Influence of substrate concentration and bicarbonate addition on the anaerobic digestion of an inulin-rich substrate as the ending stage in a dandelion biorefinery scheme

This study was focused on the suitability of dandelion plant as part of a biorefinery scheme in which anaerobic degradation (biomethanization) for biogas production is the ending process. Inulin, as the main compound in the tuberous root of dandelion, was selected as substrate and tested at different concentrations (5, 10 and 15 g TS L⁻¹). The presence of bicarbonate as a buffer on anaerobic digestion was assessed as well. Methane production curves were fitted with the modified Gompertz equation. Methane production yield (Y_CH4), specific maximum methane production rate (SR_MAX) and the first-order hydrolysis constant (k_H) were affected by the substrate concentration. Bicarbonate was found not to be determinant for the overall biomethanization process because no significant effect over the Y_CH4 was achieved in the presence or absence of bicarbonate; between 0.19 to 0.23 m³ kg^-1 VS added. However, k_H and SR_MAX were affected by the presence of this inorganic compound. Without the addition of bicarbonate, k_H and SR_MAX decreased as the TS increased. These results will be key for a dandelion biorefinery proof-of-concept under the proposed conditions.