Processes are described for making methacrylic acid via methacrolein from a biobased isobutene, wherein the biobased isobutene is prepared from ethanol or from acetic acid in the presence of a Zn.sub.xZr.sub.yO.sub.z mixed oxide catalyst, the biobased isobutene is oxidized to methacrolein and the methacrolein is further oxidized to methacrylic acid.