The improvements of natural zeolites (mordenite–clinoptilolite zeolite from Gunungkidul, Yogyakarta, Indonesia) have been successfully applied to improve biogas quality by classical and plasma treatments. The classical treatments were conducted by physicochemical treatment and alkali impregnation. A promising novel approach involving plasma polymerization was used to incorporate solid state amines and promote the development of advanced CO2 adsorbents. Air-plasma activation also successfully use