Sustainable biofuels and biochar production from olive mill wastes via co-pyrolysis process

This work aims to investigate experimentally the co-valorisation of olive mill wastewater (OMW) and olive pomace (OP), using two ratios: OMW:OP 50:50 and 30:70, into renewable biofuels, bio-chemicals and nutrient-rich bio-char via co-pyrolysis process. Co-pyrolysis trials were conducted at 600 °C, with a ramp 15 °C/min and 1 h of residence time at the highest temperature in a fixed-bed reactor. The OMW pyrolysis generates 20, 20 and 60 wt.% of bio-oil, biochar and syngas, respectively. The addition of OP not only enhance the pyrolytic-oil and biochar amounts (pyrolytic-oil up to 23 wt.% and biochar up to 31 wt.%) but also up-grade their energy contents (pyrolytic-oil HHV achieves 12.78 MJ/kg and biochar HHV reaches 28.65 MJ/kg). The produced bio-oil characterisation highlights their potential as precursor of active molecules whereas the inorganic content of biochar emphasise their use as biofertilisers. This integrated approach can be adopted by olive-oil industrials for added-value recovery from these abundant agricultural waste. Graphical abstract: [Figure not available: see fulltext.]