In situ Growth of Zeolite Imidazole Frameworks (ZIF-67) on Carbon Cloth for the Application of Oxygen Reduction Reactions and Microbial Fuel Cells

Developing high surface area catalysts is an effective strategy to enhance the oxygen reduction reaction (ORR) in the application of microbial fuel cells (MFCs). This can be achieved by developing a catalyst based on metal-organic frameworks (MOFs) because they offer a porous active site for ORR. In this work, a novel in situ growth of 2D shell nanowires of ZIF-67 as a template for N-doped carbon (Co/NC) via a carbonization route was developed to enhance the ORR performance. The effects of different reaction times and different annealing temperatures were studied for a better ORR activity. The growth of the MOF template on the carbon cloth was confirmed using scanning electron microscopy, field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared. The Co/NC-800 exhibited an enhancement in the ORR activity as evidenced by an onset potential and half-wave potential of 0.0 vs V Ag/AgCl and -0.1 vs V Ag/AgCl, respectively, with a limited current density exceeding the commercial Pt/C. Operating Co/NC-800 on MFC revealed a maximum power density of 30 ± 2.5 mW/m2, a maximum current density of 180 ± 2.5 mA/m2.

Maximization of Power Density of Direct Methanol Fuel Cell for Greener Energy Generation Using Beetle Antennae Search Algorithm and Fuzzy Modeling

Direct methanol fuel cells (DMFCs) are promising form of energy conversion technology that have the potential to take the role of lithium-ion batteries in portable electronics and electric cars. To increase the efficiency of DMFCs, many operating conditions ought to be optimized. Developing a reliable fuzzy model to simulate DMFCs is a major objective. To increase the power output of a DMFC, three process variables are considered: temperature, methanol concentration, and oxygen flow rate. First, a fuzzy model of the DMFC was developed using experimental data. The best operational circumstances to increase power density were then determined using the beetle antennae search (BAS) method. The RMSE values for the fuzzy DMFC model are 0.1982 and 1.5460 for the training and testing data. For training and testing, the coefficient of determination (R2) values were 0.9977 and 0.89, respectively. Thanks to fuzzy logic, the RMSE was reduced by 88% compared to ANOVA. It decreased from 7.29 (using ANOVA) to 0.8628 (using fuzzy). The fuzzy model's low RMSE and high R2 values show that the modeling phase was successful. In comparison with the measured data and RSM, the combination of fuzzy modeling and the BAS algorithm increased the power density of the DMFC by 8.88% and 7.5%, respectively, and 75 °C, 1.2 M, and 400 mL/min were the ideal values for temperature, methanol concentration, and oxygen flow rate, respectively.

Engineering of nickel, cobalt oxides and nickel/cobalt binary oxides by electrodeposition and application as binder free electrodes in supercapacitors

Cobalt oxide, nickel oxide and cobalt/nickel binary oxides were synthesised by electrodeposition. To fine tune composition of CoNi alloys, growth parameters including voltage, electrolyte pH/concentration and deposition time were varied. These produced nanomaterials were used as binder free electrodes in supercapacitor cells and tested using three electrode setup in 2 MKOH aqueous electrolyte. Cyclic voltammetry and galvanostatic charge/discharge were used at different scan rates (5-100 mV/s) and current densities (1-10 A/g) respectively to investigate the capacitive behaviour and measure the capacitance of active material. Electrochemical impedance spectroscopy was used to analyse the resistive/conductive behaviours of these electrodes in frequency range of 100 kHz to 0.01 Hz at applied voltage of 10 mV. Binary oxide electrode displayed superior electrochemical performance with the specific capacitance of 176 F/g at current density of 1 A/g. This hybrid electrode also displayed capacitance retention of over 83% after 5000 charge/discharge cycles. Cell displayed low solution resistance of 0.35 Ω along with good conductivity. The proposed facile approach to synthesise binder free blended metal electrodes can result in enhanced redox activity of pseudocapacitive materials. Consequently, fine tuning of these materials by controlling the cobalt and nickel contents can assist in broadening their applications in electrochemical energy storage in general and in supercapacitors in particular.

A critical insight on nanofluids for heat transfer enhancement

There are numerous reports and publications in reputable scientific and engineering journals that attribute substantial enhancement in heat transfer capabilities for heat exchangers once they employ nanofluids as working fluids. By definition, a nanofluid is a working fluid that has a small volume fraction (5% or less) of a solid particle with dimensions in the nanoscale. The addition of this solid material has a reported significant impact on convective heat transfer in heat exchangers. This work investigates the significance of the reported enhancements in many recent related publications. Observations on these publications' geographical origins, fundamental heat transfer calculations, experimental setups and lack of potential applications are critically made. Heat transfer calculations based on methodologies outlined in random selection of available papers were conducted along with a statistical analysis show paradoxically inconsistent conclusion as well as an apparent lack of complete comprehension of convective heat transfer mechanism. In some of the surveyed literature for example, heat transfer coefficient enhancements were reported to be up to 27% and 48%, whereas the recalculations presented in this work restrain proclaimed enactments to ~ 3.5% and - 4% (no enhancement), respectively. This work aims at allowing a healthy scientific debate on whether nanofluids are the sole answer to enhancing convective heat transfer in heat exchangers. The quantity of literature that confirms the latter statement have an undeniable critical mass, but this volition could be stemming from and heading to the wrong direction. Finally, the challenges imposed by the physical nature of nanoparticles, as well as economic limitations caused by the high price of conventional nanoparticles such as gold (80$/g), diamond (35$/g), and silver (6$/g) that hinder their commercialization, are presented.

