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Hydrogen (H 2) is pivotal to phasing out fossil fuel-based energy systems. It can be produced from different sources and using different technologies. Very few studies comprehensively discuss all available state-of-the-art technologies for H 2 production, the challenges facing each process, and their economic feasibility and sustainability. The current study thus addresses these gaps to effectively direct future research towards improving H 2 production techniques. Many conventional methods contribute to large greenhouse gas footprints, with high production costs and low efficiency. Steam methane reforming and coal gasification dominate the supply side of H 2 , due to their low production costs (<$3.50/kg). Water-splitting offers one of the most environmentally benign production methods when integrated with renewable energy sources. However, it is considerably expensive and ridden with the flaw of production of harmful by-products that affect efficiency. Fossil fuel processing technologies remain one of the most efficient forms of H 2 production sources, with yields exceeding 80% and reaching up to 100%, with the lowest cost despite their high reliance on expensive catalysts. Whereas solar-driven power systems cost slightly less than $10 kg−1, coal gasification and steam reforming cost below $3.05 kg−1. Future research thus needs to be directed towards cost reduction of renewable energy-based H 2 production systems, as well as in their decarbonization and designing more robust H 2 storage systems that are compatible with long-distance distribution networks with adequate fuelling stations. • H 2 production technologies, their economic feasibility and sustainability are reviewed. • Low-cost steam methane reforming and coal gasification dominate the supply side of H 2. • Water-splitting coupled with renewable sources offers one of the most eco-friendly methods. • Future research should focus on decarbonizing and lowering renewable H 2 production cost. [ABSTRACT FROM AUTHOR]

Microalgae originating from wastewater has been exhibiting particularly promising results in terms of biohydrogen production and wastewater treatment. This paper aims to review the factors affecting production, pretreatment techniques to improve synthesis, advanced technologies utilized for enhancing biohydrogen production, and techno-economic feasibility evaluation of the processes at a commercial scale. Microalgae possess metabolic components to synthesize biohydrogen using photobiological and fermentative processes but must undergo pretreatment for efficient biohydrogen production. The efficiency of these processes is influenced by factors such as the microalgae species, light intensity, cell density, pH, temperature, substrates, and the type of bioreactors. Moreover, many limitations, such as oxygen sensitivity, altered thylakoid constitution, low photon conversion efficiency, light capture disruption, and the evolution of harmful by-products hinder the sustainability of biohydrogen production processes. High operational and maintenance costs serve as the major bottleneck in the scaling up of the process as an industrial technology. Therefore, future research needs to be directed towards increasing optimization of the processes by reducing energy and resource demand, recycling metabolic wastes and process components, genetically engineered microalgae to adopt more efficient routes, and conducting pilot studies for commercialization. • Wastewater-based microalgae is a potential source of biohydrogen. • Factors affecting the biohydrogen production from microalgal biomass are discussed. • Technologies related to biohydrogen production from microalgae are reviewed. • Key challenges of biohydrogen production process from microalgae are highlighted. [ABSTRACT FROM AUTHOR]

Microplastic pollution has emerged as a new environmental concern due to our reliance on plastic. Recent years have seen an upward trend in scholarly interest in the topic of microplastics carrying contaminants; however, the available review studies have largely focused on specific aspects of this issue, such as sorption, transport, and toxicological effects. Consequently, this review synthesizes the state-of-the-art knowledge on these topics by presenting key findings to guide better policy action toward microplastic management. Microplastics have been reported to absorb pollutants such as persistent organic pollutants, heavy metals, and antibiotics, leading to their bioaccumulation in marine and terrestrial ecosystems. Hydrophobic interactions are found to be the predominant sorption mechanism, especially for organic pollutants, although electrostatic forces, van der Waals forces, hydrogen bonding, and pi-pi interactions are also noteworthy. This review reveals that physicochemical properties of microplastics, such as size, structure, and functional groups, and environmental compartment properties, such as pH, temperature, and salinity, influence the sorption of pollutants by microplastic. It has been found that microplastics influence the growth and metabolism of organisms. Inadequate methods for collection and analysis of environmental samples, lack of replication of real-world settings in laboratories, and a lack of understanding of the sorption mechanism and toxicity of microplastics impede current microplastic research. Therefore, future research should focus on filling in these knowledge gaps. [Display omitted] • This review investigates MPs to guide better policy action toward MP management. • MPs absorb pollutants like persistent organic pollutants, heavy metals, and antibiotics. • Hydrophobic interactions are the primary sorption mechanism for organic pollutants. • MPs influence the growth and metabolism of organisms. • Innovative sampling and analytical methods are needed to identify MP sources. [ABSTRACT FROM AUTHOR]

Emerging contaminants (ECs) are increasingly recognized as threats to human health and ecosystems. This review evaluates advanced analytical methods, particularly mass spectrometry, for detecting ECs and understanding their toxicity, transformation pathways, and environmental distribution. Our findings underscore the reliability of current techniques and the potential of upcoming methods. The adverse effects of ECs on aquatic life necessitate both in vitro and in vivo toxicity assessments. Evaluating the distribution and degradation of ECs reveals that they undergo physical, chemical, and biological transformations. Remediation strategies such as advanced oxidation, adsorption, and membrane bioreactors effectively treat EC-contaminated waters, with combinations of these techniques showing the highest efficacy. To minimize the impact of ECs, a proactive approach involving monitoring, regulations, and public education is vital. Future research should prioritize the refining of detection methods and formulation of robust policies for EC management. [Display omitted] • Emerging contaminants (ECs) pose significant risks to aquatic ecosystems and human health. • Advanced analytical techniques are effective in detecting ECs in diverse environments. • A comprehensive strategy is most effective for remediating EC-contaminated water. • Future research must focus on detection, source control, monitoring, and public engagement. [ABSTRACT FROM AUTHOR]

Turbulent flows play a major role in many fields of science and industry. Noticeable attention is seen on turbulent flows of suspending fibers because of the sensitivity of the electrical, thermal, and mechanical properties of the connecting fiber composites to the spatial configuration and orientation of fibers. The involvement of fibers in the turbulent flow greatly affects the turbulent energy. It is more influenced when the turbulent flow occurs in a rotating system. The effect of fibers on the turbulent energy in the rotating frame must therefore be investigated. For turbulent energy with fiber suspension, a mathematical model can be built in a rotating system that is very important to enhance the quality of industrial goods. This paper, therefore, develops a mathematical model for turbulent energy motion in a rotating frame with a fiber suspension. The model was formulated using the averaging procedure. The momentum equation for incompressible and viscous fluid turbulent flow was considered to develop the model. The turbulent energy motion of the fiber suspensions was presented in the rotating frame in second-order correlation tensors, W i , j , S i , j , L i , j , F i , j , G i , j , D i , j , Q i , j , and H i , j , where all the tensors are the function of time, distance, and space coordinates. [ABSTRACT FROM AUTHOR]

This paper offers a comprehensive analysis of algal-based membrane bioreactors (AMBRs) and their potential for removing hazardous and toxic contaminants from wastewater. Through an identification of contaminant types and sources, as well as an explanation of AMBR operating principles, this study sheds light on the promising capabilities of AMBRs in eliminating pollutants like nitrogen, phosphorus, and organic matter, while generating valuable biomass and energy. However, challenges and limitations, such as the need for process optimization and the risk of algal-bacterial imbalance, have been identified. To overcome these obstacles, strategies like mixed cultures and bioaugmentation techniques have been proposed. Furthermore, this study explores the wider applications of AMBRs beyond wastewater treatment, including the production of value-added products and the removal of emerging contaminants. The findings underscore the significance of factors such as appropriate algal-bacterial consortia selection, hydraulic and organic loading rate optimization, and environmental factor control for the success of AMBRs. A comprehensive understanding of these challenges and opportunities can pave the way for more efficient and effective wastewater treatment processes, which are crucial for safeguarding public health and the environment. [Display omitted] • Algal-based MBRs effectively remove hazardous contaminants. • Challenges remain in biomass accumulation, nutrient limitation, and toxicity. • Mitigation strategies include system optimization and use of renewable energy. • Potential applications beyond wastewater treatment include biofuel and bioproduct production. [ABSTRACT FROM AUTHOR]

