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The effect of substrate changes on the performance and microbial community of two-chamber microbial fuel cells (MFCs) was investigated in this study. The MFCs enriched with a single substrate (e.g., acetate, glucose, or butyrate) had different acclimatization capability to substrate changes. The MFC enriched with glucose showed rapid and higher power generation, when glucose was switched with acetate or butyrate. However, the MFC enriched with acetate needed a longer adaptation time for utilizing glucose. Microbial community was also changed when the substrate was changed. Clostridium and Bacilli of phylum Firmicutes were detected in acetate-enriched MFCs after switching to glucose. By contrast, Firmicutes completely disappeared and Geobacter-like species were specifically enriched in glucose-enriched MFCs after feeding acetate to the reactor. This study further suggests that the type of substrate fed to MFC is a very important parameter for reactor performance and microbial community, and significantly affects power generation in MFCs.

The metropolitan cities of developed countries comprise more than 50% of the global population and consume over 60% of the world's energy. Many governments plan to enhance their energy infrastructure and the electricity supply–demand reliability of their energy sources. Among them, South Korea's government has developed electricity generation facilities, most of which use renewable resources such as photovoltaic and wind energy. This study determines the optimal renewable electricity generation configuration for one of the largest metropolitan cities in South Korea, Busan metropolitan city. A simulation using 2013 Busan electricity demand data produces this optimal configuration, which includes photovoltaic panels, wind facilities, converters, and batteries with $0.399 of COE (Cost of Electricity) and 100% of renewable fractions. Both the study's practical limitations and implications are discussed.

The separation of biogas leads to not only recovery and sequestration of CO2, but also to much greater purification and recovery of value-added CH4 able to be used, for example, to directly feed pipelines for domestic or small plants. In this work, an alternative approach for a preliminary design of separation process based on the use of polymeric membranes is proposed. Two different types of polymeric membranes were taken into account, Hyflon AD60 and Matrimid 5218, the first showing a higher permeability with respect to other membranes but a quite low selectivity (12.9), the second exhibiting a higher selectivity with respect to other membranes (41 and 100) even though a lower permeability. Four possible operation schemes using two different types of membranes in multistage configuration system are analysed as functions of the main design parameters, i.e., pressure ratio and permeation number. The achieved results are compared with certain targets and are also discussed in terms of process metrics, according to the Process Intensification strategy. This latter analysis, coupled with a conventional one, provides an alternative point of view over the evaluation of the plant performance taking into account not only the final characteristics of the streams but also process efficiency, exploitation of raw material and energy, and the footprint occupied by the installation.

Although desalination market is today dominated by Seawater Reverse Osmosis (SWRO), important technological issues remain unaddressed, specifically: relatively low water recovery factor (around 50%) and consequent huge amount of brine discharged, and energy consumption (3-5 kWh/m3) still far from the minimum thermodynamic value (~1 kWh/m3). Herein, the energy performance of an innovative systems combining SWRO, Membrane Distillation (MD) and Reverse Electrodialysis (RED) for simultaneous production of water and energy is investigated. The valorization of hypersaline waste brine by Salinity Gradient Power production via RED and the achievement of high recovery factors (since MD is not limited by osmotic phenomena) represent a step forward to the practical implementation of Zero Liquid Discharge and low-energy desalination. The analysis is supported by lab-scale experimental tests carried out on MD and RED over a broad set of operational conditions. Among the different case studies investigated, exergetic efficiency reached 49% for the best scenario, i.e. MD feed temperature of 60°C, MD brine concentration of 5M NaCl, RED power density of 2.2 W/m2MP (MP: membrane pair). Compared to the benchmark flowsheet (only SWRO), up to 23% reduction in electrical energy consumption and 16.6% decrease in specific energy consumption were achieved when including a RED unit. The analysis also indicates that optimization of thermal energy input at the MD stage is critical, although it can potentially be fulfilled by lowgrade waste heat or solar-thermal renewable sources. Overall, the proposed integrated system is coherent with the emergent paradigm of Circular Economy and the logic of Process Intensification.

