Thermodynamics gives a good idea. You need to pull a huge amount of air through your machine to get some carbon out of it. "At present there are no proven tech

Thermodynamics gives a good idea. You need to pull a huge amount of air through your machine to get some carbon out of it. "At present there are no proven technologies capable of large-scale air capture of CO2. It has been suggested that, with strong research and development support and industrial scale pilot projects sustained over decades, costs as low as ∼$500/tC may be achievable [226]. Thermodynamic constraints [227] suggest that this cost estimate may be low. An assessment by the American Physical Society [228] argues that the lowest currently achievable cost, using existing approaches, is much greater ($600/tCO2 or $2200/tC)." https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0081648#s6 https://journals.plos.org/plosone/article?id=10.1371/journal...