Perovskite Membranes: Advancements and Challenges in Gas Separation, Production, and Capture

Perovskite membranes have gained considerable attention in gas separation and production due to their unique properties such as high selectivity and permeability towards various gases. These membranes are composed of perovskite oxides, which have a crystalline structure that can be tailored to enhance gas separation performance. In oxygen enrichment, perovskite membranes are employed to separate oxygen from air, which is then utilized in a variety of applications such as combustion and medical devices. Moreover, perovskite membranes are investigated for carbon capture applications to reduce greenhouse gas emissions. Further, perovskite membranes are employed in hydrogen production, where they aid in the separation of hydrogen from other gases such as methane and carbon dioxide. This process is essential in the production of clean hydrogen fuel for various applications such as fuel cells and transportation. This paper provides a review on the utilization and role of perovskite membranes in various gas applications, including oxygen enrichment, carbon capture, and hydrogen production.

Membrane processes for environmental remediation of nanomaterials: Potentials and challenges

Nanomaterials have gained huge attention with their wide range of applications. This is mainly driven by their unique properties. Nanomaterials include nanoparticles, nanotubes, nanofibers, and many other nanoscale structures have been widely assessed for improving the performance in different applications. However, with the wide implementation and utilization of nanomaterials, another challenge is being present when these materials end up in the environment, i.e. air, water, and soil. Environmental remediation of nanomaterials has recently gained attention and is concerned with removing nanomaterials from the environment. Membrane filtration processes have been widely considered a very efficient tool for the environmental remediation of different pollutants. Membranes with their different operating principles from size exclusions as in microfiltration, to ionic exclusion as in reverse osmosis, provide an effective tool for the removal of different types of nanomaterials. This work comprehends, summarizes, and critically discusses the different approaches for the environmental remediation of engineered nanomaterials using membrane filtration processes. Microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) have been shown to effectively remove nanomaterials from the air and aqueous environments. In MF, the adsorption of nanomaterials to membrane material was found to be the main removal mechanism. While in UF and NF, the main mechanism was size exclusion. Membrane fouling, hence requiring proper cleaning or replacement was found to be the major challenge for UF and NF processes. While limited adsorption capacity of nanomaterial along with desorption was found to be the main challenges for MF.

Membrane-based carbon capture: Recent progress, challenges, and their role in achieving the sustainable development goals

The rapid growth in the consumption of fossil fuels resulted in climate change and severe health issues. Among the different proposed methods to control climate change, carbon capture technologies are the best choice in the current stage. In this study, the various membrane technologies used for carbon capture and their impact on achieving sustainable development goals (SDGs) are discussed. Membrane-based carbon capture processes in pre-combustion and post-combustion, which are known as membrane gas separation (MGS) and membrane contactor (MC), respectively, along with the process of fabrication and the different limitations that hinder their performances are discussed. Additionally, the 17 SDGs, where each representing a crucial topic in the current global task of a sustainable future, that are impacted by membrane-based carbon capture technologies are discussed. Membrane-based carbon capture technologies showed to have mixed impacts on different SDGs, varying in intensity and usefulness. It was found that the membrane-based carbon capture technologies had mostly influenced SDG 7 by enhancement in the zero-emission production, SDG 9 by providing 38-42% cost savings compared to liquid absorption, SDG 3 through reducing pollution and particulate matter emissions by 23%, and SDG 13, with SDG 13 being the most positively influenced by membrane-based carbon capture technologies, as they significantly reduce the CO₂ emissions and have high CO₂ capture yields (80-90%), thus supporting the objectives of SDG 13 in combatting climate change.

Membrane-based water and wastewater treatment technologies: Issues, current trends, challenges, and role in achieving sustainable development goals, and circular economy

Membrane-based technologies are recently being considered as effective methods for conventional water and wastewater remediation processes to achieve the increasing demands for clean water and minimize the negative environmental effects. Although there are numerous merits of such technologies, some major challenges like high capital and operating costs . This study first focuses on reporting the current membrane-based technologies, i.e., nanofiltration, ultrafiltration, microfiltration, and forward- and reverse-osmosis membranes. The second part of this study deeply discusses the contributions of membrane-based technologies in achieving the sustainable development goals (SDGs) stated by the United Nations (UNs) in 2015 followed by their role in the circular economy. In brief, the membrane based processes directly impact 15 out of 17 SDGs which are SDG1, 2, 3, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16 and 17. However, the merits, challenges, efficiencies, operating conditions, and applications are considered as the basis for evaluating such technologies in sustainable development, circular economy, and future development.

Role of microalgae in achieving sustainable development goals and circular economy

In 2015, the United Nations General Assembly (UNGA) set out 17 Sustainable Development Goals (SDGs) to be achieved by 2030. These goals highlight key objectives that must be addressed. Each target focuses on a unique perspective crucial to meeting these goals. Social, political, and economic issues are addressed to comprehensively review the main issues combating climate change and creating sustainable and environmentally friendly industries, jobs, and communities. Several mechanisms that involve judicious use of biological entities are among instruments that are being explored to achieve the targets of SDGs. Microalgae have an increasing interest in various sectors, including; renewable energy, food, environmental management, water purification, and the production of chemicals such as biofertilizers, cosmetics, and healthcare products. The significance of microalgae also arises from their tendency to consume CO2, which is the main greenhouse gas and the major contributor to the climate change. This work discusses the roles of microalgae in achieving the various SDGs. Moreover, this work elaborates on the contribution of microalgae to the circular economy. It was found that the microalgae contribute to all the 17th SDGs, where they directly contribute to 9th of the SDGs and indirectly contribute to the rest. The major contribution of the Microalgae is clear in SDG-6 "Clean water and sanitation", SDG-7 "Affordable and clean energy", and SDG-13 "Climate action". Furthermore, it was found that Microalgae have a significant contribution to the circular economy.

