Adaptation of biofuel cell technology for electricity generation from wastewater and lactose measurement : a thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy

Biofuel cell (BFC) is an emerging renewable technology that can perform high direct energy conversion efficiency to electricity. BFC system uses low energy density sources, such as organics in wastewater and converts them into electricity. The system is based on biological catalysts such as microorganisms and enzymes, which are capable of consuming the organics in the sewage for metabolism. In the process, the BFC system will convert the organics in the wastewater and reduce the biological oxygen demand of the sewage to a safe level before it is released to the environment. Nevertheless, commercialisation of BFC applications are still a long way to go due to many weaknesses that have to be overcome. Culturing exoelectrogenic bacteria and applying new materials to enhance catalytic process in microbial fuel cell (MFC) are some of the options to improve MFC operation. The aims of this study are two-fold: To develop (i) a MFC for electricity generation from wastewater by bacteria isolated from a trickling filter, and (ii) an enzymatic fuel cell (EFC) for continuous measurement of lactose concentration in dairy wastewater as well as electricity generation. This thesis shows that the multi-cultured bacteria could generate electricity after 30 days exposure to oxygen at a concentration of 7.5 ppm and that the fabricated graphite-epoxy composite anodes possess the desired characteristics of a good electrode. Such fabricated electrodes can be prepared within a very short time-span compared to commercial electrodes. These electrodes are cheap and flexible for surface modification. However, due to inherent high resistance of the graphite-epoxy composite, it was unable to generate as much current intensity as commercial material electrodes. This study has highlighted several areas that can be further explored such as reducing inherent resistance in graphite composite electrode and the potential use of combined multi-walled carbon nanotube (MWCNT)-diazonium salt within graphite matrix as a reusable high performance electrode

Aryl diazonium modification on graphite electrode in microbial fuel cell: a review

Usage of graphite electrode in a microbial fuel cell (MFC) is favored due to their electron conductivity and stability as a base material for the electrode. Also, graphite is favored as it allows the growth of biofilm, which can enhance the cell’s performance. The efficiency is reported improved through modification. Aryl diazonium modification has been reported to induce biofilm formation on the electrode faster. The modification can be done spontaneously or through electrografting of aryl diazonium salt onto the electrode surface. Control over the quantity of grafted aryl diazonium is essential. A thick layer will cause the performance of the system to drop, which may impede the electron transfer from biofilm to the electrode. Aryl diazonium is preferred as it allows a robust biofilm formation when used as a surface modification on the graphite electrode. Modification using aryl diazonium allows the electrode to be more accommodative for biofilm growth, which will increase the performance of the system. However, it does not act as a redox mediator for the system. It has been reported that power density obtained using aryl diazonium modified electrode is 250 mW.m-2, higher than unmodified graphite electrode of 125 mW.m-2. However, not all bacterial species is compatible with aryl diazonium modification. The unmodified graphite biocathode allows a higher power density compared to aryl diazonium modified biocathode. Hence, depending on the quality of aryl diazonium modification and the types of inoculum used, MFC performance can be further maximized

Aryl diazonium modification for improved graphite fibre brush in microbial fuel cell

Aryl diazonium salts are coupling agents that assist in molecules attachment to interfaces for sensing purposes. Despite not being fully explored and not yet widely applicable for cell-based sensors, the high stability of aryl diazonium salt formed sensing system is highly favorable in biological applications. Carbon-based electrodes are the most commonly used in aryl diazonium modification due to its post grafting stable C-C bond formation. Here, salt bridge based microbial fuel cells (MFCs) were used to study on the effect of aryl diazonium modification on the anode graphite fibre brush. Aryl diazonium salts were in situ generated by the diazonation of p-phenylenediamine with NaNO2 in HCl solution. The electrochemical performance of the aryl diazonium modified graphite brush MFC was measured and compared with the unmodified graphite brush MFC. The power output of the modified graphite brush bioanode was higher (8.33 W/m3) than the unmodified graphite brush (7.60 W/m3) after 20 days of operation with ferricyanide as the catholyte. After 70 days of operation using phosphate buffer solution as the catholyte, the Pmax of modified brush was three times higher (0.06 W/m3) than of the unmodified brush (0.02 W/m3), which indicates an enhanced binding towards the substrate that facilitates a better electron transfer between the microbial and electrode surface

Aplikasi keluli tahan karat sebagai elektrod logam di dalam sistem bioelektrokimia

Kertas kerja ini meninjau akan penggunaan dan prestasi terkini beberapa jenis logam sebagai elektrod dalam pembangunan sistem bioelektrokimia (BES) termasuk sel bahan api mikrob (MFC) dan sel elektrolisis mikrob (MEC). Elektrod konvensional yang berasaskan karbon biasanya digunakan sebagai anod atau katod disebabkan struktur bahan berliang dan paling sesuai untuk pertumbuhan bakteria aktif elektrokimia (EAB). Walau bagaimanapun, perkembangan baru menunjukkan penggunaan elektrod logam mampu menghasilkan ketumpatan arus yang lebih tinggi dan kuasa maksimum daripada karbon, kerana sifat-sifat logam seperti kekonduksian yang tinggi dan kekuatan mekanikal, anti-karat serta kestabilan struktur kimia. Strategi pengubahsuaian permukaan logam menggalakkan perlekatan EAB serta meningkatkan tahap biokompatibiliti atau pemindahan elektron di antara sel bakteria dan elektrod. Di samping itu, kos efektif serta mudah beroperasi untuk jangka masa panjang merupakan faktor penyumbang kepada penggunaan elektrod logam. Dari kajian yang dijalankan sehingga kini, keluli tahan karat merupakan logam yang sering digunakan dalam pembangunan BES

Electrochemical characterisation of heat-treated metal and non-metal anodes using mud in microbial fuel cell