Abstract There are numerous different sorts of pre-treatment technique have been utilized with a few impediments regarding supportable natural administration in anaerobic assimilation for improvement of biogas generation. Albeit corrosive and salt pretreatment have a huge impact on the corruption of biomass, these techniques have some negative effects on the condition because of their perilous nature, while the enzymatic pre-treatment is more environmentally friendly. In this investigation is to streamline the biogas generation by enzymatic pre-treatment from Palm Oil Mill Effluent (POME) with assessing the improved biogas creation in a pilot scale bioreactor. It is to concentrate coordinate utilization of protein as enzymatic pre-treatment on POME to the improved generation of biogas. Proficiency of privately manufactured chemical with Up-flow Sludge Blanket (UASB) has not been researched in pilot scale previously. In this examination proficiency of COD expulsion and aggregate methane emanation is explored through pilot scale UASB bioreactor from POME through the application of enzyme and reviewed a study with the discussion. [ABSTRACT FROM AUTHOR]

Abstract The oil from waste coffee possesses the potential as a feedstock for biodiesel production. In this study, waste coffee grounds were collected from Turkey. Then the oil was extracted from waste coffee grounds using N-hexane. The two-step acid-base catalyst transesterification process was used to produce biodiesel as the acid value of the crude oil was found higher (15.4 mgKOH/g).This was followed by an investigation of some physical and chemical properties. It was found that the properties of waste coffee biodiesel fell within the limit of ASTM standards. So the studied physicochemical properties of the waste coffee biodiesel suggest that this fuel can be used as a fuel in diesel engines. [ABSTRACT FROM AUTHOR]

Abstract Global energy demand has risen sharply over the years with developing countries recording the greatest share in this trend. Biomass as an energy resource is mostly available locally and can easily be converted into secondary energy without huge capital investments. Nowadays, Bangladesh shares a percentage of renewable energy only 3% of total energy ratio, Bangladesh has already taken a master plan in the renewable energy sector. Whereas installed electricity generation installed capacity of Bangladesh rapidly increased to 13265 MW with captive generation capacity which is insufficient for fulfilling the demand of electricity of the nations. One-third of the power production of Bangladesh depends on expensive imported fossil fuel energy resources and 65% of power generation depends on a natural gas reserve of the country, though one day the reserve of current gas will be diminished. Moreover, inadequate electricity production leads the country in a un-industrialization. The present and future crucial energy crisis situation adapted by installing renewable power into electricity production. The current renewable energy agenda of Bangladeshi government force the specialization of renewable energy generation budget by decreasing global pollution with saving movement of biomass, solar, hydro, wind, and tidal power sector. This paper presents the currents national energy scenario of Bangladesh. According to this, the greater potentiality of renewable energy resources is also reviewed and presented in this paper. [ABSTRACT FROM AUTHOR]

Abstract Presently, the crisis of energy has become a growing concern all over the world and a serious barrier for the developing nations. Conversely, the resources of fossil fuels are limited and depleting due to the exploration and higher production activities around the glove. The impact of fossil fuels exploration has become a serious threat for naturalism and creates environmental hazardous accidents. However, the demand for energy in Bangladesh is increasing day by day and fossil fuel reserves continue the countries demand almost only 50 years. So, it is the high time to utilize its natural biomass resources to fulfill energy demand. The climate condition and waste generation rate of Bangladesh is key factors for biomass energy production. Nowadays the Bangladeshi government has made an agenda "waste to electricity" thus the utilization of biomass resources has become a blessing for the static economic growth in the nation. Recently Bangladeshi government has made an extra effort for the commercialization and marketable of biomass energy engendering and production in the country. This paper explored the potential of biomass energy as a sustainable energy source and their future implementation challenges in Bangladesh. [ABSTRACT FROM AUTHOR]

Abstract Household waste generation has become a serious environmental issue in recent years. However, some technologies are available to convert household domestic waste into energy. One of such techniques is the biogas generation using household waste. The biogas generation technique is not a new method of energy generation, but its production efficiency is questionable. Biogas yield from domestic waste are influenced by pH level, temperature, HRT and C/N ratio. Moisture and the temperature levels in the biogas generation systems are very critical to its production efficiency, especially this is highly affected in the colder weather condition. Solar assisted biogas plant may provide better production efficiency compared to the traditionally designed biogas plant. In this paper, the scopes and opportunities of solar assisted biogas generation are reviewed. Possible benefits and challenges associated with the solar assisted biogas generation are highlighted. [ABSTRACT FROM AUTHOR]

Abstract This paper studied the production of waste cooking biodiesel as an alternative fuel for diesel engine. The biodiesel was produced through conventional transesterification process using the base catalyst (KOH). A multi-cylinder diesel engine was used to evaluate the emission of 20% (B20) waste cooking biodiesel fuel at different engine speeds and full load condition. It was found that the characteristics of biodiesel are within the limit of specified standards (American Society for Testing and Materials, ASTM D6751) and comparable to diesel fuel. Engine emission results indicated that waste cooking biodiesel fuel sample reduces the average carbon monoxide (CO) and particulate matter (PM) emissions except nitrogen oxides (NO x) than diesel fuel. Finally, it can be concluded that 20% of waste cooking biodiesel can significantly contribute to lower the harmful emission of an unmodified stationary diesel engine to the environment. [ABSTRACT FROM AUTHOR]

Abstract Increasing global energy demand at a rate faster than the population growth has led the researcher to look for alternative fuel. Amongst the options, biodiesel is an environmentally sustainable substitute of diesel fuel being renewable, biodegradable and have similar properties of fossil diesel. Among the biodiesel sources, microalgae is a potential third generation biodiesel feedstock which can be produced throughout the year and its oil yield is higher than any other crops. This paper reviews recent development in microalgae biodiesel in terms of its oil extraction technics, challenges of oil extraction, production of biodiesel from microalgae oil and its fuel properties. Finally, the paper discusses the performance and combustion analysis of diesel engine fuelled with microalgae biodiesel. This paper provides a clear understanding of the potential use of microalgae biodiesel as an alternative source to fossil diesel for diesel engines. [ABSTRACT FROM AUTHOR]

[Display omitted] • Marine emission possesses both environmental and human health risks. • Alternative fuels including hydrogen can reduce harmful emissions from marine transport. • Alternative fuels have the potential to promote UN Sustainable Development Goals. • The potential challenges of alternative fuel in marine transport are highlighted. The International Maritime Organization (IMO) has placed stricter controls on several aspects of global maritime transport operations to protect the environment. In light of this, the goal of this study is to examine and assess the different prospective paths and technologies that will assist the shipping industry in decarbonizing its operations. We consider how the utilisation of various alternative energy sources reduces greenhouse gas (GHG) emissions from marine transportation and contributes to the promotion of the United Nations Sustainable Development Goals (SGDs). The complexities associated with maritime industry operations using alternative energy sources are also explored. Biofuel as an alternative energy source, including biomethanol and biodiesel, can reduce greenhouse gas emissions in the shipping industry by 25% to 100%. However, the current supply of biofuels can only meet about 15% of the total demand which is not sufficient to sustainably power the entire marine fleet. There are several issues associated with these biofuels, including oxidation, ecological consequences, feedstock availability, technical and operational constraints, and economic factors that must be addressed before their full potential may be achieved. [ABSTRACT FROM AUTHOR]

