Date of Award
Civil and Environmental Engineering
Aanaerobic digestion, Black liquor, Lignin, Microbial fuel cell, Photocatalysis, Titanium dioxide
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Depleting fossil fuel resources, environmental damage and energy security are key factors driving the search for renewable energy supplies. Anaerobic digestion (AD), a well-developed technology, is widely used globally to produce an energy rich biogas from degradable organic matter. An alternative technology under development which produces electricity from the degradation of organic matter is microbial fuel cells (MFCs). Lignin, an abundant renewable organic chemical, is difficult to degrade using biological methods. This dissertation is focused on generating electricity from lignin-rich organic matter using a two-step process which included producing a chemical feedstock using photocatalysis followed by a bioelectrochemical conversion in an MFC. Studies were conducted using sodium lignosulfonate (LS), a model lignin compound, and black liquor (BL), a lignin-rich waste product from pulp and paper industries. Titanium dioxide (TiO2) plus ultraviolet light was used in the photocataysis step. Optimization and modeling of the photocatalytic degradation process was performed using the Box-Behnken design method to achieve a maximum biological oxygen demand (BOD5) to chemical oxygen demand (COD) ratio. The effluent from the photocatalytic degradation process was fed into a single chamber air-cathode microbial fuel cell (SCMFC) to generate electricity. In this study, commonly available electrode materials were selected, evaluated and compared with a focus on selecting the best performing type of electrode. Cyclic voltammetry and linear sweep voltammetry were used to evaluate the performance of the electrodes. The biofilm microbial diversity and performance of SCMFCs fed pretreated vi LS (PrLS) and pretreated black liquor (PrBL) were compared to SCMFCs fed glucose at the same COD loadings and operating conditions. The energy production from PrBL using SCMFCs was also compared with the anaerobic digestion (AD) process. A total biogas production of 195±30 mL CH4 per g CODadded was obtained from two-stage AD of PrBL. The PrBL feed SCMFCs, generated maximum current and power densities of 8045±440 mA m-3 and 2815±120 mW m-3, respectively. The SCMFCs removed 89.3±0.8% of the COD of PrBL and achieved coulombic and potential efficiencies of 7.8±0.6% and 65.7% respectively. This dissertation demonstrated that combining photocatalysis together with a bioelectrochemical process was useful for treating and generating electricity from lignin rich waste matter simultaneously.
Shewa, Wudneh Ayele, "CONVERTING LOW VALUE LIGNOCELLULOSIC RESIDUES INTO VALUABLE PRODUCTS USING PHOTO AND BIOELECTROCHEMICAL CATALYSIS" (2016). Electronic Theses and Dissertations. 5667.