Piperazine's solubility is low, so it is often used in relatively small amounts to supplement another amine solvent. One or more of piperazine's performance advantages are often compromised in practice due to its low concentration; nonetheless, the CO2 absorption rate, heat of absorption, and solvent capacity are increased through the addition of piperazine to amine gas treating solvents, the most common of which is MDEA due to its unmatched high rate and capacity efficiency. For example, a 5 m PZ/5 m MDEA blend yields an 11% larger difference in CO2 concentration than 8 m PZ between the lean (inlet absorbent) and rich (outlet absorbent) amine solvent streams, or in other words, more CO2 is removed from the sour (flue) gas stream per unit mass of solvent, and an almost 100% larger concentration difference than 7 m MEA.