The development of fuel cells has seen rapid progress with the interest of car manufacturers for in particular in the polymer fuel cells at the end of the 1990s. But also other types of fuel cells have made important steps towards commercialization. This paper provides the state of the art of the most important fuel cell technologies and moreover provides new design concepts, integrated use of novel materials and how fuel cells can be integrated in the chemical industry and in larger energy providing systems using renewables. In this paper we follow two lines of discussion. The first deals with the need for more efficient fuel cells by improving material and component properties and the second deals with integration of various technologies and functions in a full systems approach. The first approach is more relevant for low temperature fuel cells while the second is more suited for new developments in high temperature fuel cells.

Solid oxide fuel cell (SOFC) is a promising technology for electricity generation. Sulfur-free syngas from a gas-cleaning unit serves as fuel for SOFC in integrated gasification fuel cell (IGFC) power plants. It converts the chemical energy of fuel gas directly into electric energy, thus high efficiencies can be achieved. The outputs from SOFC can be utilized by heat recovery steam generator (HRSG), which drives the steam turbine for electricity production. The SOFC stack model was developed using the process flow sheet simulator Aspen Plus, which is of the equilibrium type. Various ranges of syngas properties gathered from different literature were used for the simulation. The results indicate a trade-off efficiency and power with respect to a variety of SOFC inputs. The HRSG located after SOFC was included in the current simulation study with various operating parameters. This paper describes IGFC power plants, particularly the optimization of HRSG to improve the efficiency of the heat recovery from the SOFC exhaust gas and to maximize the power production in the steam cycle in the IGFC system. HRSG output from different pressure levels varies depending on the SOFC output. The steam turbine efficiency was calculated for measuring the total power plant output. The aim of this paper is to provide a simulation model for the optimal selection of the operative parameters of HRSG and SOFC for the IGFC system by comparing it with other models. The simulation model should be flexible enough for use in future development and capable of predicting system performance under various operating conditions.

Nitrate ions were used as the oxidant in the cathode chamber of a microbial fuel cell (MFC) to generate electricity from organic compounds with simultaneous nitrate removal. The MFC using nitrate as oxidant could generate a voltage of 111 mV (1,000 Ω) with a plain carbon cathode. The maximum power density achieved was 7.2 mW m(-2) with a 470 Ω resistor. Nitrate was reduced from an initial concentration of 49 to 25 mg (NO (3) (-) -N) L(-1) during 42-day operation. The daily removal rate was 0.57 mg (NO (3) (-) -N) L(-1) day(-1) with a voltage generation of 96 mV. In the presence of Pt catalyst dispersed on cathode, the cell voltage was significantly increased up to 450 mV and the power density was 117.7 mW m(-2), which was 16 times higher than the value without Pt catalyst. Significant nitrate removal was also observed with a daily removal rate of 2 mg (NO (3) (-) -N) L(-1) day(-1), which was 3.5 times higher compared with the operation without catalyst. Nitrate was reduced to nitrite and ammonia in the liquid phase at a ratio of 0.6% and 51.8% of the total nitrate amount. These results suggest that nitrate can be successfully used as an oxidant for power generation without aeration and also nitrate removal from water in MFC. However, control of the process would be needed to reduce nitrate to only nitrogen gas, and avoid further reduction to ammonia.

Water gas shift reaction for hydrogen production was studied in a catalytic membrane reactor using a supported silica membrane at 220-290 °C temperature and 2-6 bar pressure ranges. A CO conversion higher than the thermodynamic equilibrium of a traditional reactor was obtained. The best result, 95% CO conversion, was achieved at 4 bar and 280 °C. The membrane was also characterized in terms of permeance and selectivity by means of permeation tests carried out before and after reaction. In addition, permeance and separation factor were also measured during the reaction. Permeance of all species (H2: 9.7-29; CO: 0.3-1.1; CO2: 0.4-1.5 nmol/m2 s Pa), selectivity (H2/CO, H2/CO2 and H2/N2) ranging from 15 to 40 and separation factors (H2/CO = 20-45), showed no dependence on the related permeation driving force. Differences between selectivity and separation factor were registered. Furthermore, no inhibition effects of other gases on the hydrogen flux were observed. The membrane was prepared by the soaking roller procedure depositing a silica layer on a stainless steel support with an intermediate -alumina layer. The membrane reactor allowing selective hydrogen permeation presents a good performance exceeding also the equilibrium conversion of a traditional reactor.