LAUSR

Abstract Agro-food industries produce large amounts of bio-waste, challenging innovative valorisation strategies in the framework of circular economy principles. Anaerobic digestion technology is an interesting route to stabilise organic matter and produce biogas as a renewable energy source. This paper aimed to study the optimal performance conditions for anaerobic co-digestion (AcoD) of pig slurry with pineapple ( Ananas comosus ) peel bio-waste. The anaerobic digestion (AD) trials were performed at lab scale, in a continuous stirred reactor, for 16 days’ hydraulic retention time in mesophilic conditions (37 ± 1 °C). Three hydraulic retention time were performed, one for the reference scenario (T 0 ) and two for AcoD trials (T 1 , T 2 ). Feeding mixtures (20:80; v:v) of pineapple peel liquor and pig slurry, with an OLR of 1.46 ± 0.04 g TVS L −1 reactor day −1 were used during AD/AcoD trials, presenting high values for soluble chemical oxygen demand and C/N ratio. This operational conditions highlight bioenergy recovery up to 0.58 L CH 4 g TVS added −1 , in comparison with that obtained with pig slurry substrate (0.31 L CH 4 g VS added −1 ). The AD performance showed a total volatile solids and chemical oxygen demand removal efficiency of 23% to 47% and 26% to 48%, comparing T 0 with the average of T 1 and T 2 , respectively. The digester stability, evaluated by specific energetic loading rate, was below the limit (0.4 day −1 ) throughout the trials. Pig slurry co-digestion with pineapple peel liquor seems to be a promising approach for potential bioenergy recovery. Graphic Abstract