Graphene Synthesis Techniques and Environmental Applications

Graphene is fundamentally a two-dimensional material with extraordinary optical, thermal, mechanical, and electrical characteristics. It has a versatile surface chemistry and large surface area. It is a carbon nanomaterial, which comprises sp² hybridized carbon atoms placed in a hexagonal lattice with one-atom thickness, giving it a two-dimensional structure. A large number of synthesis techniques including epitaxial growth, liquid phase exfoliation, electrochemical exfoliation, mechanical exfoliation, and chemical vapor deposition are used for the synthesis of graphene. Graphene prepared using different techniques can have a number of benefits and deficiencies depending on its application. This study provides a summary of graphene preparation techniques and critically assesses the use of graphene, its derivates, and composites in environmental applications. These applications include the use of graphene as membrane material for the detoxication and purification of water, active material for gas sensing, heavy metal ions detection, and CO₂ conversion. Furthermore, a trend analysis of both synthesis techniques and environmental applications of graphene has been performed by extracting and analyzing Scopus data from the past ten years. Finally, conclusions and outlook are provided to address the residual challenges related to the synthesis of the material and its use for environmental applications.

Pathways resilient future for developing a sustainable E85 fuel and prospects towards its applications

The utilization of ethanol as a component of motor gasolines is an extremely effective way to increase the detonation resistance and environmental properties. In Russia, despite the existing prerequisites for the development of bioethanol industry, the real production of bioethanol is not executed, which is associated with its high price. One of the promising ways of leveling this drawback is the utilization of water-cut waste from its production, involving ethyl alcohol impurity concentrate (EAIC) instead of pure ethanol. This is a mixture of head and bottoms fractions obtained in the process of ethyl alcohol purification by distillation. This research paper investigates the impact of the nature of hydrocarbon fraction blended with ethyl alcohol impurity concentrate on the final characterization of E85 fuel and, in particular, on its phase stability and Reid vapor pressure. Physicochemical characteristics of the developed fuel composition were studied. The results indicated that none of the possible classes of hydrocarbons could effectively solve the problems of phase stability and volatility of E85 fuel. Additionally, methyl tert-butyl ether (MTBE) was the only promising component. The composition, consisting of 70 % ethyl alcohol impurity concentrate and 30 % methyl tertiary butyl ether, met the requirements of American society for testing and materials (ASTM 5798) in almost all respects. A significant discrepancy is observed only in the water content, which is compensated by the great phase stability of the composition at low temperatures. In addition, this fuel composition is characterized by great potential competitiveness in Russian conditions and without fiscal support, which was proved by preliminary calculations of the cost of E85 fuel.

Recent Progress in Renewable Energy Based-Desalination in the Middle East and North Africa MENA Region

BACKGROUND

The Middle East and North African (MENA) countries are rapidly growing in population with very limited access to freshwater resources. To overcome this challenge, seawater desalination is proposed as an effective solution, as most MENA countries have easy access to saline water. However, desalination processes require massive demand for energy, which is mostly met by fossil fuel-driven power plants. The rapid technological advancements in renewable energy technologies, along with their gradually decreasing cost place renewable energy-driven power plants and processes as a promising alternative to conventional fuel-powered plants.

AIM OF REVIEW

In the current work, renewable energy-powered desalination in the MENA region is investigated. Various desalination technologies and renewable energy resources, particularly those available in MENA are discussed. A detailed discussion of suitable energy storage technologies for incorporation into renewable energy desalination systems is also included.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The progress made in implementing renewable energy into power desalination plants in MENA countries is summarized and analyzed by describing the overall trend and giving recommendations for the potential amalgamation of available renewable energies (REs) and available desalination technologies. Finally, a case study in the MENA region, the Al-khafji solar seawater reverse osmosis (SWRO) desalination plant in the Kingdom of Saudi Arabia KSA, is used to demonstrate the implementation of REs to drive desalination processes.

Geopolymer concrete as green building materials: Recent applications, sustainable development and circular economy potentials

Environmental degradation and increased greenhouse gas emissions force communities to achieve sustainable green building and construction materials. The environmental and financial aspects of sustainable development and circular economy strongly depend on the recycling of wastes into new products. Geopolymers gained increasing attention because of their eco-friendly and superior mechanical characteristics and their ability to utilize numerous wastes as precursors. Although there are numerous studies on geopolymer, little attention was focused on geopolymer concrete (GeoC). Hence, This review follows the Preferred Reporting Items for Systematic Reviews (PRISMA) investigated in detail GeoC. The first part of this study explores the recent synthesis processes, different precursors, and applications of geopolymer concrete (GeoC) in numerous sectors as well as the mechanical, microstructural, and physical related characteristics of GeoC developed from various wastes. The second part discusses in detail the contributions of GeoC to the sustainable development goals (SDGs) stated by the United Nations. The last part discusses the implementation of different wastes to develop GeoC-based circular economy to provide recommendations and prospects for GeoC science and technology. An eco-friendly, sustainable, structurally sound GeoC matrixes can be developed from numerous industrial, municipal, and agricultural wastes. Such GeoC is a good candidate to traditional concrete and some other building materials. GeoC is strongly contribute into 12 SDGs of the main 17 SDGs. Optimizing the elements of GeoC would decrease its cost and thus promote a green circular economy.

