The present invention provides a recycled building material such as roof/Geo membrane that comprises (i) a polyolefin, (ii) a polymer containing a carboxyl group or a hydroxyl group, and (iii) a compatabilizer for the components (i) and (ii) which contains an epoxy group or an anhydride group. The present invention also provides a method of recycling building material as well as an article of manufacture such as a TPO membrane using the recycled building material. The TPO membrane has gained better physical properties such as consistent product quality, tensile strength, tear strength, wind resistance, and avoidance of tedious screening processes, among others.