Anaerobic co-digestion of by-products from sugar production with cow manure

Sugar beet leaves (SBL), sugar beet top (SBT), sugar beet pulp (SBP) and desugared molasses (DM) are by-products from the sugar production. In the present study we investigated the potential of SBL, SBT and SBP as feedstock for biogas production. The maximum methane potential of SBL, SBT and SBP determined by batch assays was found to be 490, 500 and 240 mL-CH4/gVS-added respectively. Three reactor experiments were carried out to investigate the effect of co-digestion of SBP, DM and manure at different ratios, on biogas process efficiency and stability. The results showed that DM was potentially inhibiting the biogas process and the co-digestion of SBP and DM was only successful at high dilution with manure or water. In contrast, SBP was shown to be a good substrate for biogas production and the methane yield of 280 mL-CH4/gVS-added was obtained in a thermophilic continuously operated reactor, co-digesting 50% of SBP with cow manure.

► We investigated energy recovery in terms of methane from four types of sugar industrial wastewater and residues.
► High concentration of desugared molasses and sugar beet pulp are inhibiting biogas processes.
► Co-digestion is a sustainable method to dilute waste stream also avoid extra cost of adding nutrients or bicarbonates.
► Other sugar industrial residues, i.e. sugar beet leaves, sugar beet tops, showed good potential as feedstock for biogas production.