Research & Development Pathways/Challenges in Direct Air Capture of CO₂

Economic growth, due to increased consumerism, extravagance and human greed, necessitates higher energy demand. Fossil fuels burning, which generates carbon dioxide, a greenhouse gas, provides this energy resulting in a quantum jump in carbon dioxide emission and accumulation. Carbon cycle and other natural processes like mineralization of carbon dioxide through weathering of rocks rich in magnesium or calcium are inadequate to remove excess greenhouse gases. This has caused global climate change, threatening the existence of living beings including Homo sapiens. Removing carbon dioxide from atmosphere, either at the sites of carbon dioxide generation like power plants, called point capture of carbon dioxide (PCC) or in ambient air popularly known as direct air capture (DAC), therefore has become a necessity. In this chapter, DAC techniques like biosequestration, absorption and adsorption are discussed along with the challenges in their implementation. The DAC machines offer a greater flexibility of usage, as they are not tethered to the generation plants and can be placed at the site of subsequent usage of carbon dioxide or sequestration. Challenges in DAC are requirement of high energy, high water consumption and economic viability. Few companies have incorporated these techniques in their startups, and these have been deliberated along with the financial costs. It is concluded that initiating direct air capture as research and development projects on larger scale will help in developing viable options for carbon dioxide reduction as a future strategy.