“…Related calculations involved in the preliminary energy analysis are shown in Figure 1, where C = specific heat of influent, which approximated to water, 4.18 KJ/(kg • C); V I = the flow volume fed to the digester per day; φ = the electricity energy used for pumping, 0.5 KWh/m 3 (Lu et al, 2008;Mu et al, 2018); ω = the electricity energy used for stirring, 0.08 KWh/(m 3 •d) (Lu et al, 2008;Mu et al, 2018); The material used for the designed reactor was 300 mm thick insulated concrete wall, U = heat transfer coefficient, 1.99 W/(m 2 • • C) (Liu et al, 2017a); A = superficial area of reactor, which was calculated according to the calculation formula, 1152 m 2 ; T 1 = ambient temperature, which is close the average annual temperature in China, 10.3 • C; T 2 = reactor temperature, 35 • C for mesophilic condition or 55 • C for thermophilic condition; The efficiency of the CHP in converting biogas into thermal and electricity energy were 33 and 50%, respectively (Feiz et al, 2019;Valentino et al, 2019), H M = calorific value of methane, 35.8 kJ/L (Chen et al, 2019), and V M = volume of methane produced.…”