By Cynthia A. Gosselin, The ChemQuest Group

The long-term effects of global emissions are widely debated in society. Some tout a doomsday scenario whereby life and geography will cease to exist. Others take a more measured approach.

What is agreed upon by all parties is that the planet would benefit greatly from a lessening of overall pollution and the enactment of good mitigation strategies to reduce emissions around the world. Everyone wants clean air and water and a habitable environment for all living organisms.

The way to achieve this cleansing must come in practical forms. Science and technology abound with clever solutions—some of which are ripe for immediate use, but not well-known or advertised.

Let’s start with a current topic of intense interest: carbon dioxide (CO2) emissions. It was a very telling visual a few months into the pandemic when satellite images of Beijing showed a clear view of the city. Smog was almost non-existent because vehicular traffic was essentially eliminated when most people were trapped in their homes for so many months in 2020.

Global CO2 emissions peaked in 2019 at 33.4 gigatons (GT). In 2020, CO2 emissions dropped to 31.5 GT, only to rebound to near 2019 highs in 2021 to 33 GT once the world began to move again.1 It is not practical to assume that everyone will buy an electric car or governments will simply dismantle commerce. Therefore, we must come up with novel ways to take care of our planet by neutralizing CO2 emissions and perhaps more importantly, finding uses for them as precursors for realistic green product manufacture.

An XPRIZE Carbon Removal competition is doing just that. One of this organization’s chief tenets is aimed at tackling climate change and rebalancing earth’s carbon cycle. Funded by Elon Musk and the Elon Musk Foundation, this $100 million competition is the largest incentive prize in history.2

So far, two cohorts of competitors from the United States, Canada, India, China, and United Kingdom have developed methods of capturing CO2 and manufacturing materials for products as diverse as vodka, toothpaste, foams, cutlery, straws, building materials, crayons, fuels, tiles, jewelry, purses minerals, yoga mats, and slippers—all of which are ultimately green products and even ocean biodegradable. In one case, using vehicle fuel manufactured by Team Breathe in India is projected to lower the country’s carbon emissions 33-35% by 2030.

Unfortunately, there is a notable absence of representation by the coatings industry in the XPRIZE Carbon Removal competition. But, thanks to work being done by a consortium from the Universities of Texas at Austin, Southern Mississippi, and Alabama, large-scale use of carbon capture coatings is on the horizon. Coating Innovations for Electric Vehicles3 These coatings borrow from photosynthesis—nature’s way of removing CO2 from the atmosphere. The natural process requires water (moisture) and sunlight to convert CO2 into oxygen and carbohydrates. Algae that form a thin layer on the ocean surface provides 70-80% of photosynthetic capture of atmospheric carbon and oxygen release.

Building upon nature, the working premise is that coatings that adhere to surfaces exposed to light could be modified to exploit a biomimetic system similar to surfaces covered with photosynthetic lichen in order to capture, fix, and sequester CO2.4 Coatings applied over large surfaces could rival natural carbon sinks in their ability to remove excess carbon.

By capturing large quantities of greenhouse gases and turning the captured carbon into carbohydrates such as cellulose, these paints are capable of manufacturing useful byproducts. These byproducts could be used as a basis for manufacturing the next generation of green products. In that way the coatings industry would contribute to fulfilling the XPRIZE goals of cleaner air AND green manufacturing of useful materials.

Man-made and fossil fuel additions to naturally occurring greenhouse gases tax the ability of nature to mitigate the “extra” CO2 which has reportedly increased from 280 parts per million (ppm) in the 1700s to 411 ppm as of mid-2019. Carbon capture coatings could offer a solution that could easily be incorporated into the normal course of business because of the sheer magnitude of painted surface area in the world.

Steve McDaniel, a U.S. molecular biologist, and Dominic Lam Man-kit, a Hong Kong medical professor, have jointly developed and tested algae-infused paints that can capture atmospheric CO2.5 Promising early formulations used latex paints but so far, no paint chemistry is off limits. Indications are that these modified paints are “carbon sinks” that rival forests and ocean algae in their ability to capture carbon. The coatings contain live photosynthetic algae that use CO2 as the food source through photosynthesis and form carbohydrates in the form of cellulose.

Preliminary studies show that these nature-mimicking carbon capture coatings applied to the interior of tree-sized plastic cylinders, known as algae trees, can capture 0.024 tons of atmospheric CO2 per year. This is the same amount as a mature tree, which reaches this level of carbon capture only after 50 years of maturation. These algae trees, by comparison, become fully functional after 45 days. Another advantage of these algae trees is that where only 100,000 trees can fit into a square kilometer, 100,000 million algae trees can fit into the same area, and they don’t need fertile land or room to grow.

