Lignin liquefaction could be achieved under subcritical methanol; instead, the reported supercritical status using ZrO2/TiO2 nanofibers prepared by calcination of poly(vinyl-acetate)/titanium isopropoxide/zirconium isopropoxide electrospun mats. ZrO2 content in the final nanofibers has been adjusted at 0, 25, 50, 75 and 100 wt%. The nanofibers having 75 wt% ZrO2 showed the best catalytic activity toward lignin liquefaction, 57.1 wt% weight losses at 180 degrees C. The results indicated that 2 h and 15 wt% are the optimum holding time and catalyst content, respectively. Liquefaction of sawdust was performed; more than 60 wt% of the solid waste was converted to simple alcohols at 300 degrees C (supercritical conditions).