In Iceland, CO2 is captured directly from the air. However, the most cost-effective way to capture the CO2 is by extracting it from the smoke at large industrial emitters, e.g cement production, biogas plants, district heating plants etc. 

Yes. CO2 capture is conducted with well-known technologies, many of which have been in use for decades and as such are well tested.

The gaseous CO2 is compressed into liquid because transporting and storing CO2 in liquid form is more cost-effective.

When carbon dioxide is in a gaseous state, it occupies a larger volume, but when it is cooled and liquefied, its volume is substantially reduced. Typically, the process of liquefying CO2 involves cooling it to temperatures below -78.5 degrees Celsius at atmospheric pressure. At this point, CO2 transitions from a gas to a liquid, and the volume reduction is approximately 600 times.

This significant reduction in volume makes it more practical for storage and transportation, especially in industrial applications where space considerations are important.

Yes. The well-known technique used for compressing gasses into liquid is also used for compressing the methane gas you might use for your garden barbeque.