Scrubbing the sky: Sequestering CO2 using an unlikely material

Gaia’s method of direct air capture requires far less energy than traditional systems. Its secret? Biomass.

It’s one thing to study climate change — it’s quite another to take direct action to stop it.

In 2019, while doing postdoctoral research at McGill, Qinhong Cai (better known as Tammy) travelled to Nunavut to join the Oceans Protection Plan. The then-new federal initiative was designed to improve marine safety and increase the protection and restoration of coastal and seaway ecosystems. Cai, an environmental engineer, was sent to monitor hydrocarbon contaminants and microbial genomics along the Kivalliq transportation corridor. She loved being in the north — “I’m a person who’s on the warmer side so I really enjoy colder climates” — and the work built on the microbiological research she’d done in her native China. But after talking with Inuit elders, who told her about the significant changes they’d observed in the region, she had a change of heart.

“All this work is important,” she says, “and I really enjoyed doing it. But I realized that all that effort won’t be enough if we can’t stop or mitigate global warming.”

Where to start, though? For Cai, the answer lay in a cutting-edge technology that is gathering considerable momentum — direct air capture (DAC). If we’re to avoid climate catastrophe, cutting carbon emissions is now no longer sufficient; we also need to remove and sequester the carbon dioxide we’ve already pumped in the atmosphere. Carbon capture, broadly speaking, occurs at a point of emission — a smokestack, say — but DAC can be located anywhere, and plucks carbon dioxide directly from the air through a variety of processes. Like carbon capture, it then either permanently stores that carbon underground or converts it into chemical components that can be used in products like concrete, laundry detergent, even sustainable jet fuel. In the last five years or so, a number of major international companies, from Switzerland’s Climeworks to B.C.’s Climate Engineering, have developed the technology, with many smaller firms rapidly creating other DAC solutions and by-products. The global market for carbon removal is now poised to explode; according to a 2023 Boston Consulting Group report, it could reach up to U.S.$40 billion by 2030 and $135 billion a decade later.

In 2020, while still at McGill, Cai devoted evenings and weekends to developing her own unique DAC system. While most DAC systems use massive amounts of heat to separate carbon dioxide from the atmosphere, Cai figured out a novel way to use biomass (that is, any matter derived from any living thing like organic waste or agricultural byproducts) to achieve the same results.

Cai was still validating the tech in the lab and filing for a patent when she founded Gaia Refinery to commercialize her system. In early 2023, she brought on Genny Shaw, an entrepreneur and consultant, as CEO, with Cai the startup’s chief technical officer. Although the firm is headquartered in Halifax, Cai currently works out of Ottawa, where Gaia has a research partnership with Collège La Cité and Lambton College.

Here, Cai talks about the qualities that set Gaia’s system apart, the role DAC must play in our decarbonization efforts and the love she has for the natural world.

 

After witnessing environmental changes in Nunavut, Gaia founder Tammy Cai was inspired to develop a direct air capture system that could help mitigate climate change.

 
I know you’re an environmental engineer, but how did you arrive at carbon removal technology specifically?

Climate change has become such a huge contributor to the destabilization of our ecosystem and of society in general. So I wanted to focus on carbon removal because I see that as an avenue with a lot of potential. It’s a globalized industry, and because it’s so nascent, it really pushes innovation and new solutions. No matter where you are, if you bring technology that’s economically efficient, you can plant a seed to change the world.

Can you tell me about your system and how it works?

We researched all the existing DAC technologies and found they were limited by how much energy they needed to release captured carbon. The current methods are very energy intensive. Carbon dioxide is trapped in a sorbent [an absorbent material] and then you need a lot of electricity or heat to separate it. Electricity does this by creating acidity, which displaces the CO2. But I knew that acid is very common in biological systems, and there are many industries that produce organic acid in their waste streams, such as pulp and paper mills and ethanol producers. We purchase that feedstock, extract the acid and then add that acid in a sorbent, which produces a neutralization reaction. That reaction releases the carbon and leaves behind a salt. We create a synergy in that we use the acid to release the carbon, and the salt has carbon in it, too, and we can convert that to pure CO2. That process also releases energy that regenerates the sorbent used to capture the CO2.

So, it’s a circular process?

Yes, it’s a closed-loop pathway. There’s also very low energy input — it doesn’t require us to build a wind or solar farm to power it. It’s really quite unique.

Were you the first to conceive this process?

Similar technology is used in desalinating seawater. But we were the first to apply it to DAC.

Where’s the carbon being sequestered once it’s captured?

We have a lot of partners who’ve signed letters of intent with us. They’ll either provide sustainable biomass feedstock or sequester the captured carbon dioxide by injecting it underground where it reacts with specific minerals to form carbonates that fill in the pores of the rock formation.

You’ve said how your technology uses less energy. There are other concerns about DAC, however, such as that it distracts from the hard work of shifting away from fossil fuels, and that it’s too expensive. What do you say to that?

We see a lot of pathways to a price that’s much more reasonable than what’s currently offered in the market. As for DAC in general, I think it’s an important tool — it has a small footprint, doesn’t use much water and is a clean-cut engineering process. And we absolutely have to use all the tools we have at our disposal to remove carbon.

Where are you now with the technology? Do you have a prototype you’re developing?

We’ve already validated our technology with a lab-scale prototype. We’ve started a pilot that’s going to remove 50 tonnes a year of carbon, and are building that with a partner in Hamilton, Ont. With that, we can run tests on different wastewater and biomass resources to see the performance.

Assuming it all goes well, what would it take you to scale up this technology and get the results we really need to mitigate climate change?

The biggest factor is still public understanding of carbon dioxide removal as a whole. Financiers need to accept that it’s something we need to do, it’s reliable and the results are good. Industrial partners have a very important role to play, too. We see the strategic alignment with different industries and their need to bring down their carbon intensity — like ethanol, for example, so that they can move into sustainable aviation fuel.

Once you do get to scale, how much carbon could you potentially remove using this system?

Conservatively, I’d say 100 million tonnes a year.

Why is this work so important to you?

I just have always loved being in nature and working for nature. This is the time when people really should step up and help the environment regain its balance, to prevent ecosystem damage. It’s also a great learning experience. I was trained in academia, so scaling a business is actually out of my comfort zone. It’s challenging. But if you just write papers and don’t try to bring things to market, nothing will happen.

You must be incredibly busy, though. Do you actually get to spend much time in nature?

Definitely. I can’t wait to go kayaking out here on the canal.

 
Gaia is one of six companies in Mission from MaRS: Carbon Management, a special initiative that aims to help Canada achieve its net-zero goals by accelerating the adoption of carbon removal solutions.

 
Photo illustration by Stephen Gregory; Images: Unsplash; Photo courtesy of Gaia