Continuous mesophilic anaerobic digestion of manure and rape oilcake – Experimental and modelling study

[Display omitted] •The stability of continuous fermentation of rapeseed oilcake and manure was confirmed.•The kinetic constants of rapeseed cake decomposition and hydrolysis were evaluated.•Rapeseed cake is digested faster than many other agricultural substrates.•Optimised ADM1 model simulated continuous fermentation process with high accuracy. Rape oilcake is a by-product formed after the removal of oil from rapeseed. Due to the high content of organic matter rape oilcake seems a good substrate for anaerobic digestion when it cannot be used as fodder. The aim of this work was to optimise the parameters used in a mathematical model of anaerobic digestion for rapeseed oilcake and cattle manure. The composition of these substrates was determined in order to estimate model inputs. Optimised kinetic constants of hydrolysis and decomposition for oilcake (Kdis=0.77, KhydCH=0.55, khydPr=0.57, khydLi=0.30) were estimated based on batch fermentation. The accuracy of the model with improved input parameters was confirmed by continuous fermentation. The average concentration of methane in biogas was about 50%. The biogas production efficiency from organic matter (defined as volatile solids) was 0.42m3kg−1 with an organic substrate loading rate equal to 3.18kgm−3d−1. The fermentation process demonstrated good stability and efficiency. The accuracy of the optimised model seems sufficient for use in modelling of a full scale process.