Biogas production from piloted wood-based bioethanol process using high-rate anaerobic treatment – Focusing for inhibition and improving biodegradability

To promote the bioeconomy, biorefineries with novel processes are developed. Biogas technology is commonly applied in biorefineries, and in this study, its feasibility for biogas production from wastewaters generated in a novel piloted wood-based bioethanol process was examined in expanded granular sludge bed reactors (EGSB). The novel wastewater was found to have high organic matter content and contained potentially inhibitory compounds. Wastewater was diluted with reactor effluent or tap water (control), and the proportion of wastewater in the feed was increased gradually to increase the organic loading rate. The wastewater was acidic (pH 4.2–4.6) and contained high concentrations of soluble chemical oxygen demand (sCOD 21–51 g/L) and sulfate (1–2.5 g/L). EGSB reactors had high sCOD_ww (sCOD in the wastewater) removal of 74–77 % with OLRs up to 22 kg-sCOD_ww/m³d and no inhibition either by the sulfide resulting from the high influent sulfate concentration or by the re-use of reactor effluent was seen. Integration of anodic oxidation (AO) to the EGSB reactor was studied in batch experiments increasing the biodegradability and total sCOD removal to 80–83 % and enhancing the methane production by 3 %. The results provide valuable information to support the implementation of anaerobic treatment plants as part of new industrial scale bioproduct production processes and encourages further studies on AO.