That adds up to a real problem if you put us in a place with no ventilation, such as underwater. Two things are most important for optimal operation of a scrubber. This worked if you did not mind having to deal with 8 to 10 pounds of absorbent. For a two to four hours dive. A two hour dive should require only two pounds of absorbent if the device is optimal.
Carbon dioxide is an acid gas.
Acid gases can be reduced by oxides, peroxides and hydroxides. Hydroxides are used in most scrubbers because of their stability and ease of handling. Other companies make similar compounds with other additives such as barium and lithium. More or less moisture will slow the reaction. The absorption of CO2 is a chemical process.