• Novel conceptual methods for tuning microalgae to aviation biofuel were presented. • Conversion methods that directly act on wet algae biomass are highly desired. • Chemical methods are able to obtain a maximum lipid yield of 98% • Microalgae bio-jet fuel parameters are compiled with ASTM standards. • Zeolite catalytic pyrolysis increased the bio-oil yield from Microalgae to 80 %. Concerns have been raised about the effects of fossil fuel combustion on global warming and climate change. Fuel consumer behavior is also heavily influenced by factors such as fluctuating fuel prices and the need for a consistent and reliable fuel supply. Microalgae fuel is gaining popularity in the aviation industry as a potential source of energy diversification. Microalgae can grow in saltwater or wastewater, capture CO 2 from the atmosphere and produce lipids without requiring a large amount of land. As a result, the production of oil from microalgae poses no threat to food availability. The low carbon footprint of microalgae-derived fuels has the potential to mitigate the impact of traditional aviation fuels derived from petroleum on climate change and global warming. Therefore, aviation fuels derived from microalgae have the potential to be a more environmentally friendly and sustainable alternative to conventional fuels. Gathering microalgal species with a high lipid content, drying them, and turning them into aviation fuel is an expensive process. The use of biofuels derived from microalgae in the aviation industry is still in its infancy, but there is room for growth. This study analyses the potential routes already researched, their drawbacks in implementation, and the many different conceptual approaches that can be used to produce sustainable aviation fuel from microalgal lipids. Microalgae species with fast-growing rates require less space and generate lipids that can be converted into biofuel without imperiling food security. The key challenges in algal-based aviation biofuel include decreased lipid content, harvesting expenses, and drying procedure that should be enhanced and optimized to increase process viability. [ABSTRACT FROM AUTHOR]

• Second-generation feedstocks have potential to be used as aviation fuel. • A multicriteria decision analysis tool is used to assess the suitability of the feedstocks. • The fatty acid-based properties of more than 50% feedstocks meet international biofuel standards. • The modification of some fuel properties is needed to meet the strict aviation fuel standards. This paper examines the potential of suitable second-generation feedstocks for sustainable aviation fuel production, theoretically based on fatty acid-based fuel properties. The fatty acid composition of 38 s-generation feedstocks was collected from the literature. The fuel properties of these feedstocks were then calculated using empirical formula and assessed according to international fuel standards including American and European standards. The selected feedstocks were assessed and ranked using a multi-criteria decision analysis (MCDA) tool, i.e., PROMETHEE GAIA, to identify the suitability of the sources based on kinematic viscosity (KV), density (D), higher heating value (HHV), cetane number (CN), iodine value (IV), oxidation stability (OS), and cold filter plugging point (CFPP). It was found that 20 of the 38 feedstocks meet international fuel standards. The utilisation of the MCDA tool indicates that Ricinus communis is the highest-ranked feedstock for sustainable aviation fuel production, followed by the Azadirachta indica feedstock, with Sterculia feotida L. the lowest-ranked feedstock. The assessment of the properties of ranked feedstock against aviation fuel standards, including Jet A and Jet A1, reveals that the kinematic viscosity of all the feedstocks meets both these standards. However, fatty acid-based fuel properties could not satisfy the international aviation fuel standards for D, HHV, and freezing points. Further experimental work is recommended, including improvements in the processing and modification of biofuel produced from second-generation feedstocks. It is recommended that a comprehensive action plan is required to facilitate the introduction of sustainable biofuel from non-edible sources for the aviation industry, such as the adjustment of the current jet fuel standards. [ABSTRACT FROM AUTHOR]

• P and K recovery from actual swine wastewater was found to be feasible. • The maximum recoveries were 97.8% and 69.1% for P and K, respectively. • The recovered K-struvite pellets had low water content (5.5%) and high purity (71.8%). • FBHG recovery can yield a profit of 0.126USD/m3-swine wastewater. The last few decades have seen the critical role of global cattle industry in agricultural development. However, while giving prosperity and significant benefits to the countryside, the industry also produces wastewater streams, that cause eutrophication in water bodies. The streams, if treated effectively, could act as a valuable nonconventional water source to help address the global freshwater crisis. Moreover, resources recovered from these wastewater streams, e.g., potassium (K) and phosphorus (P), could be converted to valuable commodities such as fertilizers. We, therefore, propose to use a continuous K–struvite granulation process as an effective method for the treatment of swine wastewater (SW) and recovery of K–struvite. Results show that the P and K were efficiently removed and that wastewater-derived K–struvite is a promising green chemistry agent for a slow–release, reinforcing a promising pathway to global P and K conservation. The fluidized-bed homogeneous granulation (FBHG) has recently emerged as an advanced metal recovery technology with high efficiencies for several metals and low moisture products. Based on the principle of chemical precipitation, FBHG technology requires less chemicals while producing insignificant amounts of sludge, thereby alleviating burden on sludge management often encountered in conventional chemical precipitation and others. Herein, we investigate the potential use of FBHG technology for simultaneous recovering K and P while treating swine wastewater. The recovered products are in the form of K–struvite pellets having a studded quasi-spherical form with a rough surface and sharp spikes that resemble sea urchins. The pellets are almost free of heavy metals, which make them promising candidates for use as fertilizer without significant harm. We observed that the release of K was faster than that of P. The formation, size, morphology, purity, and crushing strength of the pellets greatly affected the up-flow velocity value condition. The FBHG could potentially be scaled up for more extensive nutrient recovery. [Display omitted] [ABSTRACT FROM AUTHOR]

Bio-electrochemical systems, such as microbial fuel cells (MFCs), serve as greener alternatives to conventional fuel energy. Despite the burgeoning review works on MFCs, comprehensive discussions are lacking on MFC designs and applications. This review paper provides insights into MFC applications, substrates used in MFC and the various design, technological, and chemical factors affecting MFC performance. MFCs have demonstrated efficacy in wastewater treatment of at least 50% and up to 98%. MFCs have been reported to produce ∼30 W/m2 electricity and ∼1 m3/d of biohydrogen, depending on the design and feedstock. Electricity generation rates of up to 5.04 mW/m−2–3.6 mW/m−2, 75–513 mW/m−2, and 135.4 mW/m−2 have been found for SCMFCs, double chamber MFCs, and stacked MFCs with the highest being produced by the single/hybrid single-chamber type using microalgae. Hybrid MFCs may emerge as financially promising technologies worth investigating due to their low operational costs, integrating low-cost proton exchange membranes such as PVA-Nafion-borosilicate, and electrodes made of natural materials, carbon, metal, and ceramic. MFCs are mostly used in laboratories due to their low power output and the difficulties in assessing the economic feasibility of the technology. The MFCs can generate incomes of as much as $2,498.77 × 10−2/(W/m2) annually through wastewater treatment and energy generation alone. The field application of MFC technology is also narrow due to its microbiological, electrochemical, and technological limitations, exacerbated by the gap in knowledge between laboratory and commercial-scale applications. Further research into novel and economically feasible electrode and membrane materials, the improvement of electrogenicity of the microbes used, and the potential of hybrid MFCs will provide opportunities to launch MFCs from the laboratory to the commercial-scale as a bid to improve the global energy security in an eco-friendly way. [Display omitted] • MFCs, serve as greener alternatives to conventional fuel energy. • 30 days of MFC operation can yield up to 10.38 mA current and remove 94.3% of COD by bacterial strains. • MFCs are capable of generating ∼30 W/m2 of electricity and ∼1 m3/d of biohydrogen. • MFCs have a wastewater treatment efficacy of at least 50% and up to 98%. • MFC technology is narrow due to its microbiological, electrochemical, and technological limitations. [ABSTRACT FROM AUTHOR]

