where rm is the density of the manure (kgm3), Vm is the volume of the manure (m3), Cp is the specific heat of the manure (kJ kg1 C1), Qth is the rate of thermal heat energy delivered from the CHP unit to the reactor (kW), Qm is the rate of energy delivered to the incoming manure (kW), and QD is the total heat losses through the digester (kW).