Thermophilic anaerobic fermentation of olive pulp for hydrogen and methane production: modelling of the anaerobic digestion process

The present study investigates the thermophilic biohydrogen and methane production from olive pulp, which is the semi-solid residue coming from the two-phase processing of olives. It focussed on: a) production of methane from the raw olive pulp; b) anaerobic bio-production of hydrogen from the olive pulp; c) subsequent anaerobic treatment of the hydrogen-effluent with the simultaneous production of methane; and d) development of a mathematical model able to describe the anaerobic digestion of the olive pulp and the effluent of hydrogen producing process. Both continuous and batch experiments were performed. The hydrogen potential of the olive pulp amounted to 1.6 mmole H₂ per g TS. The methane potential of the raw olive pulp and hydrogen-effluent was as high as 19 mmole CH₄ per g TS suggesting that: a) olive pulp is a suitable substrate for methane production; and b) biohydrogen production can be very efficiently coupled with a subsequent step for methane production.