Effect of dust and methods of cleaning on the performance of solar PV module for different climate regions: Comprehensive review

Recent achievement and progress in solar PV play a significant role in controlling climate change. This study reviewed comprehensively electrical characteristics, life cycle of dust, optical characteristics, and different cleaning techniques related to the effect of dust on the performance of PV modules throughout different climate regions of the world. The power maximum power point (MPP) and curve of PV module under the effect of irradiance and temperature were presented. The effect of dust (shading) on the electrical efficiency of PV module was discussed based on soft, partial, and complete (soiling) shading. The physical properties of dust around the globe such as PM₁₀ concentration, dust loading (mgm^-2), and fine dust particles concentration were covered and discussed. Reasons behind the accumulation of dust based on, location and installation factors, dust type, and environmental factors. Environmental reasons causing dust and dust removal in accordance with the life cycle of dust was covered in detail. All the reasons that cause the generation, accumulation and removal of dust during its life cycle were explained. All forces responsible for the adhesion phase of the dust life cycle were presented. The effect of dust on PV module transmittance and electrical parameters module were discussed in detail based on physical properties of the dust at its location and installation conditions. Self-cleaning super hydrophobic surfaces based on methods such as solvents, vapor-assisted coating, powder coating, and polymerization were discussed. All cleaning technologies, including self-cleaning technologies, based on the material coating used, and the manufacturing of PV cells was compared. The future prospective for PV technologies and cleaning methods were also covered.

All Transition Metal Selenide Composed High-Energy Solid-State Hybrid Supercapacitor

Transition metal selenides (TMSs) have enthused snowballing research and industrial attention due to their exclusive conductivity and redox activity features, holding them as great candidates for emerging electrochemical devices. However, the real-life utility of TMSs remains challenging owing to their convoluted synthesis process. Herein, a versatile in situ approach to design nanostructured TMSs for high-energy solid-state hybrid supercapacitors (HSCs) is demonstrated. Initially, the rose-nanopetal-like NiSe@Cu₂ Se (NiCuSe) positive electrode and FeSe nanoparticles negative electrode are directly anchored on Cu foam via in situ conversion reactions. The complementary potential windows of NiCuSe and FeSe electrodes in aqueous electrolytes associated with the excellent electrical conductivity results in superior electrochemical features. The solid-state HSCs cell manages to work in a high voltage range of 0-1.6 V, delivers a high specific energy density of 87.6 Wh kg^-1 at a specific power density of 914.3 W kg^-1 and excellent cycle lifetime (91.3% over 10 000 cycles). The innovative insights and electrode design for high conductivity holds great pledge in inspiring material synthesis strategies. This work offers a feasible route to develop high-energy battery-type electrodes for next-generation hybrid energy storage systems.

New insights on introducing modern multifunctional additives into motor gasoline

Multifunctional additives should be added into motor gasoline to raise the life of engine parts, increase the engine power, as well as reduce the exhaust emission and fuel consumption. This research article proposes new insights to produce modern multifunctional motor gasoline additives. The main components of these additives are detergents, corrosion inhibitors, and friction modifier. Additionally, original methods for assessing the effectiveness of detergent and tribological properties were studied. The test method for the interfacial surface tension is unsuitable for the primary assessment of the effectiveness of the detergent component of the additive package. However, it can well be used to control the quality of individual batches of multifunctional additives directly in production, if further comparison is made with the data obtained during the current control in production. For the initial assessment of detergent properties, the bench method can be modified by accelerating the formation of deposits on engine parts by running for 20 h on gasoline containing 3% wt of N-methylaniline (NMA). The results presented that the relative decrease in mechanical power losses when using the additive package correlates with the indicator of reducing the diameter of the wear scar. Moreover, new technical solutions were proposed to increase the availability of experimental evaluation of multifunctional additives into gasoline. Finally, these make it possible to achieve significant savings in time and money in the development and modification of multifunctional additives compositions into motor gasoline.

High energy storage quasi-solid-state supercapacitor enabled by metal chalcogenide nanowires and iron-based nitrogen-doped graphene nanostructures

Transition metal selenides (TMS) have excellent research prospects and significant attention in supercapacitors (SCs) owing to their high electrical conductivity, superior electrochemical activity and excellent structural stability. However, the commercial utilization of TMS remains challenge due to their elaborate synthesis. Present study designed a hierarchical cobalt selenide (CoSe₂) nanowire array on Ni-foam to serve as a positive electrode for asymmetric SCs (ASCs). The nanowires-like morphology of CoSe₂ was highly advantageous for SCs, as it offered enhanced electrical conductivity, plenty of surface sites, and short ion diffusion. The as-obtained, CoSe₂ nanowire electrode demonstrated outstanding electrochemical features, with an areal capacity of 1.08 mAh cm^-2 at 3 mA cm^-2, high-rate performance (69.5 % at 50 mA cm^-2), as well as outstanding stability after 10,000 cycles. The iron titanium nitride@nitrogen-doped graphene (Fe-TiN@NG) was prepared as a negative electrode to construct the ASCs cell. The obtained ASCs cell illustrated an energy density of 91.8 W h kg^-1 at a power density of 281.4 W kg^-1 and capacity retention of 94.6% over 10,000 cycles. The overall results provide a more efficient strategy to develop redox-ambitious active materials with a high capacity for advanced energy-storage systems.

Uniqueness technique for introducing high octane environmental gasoline using renewable oxygenates and its formulation on Fuzzy modeling

The depletion of fuel production and raising ecological issues have paid the progress of biofuels in the entire world. Among different biofuels is introducing renewable fuel additives as prospective beneficial blendstocks towards fulfilling systematic, low-carbon technologies internal combustion engines. This research article proposes a new approach to formulate a Fuzzy modeling for examining various promising alternative renewable oxygenated compounds, including ethanol, isopropanol, MTBE, and 2-methyl furan into heavy hydrocracked gasoline a base fuel. No previous study has utilized Fuzzy modeling in formulation of producing high octane fuel based on renewable additives compounds. The effect of selected additives was investigated on the antiknock characteristics. The results reported that the quality and quantity of heavy hydrocracked naphtha have been reinforced, using low carbon oxygenates. Besides, the acquired results provided the possibility to determine the optimum range of selected renewable oxygenates percentages of 30-50% wt. The calculated data of Fuzzy modeling were verified with experimental results. It illustrated that predicted environmental gasoline yields agreed well with experimental results. Finally, low carbon liquid fuel could contribute to produce high quality environmental gasoline, improve environmental characteristics, in terms of decreasing greenhouses emissions, and maximize the vehicles technologies.

