Evolution of control parameters in biochemical methane potential tests of olive mill solid waste (OMSW), thermal pre-treated OMSW, and its co-digestion with Dunaliella salina

Abstract

The aim of the present work was to compare the mesophilic anaerobic digestion of untreated olive mill solid waste (OMSW), soft hydrothermal pre-treated OMSW (SHP OMSW) and a co-digestion mixture of 95% OMSW and 5% microalga Dunaliella salina (Co-OMSW). During the co-digestion experiment, the volatile fatty acid accumulation decreased in comparison with that obtained for OMSW and SHP OMSW, reducing the slight inhibition observed during the OMSW and SHP OMSW experiments. Final values of methane yield of 380±1 mL CH4 g -1 VSadded for the OMSW, 424±2 mL CH4 g -1 VSadded for the SHP OMSW and 491±1 mL CH4 g -1 VSadded for the co-OMSW were determined. Two mathematical models, first-order kinetics and modified Gompertz model, were employed to fit the experimental data with the aim of elucidating the anaerobic biodegradation and obtain the kinetic constants. Both models allowed for adequately fitting the experimental results of methane production with time. The kinetic constant, k, of the first-order model increased by 12% for the Co-OMSW compared with the values achieved for OMSW and SHP OMSW. The modified Gompertz model revealed that the maximum methane production rate, Rm, for the Co-OMSW and SHP OMSW increased by 34.7% and 10.3% compared to the value obtained for OMSW.

Performance and kinetic evaluation of the anaerobic digestion of olive pomace derived from a novel manufacturing process based on an olive cold-pressing system: influence of the fruit ripening level

“…By contrast, similar k values to those found in the present research were reported when the classical OP was previously pre-treated at 121 °C, for 30 min and at 1 bar of pressure and later subjected to AD (k = 0.19 day −1 ) and when the OP was codigested with the microalga Dunaliella salina (k = 0.21 day −1 ) [21]. During the AD of OP, hydrolysis step was detected as the main drawback due to the low biodegradability of this substrate [22].…”

Enhancing methane production from the invasive macroalga Rugulopteryx okamurae through anaerobic co-digestion with olive mill solid waste: process performance and kinetic analysis

“…In addition, very recent studies (Fernández-Rodríguez et al 2021a) have shown that the anaerobic co-digestion of 95% OMSW-5% Dunaliella salina achieved specific rate constant values of 0.19 days −1 , a value 2.8 times higher than the maximum value reached in the present study for the mixture 1.5 OMSW-1 R. okamurae. The mentioned kinetic constant value for the mixture 95% OMSW-5% D. salina was also 12% higher than that obtained for the single OMSW, similar trend than that observed in the present research work.…”

“…As can be seen, the highest value of the maximum methane production rate (R max ) was found for the mixture 1 R. okamurae-1.5 OMSW (30.4 mL CH 4 g −1 VS day −1 ), which was 1.6 and 2.2 times higher than the corresponding to the mono-digestions of the single OMSW (18.9 mL CH 4 g −1 VS day −1 ) and sole R. okamurae (13.6 mL CH 4 g −1 VS day −1 ), respectively. In the same way, it was recently reported that the maximum methane production rate, R max , for the anaerobic co-digestion of the mixture 95% OMSW-5% D. salina increased by 34.7% compared with the value obtained for the single OMSW (Fernández-Rodríguez et al 2021a).…”

“…The mentioned kinetic constant value for the mixture 95% OMSW-5% D. salina was also 12% higher than that obtained for the single OMSW, similar trend than that observed in the present research work. Dunaliella salina is a halophilic flagellate alga able to tolerate and acclimate to a wide range of salinities (Fernández-Rodríguez et al 2021a).…”

Anaerobic digestion and agronomic applications of microalgae for its sustainable valorization

“… 93 Recently, codigestion of Dunaliella salina and olive mill solid waste was studied at a ratio of 5/95 and resulted in 29% high methane production compared to olive mill solid waste alone. 94 When mixing Scenedesmus sp. with pig manure at a ratio of 1/1, methane production was enhanced by 50% compared to microalgae alone, however, no synergetic effect was observed.…”