Carbon capture and storage has been considered as a realistic approach to reducing atmospheric CO₂ concentrations. However, the cost of capturing high-purity CO₂ typically used for geological storage (e.g., 98%) is high. Direct air capture (DAC), a technology that extracts CO₂ of relatively low-purity from the ambient atmosphere, has been recently proposed as a means to achieve negative CO₂ emissions when the product is sequestered underground. Although the CO₂ produced by DAC is of low-purity, the other gaseous components (mainly nitrogen and oxygen) are not hazardous materials like NO_x and SO_x that must be typically dealt with by conventional projects in coal-burning plants. Here, we evaluate geological storage of the low-purity CO₂ captured via advanced membrane-based DAC technology. The ubiquity of ambient air is important in reducing transport costs and ensuring social acceptance as the CO₂ product can be both produced and stored at sites in remote areas, such as deserts and offshore platforms. We calculated the density of CO₂–N₂–O₂ mixtures via molecular dynamics simulation and evaluated the cost of the low-purity CO₂ storage. Our evaluation suggests that the storage of low-purity CO₂ in geological formations is environmentally acceptable and economically viable. © 2021 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd.

中文翻译：

---

基于膜的直接空气捕获 (DAC) 产生的 CO2–N2–O2 混合物的地质储存

碳捕获和储存被认为是降低大气 CO ₂浓度的现实方法。然而，捕获通常用于地质封存的高纯度CO ₂的成本（例如98%）很高。直接空气捕获 (DAC) 是一种从环境大气中提取相对低纯度CO ₂的技术，最近已被提议作为当产品被隔离在地下时实现负 CO ₂排放的一种手段。虽然DAC产生的CO ₂纯度较低，但其他气态成分（主要是氮和氧）不是NO _x和SO _x等有害物质这通常必须通过燃煤电厂的常规项目来解决。在这里，我们评估了通过先进的基于膜的 DAC 技术捕获的低纯度 CO _{2 的}地质存储。无处不在的环境空气对于降低运输成本和确保社会接受度非常重要，因为 CO ₂产品可以在偏远地区（如沙漠和海上平台）生产和储存。我们通过分子动力学模拟计算了 CO ₂ –N ₂ –O ₂混合物的密度，并评估了低纯度 CO ₂存储的成本。我们的评估表明，低纯度 CO ₂的储存在地质构造中是环境可接受且经济上可行的。© 2021 作者。温室气体：科学与技术由化学工业协会和约翰威利父子公司出版。