Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Chemical and Biochemical Engineering

Supervisor(s)

Dr. George Nakhla

Abstract

The main purpose of this study was to investigate the impact of furfural on mixed cultures during fermentative hydrogen production from lignocellulosic biomass. Small batch studies using synthetic lignocellulosic hydrolysate grown on mesophilic mixed cultures, revealed a threshold furfural concentration of greater than 1 g/L with enhancement to the yields (from the control) observed at 0.5 g/L furfural (at initial substrate-to–biomass (S°/X°) ratios of 0.5 and 1 gCOD/gVSS) and at both 0.5 g/L and 1 g/L furfural (at S°/X° of 2 and 4 gCOD/gVSS). This study was scaled-up from 200 mL to 11 L working volume batches, using half the substrate concentration of the small batch studies, at an S°/X° of 4 gCOD/gVSS in order to determine the Monod microbial kinetics of mixed cultures in the presence of furfural at both mesophilic and thermophilic temperatures. A 45 % enhancement at 1 g/L furfural was observed in the mesophilic experiment but a 50 % reduction at the same furfural concentration was observed at thermophilic conditions both relative to the yields from their respective controls. Enhanced kinetics observed in the control without furfural at both temperatures emphasized that although furfural is indeed an inhibitor, it can be broken down at low concentrations by mesophilic hydrogen-producers to increase hydrogen yields. Liquid and solid real waste hydrolysates obtained from poplar wood biomass treated using twin-screw extrusion technology were evaluated for their biohydrogen potential and the feasibility of a two-stage anaerobic digestion process. This study proved that acidification of the first-stage biohydrogen production process brought about a 50 % increase (on average) in TVFA/SCOD initial which enhanced methane yields in the second-stage. In the two-stage anaerobic digestion process, energy yields were 33 % and 18 % higher, while feedstock COD removal efficiencies were 16 % and 14 % higher than the single-stage BMP tests for the liquid and solid samples respectively.


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