the sorbent works until

real air touches it

Problem statement

Solid-sorbent direct air capture (DAC) systems use amine-functionalized materials to adsorb CO2 from ambient air at ~400 ppm (0.04%). These sorbents degrade through oxidative, thermal, and humidity-driven mechanisms, and lifetimes are short: state-of-the-art sorbent replacement time is roughly 3 months, and reviews put typical sorbent lifetime at a year or less. Sorbent durability has an outsized impact on cost — a recent analysis found that extending replacement time from 3 months to 1 year would cut the levelized cost of net CO2 removal by more than 60% — so DAC cannot approach the US DOE target of <$100/net tonne CO2e without substantially more durable sorbents. Yet most degradation data comes from lab tests that omit real-world contaminants.

Why this matters

Meeting climate goals will likely require negative emissions technologies to remove ~10 Gt CO2/year globally by mid-century and ~20 Gt/year by century's end (NASEM 2019). DAC is among the most location-flexible negative emissions technologies. Deployed capture costs have run as high as ~$600/tonne CO2 (NASEM 2019; Climeworks reported a levelized capture price of $500–600/tonne), while the DOE Carbon Negative Shot targets <$100/net tonne CO2e by 2032 — a five- to six-fold reduction in which sorbent lifetime is a major variable.

What’s been tried and why it hasn’t worked

Metal-Organic Frameworks (MOFs), supported amines on silica/alumina, and temperature-swing adsorption (TSA) processes have all been tested at lab scale. Climeworks has deployed commercial plants and Global Thermostat has run pilot-scale systems. However, accelerated-aging protocols have historically interrogated one variable at a time (e.g., O2 introduced into inert gas) and cannot be expected to reflect real DAC operating conditions; ambient air also carries acidic gases (SOx, NOx), VOCs, and particulate matter that vary with location, season, and events like wildfires. SO2 and NO2 irreversibly react with surface amines and reduce CO2 capacity even at part-per-million concentrations, and their long-term impact at true ambient (part-per-billion) levels remains poorly characterized. Repeated regeneration heating (typically 80–120°C per cycle for solid sorbents) compounds degradation, since oxygen exposure plus elevated temperature is the primary driver of sorbent breakdown. No standardized degradation testing protocol exists that replicates real atmospheric contaminants across diverse climates.

What would unlock progress

Standardized accelerated aging protocols that replicate real atmospheric contaminant profiles (humidity, SOx, NOx, particulates) across different climatic regions. Sorbent chemistries resistant to oxidative degradation while maintaining high CO2 capacity. Field-validated lifetime data from operating DAC plants in diverse climates to calibrate lab predictions against actual performance.

Entry points for student teams

A team could design an accelerated aging test rig that exposes DAC sorbent samples to controlled atmospheric contaminant profiles (SO2, NO2, humidity cycles) and measures capacity degradation over time. Comparing degradation rates under lab-clean vs. contaminant-loaded air would quantify the real-world performance gap. Chemistry, materials science, and environmental engineering skills apply.