Process-based lifecycle climate, energy, water and material constraints of solid adsorbent production for gigaton-scale direct air capture

[Geoengineering News]

https://pubs.rsc.org/ee/article/doi/10.1039/d6ee03173k/1280878/Process-based-lifecycle-climate-energy-water-and

Authors: Ioannis Keroglou, Rebecca Ciez

14 July 2026

Abstract 

Negative emissions technologies like direct air capture are critical for achieving global decarbonization targets. Sorbent materials are central to direct air capture systems, with solid adsorbents requiring lower regeneration temperatures and avoiding the evaporative losses of liquid sorbents. As use-phase emissions decline due to technological advances and the use of low-carbon power sources, sorbent manufacturing impacts become increasingly important. Prior studies of sorbent manufacturing rely on oversimplified life cycle inventories and proxy data, resulting in substantial uncertainty. Here, we apply a process-based model to develop sorbent-specific inventories for scaling the production of polyethyleneimine-based solid adsorbents and evaluate their cradle-to-gate climate change, fossil resource scarcity, and water use impacts in the United States. Our results reveal higher material and energy requirements than previously assumed, leading to larger environmental footprints for this stage. Depending on the sorbent type, for a sorbent lifetime of 1 year, sorbent production requires an average of 0.40 × 10−3–6.43 × 10−3 m3 water per kg CO2 captured, consumes an average of 0.019–0.150 kg oil-eq per kg CO2 captured and emits an average of 0.053–0.438 kg CO2-eq per kg CO2 captured. Longer or shorter lifetimes result in average emissions ranging from 0.027–0.877 kg CO2-eq per kg CO2 captured. Silica gel-based adsorbent manufacturing has the lowest environmental impact, while γ-Al2O3- and MCM-41 adsorbents exhibit the highest burden. Impact uncertainty is driven by differences in support material synthesis and sorbent consumption rates. Producing sorbents with low-emitting grid electricity can reduce emissions intensity, but gigaton-scale deployment would require expanded supply chains for key chemical feedstocks.

Source: ACS Publications