Question

Who is most efficient carbon dioxide absorbent, lithium hydroxide or potassium hydroxide?

Answer 1

yes, I was just about to say the same as Michael Flynn. Water absorbs carbon dioxide to form carbonic acid ,so any base would be enough for restoring the potential diferential of carbonic acid concentration in the solution. If you want another thing you could try a suspension of plankton with enough fertilizer to transform the carbon dioxide into sugars, provided enough solar energy.