This study aims to produce levulinic acid (LA) from paper towel waste in environment-friendly and economically feasible conditions, and evaluate the difference using solid and aqueous Bronsted acids. Direct dehydration of glucose to LA required sufficiently strong Bronsted acidity, where Amberlyst 36 demonstrated rapid production of approximately 30 C mol% of LA in 20 min. However, the maximum yield of LA was limited by mass transfer. In contrast, the yield of LA gradually increased to over 40 C mol% in 1 M H2SO4 at 150 degrees C in 60 min. The SEM images revealed the conversion in dilute acids under microwave at 150 degrees C resulting in swelling structures of cellulose, which were similar to the pre-treatment process with concentrated acids. Further increase in reaction temperature to 200 degrees C significantly shortened the reaction time from 60 to 2.5 min, which saved the energy cost as revealed in preliminary cost analysis.