• Physical and chemical pretreatment show great effectiveness but need huge energy. • Biological pretreatment can address most challenges but with long incubation times. • Hybrid technologies gain popularity and improve the chemical yield. • Pretreatment of lignocellulosic biomass account for 40% of total production costs. • Optimization of process parameters need for techno-economically feasible. As the world attempts to transition from fossil fuels, lignocellulosic biomass (LCB) serves as a promising alternative due to its high abundance. Hydrolysing LCB can generate various bioproducts, such as biofuels and value-added chemicals. However, the presence of lignin inhibits the solubilization of LCBs, presenting a major techno-economic challenge in the biorefinery concept. Therefore, this paper addresses the gaps left by most of the recent review works that fail to comprehensively review different pretreatment methods and the full scope of applications of LCBs, and do not incorporate techno-economic considerations of the technologies, the latter being the greatest bottleneck in the commercialization of the processes. The literature review revealed that while many of the physical and chemical pretreatment methods exhibit great effectiveness, they have a huge dependence on energy, chemicals, water, and/or specialized equipment, and produce harmful waste and inhibitory compounds. The pretreatment of lignocellulosic biomass can account for 40% of total production costs. Biological pretreatment can address these challenges but is limited by long incubation times. For instance, the bacterial pretreatment can noticeably reduce sawdust cellulose, hemicelluloses, and lignin contents by 35.8%, 37.1%, and 46.2%, respectively. Recently, integrated/coupling (hybrid) methods, such as chemical-assisted liquid hot water/steam and microwave or ultrasound-assisted alkaline pretreatment, have been gaining popularity due to their potential to improve chemical yield, but at the expense of the high cost of operation. To make pretreatment processes more techno-economically feasible, there is a need for process integration and the standardization and optimization of process parameters. [ABSTRACT FROM AUTHOR]

Exhaust emission from transportation sector affects the human health. It is the main contributor to degrade the air quality. Biofuel is promising alternative to maintain both human health and environment quality better by reducing harmful emission from biofuel runs diesel engines. This study explores the global and Australian greenhouse gas (GHG) emission scenario along with the contribution of transportation sector to the GHG emission in Australia. Besides, the world biofuel standard with the target and mandate taken by the government of different countries to use biofuel are also discussed in the paper. This review indicated that engine emission is dependant on some factors such as engine operating condition, biofuel types, blending etc. Both biodiesel–diesel and ethanol–biodiesel–diesel blending plays a significant role in reducing the exhaust gas emission such as carbon monoxides (CO), hydrocarbons (HC), particulate matter (PM). But ethanol–biodiesel–diesel and biodiesel–diesel blends produce higher carbon dioxides emission, which is absorbed by the crops and considered as lower net CO 2 emission. Finally, about 5–10% of ethanol with 20–25% biodiesel can be added with petro-diesel effectively and efficiently to reduce global GHG emission, thus to maintain environment and human health better. [ABSTRACT FROM AUTHOR]

This paper examines the performance and emission characteristics of biodiesel produced from edible oil source (palm) and non-edible oil source (Jatropha) and compared that with fossil diesel fuel. Only 20% palm and 20% Jatropha biodiesel (described by PB20 and JB20 respectively) were examined because it has been suggested by the commercial company that up to 20% biodiesel can be used in a diesel engine without any engine modification. The physical and chemical properties of PB20 & JB20 are also presented and compared with diesel fuel (B0). The performance of these fuels and their emissions were measured in a multi-cylinder diesel engine at different engine speeds and at full load condition. The test results indicated that both PB20 and JB20 fuels produces slightly lower brake powers and higher brake specific fuel consumption compared to diesel fuel. Engine emission results indicated that the PB20 and JB20 fuel reduces the average emissions of carbon monoxide (CO) and hydrocarbons (HC). However, the PB20 and JB20 fuels slightly increases nitric oxides (NO) emissions compared to diesel fuel. Although PB20 have slightly better emission performance than JB20 biodiesel, JB20 biodiesel should be used in unmodified diesel engines to meet the global energy demand and to reduce emissions into the atmosphere because it does not create food versus fuel conflict. [ABSTRACT FROM AUTHOR]

Vehicles are the main sources for environmental pollution especially those associated with diesel engines. It causes a number of health diseases and harm to the ecosystem. It is very urgent to find alternative fuel for vehicles. Biofuel is an alternative for vehicles which have potential to reduce engine emissions and maintain the air quality better. In recent years, worldwide biofuel production and use raised drastically. Some developed countries have put their target and mandate to use biofuel. The aim of this review is to discuss the impact of biofuel on diesel engines emission. From this review it is found that biofuel significantly reduces engine emissions and it has potential to reduce more than 80% of GHG emission. Finally, biofuel can be a viable alternative to be used as a transportation fuel. [ABSTRACT FROM AUTHOR]

In this study, the oil extraction process from Australian native beauty leaf seed has been optimised in terms of seed preparation and cracking, seed kernel treatment, moisture content and oil extraction methods. Two methods: mechanical oil extraction using an electric powered screw press and chemical oil extraction using n-hexane as an oil solvent have been applied to extract oil from the seed kernel. Both whole and grated kernels have been used for mechanical oil extraction process. The study indicated that treatment of seed kernel has a significant impact on oil yields for both techniques. It has been observed that kernels prepared to 15% moisture content provided the highest oil yields for both extraction methods. Mechanical extraction using the screw press could produce oil from the prepared kernels at a low cost. In addition, it has been obtained that oil yields by using grated kernels were relatively higher than the whole kernels. However, oil extraction by using this technique is ineffective due to relatively lower oil yields compared to chemical extraction. On the other hand, chemical extraction was found to be a very effective method for oil extraction because of its consistence performance and high oil yield, but cost of production was relatively higher due to high cost of solvent. The outcomes of this study are expected to serve as the basis on which industrial scale oil extraction can be made from beauty leaf seed. [ABSTRACT FROM AUTHOR]

Present energy situation of the world is unsustainable due to unequal geographical distribution of natural wealth as well as environmental, geopolitical and economical concerns. Ever increasing drift of energy consumption due to growth of population, transportation and luxurious lifestyle has motivated researchers to carry out research on biofuel as a sustainable alternative fuel for diesel engine. Biofuel such as biodiesel and ethanol, produced from renewable feedstock’s, are the most appropriate alternative of petroleum fuels. Government of many countries has set a target to use biofuel in transportation and industrial sectors to reduce the fossil fuel demand in their countries. This report compiled the findings on global energy scenario, potential of biofuel as a renewable energy source, biofuel policy and target of some selected countries and the effect of mixed blends of biofuel and diesel on engine performance and emission parameters of a diesel engine. The study concluded that the energy consumption and CO 2 emissions in ASEAN countries increasing day by day. To reduce the energy consumption and harmful gasses emission to the environment, government of ASEAN countries have set target to use biofuel in diesel engines as biofuel-diesel blend have potential to reduce dependency on fossil fuel as well as the exhaust emissions of the engine. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study the physical and chemical properties of Moringa oleifera biodiesel and its blends of 10%-90% by volume with petro-diesel according to the American society for testing and materials (ASTM D6751) standards and European standards (EN 14214). It was found that when Moringa biodiesel is blended with diesel fuel, all its fuel properties such as kinematic viscosity (KV), density (D), calorific value (CV), flash point (FP), cloud point (CP), pour point (PP), and cold filter plugging point (CFPP). For example, B10 reduce the viscosity of B100 from 5.05 mm 2 /s to 3.54 mm 2 /s (1.4:1). Then developed empirical models of properties are show high regression value (R 2 ) between properties and MOME-diesel blend. It is believed that the results obtained and empirical model proposed in this study will help the researchers to predict the properties of biodiesel-diesel blend which are important parameters to design the fuel system of biodiesel engine. [ABSTRACT FROM AUTHOR]

