Optimization of orange peel waste ensiling for sustainable anaerobic digestion

Today, orange peel waste (OPW) is mainly used as cattle feed, often after ensiling. This storage phase can increase the efficiency of anaerobic digestion, since it allows both a better management of possible co-digestion and a reduction in the high content of essential oils (mainly composed of d-Limonene a well-known inhibitor of anaerobic digestion). The effects of ensiling on the methane potential of OPW have been little studied, particularly its microbiological profile. This study has simulated, at laboratory scale, OPW ensiling under three different conditions. Ensiled OPW samples were then either directly anaeobically digested or subjected to simple pretreatments aiming at the further removal of d-Limonene. The microbiota evolution during ensiling and the species of microorganisms present during the aforementioned process were also identified. After ensiling, up to over 70% of the initial d-Limonene content of OPW was removed and biomethane yield was preserved up to about 90%.