Faradic capacitive deionization (FCDI) for desalination and ion removal from wastewater

Capacitive deionization (CDI) is one of the emerging desalination technologies that attracted much attention in the last years as a low-cost, energy-efficient, and environmentally-friendly alternative to other desalination technologies, such as multi-stage flash desalination (MSF) and multiple effect distillation (MED). The implementation of faradaic electrode materials is a promising method for enhancing CDI systems' performance by achieving higher salt removal characteristics, lower energy consumption, and better ion selectivity. Therefore, a novel CDI technology named Faradaic CDI (FCDI) that implements faradaic electrode materials arose as a high-performance CDI cell design. In this work, the application of FCDI cells in desalination and wastewater treatment systems is reviewed. First, the progress done on using various FCDI systems for saline water desalination is summarized and discussed. Next, the application of FCDI in wastewater treatment applications and selective ion removal is presented. A thorough comparison between FCDI and conventional carbon-based CDI is carried out in terms of working principle, electrode material's cost, salt removal performance, energy consumption, advantages, and disadvantages. Finally, future research consideration regarding FCDI technology is included to drive this technology closer towards practical application.

Fuel cells for carbon capture applications

The harmful effect of carbon pollution leads to depletion of the ozone layer, which is one of the main challenges confronting the world. Although progress is made in developing different carbon dioxide (CO₂) capturing methods, these methods are still expensive and face several technical challenges. Fuel cells (FCs) are efficient energy converting devices that produce energy via an electrochemical process. Recently varying kinds of fuel cells are considered as an effective method for CO₂ capturing and/or conversion. Among the different types of fuel cells, solid oxide fuel cells (SOFCs), molten carbonate fuel cells (MCFCs), and microbial fuel cells (MFCs) demonstrated promising results in this regard. High-temperature fuel cells such as SOFCs and MCFCs are effectively used for CO₂ capturing through their electrolyte and have shown promising results in combination with power plants or industrial effluents. An algae-based microbial fuel cell is an electrochemical device used to capture and convert carbon dioxide through the photosynthesis process using algae strains to organic matters and simultaneously power generation. This review present a brief background about carbon capture and storage techniques and the technological advancement related to carbon dioxide captured by different fuel cells, including molten carbonate fuel cells, solid oxide fuel cells, and algae-based fuel cells.

A critical review on environmental impacts of renewable energy systems and mitigation strategies: Wind, hydro, biomass and geothermal

The annual growth of global energy demand and the associated environmental impacts (EIs) has an important role in the large sustainable and green global energy transition. Renewable energy systems have been attracting substantial economic, environmental, and technical attention throughout the last decade, while some have been in the market for almost a century. However, even renewable energy may negatively affect the environment, which is widely considered much less harsh than fossil energy resources. This, in return, requires more consideration and appropriate precautions to be taken. This work discusses the environmental impacts (EIs) of small and medium-sized wind, hydro, biomass, and geothermal power systems. The approach goes through all stages from planning and conception to construction and installation and throughout service life and decommissioning. For various circumstances and technically and ecologically viable guidelines for their effect on natural resources and wildlife, clear and comprehensive solutions have been given.

Environmental impacts of nanofluids: A review

Nanofluids (NFs) have been expanding their applications in many areas as high-performance heat transfer fluid (HTF) for heating and cooling purposes. This is mainly due to the improved thermophysical properties relative to the base fluid (BF). The addition of nanoparticles (NPs) to BF, to obtain NFs, increases the thermal conductivity, hence better heat transfer properties and thermal performance. The properties of NFs can be considered somehow intermediate between those of the BF and the added solid NPs. The improved heat transfer using NFs results in increased energy conversion efficiency, which results in reduced energy consumption for heating or cooling applications. BF and their environmental impacts (EIs) have been widely discussed within the scope of their applications as a HTF, with most of the attention given to the improved energy efficiency. The IEs of NPs and their toxicity and other characteristics have been extensively studied due to the widespread applications on newly engineered NPs. However, with the evolution of expanding the applications of NFs, the different EIs were not well addressed. The discussion should consider both the base fluid and NPs added in combination as the NF constitutes. The current work presents a brief discussion on the EIs of NFs. The discussion presented in this work considers the NPs as the primary contributor to the EIs of different NFs. It was found that the EIs of NFs depend significantly on the type of NP used, followed by the BF, and finally, the loading of NPs in BF. The use of non-toxic and naturally occurring NPs at lower NPs loading in water as NF promises a much lower EIs in terms of toxicity energy requirements for production, and other EIs, while still maintaining high thermal performance. The production methods of both NPs, i.e., synthesis route, and NF, i.e., one-step or two-step, were found to have a significant effect on the associated EIs of the produced NF. The simpler NP synthesis route and NF production will result in much lower chemicals and energy requirements, which in turn reduce the EIs.