Ever increasing drift of energy consumption due to growth of population, transportation and luxurious lifestyle has motivated researchers to carry out research on biofuel as a sustainable alternative fuel for diesel engine. Biofuel such as biodiesel and ethanol, produced from renewable feedstocks, are the most appropriate alternative of petroleum fuels. However, direct using of ethanol in diesel fuel face some technical problem especially in cold weather, due to low cetane number, lower flash point and poor solubility. Biodiesel can be blended with both ethanol and diesel fuel and biodiesel–alcohol–diesel blends can be used in diesel engines. The aim of this review paper is to discuss the effect of mixed blends of biodiesel alcohol and diesel on engine performance and emission parameters of a diesel engine. Most of the researchers reported that adding ethanol into biodiesel-diesel blend in diesel engines significantly reduce HC, PM, NOx and smoke emissions but slightly increase fuel consumption. The study concluded that biodiesel-diesel-ethanol blend can be used as a substitute of petro-diesel fuel to reduce dependency on fossil fuel as well as the exhaust emissions of the engine. [ABSTRACT FROM AUTHOR]

By 2050, it is predicted that biofuels will provide 27% of total transport fuel and avoid around 2.1 Gt CO2 emissions per year when produced sustainably. Biodiesel is a renewable fuel that can be produced by trans-esterification in any climate using already developed agricultural practices. This paper aims to study various physical and chemical properties of biodiesel synthesized from edible and non-edible feedstocks. These feedstocks include Croton megalocarpus, Calophyllum inophyllum, Moringa (Moringa oleifera), palm (Elaeis guineensis) and coconut (Cocos nucifera). The physical and chemical properties of biodiesel-diesel blends were also presented. Furthermore, the regression analysis method was used to predict the properties of biodiesel blends. It has been found that blending of diesel with biodiesel has resulted in much improvement in kinematic viscosity, density, calorific value and oxidation stability. However, flash point and viscosity index decrease as the percentage of diesel increases. Moreover, the mathematical relationships developed in this study show a high regression values (R²) between properties and biodiesel-diesel blends. As a conclusion, it is believed that the outcome of this study gives the readers valuable results that help to predict the properties of biodiesel and its blends with diesel which are substantial parameters in the design of fuel system for biodiesel engine. [ABSTRACT FROM AUTHOR]

Highlights: [•] Potential of biodiesel production from crude Moringa oleifera oil. [•] Characterization of M. oleifera biodiesel and its blend with diesel fuel. [•] Evaluation of M. oleifera biodiesel blend in a diesel engine. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new method is demonstrated for selecting microalgae strain for jetfuel production. • 17 microalgae strains were evaluated against all relevant jet fuel standards. • Chlorella sp. NT8a was the most suitable but could not meet some jet fuel standards. • Further biofuel modification is needed to satisfy all jet fuel standards. This study develops and applies the PROMETHEE-GAIA method as a new tool to select microalgae strains for aviation fuel production. Assessment involves 19 criteria with equal weighting in three aspects, namely biomass production, lipid quality, and fatty acid methylester properties. Here, the method is demonstrated for evaluating 17 candidate microalgae strains. Chlorella sp. NT8a is assessed as the most suitable strain for aviation fuel production. The results also show that unmodified biofuel from the most suitable strain could not meet all jet fuel standards. In particular, microalgae-based fuel could not satisfy the required density, heating value and freezing points of the international jet fuel standards. These results highlight the need for a broad action plan including improvement in the processing or modification of biofuel produced from microalgae and revision of the current jet fuel standards to facilitate the introduction of microalgae-based biofuel for the aviation industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biorefinery concept for sustainable processing of microalgae biomass has been discussed. • Reactor technologies for cultivating microalgae has been reviewed. • Factors affecting the microalgae culture system has been reviewed. • Different technologies to convert microalgae into biofuel and value-added products have been presented. • The utilisation of a biorefinery concept can make the valorisation of microalgae economically viable. Microalgal biomass has been proved to be a sustainable source for biofuels including bio-oil, biodiesel, bioethanol, biomethane, etc. One of the collateral benefits of integrating the use of microalgal technologies in the industry is microalgae's ability to capture carbon dioxide during the application and biomass production process and consequently reducing carbon dioxide emissions. Although microalgae are a feasible source of biofuel, industrial microalgae applications face energy and cost challenges. To overcome these challenges, researchers have been interested in applying the bio-refinery approach to extract the important components encapsulated in microalgae. This review discusses the key steps of microalgae-based biorefinery including cultivation and harvesting, cell disruption, biofuel and value-added compound extraction along with the detailed technologies associated with each step of biorefinery. This review found that suitable microalgae species are selected based on their carbohydrate, lipid and protein contents and selecting the suitable species are crucial for high-quality biofuel and value-added products production. Microalgae species contain carbohydrates, proteins and lipids in the range of 8% to 69.7%, 5% to 74% and 7% to 65% respectively which proved their ability to be used as a source of value-added commodities in multiple industries including agriculture, animal husbandry, medicine, culinary, and cosmetics. This review suggests that lipid and value-added products from microalgae can be made more economically viable by integrating upstream and downstream processes. Therefore, a systematically integrated genome sequencing and process-scale engineering approach for improving the extraction of lipids and co-products is critical in the development of future microalgal biorefineries. [ABSTRACT FROM AUTHOR]

The utilization of microalgae in treating wastewater has been an emerging topic focussed on finding an economically sustainable and environmentally friendly approach to treating wastewater. Over the last several years, different types of con microalgae and bacteria consortia have been experimented with to explore their potential in effectively treating wastewater from different sources. The basic features considered while determining efficiency is their capacity to remove nutrients including nitrogen (N) and phosphorus (P) and heavy metals like arsenic (As), lead (Pb), and copper (Cu). This paper reviews the efficiency of microalgae as an approach to treating wastewater from different sources and compares conventional and microalgae-based treatment systems. The paper also discusses the characteristics of wastewater, conventional methods of wastewater treatment that have been used so far, and the technological mechanisms for removing nutrients and heavy metals from contaminated water. Microalgae can successfully eliminate the suspended nutrients and have been reported to successfully remove N, P, and heavy metals by up to 99.6 %, 100 %, and 13%–100 % from different types of wastewater. However, although a microalgae-based wastewater treatment system offers some benefits, it also presents some challenges as outlined in the last section of this paper. Performance in eliminating nutrients from wastewater is affected by different parameters such as temperature, biomass productivity, osmotic ability, pH, O 2 concentration. Therefore, the conducting of pilot-scale studies and exploration of the complexities of contaminants under complex environmental conditions is recommended. • Utilization of Microalgae is an environment-friendly method to treat the wastewater. • Microalgae removes the suspended nutrients and polluting compounds from wastewater. • The efficiency of microalgae-based wastewater treatment technology is presented. • Challenges of using microalgae in wastewater treatment is discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Crude Moringa oleifera oil as a potential feedstock for biodiesel production. [•] Production of biodiesel from Moringa oleifera oil. [•] Characterization of Moringa oleifera biodiesel. [•] Evaluation of Moringa oleifera biodiesel blend in a diesel engine. [ABSTRACT FROM AUTHOR]

