Abstract
In this research solutions for the management of the essential oils (EO) inhibition of anaerobic digestion (AD) are proposed and studied: 1- the co-digestion of OPW with other substrates, 2- pre-treatments for the recovery and removal of EO from the orange peel Waste (OPW) prior to AD were assessed. Anaerobic co-digestion of OPW with organic fraction of municipal solid waste (OFMSW) was carried out in order to reduce limonene concentration.. The maximum organic loding rate (OLR) that resulted in stable anaerobic co-digestion process performance was 2gVS/(L·day) corresponding to 26.7 mg Limonene/(L digester·day) of limonene dosage. The highest methane production obtained with such an OLR was around 0.70±0.05 LCH4/(Ldigester·day).
Three EO extraction methods were evaluated: extraction using the Naviglio extractor, mechanical extraction (cold pressing) and steam distillation, each pre-treatment was tested based on variating the different operational condition (extraction time, extracting solvent, ….) for optimization purposes in terms of Limonene removal efficiency. All three treatment results showed efficient removal capacity, 94.36%, 99.09% and 27.44% for Naviglio extraction, steam distillation and mechanical extraction respectively and biogas production was increased significantly. De-oiled OPW was used as substrate for batch anaerobic digestion, for the evaluation of two pretreatments: enzymatic using a commercial enzyme “Cellulase Trichoderma Reesei”, and ultrasonic using (305 W, 47 Hz ; Soltec Ultrasonic Baths) on hydrolysis of the substrate and on methane yields, both of them showed improvements in terms of hydrolysis evaluated based on COD solubilisation. Results showed remarkable solubilisation and an improved methane production of 54.7% and 14.3% for enzymatic an ultrasonic pre-treatment respectively. Methane yields resulting from the different BMP test conducted during the experimental set ups were evaluated using multiples non-linear models, and the fitted experimental data allowed the evaluation of AD performance based on lag phase time and potential methane yields, the Richards model was found to be the best fitted model to our experimental data.

Keywords: anaerobic digestion, D-Limonene, essential oil, Naviglio extractor, orange peel waste, steam distillation