Congratulations to Lance Dostie who published his first paper in the Journal of Cleaner Production. This study examined carbon dioxide removal through calcium oxide looping and the role of humidity. Here, we show how water vapor alone can drive CO2 capture from the air to rapidly trap CO2 into a benign Ca-carbonate mineral, meaning that water intensive processes (e.g., spraying) are unnecessary. Our experiments systematically demonstrate the important effects of relative humidity by examining a wide range of humidities and combinations during the reaction with varying amounts of humidity to determine relationships and optimal rates and conversion to form Ca-carbonate. We show how humidity-driven reactions can be controlled to design future deployments that generate the high efficiency needed for meaningful CO2 removal to help mitigate climate change.