Abstract: The global energy consumption is expected to grow in a faster rate than the population growth. By 2030, an increase of 53% of global energy consumption and 39% of greenhouse gases emissions from fossil fuels is anticipated. Therefore, it becomes a global agenda to develop clean alternative fuels which are domestically available, environmentally acceptable and technically feasible. As an alternative fuel, biodiesel seems as one of the best choices among other sources due to its environment friendly behavior and similar functional properties with diesel. The main objective of this paper is to discuss the impact biodiesel from different edible, non-edible and waste cooking oils feedstocks on combustion characteristics, engine durability and materials compatibility with biodiesel. Moreover, this paper reviews some other important related aspects to biodiesel such as biodiesel development, biodiesel feedstocks, biodiesel standards and advantages and challenges of biodiesel. [Copyright &y& Elsevier]

Abstract: As a promising alternative energy source, biofuel imparts a remarkable role for the sustainability and security in energy sector. Strategies, including policy recommendations have been set to put forward the development and implementation of biofuel by different countries. Recent exploitation of Asian biofuels policy is one step towards destination. These types of activity behind the biofuels would be the catalyst for the productiveness of policy set by individual territory like Malaysia, Thailand, Vietnam, etc. This is the high time to standardize, policy recommendation and implementation of biofuels taking into consideration on the feedstock, geographical location, and availability. Pertinent comparison with well-established ASTM and European standards are highly recommended. Sector wise (viz. transportation, industrial) bio fuel policy is now crucial as well. Factors, which would be taking into account, prior to recommend a policy includes feed-stocks available, biofuel infrastructure of the country, compatibility with present automotive materials and performance and emission behaviour. This study sought to explore the investigation of several policies with regards to biofuel and advocates some key factors which could be helpful for diminution of biofuels inferiorities. [Copyright &y& Elsevier]

Abstract: Global energy demand is increasing due to the population growth and industrialization. In order to fulfill the energy demand with considering global concern, it is necessary to find out alternative fuel sources. Biodiesel is one of the best choices because of its immense potential to be part of energy mix in the near future as well as the capability of reducing greenhouse gas emissions. This paper aims to provide information to the engineers, industrialists and researchers who are interested on biodiesel. The paper presents a comprehensive review on the impact of potential biodiesel feedstocks (edible and non-edible) on engine performance and exhaust emissions including details of engine and operating condition. A large number of literatures from highly rated journals in scientific indexes are reviewed including the most recent publications. Most of the authors showed that using biodiesel from various feedstocks in diesel engines slightly lowered brake power and brake thermal efficiency but increases BSFC than diesel fuel. It was also reported that biodiesel significantly reduced the PM, HC, CO and CO2 emissions but gives slightly higher NO x emissions. It was shown that NO x can be reduced by some approaches such as blending with additives and EGR technique. The study concluded that biodiesel can be used in compression ignition engine with no or minor engine modification. Finally biodiesel can be used as a substitute of diesel fuel to fulfill the energy demand, reduce dependency on fossil fuel as well as the exhaust emissions of the engine. [Copyright &y& Elsevier]

Abstract: Currently, the main crop for biodiesel in Malaysia is palm oil. Recently, Jatropha curcas has drawn the attention of the Malaysian Government. This paper aims to study the feasibility of Jatropha as a potential biodiesel feedstock for Malaysia. Physico-chemical properties of Jatropha biodiesel and its blends with diesel followed by engine performance and emissions characteristics of B10, B20 and B0 were studied. The results show that viscosities of B10 and B20 are closer to diesel. Moreover, only the oxidation stability of B10 and B20 meet the European specifications (EN 590) of 20 h. Therefore, only B10 and B20 have been used to evaluate engine performance and emission. Compared to B0, the average reduction in brake power (BP) is 4.67% for B10 and 8.86% for B20. It was observed that brake specific fuel consumption (BSFC) increases as the percentage of biodiesel increase. Compared to B0, a reduction in hydrocarbon (HC) emission of 3.84% and 10.25% and carbon monoxide (CO) emission of 16% and 25% was reported using B10 and B20. However, the blends give higher nitrogen oxides (NO x ) emission of 3% and 6% using B10 and B20. As a conclusion, B10 and B20 can be used in a diesel engine without any modifications. [Copyright &y& Elsevier]

Abstract: Alternative fuels have received much attention due to the depletion of world petroleum reserves and increased environmental concerns. Thus processed form of vegetable oil (Biodiesel) offers attractive alternative fuels to compression ignition engines. The present work investigates the engine performance parameters and emissions characteristics for direct injection diesel engine using coconut biodiesel blends without any engine modifications. A total of three fuel samples, such as DF (100% diesel fuel), CB5 (5% coconut biodiesel and 95% DF), and CB15 (15% CB and 85% DF) respectively are used. Engine performance test has been carried out at 100% load, keeping throttle 100% wide open with variable speeds of 1500 to 2400rpm at an interval of 100rpm. Whereas, engine emission tests have been carried out at 2200rpm at 100% and 80% throttle position. As results of investigations, there has been a decrease in torque and brake power, while increase in specific fuel consumption has been observed for biodiesel blended fuels over the entire speed range compared to net diesel fuel. In case of engine exhaust gas emissions, lower HC, CO and, higher CO2 and NOx emissions have been found for biodiesel blended fuels compared to diesel fuel. Moreover, reduction in sound level for both biodiesel blended fuels has been observed when compared to diesel fuel. Therefore, it can be concluded that CB5 and CB15 can be used in diesel engines without any engine modifications and have beneficial effects both in terms of emission reductions and alternative petroleum diesel fuel. [Copyright &y& Elsevier]

Abstract: The increasing energy demands along with the expected depletion of fossil fuels have promoted to search for alternative fuels that can be obtained from renewable energy resources. Biodiesel as a renewable energy resource has drawn the attention of many researchers and scientists because its immense potential to be part of a sustainable energy mix in near future. This report attempts to compile the findings on current global and Malaysian energy scenario, potential of biodiesel as a renewable energy source, biodiesel policies and standards, practicability of Jatropha curcas as a biodiesel source in Malaysia as well as impact of biodiesel from Jatropha curcas. Final part of this report also describes the development of biodiesel market in Malaysia. The paper found that Jatropha curcas is one of the cheapest biodiesel feedstock and it possesses the amicable fuel properties with higher oil contents compared to others. Being non edible oil seed feedstocks it will not affect food price and spur the food versus fuel dispute. Jatropha can be substituted significantly for oil imports. Jatropha biodiesel has potential to reduce GHG emission than diesel fuel and it can be used in diesel engine with similar performance of diesel fuel. Jatropha curcas has an immense contribution to develop rural livelihoods too. Finally biodiesel production from Jatropha is eco-friendly and offers many social and economical benefits for Malaysia and can play an increasingly significant role to fulfill the energy demand in Malaysia. [Copyright &y& Elsevier]

