Comment by akshatjiwan

I think you have a point. It could be difficult to justify the cost of carbon capture based on sequestration alone. One of the reasons I think this might still work is that captured carbon can be used to create platform chemicals (various hydrocarbons) using the fischer tropsch process. Electrofuels are using direct air capture to generate fossil replacements.

Only requirement is energy and there too it isn't all that expensive to pull air in from the atmosphere or to seperate CO2 from adsorbent via low grade heat (70-100c)

So far into the future this method could allow us to continue produce critical hydrocarbon materials (used everywhere from plastics to pharamaceuticals) without having to depend upon concentrated and contested oil supplies.

More than energy efficiency its volumetric efficiency that's the issue. At the moment (to the best of my knowledge) kg of capturing materials capture tens of grams of CO2. Pulling it from air is not that energy intensive but finding materials that can actually filter out CO2 from that air is difficult. If breakthroughs are made in this area it will have industrial applications. Then it won't be just sequestering.

Of course the easier solution is to plant more trees and grasses but they grow very slowly and require valuable land. Still this approach is feasible in some uncultivable lands. Crops like cottongrass[1] can grow even in tundra climate and can be valuable source of both technically imp carbon via cellulose and a means to capture CO2. We don't have to make a choice. We can do both simultaneously.

[1] https://www.fs.usda.gov/database/feis/plants/graminoid/eriva...