousands of Watt hours per area,” he noted, adding that the technology could also be used on roads.

The technology could be used anywhere—from high-rise buildings in urban centers to remote villages without infrastructure. Picture a remote community, 1000s of kilometers from a power plant, said Martel. The infrastructure needed to run power to those residents would be astronomical. But a small, hemp-battery could store energy produced from a solar panel or stream turbine, independent of a power grid.

“This is what I’m actually trying to develop: these sorts of things where people can learn how to make a battery themselves using very cheap and abundant materials available to them,” said Martel. “In the future, whole batteries can be grown in the ground, not mined from the ground.”

One of the key factors that still needs to be addressed is the life cycle of the batteries—in other words, how many times energy can build up in storage then be released for power. “One of the problems with having [the battery] locked into concrete, is the charge cycle is only 500,” he noted. “That’s not going to last very long—we’ll have to tear down the building in two years and rebuild it.”

Martel knows that to be a viable solution, engineers will have to find a way to produce something more long-lasting, say 40,000 to 1000,000 charge cycles. “You need something that’s going to last 40 to 100 years,” he noted.

The solution may be found in the way carbon is used in the battery. Martel said there needs to be more research into the benefits of biochar (charcoal that is produced by heating vegetative waste in the absence of oxygen) and how it can be best used.

“I think the 21st Century will be the century of carbon,” he said.

Michigan-based Sarah Derouin is a geologist and science writer and editor and contributor to the Big Picture Science radio show.