Microbial fuel cells (MFCs) have a high potential application for simultaneous wastewater treatment and electricity generation. However, the choice of the electrode material and its design is critical and directly affect their performance. As an electrode of MFCs, the anode material with surface modifications is an attractive strategy to improve the power output. In this study, stainless steel (SS) and carbon steel (CS) was chosen as a metal anode, while graphite felt (GF) was used as a common anode. Heat treatment was performed to convert SS, CS and GF into efficient anodes for MFCs. The maximum current density and power density of the MFC-SS were achieved up till 762.14 mA/m2 and 827.25 mW/m2, respectively, which were higher than MFC-CS (641.95 mA/m2 and 260.14 mW/m2) and MFC-GF (728.30 mA/m2 and 307.89 mW/m2). Electrochemical impedance spectroscopy of MFC-SS showed better catalytic activity compared to MFC-CS and MFC-GF anode, also supported by cyclic voltammetry test

Popular game elements used in designing game-based learning STEM application for school students – A review

There are a variety of educational games produced for studies in game-based learning (GBL) with a specific design to achieve the most efficient stage of learning for school students. However, there is a lack of evidence showing the most suitable and effective game element instilled in the GBL STEM application. Most of the papers studied on GBL have proven the effectiveness aspect in other STEM subjects, however very little discussed in the domain of sustainable energy. Thus, this study aimed to analyse the most common game element applied in designing GBL that achieved the best result for students in learning the STEM subjects. Each game element targeted a different kind of learning results such as student’s learning performance, knowledge level, cognitive effect, and enjoyment. A systematic review was conducted following the specification of the PRISMA checklist to examine past studies. After carefully screening the articles, only twelve published articles met the specification. The finding showed that most common game elements included in designing the GBL, dominated by the level of challenges, followed by rewards/items, feedback, clear goal and time pressure. The finding also included the percentage of most STEM subject studied in GBL and the impact from the GBL STEM application. This review hopes to assist researchers in making a better decision when designing a game application for GBL in sustainable energy subject, from the aspect of students’ age and gender

Review on high-performance air cathode microbial fuel cell for power generation and COD reduction

The world population is projected to increase by one billion for the next ten years from the year 2016. Unfortunately, global power plants still using non-renewable energy sources. Consumption of fossil fuels harms the environment, while nuclear energy could release a significant amount of radioactive material. Besides the energy issues, the growth in population contributes to the high production of wastewater. Every year, the wastewater treatment industry consumes a high input of energy for treatment purposes. These issues invigorate research interest in microbial fuel cell (MFC) technology that can generate green power electricity while breaking down the organic matter in the wastewater. One of the research advancement in MFC is the air-cathode MFC that is scaled-up friendly due to its simple structure, and ability to utilize the abundance of oxygen in the air as the membrane and scaling up arrangements. Therefore, this review aims to discuss the main positive findings contributing to the recent improvement of air-cathode MFC and the obstacles faced for upscaling

UKM2 Chlorella sp. strain electricity performance as bio-anode under different light wavelength in a biophotovoltaic cell

A biophotovoltaic cell (BPV) is an electrobiochemical system that utilises a photosynthetic microorganism for instance is algae to trap sunlight energy and convert it into electricity. In this study, a local algae strain, UKM2 Chlorella sp. was grown in a BPV under different trophic conditions and light wavelengths. Once the acclimatisation phase succeeded, and biofilm formed, power generation by UKM2 algae at the autotrophic mode in synthetic Bold’s Basal media (BBM) under white, blue and red lights were tested. Polarisation and power curves were generated at these different conditions to study the bioelectrochemical performance of the system. Later, the condition switched to algal mixotrophic nutritional mode, with palm oil mill effluent (POME) as substrate. Maximum power generation obtained when using UKM2 in BBM under red light where a power density of 1.19 ± 0.16 W/m3 was obtained at 25.74 ± 3.89 A/m3 current density, while the open circuit voltage OCV reached 226.08 ± 8.71 mV. UKM2 in POME under blue light recorded maximum power density of 0.85 ± 0.18 W/m3 at current density of 16.75 ± 3.54 A/m3 , while the OCV reached 214.05 ± 23.82 mV. Chemical oxygen demand (COD) removal reached an efficiency of 35.93%, indicating the ability of wastewater treatment and electricity generation in BPV at the same tim

Biotic Cathode of Graphite Fibre Brush for Improved Application in Microbial Fuel Cells

The biocathode in a microbial fuel cell (MFC) system is a promising and a cheap alternative method to improve cathode reaction performance. This study aims to identify the effect of the electrode combination between non-chemical modified stainless steel (SS) and graphite fibre brush (GFB) for constructing bio-electrodes in an MFC. In this study, the MFC had two chambers, separated by a cation exchange membrane, and underwent a total of four different treatments with different electrode arrangements (anodeǁcathode)—SSǁSS (control), GFBǁSS, GFBǁGFB and SSǁGFB. Both electrodes were heat-treated to improve surface oxidation. On the 20th day of the operation, the GFBǁGFB arrangement generated the highest power density, up to 3.03 W/m3 (177 A/m3), followed by the SSǁGFB (0.0106 W/m3, 0.412 A/m3), the GFBǁSS (0.0283 W/m3, 17.1 A/m3), and the SSǁSS arrangements (0.0069 W/m−3, 1.64 A/m3). The GFBǁGFB had the lowest internal resistance (0.2 kΩ), corresponding to the highest power output. The other electrode arrangements, SSǁGFB, GFBǁSS, and SSǁSS, showed very high internal resistance (82 kΩ, 2.1 kΩ and 18 kΩ, respectively) due to the low proton and electron movement activity in the MFC systems. The results show that GFB materials can be used as anode and cathode in a fully biotic MFC system