Use CO2 to fill the bubbles in styrofoam panels for building insulation. It will work as good as regular panels and sequester perfectly good carbon for the freebies to feel better about their souls.
Of course you could sequester about a whole city block worth of buildings by burying a bag of charcoal briquets sealed in a 5 gallon plastic paint bucket in the local land fill, but I suspect the greenies would not get the warm fuzzies over that.
The Germans used another gas, HCN, instead of hot water to heat some shower rooms in WWII.
Bitter sarc/