The effect of termal pre-treatments on mesophilic anaerobic digestion of a food residue

The influence of thermal pre-treatments in mesophilic anaerobic digestion of a potato peel residue was studied in this work. The samples, were submitted to a mechanical pre-treatment (grinding to a particle size below 2 mm). The thermal pre-treatments performed were as follows: autoclaving at 122 °C under a gauge pressure of 1.2 bar for 20, 35 and 55 minutes. These assays are referred along the article as E122.20, E122.35 and E122.55, respectively. After the pre-treatment, the residues were subjected to anaerobic digestion in a UASB reactor at 37±1°C. The highest values of biogas and methane yields as a function of CODremoved were reached for assay E122.35 with 669±60 cm3biogas.g-1 CODremoved and 433±27 cm3CH4.g-1 CODremoved, respectively. These values represented increases of 41% and 32%, respectively, when compared with the control assay. Also the assay E122.35 presented the highest values for biogas and methane yields relatively to VSremoved with values of 771±52 cm3biogas.g-1 VSremoved and 498±20 cm3CH4.g-1 VSremoved, respectively, which represented increments of 39% and 30% when compared with the control assay. Therefore, to autoclave the residue at 122ºC for 35 min under a gauge pressure of 1.2 bar seemed to be advantageous for the mesophilic anaerobic digestion of potato peel residue.