Direct air capture (DAC) companies are shifting away from steam-based heating toward electrical methods to free captured CO2 from sorbents more efficiently. AirCapture uses microwaves and recently won a Tencent CarbonX 2.0 award; Sustaera uses resistive (Joule) heating and claims over 3x the efficiency of steam; Mission Zero Technologies and RepAir Carbon use electrochemical methods that skip heat entirely. Steam remains mature and cheap where waste heat is available, but electrical approaches offer more targeted heating and better cold-weather performance. The sector still faces funding setbacks, political headwinds, and wavering demand—illustrated by Microsoft's on-again, off-again carbon credit purchases and CarbonCapture's cancelled Wyoming facility.
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Steam vs. Electric DAC EfficiencyResistive Heating for Carbon CaptureElectrochemical Direct Air CaptureQuestions this post answers
How does resistive heating work in direct air capture systems compared to steam heating?
Resistive (Joule) heating passes an electric current through a conductive sorbent material, causing electron vibrations that heat only the sorbent rather than the entire collector chamber. This targeted heating is more efficient than steam, which heats everything it touches and undergoes thermodynamically limited phase changes. Sustaera reports its resistive-heating approach reaches efficiency more than three times higher than steam-based desorption. Engineers evaluating carbon capture heating methods can follow efficiency comparisons like this on daily.dev.
Why are direct air capture companies moving away from steam-based CO2 desorption?
Steam heats the entire collector chamber rather than just the sorbent, wastes energy through required phase changes between vapor and liquid, and performs poorly in cold environments. Electrical methods like microwaves, resistive heating, and electrochemical reactions target only the sorbent or the CO2 bonds themselves, cutting energy use. Companies including AirCapture, Sustaera, and Mission Zero Technologies are pursuing these electrical alternatives instead. Anyone tracking climate tech engineering shifts can follow carbon capture heating trade-offs on daily.dev.
How does microwave-based CO2 desorption work in direct air capture?
Microwaves are beamed at sorbent material to selectively heat the chemical bonds holding captured CO2, freeing the gas for collection. CO2 itself is transparent to microwaves, but when bonded to a sorbent the bonds behave like water and absorb microwave energy. AirCapture has run a pilot-scale machine using this method at its Berkeley facility for about a year, alongside its established steam-based process. Readers deciding between DAC heating approaches can track microwave and steam trade-offs on daily.dev.