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Electrodes are important components of bioelectrochemical systems (BESs), such as the microbial fuel cells (MFCs). The low-cost cathodes of titanium–nickel (Ti/Ni) and graphite felt-nickel (GF/Ni) are important to be evaluated as cathodes for MFCs. In this study, Ni particles are deposited onto the Ti and GF surface using a simple and low-cost electrodeposition technique. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to analyse the cathode surfaces. The electrodeposition of Ni onto GF appears more uniform without significant agglomeration compared with that onto Ti. This uniform deposition is perhaps the reason for a higher maximum power density (Pmax), lower internal resistance (Rin) and higher Columbic efficiency (CE) for MFC with GF/Ni cathode (113.4 ± 0.6 mW/m2, 1264.4 Ω and 29.6%, respectively) than those measured with Ti/Ni cathode (110.7 ± 8.0 mW/m2, 3375.8 Ω and 23.7%, respectively). However, the performance of these cathodes remains lower compared with the GF/Pt cathode (140.0 mW/m2, 845.7 Ω and 42.0%, respectively). Based on the preparation technique, material cost and performance, both Ti/Ni and GF/Ni cathodes can be considered as alternative to Pt catalyst for MFC application.

Immobilized cell technology is a new technique to produce biogas. In the present study, an immobilized mixed-culture reactor (IMcR) in batch-mode operation was used for the production of hydrogen and methane simultaneously from glucose. Several factors, such as glucose concentration, temperature and fermentation time, were evaluated to determine the optimal conditions for hydrogen and methane production. Gas chromatography with a thermal conductivity detector (GC-TCD) and high-performance liquid chromatography (HPLC) were used to analyse the gas and effluent. The morphologies of the immobilized cells were characterized using scanning electron microscopy (SEM). The optimal conditions for hydrogen and methane production were obtained using a substrate with 5.0 g/L glucose at 60 °C for fermentation times of 48.0 h (hydrogen) and 72.0 h (methane). The maximum yields of hydrogen and methane at these optimal conditions were 37.0 ± 0.0 (×10 −3 ) mol/mol glu and 39.0 ± 0.0 (×10 −3 ) mol/mol glu, respectively. The chemical oxygen demand ( COD ) and pH gradually decreased with increasing fermentation time and temperature. However, the performance of the IMcR decreased over time due to cell damage and microorganism detachment from the cell. In conclusion, the IMcR system is a potential system for the simultaneous production of hydrogen and methane.

The production of hydrogen from glucose by using Enterobacter aerogenes ATCC 13048 (E. aerogenes) in an immobilized cell reactor (ICR) was investigated. The effect of several factors, such as the glucose concentration, feed flow rate, and fermentation time were examined. The highest amount of hydrogen (9.44 mmol H2/g glucose) was obtained at a glucose concentration of 8 g/L, flow rate of 0.5 mL/min, retention time of 24 h and at a temperature of 30 °C. Meanwhile, the highest amount of carbon dioxide (1.68 mmol CO2/g glucose) was obtained at a glucose concentration of 10 g/L, flow rate of 0.7 mL/min, hydraulic retention time of 24 h and at a temperature of 30 °C. The hydrogen and carbon dioxide production were affected by glucose concentration, hydraulic retention time (HRT) and fermentation time. This study showed that the ICR was a very efficient method for the production of hydrogen and carbon dioxide gases.

The high cost of Pt-based cathode, and its possibility of being poisoned by the presence of buffer in the electrolyte are two paramount issues in the BES system. The Ni-Fe has become one of the good alternatives because it has excellent catalytic properties, inexpensive, commercially available and low toxicity to microorganisms. In this study, Ni-Fe foam applied as a cathode in dual-chamber BES, while effluent of glucose fermentation as a substrate in the anode side. The characteristic of Ni-Fe surface was analyzed by using field emission scanning electron microscopy. Whereas, the catalytic property of Ni-Fe was evaluated by using linear sweep voltammetry test. The maximum hydrogen production rate and yield obtained were 500 ± 80 m3/m3/d and 470.2 ± 11.2 mL/g COD, respectively. The results show that the Ni-Fe has comparable performance to GF/Pt. Hence it could be used as an alternative cathode in BES application.

Biodiesel (B2γ-300) derived from second-generation gamma-irradiated Jatropha curcas (JCO2γ-300) was analyzed. HPLC and NMR were used to determine the purity of B2γ-300, and a value of greater than 99.0% was verified. Phorbol ester (PE) composition in B2γ-300 was analyzed by HPLC but could not be detected. Elemental content of nitrogen (N), carbon (C), hydrogen (H), sulfur (S) and oxygen (O) were analyzed by using NCHS. No sulfur content in B2γ-300 could be detected, but N, C, H and O had values of 0.24%, 80.54%, 6.65% and 12.57%, respectively. Overall, it was concluded that the physicochemical properties of B2γ-300 have potential as source of alternative fuels.