Biogas Recovery from Refinery Oily Sludge by Co-Digestion Followed by Sustainable Approach for Recycling the Residual Digestate in Concrete Mixes

This study investigated the potential of biogas recovery from refinery oily sludge (ROS) inoculated with animals’ manure by co-digestion of in lab-scale biodigesters at mesophilic conditions. Cow dung (CD), cattle manure (CM), and poultry manure (PM) were utilized as co-substrates. The biogas production from the co-digestion process exceeds its production from uninoculated ROS by approximately 67.5 %, 22.13% and 21.6% for PM, CM, and CD, respectively. Kinetics of the co-digestion process was well described by the modified Gompertz model. The predicted and experimental values of biogas production were well fitted with R2 > 0.96, suggesting favorable conditions of the digestion process. New approach for recycling the residual digestate to replace freshwater in concrete mixes was carried out. Results of examining the mechanical properties of the residual digestate-modified concrete mixes demonstrated a potential sustainable approach for the disposal of residual digestate in concrete mixes.