Progress in carbon capture technologies

Human factors are one of the key contributors to carbon dioxide emissions into the environment. Since the industrial revolution, the atmospheric carbon dioxide levels have increased appreciably. This has been attributed to the utilization of fossil fuels for energy generation coupled with the clearing of forests and extensive manufacturing of some industrial products such as cement. The increase in atmospheric concentrations of carbon dioxide has been widely linked to climate change and the Earth's temperature. A drastic approach is therefore needed in terms of policy formulation to address this global challenge. Carbon capture and storage are reliable tools that can be introduced to the industrial sector to address this issue. Therefore, this review presents a thorough investigation of the various technologies that can be harnessed to capture carbon dioxide. The cost associated with the capture, transport, and storage of the carbon dioxide is discussed. Socio-economic aspects of carbon capture and storage technologies are also presented in this review. Factors influencing public awareness of the technology and perceptions associated with carbon capture and storage should be a point for consideration in future research activities relating to this novel technology. This, in effect, this will ensure effective expert knowledge communication to the general public and foster social acceptance of this technology.

Hybrid low-carbon high-octane oxygenated gasoline based on low-octane hydrocarbon fractions

Low-carbon fuel is the main trend in the development of oil refining in leading countries. Likewise, efforts continue optimizing internal combustion engines for increasing their fuel economy, and therefore exhaust emissions will be reduced. This research proposes a novel approach for producing low-carbon high-octane oxygenated environmentally friendly motor gasoline based on low-octane hydrocarbon fractions. Experimental studies of the antiknock performance for four representatives of oxygenated compounds, involving bioethanol, methyl tertiary butyl ether (MTBE), isopropanol, and 2-methylfuran with low-octane hydrocarbon fractions, as well as low-octane blends of individual hydrocarbons of surrogate fuels were carried out. Additionally, the change in antilocking performance of oxygenated compounds has been dependent on their types and group composition of the base low-octane motor fuel. The results illustrated that high-octane environmentally friendly motor gasolines RON 91 and RON 95 have been produced. Besides, the injectivity of hydrocarbons to oxygenated compounds by the ability to increase the octane rating by the research method will increase in the series: olefins < naphthenes < aromatics < paraffins, and by the motor method:naphthenes < olefins < aromatics < paraffins. Finally, environmentally friendly motor gasoline can decrease the environment impacts, reduce the overhead charges, as well as maximize the product quality.

Environmental impacts of solar energy systems: A review

The annual increases in global energy consumption, along with its environmental issues and concerns, are playing significant roles in the massive sustainable and renewable global transmission of energy. Solar energy systems have been grabbing most attention among all the other renewable energy systems throughout the last decade. However, even renewable energies can have some adverse environmental repercussions; therefore, further attention and proper precautional procedures should be given. This paper discusses in detail the environmental impacts of several commercial and emerging solar energy systems at both small- and utility-scales. The study expands to some of the related advances, as well as some of the essential elements in their systems. The approach follows all the stages, starting with the designs, then throughout their manufacturing, materials, construction or installation phases, and over operation lifetime and decommissioning. Specific solutions for most systems such as waste minimization and recycling are discussed, alongside with some technically and ecologically favorable recommendations for mitigating the impacts.

Evaluation of the nanofluid-assisted desalination through solar stills in the last decade

Remote areas and poor communities are occasionally deprived of access to freshwater. It is, therefore, critical to providing a cheap and efficient desalination system that encourages the development of those communities and benefiting society at large. Solar stills are an affordable, direct method of water desalination, but its productivity is the critical challenge hindering its application. To ease this, research has focused on the role of nanofluids to improve heat transfer. Other works have focused on improving the design in consort with utilizing the nanofluids. This review reports and discusses the substantial role of nanofluids to enhance the productivity and energy utilization efficiency of the solar stills. Specifically, the mechanism of energy transfer between the nanoparticles and the base fluid. This includes both plasmonic and thermal effects. It is evident that nanofluid utilization in small fraction enhanced the thermal conductivity compared to base fluid alone. Alumina was found to be the most suitable nanoparticle used as nanofluid inside the solar stills due to its availability and lower cost. Still, other competitors such as carbon nanostructures need to be investigated as it provides higher enhancement of thermal conductivity. Also, several aspects of energy utilization enhancement have been discussed, including innovative application techniques. The challenges of such integrated systems are addressed as well.

Recent progress of graphene based nanomaterials in bioelectrochemical systems

The application of graphene (Gr) to microbial fuel cells (MFCs) and microbial electrolysis cell (MECs) is considered a very promising approach in terms of enhancing their performance. The superior Gr properties of high electrical and thermal conductivities, along with: superior specific surface area, high electron mobility, and mechanical strength, are the key features that endorse this. Factors impeding the advancement of a microbial fuel cell into commercialization involve primarily the cost of their components, and their production on a small scale. Gr with such outstanding characteristics can help mitigate these challenges, when used as electrode material. The application of Gr as an anode material improves the efficiency of electron transfer and bacterial attachment. When used as a cathode material, it supports the oxygen reduction reaction. This investigation, presents a thorough analysis of the feasibility of Gr as an electrode material in both MFC and MEC applications - based on experimental results from the investigation. Current technological advancements in the implementation of Gr in MFC and MEC are also highlighted in this review. To summarise, the investigation exposes critical issues impeding the advancement of microbial fuel cells, and proposes possible solutions to mitigate these challenges.

Review of the regulations and techniques to eliminate toxic emissions from diesel engine cars

One of the challenging issues affecting the automotive industry in recent times has to do with the total emissions produced by the sector annually. This investigation sums up some of these toxic emissions generated by diesel engine cars. Legislations related to these emissions were also discussed thoroughly. Techniques that can be adopted to eliminate these gases were also investigated as well. In spite of the successes made in this sector, there is still more room for improvement in terms of commitments by all stakeholders in the industry and this has been carefully discussed in this report.

