A n aerobic digested is used to produce biogas using 100 kg o f food waste with 70 % being putrescible and in the process only 5 % o f volatile solids in the putrescible waste is decomposable by bacterial action to produce 0.8 m3/kg of volatile solids of biogas, the gross calorific value of biogas being 25 MJ/m3. Calculate the total energy output that can be obtained from the digester.