Abstract: The results of an experimental work carried out to evaluate the effect of palm oil methyl esters, also known as palm oil diesel (POD) and its emulsions as alternative fuel on unmodified indirect injection diesel engine''s wear and lube oil performance are presented in this paper. Half throttle engine with constant 2500 rpm setting was maintained throughout the wear debris and lube oil analysis such as for a period of twenty hours for each fuel system. The sample of lube oil was collected through a one - way valve connected to the crankcase sump at the interval of four hours. When the engine warmed up, first sample has collected immediately. The same conventional lubricating oil SAE 30 was used for each fuel system. To measure wear metal debris and lubricating oil additives depletion of used lubricating oil, Multi element oil analyzer (MOA) was used. To measure the viscosity of lub oil an ISL automatic houillon viscometer (ASTM D445) has been used. Very satisfactory results have been obtained by comparing the lub oil analysis results of Ordinary Diesel and Palm Oil Diesel and their emulsions with 10 percent water by volume. In crankcase oil samples, accumulation of wear metal debris was lower with Palm Oil Diesel and emulsified fuels compare to baseline Ordinary Diesel fuel. Both Ordinary Diesel and Palm Oil Diesel emulsions with 10 per cent water by volume showed promising trends for resisting wear. [Copyright &y& Elsevier]

Abstract: Among the alternative fuels the Bio diesel is one the most common and familiar to all. It''s biodegradable, environment friendly as well as suitable source, to meet the future energy crises. The main concern of this experimental analysis is to reach a tentative goal, how this fuel can be utilised with maximum effective way. To find this,an experiment data analysis of different parameter such as break power, break specific fuel consumption, emission characteristic(NOx, HC,CO. etc) and exhaust temperature, is done through bio diesel fuel and also compared with ordinary diesel which is also known as petro diesel. This investigation is carried out through eddy current dynamometer and load cell arrangement which is controlled by a computer in case of finding the break power and BSFC respectively. And the emission characteristics are observed using Bosch and Bacharach exhaust analyzers. And finally the result is compared with diesel engine which is run by ordinary diesel. The final result implied that the bio diesel with some additives (B20+1%) shows best performance and reduce the exhaust emission including NOx.Thus the decision may be taken,20% blended bio diesel with 1% additive as a best alternative fuel considering all the view aspects and alternatives. [Copyright &y& Elsevier]

Abstract: Experimental study has been carried out to analyze engine performance and emissions characteristics for diesel ngine using different blend fuels without any engine modifications. A total of four fuel samples, such as DF (100% iesel fuel), JB5 (5% jatropha biodiesel and 95% DF), JB10 (10% JB and 90% DF) and J5W5 (5% JB, 5% waste ooking oil and 90% DF) respectively were used in this study. Engine performance test was carried out at 100% load eeping throttle 100% wide open with variable speeds of 1500 to 2400rpm at an interval of 100rpm. Whereas, mission tests were carried out at 2300rpm at 100% and 80% throttle position. As results of investigations, the erage torque reduction compared to DF for JB5, JB10 and J5W5 was found as 0.63%, 1.63% and 1.44% and verage power reduction was found as 0.67%, 1.66% and 1.54% respectively. Average increase in bsfc compared to F was observed as 0.54%, 1.0% JB10 and 1.14% for JB5, JB10 and J5W5 respectively. In case of engine exhaust as emissions, compared to DF average reduction in HC for JB5, JB10 and J5W5 at 2300rpm and 100% throttle osition found as 8.96%, 11.25% and 12.50%, whereas, at 2300 and 80% throttle position, reduction was as 16.28%, 0.23% and 31.98% respectively. Average reduction in CO at 2300rpm and 100% throttle position for JB5, JB10 and 5W5 was found as 17.26%, 25.92% and 26.87%, whereas, at 80% throttle position, reduction was observed as 0.70%, 33.24% and 35.57%. Similarly, the reduction in CO2 compared to DF for JB5, JB10 and J5W5 at 2300rpm nd 100% throttle position was as 12.10%, 20.51% and 24.91%, whereas, at 80% throttle position, reductions was bserved as 5.98%, 10.38% and 18.49% respectively. However, some NOx emissions were increased for all blend els compared to DF. In case of noise emission, sound level for all blend fuels was reduced compared to DF. It can e concluded that JB5, JB10 and J5W5 can be used in diesel engines without any engine modifications However, 5B5 produced some better results when compared to JB10. [Copyright &y& Elsevier]

Emerging contaminants (ECs) in wastewater have recently attracted the attention of researchers as they pose significant risks to human health and wildlife. This paper presents the state-of-art technologies used to remove ECs from wastewater through a comprehensive review. It also highlights the challenges faced by existing EC removal technologies in wastewater treatment plants and provides future research directions. Many treatment technologies like biological, chemical, and physical approaches have been advanced for removing various ECs. However, currently, no individual technology can effectively remove ECs, whereas hybrid systems have often been found to be more efficient. A hybrid technique of ozonation accompanied by activated carbon was found significantly effective in removing some ECs, particularly pharmaceuticals and pesticides. Despite the lack of extensive research, nanotechnology may be a promising approach as nanomaterial incorporated technologies have shown potential in removing different contaminants from wastewater. Nevertheless, most existing technologies are highly energy and resource-intensive as well as costly to maintain and operate. Besides, most proposed advanced treatment technologies are yet to be evaluated for large-scale practicality. Complemented with techno-economic feasibility studies of the treatment techniques, comprehensive research and development are therefore necessary to achieve a full and effective removal of ECs by wastewater treatment plants. [Display omitted] • Emerging contaminants (EC) pose significant risks to public health and wildlife. • Different treatment techniques of EC in wastewater have been reviewed. • Hybrid systems have often been found to be more successful at EC removal. • Challenges of EC and direction of further research have been presented. [ABSTRACT FROM AUTHOR]

The farm animal and meat processing industry generate waste, including manure, fat, blood, sludge, bones, and wastewater, which create environmental problems worldwide. The effluents generated by this industry are rich in proteins, lipids, fibres, and carbohydrates. All these pollutants have the potential to be used as a resource for energy recovery. The organic matters obtained from the farm animal and meat processing industry are critical sources for biogas production via anaerobic digestion. This process leads to the production of energy-rich biogas, reducing greenhouse gas emissions. This study attempts to determine biogas amount and the energy value produced from the farm animal and meat processing industry in Australia. Australia's livestock population mainly consists of dairy cattle, meat cattle, sheep and lambs, pigs, layers, and meat chickens. Results show a potential biogas amount of 23,874,165 million m3 (Mm3), 215,670 Mm3, 288,228 Mm3, 18,430 Mm3, and 392,284 Mm3 can be obtained from cattle, lamb, sheep, pig, and poultry annually, respectively. The methane generated from slaughterhouse waste and wastewater is estimated to provide 4.52E+ 14 MJ/yr of heat energy with total electricity generation potential from livestock wastes of 4.4E+ 13 kWh/yr. About half of the electricity can be generated in Queensland State. Finally, the present study suggests farm animal and meat processing industry effluent as a potential sustainable energy source in Australia. [Display omitted] • Technologies for biogas production from slaughterhouse waste is presented. • Utilizing biogas as a source of power and value-added products are discussed. • Slaughterhouse waste and wastewater is a promising renewable energy source. • Biogas from slaughterhouse waste and wastewater reduces GHG emission significantly. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic has exerted great shocks and challenges to the environment, society and economy. Simultaneously, an intractable issue appeared: a considerable number of hazardous medical wastes have been generated from the hospitals, clinics, and other health care facilities, constituting a serious threat to public health and environmental sustainability without proper management. Traditional disposal methods like incineration, landfill and autoclaving are unable to reduce environmental burden due to the issues such as toxic gas release, large land occupation, and unsustainability. While the application of clean and safe pyrolysis technology on the medical wastes treatment to produce high-grade bioproducts has the potential to alleviate the situation. Besides, medical wastes are excellent and ideal raw materials, which possess high hydrogen, carbon content and heating value. Consequently, pyrolysis of medical wastes can deal with wastes and generate valuable products like bio-oil and biochar. Consequently, this paper presents a critical and comprehensive review of the pyrolysis of medical wastes. It demonstrates the feasibility of pyrolysis, which mainly includes pyrolysis characteristics, product properties, related problems, the prospects and future challenges of pyrolysis of medical wastes. [Display omitted] • Medical wastes are highly potential environmental hazards on public health risks. • Pyrolysis of medical waste together with associated problems were reviewed. • Prospects and future challenges of medical waste pyrolysis were discussed. • Pyrolysis of medical wastes presents great environmental and economic benefits. Before the COVID-19 pandemic, medical wastes were often mixed with municipal solid waste and disposed of in waste landfills or improper treatment facilities. Many reviews have been devoted to the pyrolysis of plastics and other solid wastes. However, a review on the pyrolysis potential of medical wastes has not been reported previously, prompting its publication during this pandemic. Pyrolysis of medical wastes can deal with wastes and generate valuable products like bio-oil and biochar. [ABSTRACT FROM AUTHOR]