Environmental impact of desalination processes: Mitigation and control strategies

Freshwater supplies are in shortage relative to the high demand for different human activities, making desalination of saline water a must. Desalination to extract water from saline water has been well established as a reliable non-conventional water supply. However, desalination as any human-based process has resulted in many impacts on the environment. Brine loaded with chemicals being discharged back to the environment, along with greenhouse gases (GHGs) emissions being released to the atmosphere, are the most significant impacts, which has been extensively studied, with some efforts given to its mitigation and control. The current work discusses the mitigation and control strategies (M&CS) to the different environmental impacts (EIs) of desalination processes. The article compiles the M&CS in one work, instead of the distributed and separate treatment of the EIs of each desalination step and its respective M&CS as currently present in literature. The article tracks the water flow in an intake-to-outfall approach exploring how to minimize the impacts at each step and as a whole process. This starts from intake, pretreatment processes, desalination technology, and finally, brine discharge. The EIs associated with each desalination process element is thoroughly discussed with proposed M&CS. The work shows clearly that many EIs can be eliminated or minimized by incorporating specific design criteria and process improvements. The feedwater source has shown to have a great effect on EIs. Similarly, desalination technology has shown a considerable effect on the EIs related to brine characteristics and energy consumption. Hybrid and emerging desalination systems have shown reduced EIs relative to conventional thermal and membrane desalination technologies, while the utilization of renewable and waste energy sources has shown a significant reduction in EIs related to energy consumption.

Data on fuzzy logic based-modelling and optimization of recovered lipid from microalgae

This article presents the data of recovered lipid from microalgae using fuzzy logic based-modelling and particle swarm optimization (PSO) algorithm. The details of fuzzy model and optimization process were discussed in our work entitled “Application of Fuzzy Modelling and Particle Swarm Optimization to Enhance Lipid Extraction from Microalgae” (Nassef et al., 2019) [1]. The presented data are divided into two main parts. The first part represents the percentage of recovered lipid using fuzzy logic model and ANOVA. However, the second part shows the variation of the cost function (recovered lipid) for the 100 runs of PSO algorithm during optimization process. These data sets can be used as references to analyze the data obtained by any other optimization technique. The data sets are provided in the supplementary materials in Tables 1–2.

Effect of humidification of reactive gases on the performance of a proton exchange membrane fuel cell

This work studies the impact of water formation on the performance of Proton Exchange Membrane Fuel Cells (PEMFCs). The work examines water management in PEM fuel cells both experimentally and theoretically. Experiments are conducted using a one stack PEM fuel cell fitted with Nafion membrane to evaluate its performance using both dry and humidified hydrogen and air. Results obtained confirms the importance of fuel humidification in improving the performance of the fuel cell with all levels of humidification producing better performance than that obtained using dry hydrogen or dry air. Experiments using air with 50% relative humidity indicate drop in the fuel cell performance when comparing the results to those from air with 100% relative humidity. The experimental data provides the basis to validate a computation fluid dynamics model for the fuel cell that is used to carry out further studies and conduct a parametric analysis of the fuel cell performance to examine the effects of flow plates designs, flow patterns such as parallel and counter flow and level of humidification on membrane water saturation, flooding, water management, reactants concentrations and overall cell performance by observing parameters such as membrane protonic conductivity, current density, cell voltage and power. The CFD model studies and compares the use of air and oxygen in PEM fuel cells and the results show that for 100% relative humidity the performance obtained using pure oxygen is only marginally better than the one obtained when using air. This indicates that it is more beneficial to use air at the right conditions in PEM fuel cells given the cost of pure oxygen as the overall economic balance and the ease of use favour the utilisation of air.

Numerical modelling and CFD simulation of a polymer electrolyte membrane (PEM) fuel cell flow channel using an open pore cellular foam material

Fuel cell performances vary with different structural configurations and materials. However, the two main areas that determine this performance metric are the membrane electrode assembly (MEA) and the bipolar plates. The MEA provides the platform for the electrochemical reaction to occur and the bipolar plate serves as a medium between the reactants (hydrogen and air) and the catalyst layer. The bipolar plate is the first point of contact for the reactants inside the fuel cell, so a badly designed item with a high pressure drop will have a negative impact on fuel cell performance. Numerical modelling and simulation tools like ANSYS have a huge impact on engineering industry as they help designs to be validated and analysed before any physical construction. This investigation considers five suitable flow plate designs for PEM fuel cell, each completely different from the readily available, traditional serpentine designs on the market. The work explored the possibility of replacing these flow channels with an aluminium cellular foam with different inlet and outlet orientations. The designs were further optimised and modelled in ANSYS. The results obtained were compared with other designs in the literature. Compared to the serpentine flow design, the open pore cellular foam material showed a very small pressure drop in the range of 30-40 Pa. This indicates a possibility of replacing the traditional flow plate designs with the proposed ones.

Fuzzy modeling and parameters optimization for the enhancement of biodiesel production from waste frying oil over montmorillonite clay K-30

Transesterification is a promising technology for the biodiesel production to provide an alternative fuel that considers the environmental concerns. From the economic and environmental protection points of view, utilization of waste frying oil for the production of biodiesel addresses very beneficial impacts. Production of higher yield of biodiesel is a challenging process in order to commercialize it with a lower cost. The current study focuses on the influence of different parameters such as reaction temperature (°C), reaction period (min), oil to methanol ratio and amount of catalyst (wt%) on the production of biodiesel. The main objective of this work is to develop a model via fuzzy logic approach in order to maximize the biodiesel produced from waste frying oil using montmorillonite Clay K-30 as a catalyst. The optimization for the operating parameters has been performed via particle swarm optimization (PSO) approach. During the optimization process, the decision variables were represented by four different operating parameters: temperature (40-140 °C), reaction period (60-300 min), oil/methanol ratio (1:6-1:18) and amount of catalyst (1-5 wt%). The model has been validated with the experimental data and compared with the optimal results reported based on other optimization techniques. Results showed the increment of biodiesel production by 15% using the proposed strategy compared to the earlier study. The obtained biodiesel production yield reached 93.70% with the optimal parameters for a temperature at 69.66 °C, a reaction period of 300 min, oil/methanol ratio of 1:9 and an amount of catalyst of 5 wt%.