Additional development of this novel system would seem to allow actual building surfaces to be painted with these formulations where climates are hospitable—thereby further increasing both the macro-surface and micro-surface area generated by paint porosity—increasing the carbon capturing capability on the CO2 generating site.

Manufacturing sites such as traditional integrated steel mills could reduce their carbon footprint via either on-site “algae tree forests” or by painting the enormous vertical building surfaces with thin algae-containing topcoats and still carry on the necessary manufacturing functions in a cost-effective manner. It might even be possible to ultimately tailor these algae-infused coatings (via algae level or paint coating weight) to capture the exact amount of CO2 generated onsite, rendering a massive integrated steel mill complex carbon neutral.

Following the theme of sustainability and carbon capture, a paint has been manufactured from waste concrete powder that can absorb 20% of its weight in carbon. This paint can sequester 27 grams (g) of CO2 for every 135 g of paint—which is the same amount of CO2 absorbed by a normal tree in one day.6

Surprisingly, cement is the most carbon-intensive ingredient in concrete, responsible for 8% of global emissions—but it naturally reabsorbs approximately 43% of the CO2 generated during production through mineral carbonization. This process leads to the formation of calcium carbonate or limestone. Usually only the outer layers exposed to CO2 are affected and the core remains uncarbonated due to lack of CO2 exposure.

When concrete is recycled, the aggregate is reused, but the remainder is pulverized and usually sent to a landfill. This waste is high in calcium oxide and over time, buried and in contact with groundwater, it turns to calcium hydroxide—a highly alkaline material that disturbs the pH balance of the local ecosystems.

Rather than dump the residue into a landfill, the waste concrete is filtered, pulverized, mixed with binders, pigments and water. Through the process of mineral carbonation, this thin film indoor/outdoor paint reacts with CO2 in the air and absorbs it. While it is not yet known how many decades this paint remains active, it is known that only extreme heat would alter the structure of the carbonate, rendering it ineffective.

Building and construction industries world over are looking for ways to help reach some of the new legally binding net zero greenhouse gas emissions by 2050. Again, the coatings industry, by virtue of the sheer amount of surface area coverage can play a vital role. For example, a highly pure artisan lime and graphene infused paint has been developed for use on gypsum, plaster, mortars, old paint, prefabricated panels, brick, perlite and unlaminated wallpaper.7, 8 These pure-carbon paints can absorb 129 g of carbon dioxide per square meter of application. Three 15-liter buckets of paint absorb 14 kg of CO2 per year—the same amount as a 250 kg adult tree absorbs in one year.

This paint was specially formulated for indoor use and purifies the environment by absorbing CO2 through a natural carbonation process. During the drying cycle, a stoichiometric reaction occurs whereby the lime reacts with atmospheric CO2, forming calcium carbonate. It becomes limestone again in the “lime cycle” process. CO2 absorption is highly concentrated during the first weeks after application of the paint, reducing atmospheric carbon in a room by 75%.

The reaction is continuous over time, although on a smaller scale, continuing to clean the air for the life of the coating. Graphene imparts strength, flexibility and durability without the need for synthetic polymers or resins. It is also practical for the user, with good hiding power, matt finish, cleanability and a collection of soft colors to lend comfort and ambience to the home. Further, the coating allows the walls to breathe, eliminating condensation issues, and the high pH inhibits undesirable fungi and microorganism growth.

Coupled with CO2 absorption qualities, another advantage of this paint system is that graphene is 1,000 times more conductive than copper. The paint can also improve the thermal regulation of buildings. This thermal insulating paint uses glass microspheres to create an air chamber that generates a thermal bridge to maintain ambient temperature. This saves energy by requiring less heating and air conditioning while avoiding condensation, maintaining optimum humidity and air quality levels.

The ultimate carbon capture paint would not only clean the air but heat homes. The European Research Council (ERC) has encouraged the development of these innovative paints for the renovation of old houses to improve energy efficiency without huge retrofitting investments.9 Innovation of new paints for storage and controlled release of thermal energy is critical to practically and cost effectively meet future green energy efficiency standards under the European Union (EU) Directive 2102/27/EU.

