Abstract: The present invention consists of an absorption process with a chemical reaction to capture acid gases such as carbon dioxide, sulphur dioxide and nitrogen dioxide from the ambient air and from combustion gases from burners and internal combustion engines using fossil fuels; the aim of the invention being the acquisition of carbon credits in accordance with the “Kyoto protocol on climate change”. The process is carried out in a horizontal spray absorber using an 8% solution of sodium hydroxide as absorption liquid, obtaining sodium carbonate, sodium sulphite, sodium nitrite and nitrate as byproducts. These byproducts are converted into commercial products such as calcium carbonate, barium sulphate and ammonium nitrate; for which purpose both the sodium sulphite and the sodium nitrite must previously be converted into sodium sulphate and nitrate by means of an oxidizing agent.