Algae-Based Coating Enables Modular Carbon Capture Removal System

What will it take to meet global climate change targets?

Reducing carbon emissions during manufacture and product use, certainly, but another key technology area that many are working on is the industrialization of carbon capture — in other words, technologies that remove and sequester already emitted carbon from the air or directly from the point of emissions.

As it turns out, coatings could be a vital component in these efforts.

There are a number of paint and coating technologies available or in development today that claim to have carbon removal capabilities, including a purifying, graphene-based “eco-paint” said to capture CO₂ and other toxins; research into coatings based on living cyanobacteria mixed with latex and clay to absorb CO₂ and release oxygen; and lime-based paints said to reabsorb carbon emissions from the construction process.

One company working on this is leveraging its experience in coatings to create a paint inspired by nature — specifically, lichen.

Developing Carbon Capture Coatings

For more than 20 years, coatings business Reactive Surfaces (Austin, Texas, U.S.) has considered itself to be “an innovator in the paint and coatings space,” says Beth McDaniel, president.

Specifically, the company’s team of microbiologists and biochemists work to “merge biotech with materials science to create functionality of surfaces. We work with biomolecules that have a functionality in nature, and put that into a coating system. Then we apply that coating to a particular surface, and that surface becomes functional,” McDaniel explains.

Examples of the company’s functional additives and coatings include its DeGreez self-cleaning enzymatic coating additive, WMDtox coatings for detoxifying surfaces contaminated with certain organophosphorus pesticides or nerve weapons, and ProteCoat antimicrobial coating additives for eliminating microbes including some viruses. Of the latter, McDaniel notes, “This is very different from, say, a spray-on product like a disinfectant, which only lasts until the surface gets fouled again. This coating’s functionality is designed to be active for the life of the coating.” She adds that Reactive Surfaces’ additives are also naturally occurring and nontoxic.

Since 2018, the company has been working on extending its experience in bio-based coatings and coating additives to meet the need for carbon capture removal technologies.

“You see statistics all the time about where we’ll be in eight years or 20 years if everything stays the same, and we felt like this was an urgent problem and there was no time to waste. We wanted to use our experience in coatings and biological systems to add a tool to the climate change toolbox,” she says.

The company took its idea from lichen, a plantlike organism consisting of algae and fungi coexisting symbiotically, forming a growth that spreads across surfaces like rocks and trees. Lichen captures CO₂ from the atmosphere naturally, by providing a fungal surface area for photosynthetic, CO₂-absorbing algae to spread out and work their magic.

Starting from this idea, the company first developed an algae-based coating — “this time, not using a biomolecule, but rather a living organism, a blue-green algae, actually,” McDaniel clarifies — “with the idea of creating a paint that harnessed the natural role of algae in nature, which is to capture carbon dioxide, and that could be spread on surfaces the way lichen works. This worked well and has evolved into several embodiments of the technology.”

One of these embodiments, spurred by Reactive Surfaces’ involvement in the ongoing XPrize Carbon Removal competition (they are called Team Lichen, of course), is a stackable module for concentrated carbon removal.

Algae-based carbon removal

The technology starts with growing algae from pellets, which is then used to inoculate sheets of a cellulose-based matrix — which are flexible, porous materials that act like the fungus in lichen and provide a surface area for the algae to grow on.

The inoculated polymeric panels are then carefully draped in modular, 4-square-meter repurposed cargo containers that, McDaniel says, “act as a terrarium” for the algae on the sheets, enabling the algae to access needed gas exchange and light. Specially-formulated coatings and surface treatments, such as those that help absorb ambient moisture, can also be used to enhance the efficiency of the carbon capture process. “The idea is to create a whole bunch of surface area within these modules to do the work of photosynthesis,” McDaniel says.

The modules can either be installed in an open environment — for direct air capture — or directly next to a facility that emits carbon dioxide as part of its operations — to capture industrial point-source emissions.

At that point, the algae does what it does best, and begins naturally capturing carbon dioxide from the air.

How is the carbon removed and sequestered? Reactive Surfaces installs monitoring systems in each module to track humidity and temperature data to determine when the algae has captured enough carbon for “harvesting.” The sheets are removed and wrung out — the liquid, containing algae and water, is saved and reused to inoculate new sheets. The wrung-out sheets, containing now only the base cellulose/polymer material and the captured CO₂ caught in the material’s pores, are dried out in a solar-powered oven and then pyrolyzed down into biochar.

“Biochar is a widely recognized way of sequestering CO₂ and is a very valuable byproduct,” McDaniel explains, which can be added to soil to help retain water. She adds that producing biochar is also a less risky and costly solution compared to some other carbon capture removal technologies, that result in gaseous or liquid carbon which is piped into underground wells. “This is a fully encapsulated system and a permanent carbon removal process,” McDaniel emphasizes.

How much does it cost? McDaniel notes that the total cost — including capital expense, operating expenses and maintenance — is less than $500 per ton of CO₂ removed, less than half of what some similar technologies cost. “Cost comparisons aren’t quite apples to apples at this point, but we know it’s a cost-competitive technology and we’re still working to optimize it further,” she says.

Next steps: Pilot plants, optimization, surface coatings

Currently, the company has a pilot plant full of carbon capture modules up and running next to a desalination plant in California, capable of capturing either ambient or point-source CO₂. It takes approximately 33 1m³ modules to capture a ton of CO₂, McDaniel says, and the company plans initially to scale up to multiple sites to capture at least 1,000 tons of CO₂.

McDaniel emphasizes, “This could work with industrial emitters of CO₂. We’ve been working with manufacturers in hard-to-abate industries — like oil and gas or steel manufacturing — to work out how we might design a system for them. The system is modular and they can be stacked up in order to optimize the amount of CO₂ capture per site. We could build these around, say, a big steel manufacturer for instance, and they could pipe in their CO₂.”

At the same time, the company continues to develop its carbon capture technology and algae-based coatings. “We’re still optimizing and automating everything, it’s still a work in progress,” McDaniel says.

Looking ahead for the carbon capture modules, she envisions fields of modules — “think like a wind farm, except full of direct air capture modules, powered by solar energy” — as well as source-point emissions installed at steel plants and other manufacturing operations that produce carbon emissions directly. “And there are a lot of other possibilities in between, such as infrastructure for individuals to install in their backyards, for example. We plan to create a blueprint for this to make it accessible for companies, farmers or individuals to set up systems themselves,” she says.

Beyond the modules themselves, Carbon Capture Coatings have potential in and of themselves as a coating system for architecture and construction applications and beyond. “For our first product, we built the modules to cram as much dedicated surface area as possible for these, but in future we’ll develop more versions that can be used to capture emissions in other environments and on other surfaces,” McDaniel says.