Potential of tri-reforming process and membrane technology for improving ammonia production and CO2 reduction

In this work, a tri-reforming process was coupled with a membrane separation unit to enhance efficiency of ammonia (NH₃) synthesis process in terms of CO₂ emission, NH₃ production, and NO_x emission. Primary and secondary reformers were replaced by a tri-reforming process, while a Perovskite membrane was applied to separate nitrogen (N₂) from oxygen (O₂). A conventional NH₃ synthesis process and the proposed process were simulated by Aspen-Hysys and compared in order to investigate the performance of the proposed sterategy. The simulation results indicated that when temperature increased and pressure decreased, conversion of hydrocarbons and H₂/CO ratio were improved from 1.73 to 2.54, which resulted in an increase in NH₃ production by 27 %, and a decrease in CO₂ emission rate from 1192 kg/h to approximately 1 kg/h. The proposed sterategy was optimized in terms of different parameters e.g., temperature and pressure. Optimum reaction pressure and temperature were determined to be between 1 and 10 bar and 500-800 °C, respectively. The results of the study revealed that the proposed strategy not only removed amine and methanol sweeteners which reduce the operational costs of the process, but also decreased the NO_x content from 8220 ppm to almost 10 ppm.

Prospects and challenges of concentrated solar photovoltaics and enhanced geothermal energy technologies

Reducing the total emissions of energy generation systems is a pragmatic approach for limiting the environmental pollution and associated climate change problems. Socio economic activities in the 21st century is highly determined by the energy generation mediums, particularly the renewable resources, across the world. Therefore, a thorough investigation into the technologies used in harnessing these energy generation mediums should contribute to their further advancement. Concentrated Solar Photovoltaics (CSP) and Enhanced Geothermal Energy (EGE) are considered as emerging renewable energy technologies with high potential to be used as suitable replacements for fossil products (petroleum, coal, natural gas etc.). Despite the accelerated developments in these technologies, they are still facing many challenges in terms of cost. This review paper presents a detailed background about these renewable energy technologies and their main types such as solar tower, parabolic trough, and so on. Also, the principle challenges impeding the advancement of these energy technologies into commercialisation are discussed. Possible solutions for the main challenges are presented and the future prospects for such energy generation mediums are reported.

Improving the environmental impact of palm kernel shell through maximizing its production of hydrogen and syngas using advanced artificial intelligence

Fossil fuel depletion and the environmental concerns have been under discussion for energy production for many years and finding new and renewable energy sources became a must. Biomass is considered as a net zero CO₂ energy source. Gasification of biomass for H₂ and syngas production is an attractive process. The main target of this research is to improve the production of hydrogen and syngas from palm kernel shell (PKS) steam gasification through defining the optimal operating parameters' using a modern optimization algorithm. To predict the gaseous outputs, two PKS models were built using fuzzy logic based on the experimental data sets. A radial movement optimizer (RMO) was applied to determine the system's optimal operating parameters. During the optimization process, the decision variables were represented by four different operating parameters. These parameters include; temperature, particle size, CaO/biomass ratio and coal bottom ash (CBA) with their operating ranges of (650-750 °C), (0.5-1 mm), (0.5-2) and wt% (0.02-0.10), respectively. The individual and interactive effects of different combinations were investigated on the production of H₂ and syngas yield. The optimized results were compared with experimental data and results obtained from Response Surface Methodology (RSM) reported in literature. The obtained optimal values of the operating parameters through RMO were found 722 °C, 0.92 mm, 1.72 and 0.06 wt% for the temperature, particle size, CaO/biomass ratio and coal bottom ash, respectively. The results showed that syngas production was significantly improved as it reached 65.44 vol% which was better than that obtained in earlier studies.

Outlook of carbon capture technology and challenges

The greenhouse gases emissions produced by industry and power plants are the cause of climate change. An effective approach for limiting the impact of such emissions is adopting modern Carbon Capture and Storage (CCS) technology that can capture more than 90% of carbon dioxide (CO₂) generated from power plants. This paper presents an evaluation of state-of-the-art technologies used in the capturing CO₂. The main capturing strategies including post-combustion, pre-combustion, and oxy - combustion are reviewed and compared. Various challenges associated with storing and transporting the CO₂ from one location to the other are also presented. Furthermore, recent advancements of CCS technology are discussed to highlight the latest progress made by the research community in developing affordable carbon capture and storage systems. Finally, the future prospects and sustainability aspects of CCS technology as well as policies developed by different countries concerning such technology are presented.

Mechanical pretreatment of waste paper for biogas production

In the anaerobic digestion of lignocellulosic materials such as waste paper, the accessibility of microorganisms to the fermentable sugars is restricted by their complex structure. A mechanical pretreatment with a Hollander beater was assessed in order to reduce the biomass particle size and to increase the feedstock' specific surface area available to the microorganisms, and therefore improve the biogas yield. Pretreatment of paper waste for 60min improves the methane yield by 21%, from a value of 210ml/gVS corresponding to untreated paper waste to 254ml/gVS. 30min pretreatment have no significant effect on the methane yield. A response surface methodology was used to evaluate the effect of the beating time and feedstock/inoculum ratio on the methane yield. An optimum methane yield of 253ml/gVS was achieved at 55min of beating pretreatment and a F/I ratio of 0.3.