Thermo dynamical assessment of the digestion process

Digestion of sludge was mostly seen as a stabilisation process prior to disposal or land application. During the last years there is an increased interest to use biogas as alternative energy source to replace the use of fossile fuels and giving the digestion process an economical value. In this paper a correlation is derived to combine the degradation of sludge with the amount of methane in the biogas produced. An overview about typical energy values of sludge is given and the amount of methane to be expected from different types of sludge.