Natural gas processing plants separating CO2 and H2S from natural gas streams are major contributors to CO2 emissions in various gas producing regions of the world. The present practice is to convert the separated H2S into elemental sulfur through a well know chemical conversion process, the Claus process and to vent the CO2 into the atmosphere. In some cases it might be possible to re-inject the acid gases into either a depleted petroleum reservoir or into aquifers thus reducing CO2 emissions from natural gas plants. A number of such acid gas re-injection projects are now operational in Alberta. This paper provides a background leading to the development of these projects.