Lawrence Krauss wants more research into extracting existing CO2 from the atmosphere as a way to address climate change. He notes that, unlike other forms of geoengineering, “direct air capture would treat the disease, not merely the symptoms”:
First, one removes CO2 from the air by using a sorbent, which is a material that can absorb gasses. Next, the CO2 has to be extracted from the sorbent and sequestered, presumably by pumping it deep underground at relatively high concentration or by binding it to minerals—a bit like how we handle nuclear waste. But another possibility includes actually converting it back into fuel. One particularly attractive possibility that has been proposed involves using an “exchange resin” sorbent which binds CO2 when dry and releases it when wet. In this way the evaporation of water could actually be used to help reduce the energy burden associated with binding and subsequently extracting the CO2.
Scott Rosenberg wonders whether geoengineering, through either carbon dioxide removal or solar radiation management, is “a slam-dunk no-brainer or a regrettable last resort”:
Unfortunately, the slam-dunkness of geoengineering turns out to be illusory at best. We really don’t know if any of these schemes can or would work. How much time, energy, and money should we put into finding out? That was the theme of a debate on geoengineering that I moderated last week, and here’s the lesson I took from it: If we expect new technology to save us from the mess old technology has made, but don’t also fix the broken political processes and social dynamics that made it impossible to avert that mess, we’re just inviting a bigger mess.
Akshat Rathi cites literature indicating that multiple types of geoengineering will be necessary to avoid climate change:
Several geoengineering initiatives plan to tackle climate change by cutting incoming sunlight, through methods such as spreading reflective aerosols in the stratosphere. But without also removing carbon dioxide from the atmosphere, such plans would fail to fully mitigate change in rainfall in the tropics, a study published in Nature Geoscience last week (21 April) suggests.