Biochar and wood ash amended anaerobic digestion of hydrothermally pretreated lignocellulosic biomass for biorefinery applications

İbrahim Alper Başar; Cigdem Eskicioglu; Nuriye Altınay Perendeci

doi:10.1016/j.wasman.2022.10.014

Biochar and wood ash amended anaerobic digestion of hydrothermally pretreated lignocellulosic biomass for biorefinery applications

Waste Manag. 2022 Dec:154:350-360. doi: 10.1016/j.wasman.2022.10.014. Epub 2022 Oct 30.

Authors

İbrahim Alper Başar¹, Cigdem Eskicioglu², Nuriye Altınay Perendeci³

Affiliations

¹ Department of Environmental Engineering, Akdeniz University, Antalya, Turkey; UBC Bioreactor Technology Group, School of Engineering, University of British Columbia Okanagan Campus, Kelowna, Canada.
² UBC Bioreactor Technology Group, School of Engineering, University of British Columbia Okanagan Campus, Kelowna, Canada.
³ Department of Environmental Engineering, Akdeniz University, Antalya, Turkey. Electronic address: aperendeci@akdeniz.edu.tr.

PMID: 36323224
DOI: 10.1016/j.wasman.2022.10.014

Abstract

This study investigated the effect of biochar and wood ash amendment on the anaerobic digestion of hydrothermally pretreated lignocellulosic biomass. Hydrothermal pretreatment was performed on switchgrass at 200, 250, and 300 °C with 0, 30, and 60 min of retention times. The pretreatment method was optimized using the response surface method for enhanced methane production. At the optimum pretreatment (200 °C/0 min retention time), a specific methane yield of 256.9 mL CH₄/g volatile solids (VS), corresponding to an increase of 32.8% with respect to the untreated substrate, was obtained. Hydrothermal pretreatment was beneficial for methane production at temperatures lower than 220 °C and retention times shorter than 20 min. At more severe pretreatment conditions than 220°-20 min, sugars were degraded into other products, causing a decrease in the methane yield. The hydrothermal degradation products, i.e., acetic acid, lactic acid, furfural, and hydroxymethylfurfural concentrations, were also measured and modeled. The addition of biochar and wood ash to BMP assays were tested at 2, 9, 16 g/g VS_inoculum ratios and <63, 63-125, 125-250 μm particle sizes. A decline in methane production was observed for all tested doses and particle sizes of both additives. The decline in the methane potential was proportional to the doses and particle sizes. Kinetic modeling of BMP test results also supported that using the additives was not beneficial. Based on the result of this study, it was found that the use of biochar and wood ash in a pretreated lignocellulosic biomass processing biorefinery would not be beneficial.

Keywords: Furfural; Hydrothermal pretreatment; Hydroxymethylfurfural; Methane; Switchgrass.