Repurposing Commercial Nonwovens into Direct Air Capture Materials

Global temperatures are currently rising due to increasing atmospheric carbon dioxide (CO₂) levels. Anticipated environmental and societal consequences include negative impacts on our climate, biodiversity, human health, food and water supply, and the economy. Direct air capture (DAC) technologies can mitigate these consequences by removing carbon dioxide from the atmosphere. A key component in DAC technologies is the adsorbent material used to separate CO₂ from the air. Solid adsorbents offer advantages such as low regeneration energy requirements, modularity, alleviation of corrosion and evaporation challenges, and rapid mass transfer to active sites. Amine-based adsorbents are frequently used due to their high CO₂ affinity, which proves essential at the low CO₂ partial pressures relevant to direct air capture. However, these amines are often added to expensive support materials for immobilization, which can comprise a major portion of the overall direct air capture cost.

Here, we evaluate the use of repurposed commercial nonwovens for carbon dioxide removal from the atmosphere. Wipes and pads found in many hygiene, cosmetic, and medical products are comprised of non-biodegradable polymeric nonwoven materials. Repurposing these inexpensive materials could not only reduce the cost of carbon capture but additionally address a second global challenge of polymer waste from the commercial use of nonwovens in relevant industries. We infused polyamines into several types of nonwoven materials and determined that the weight fraction of polyamine in a methanol solution could be used to tune the resultant polyamine amount on the immobilizing material. We then analyzed the CO₂ adsorption performance of these amine-loaded nonwovens and compared the kinetics and equilibrium uptake amounts. The relationship between a material’s water contact angle and CO₂ uptake was subsequently assessed. We then estimated the direct air capture cost as a function of contactor cost, ultimately showing the potential economic benefits of repurposing inexpensive commercial nonwovens to form direct air capture materials.