Application of organosolv technology to improve the anaerobic digestion of olive oil pomace

So far, there are few sustainable alternatives to manage the exhausted olive pomace (EOP), a dangerous waste produced by the olive oil sector. In this work, EOP resulting from organosolv pretreatment was submitted to conventional anaerobic digestion (mono-AD) or co-digestion with sewage sludge (co-AD) at different ratios using a pilot-scale stirred tank reactor. Firstly, it was observed that a shortening of the acclimation phase improved performance allowing a methane specific productivity of 575.15 LCH4 kg VS- 1 d-1. Even though the mono-AD strategy was more performant than co-AD in terms of biogas specific productivity (25.50 Lbiogas kgEOP - 1 d-1), all tested conditions yielded 67-70% methane and a negligible H2S content. Likewise, no significant differences between these strategies were found in terms of methane specific productivity and biodegradability that reached maximum values of 230.85 & PLUSMN; 19.29 LCH4 kgVS- 1 d-1 and 61.3 & PLUSMN; 5.1%, respectively. The main differences between them were observed in the overall chemical oxygen demand consumption rate (819.10 and 656.70 gCOD L-1 d-1 for Co-AD and mono-AD, respectively) and volatile solids removal (86.5% for Co-AD and 34.8% for mono-AD) when feeding 40 g of pretreated EOP. This work highlights the positive effect of organosolv to improve AD and the feasibility of the proposal to achieve the zero waste in this sector.

Automated summary

Currently, there are limited sustainable alternatives for managing exhausted olive pomace (EOP), a hazardous waste from olive oil production. This study examined the use of organosolv pretreatment to enhance anaerobic digestion (AD) of EOP, either alone (mono-AD) or in co-digestion with sewage sludge (co-AD), in a pilot-scale reactor. It was found that shortening the acclimation phase improved methane production, with a specific productivity of 575.15 LCH4 kgVS-1 d-1. Although mono-AD outperformed co-AD in terms of biogas specific productivity, both strategies achieved similar levels of methane yield and biodegradability. The study highlights the potential of organosolv pretreatment to enhance AD and achieve zero waste in the olive oil sector.