Batch and semi-continuous anaerobic digestion of Palmaria palmata: Comparison with Saccharina latissima and inhibition studies

Macroalgae are biomass resources that can represent a valuable feedstock to produce renewable energy via methane production. In order to diversify the feedstock of raw materials for anaerobic digestion new kind of macroalgae are investigated. Composition of the algae Palmaria palmata is suggested to be a good substrate for anaerobic digestion due to its high content in volatile solids and low content of cations. In this study, P. palmata was investigated and compared to Saccharina latissima for biogas production in both batch and semi-continuous reactors. P. palmata permitted a better production of methane than for S. latissima either in batch (279 mL CH4 gVS−1 vs 210 mL CH4 gVS−1) or in semi-continuous reactor (320 mL CH4 gVS−1 vs 270 mL CH4 gVS−1). In semi-continuous experiments, after 182 days of operation, a decrease in reactor performances such as methane yields occurred above a specific loading rate in the order of 408 gVS kgVSS−1 d−1. Inhibition by potassium and sodium observed in semi-continuous mode was confirmed by batch experiments. The initial methane production rate was reduced by 53% when potassium and sodium concentrations were equivalent to the ones observed at semi-continuous reactor failure (13.0 g L−1 for potassium and 4.1 g L−1 for sodium). The lower performances of semi-continuous anaerobic digestion of S. latissima than the ones obtained with P. palmata, may be increased by a higher accumulation of cations.

► Palmaria palmata, revealed to be suitable for renewable energy production in methane via anaerobic digestion.
► Anaerobic digestion of both algae is limited by potassium and sodium cations accumulation.
► P. palmata is more suitable for anaerobic digestion than Laminaria saccharina due to its composition in cations.