Mesophilic anaerobic co-digestion of cow manure and biogas crops in full scale German biogas plants: A model for calculating the effect of hydraulic retention time and VS crop proportion in the mixture on methane yield from digester and from digestate sto

Data from 24 full scale biogas plants in Germany digesting cow manure and crops were evaluated. Special emphasis was given to the effect of hydraulic retention time HRT and proportion of crops in the mixture (VS basis) p VS,Crops Inp on the methane yield from the digester y CH 4 D,VS Inp and the storage tank y CH 4 , T S,VS Inp at 37 and 22 °C. The evaluation has shown model parameters for maximal methane yield of manure and crops y max CH 4 eff,VS Inp at 270 and 420 L kg−1, respectively. For example, at HRT of 60 days, maximum methane yield result to 249 and 388 L kg−1 for a crop proportion in the input of 0.0 and 1.0, respectively. The calculation of y CH 4 , T S,VS Inp considers first order reaction rates and a temperature term fT. Hence, at any arbitrary temperature in the range of 12 °C < T < 37 °C the values of y CH 4 , T S,VS Inp in the course of time can be calculated, which correspond to methane emissions for uncovered storage tanks.