I had a chat/debate with a guy about this, and the info is:
- it costs 2.4 kWh per kg of CO2.
- there are 18 of these in the world, and the largest can sequester 8,000 tonnes pa.
- to operate at scale, it needs to be able to process billions of tonnes. So, it would have to scale to 12,760,000%
- for 1 Bn tonnes of CO2 the energy cost would be the same as for the whole energy usage of all of the EU combined.

On the other hand, simply planting trees won't fix this. Too little, too late.

The only realistic scenarios are to
- immediately halve our energy consumption.
- insulate so we don't need as much energy.
- produce as much energy as we can ourselves (solar, etc.)
- Then to use as many renewable as possible to the supply of the remainder.