One result of the ERC initiative is the development of light-activated catalysts that can neutralize airborne pollutants such as CO2 and NOx, together with the addition of nano-encapsulated phase-change materials that work to as thermo-regulators that release heat inside brick buildings whenever necessary by releasing excessive energy.10

Salt hydrates are used due to their low cost and very high volumetric energy storage density. However, since these additives are corrosive and hydrophilic, they are encapsulated in polymer shells as small as 10 nanometers for protection.

During the warm part of the day, these energy nanocapsules absorb and store heat at their melting temperature, turning into encapsulated liquids. During cold nights they crystallize at prescribed temperatures, releasing heat and warming the room.

Old energy-inefficient buildings are a large energy consumer, accounting for approximately 40% of total energy consumption and 36% of CO2 emissions in the EU. The paint is slated to be used as a form of insulation to increase energy efficiency while being cost effective for the average homeowner.

Embedding titanium dioxide nanoparticles, which are catalysts for breaking down airborne pollutants (photocatalysis) allows for electrons to be released at the surface when ultraviolet rays shine on the paint.

The electrons interact with humidity in the air, breaking water molecules into hydroxy radicals. These short-lived radicals attach to pollutant molecules and turn them into harmless substances. Further, rather than a traditional organic base that releases VOCs, this paint uses a calcium base which does not emit VOCs.

One final characteristic of many of these paints is that they are conveniently sold in powder form. Simplistically speaking, the user just adds water and pigment (if desired) prior to applying the paint with a traditional roller or brush.

In 2017, 21 street artists used these paints to create the first pollution-eating mural in Rome that stretched across 100 square meters of a seven-story building. The amount of paint used in the Hunting Pollution mural can clean the air just like a 30-tree mature forest.11 The main artist, Iena Cruz, is currently living in the United States and says he would like to paint murals in the many cities emblazoned on skyscrapers.

The U.S. Department of Energy is working with the National Carbon Capture Center and Southern Company to accelerate the commercialization of advanced technologies to reduce greenhouse gasses.12

Coatings companies have a superb opportunity to provide CO2 capturing coatings to this consortium and to sponsor coatings teams in XPRIZE competitions to take advantage of the current interest in reducing greenhouse gasses.

Coatings and paints provide an excellent opportunity to invest in the improvement of air quality around the world without eliminating those parts of society that are well established and advantageous to an excellent quality of life. It would be a worthy investment for the future of the coatings industry.

Cynthia A. Gosselin, Ph.D., is director at The ChemQuest Group/ChemQuest Technology Institute/ChemQuest Powder Coating Research; cgosselin@chemquest.com; www.chemquest.com.

References

1.              International Energy Agency. Global energy related CO2 Emissions,1990-2021. IEA, Paris. Global Energy Review 2021.

2. XPRIZE Foundation. https://www.xprize.org/ (accessed Jan 21, 2022).

3. Interview with Steve McDaniel. https://www.youtube.com/watch?v= KQsqutMGn5c  (accessed Jan 21, 2022).

4. McInnis, Brittney M.; Hurt, Jonathan D.; McDaniel, Steve; Kemp, Lisa K.; Hodges, Tyler W.; Nobles, David R. Carbon Capture Coatings: Proof of Concept Results and Call to Action. Coatings World. July 3, 2019.

5. Woskow, Beth; Li, Vanessa. Painting Our Way Out of the Climate Change Corner. China Daily, Hong Kong Edition. Nov 1, 2019. https://www.chinadailyhk.com/articles/139/50/87/1572576790141.html (accessed Jan 21, 2022).

6.  Hahn, Jennifer. Carbon Capturing Celour Paint Allows Anyone to “Participate in CO2 Removal in their Daily Lives.” Dezeen Magazine. Aug 6, 2021. https://www.dezeen.com/2021/08/06/carbon-capturing-celour-paint-allows-anyone-to-participate-in-co2-removal-in-their-daily-lives/ (accessed Jan 21, 2022).

7. Paint Which Absorbs Carbon Dioxide Launched. July 11, 2019. https://environment-analyst.com/uk/79577/paint-which-absorbs-carbon-dioxide-launched (accessed Jan 21, 2022).

8.  Flores, Adrian. Paint That Purifies Air. Graphenstone Blog. Feb 1, 2021. (accessed Jan 21, 2022).

9. European Research Council. New Thermo-Regulating Paints Based on Nanoencapsulation of Phase Change Materials. ERC-2017-PoC. H2020-EU1.1: Excellent Science. Hosted by the University of Liverpool, UK.

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