DAC sorbent degradation rates are poorly understood, making cost models unreliable

Solid sorbent direct air capture systems (used by Climeworks, Global Thermostat, and others) rely on amine-functionalized materials that degrade through oxidation, amine loss, fouling, and urea formation with each heating/cooling cycle. The rate of this degradation -- which determines how often sorbent beds must be replaced -- is the single largest source of uncertainty in DAC cost models. Existing economic models treat sorbent replacement as a simple flat rate, ignoring that capacity fades nonlinearly over thousands of cycles. A 2024 study from the Royal Society of Chemistry showed that tuning sorbent properties could reduce DAC cost by up to 30%, but only if degradation rates are accurately characterized -- which they currently are not. This matters because every DAC company's unit economics and cost-per-tonne projections depend on sorbent lifetime assumptions that have never been validated at commercial scale. Investors pricing DAC credits at $200-400/tonne for 2030 delivery are making bets on sorbent durability data that does not exist. The problem persists because accelerated aging tests in the lab do not replicate real-world conditions (humidity, temperature swings, contaminants in ambient air), and no commercial DAC plant has run long enough to generate multi-year degradation data.