The utilisation of available renewable resources and mitigating their impact on the environment boosts sustainable development and helps to achieve the United Nations Sustainable Development Goals. Biogas is a renewable energy option produced through anaerobic digestion of wastes such as livestock excreta and slaughterhouse wastes. Biogas production is treated as one of the leading processes to combat climate change as well as a waste management strategy, especially for a developing country like Bangladesh. It is also vital in meeting future demand for energy utilising indigenous sources. Livestock farming is an important economic activity in rural areas of Bangladesh. Thus, the livestock waste production, estimated biogas generation capacity, electricity generation potential, greenhouse gas (GHG) reduction potential, and estimated biofertiliser generation capacity of Bangladesh were determined for the financial year 2018–2019 in this study. The results show that Bangladesh had 486.77 million tons per year of animal waste products to produce 27,923.72 million m3/year biogas in 2018–2019. This biogas potential corresponds to a theoretical potential to produce a 512 PJ/year heating value and electric power of 50 TW h/year. Besides, about 29.232 million tons per year of organic fertiliser can be produced with the residues of the biogas plants. The findings of this study will contribute to guiding policymakers and governments who will concentrate on the use of animal waste in biogas industries and livestock farming as a potential bioenergy source to meet national energy demand. [Display omitted] • Biogas potential and GHG emission reduction capacity of livestock waste were estimated. • Animal wastes of Bangladesh have the potential to generate 27,923.72 million m3/year biogas. • The produced biogas can generate a heating value of 512 PJ/year and electric power of 50 TW h/year. • About 29.232 million tons/year of biofertilizer can be produced with residues of the biogas plant. [ABSTRACT FROM AUTHOR]

Biodiesel is a fuel that has numerous benefits over traditional petrodiesel. The transesterification process is the most popular method for biodiesel production from various sources, categorized as first, second and third generation biodiesel depending on the source. The transesterification process is subject to a variety of factors that can be taken into account to improve biodiesel yield. One of the factors is catalyst type and concentration, which plays a significant role in the transesterification of biodiesel sources. At present, chemical and biological catalysts are being investigated and each catalyst has its advantages and disadvantages. Recently, nanocatalysts have drawn researchers' attention to the efficient production of biodiesel. This article discusses recent work on the role of several nanocatalysts in the transesterification reaction of various sources in the development of biodiesel. A large number of literature from highly rated journals in scientific indexes is reviewed, including the most recent publications. Most of the authors reported that nanocatalysts show an important influence regarding activity and selectivity. This study highlights that in contrast to conventional catalysts, the highly variable surface area of nanostructure materials favours interaction between catalysts and substrates that efficiently boost the performance of products. Finally, this analysis provides useful information to researchers in developing and processing cost-effective biodiesel. Image 1 • Transesterification is the most efficient catalytic mechanism for biodiesel production. • Nanocatalysts show the important influence in selectivity in transesterification. • Nanocatalysts can be used at a lower temperature and speed up the reaction process. • Comparative benefits and challenges of nanocatalysts are discussed. [ABSTRACT FROM AUTHOR]

The majority of research in the carbon-based nanomaterials (CNMs) field has concentrated on the classification and synthesis of CNMs, with relatively few studies focusing on CNMs' roles in photocatalytic hydrogen production. CNMs have proven their potential as an effective addition to the appeal of photocatalytic hydrogen evolution because of their superior chemical and physical properties. This paper explores the recent advancements in photocatalytic hydrogen (H 2) production utilizing CNMs. As evidenced in the literature, carbon quantum dot (CQD)-sensitized titanium dioxide (TiO 2) can demonstrate to have a photocatalytic hydrogen generation activity of 472 mol g−1 h−1 and 1458 mol g−1 h−1 without and with loading metal co-catalyst (Pt). The optimum catalyst, 0.4 CQD/CdS, contributes to the highest H 2 production rate of 309 mmol g−1 h−1 (apparent quantum yield of 32.6%), which is 1.5 times greater than that of bare CdS. This would significantly accelerate the hydrogen production process. There are still challenges to reaching maximum photocatalytic hydrogen production, including low hydrogen storage. The overall price of hydrogen produced via photocatalysis is also higher because of the energy needed to store the hydrogen. Even though the problem is not directly related to the usage of CNMs, this restriction generates uncertainty and limits commercial investment. Given the rising demand for energy and the trend toward green power, it is recommended that extensive industrial uses of photocatalytic hydrogen produced by employing CNMs be investigated for better and more sustainable energy frameworks. • Recent advances in photocatalytic H 2 production are investigated utilizing CNMs. • The optimum catalyst, 0.4 CQD/CdS can produce the highest H 2 at 309 mmol g−1 h−1. • CQD-sensitized TiO 2 can generate 1458 mol g−1 h−1 photocatalytic hydrogen with Pt. • Photocatalytic H 2 production using CNMs should be investigated for industrial use. [ABSTRACT FROM AUTHOR]

• Physical and hybrid EAHE modelling techniques used in buildings have been reviewed. • The prospects, benefits, progress, and challenges of these modelling techniques are analyzed. • The hybrid modelling technique is found more effective based on overall performance. • Physical models offer improved performance in terms of generalization capability. Noteworthy advancements are seen in developing the earth-air heat exchanger (EAHE) models in the past several decades to reduce building energy consumption. However, it is still an ongoing challenge in selecting and implementing the most suitable and appropriate EAHE modelling technique in buildings based on the climates, performance, and limitations of the techniques. Therefore, this paper aims to review the published research related to the physical, and hybrid EAHE modelling techniques used in buildings, and highlight the prospects, benefits, progress, and challenges of these techniques. This is the first study that comprehensively evidences the prospects and technical challenges caused by unmeasured disturbances, assumptions, or the uncertainties generated in experimental and numerical works of all EAHE modelling techniques. Nevertheless, this study found that hybrid modelling is more effective than physical models for accurate prediction. On the contrary, the hybrid models suffer from high complexity if EAHE operating conditions and all key parameters are considered during the model development. Regarding the generalization capability, the physical models offer improved performance followed by the hybrid models. A minimum number of training data is needed for developing physical models, whereas medium training data is required for the hybrid models. The outcome of this study also provides valuable information regarding the physical and hybrid EAHE modelling techniques to the scientists, researchers, and so on in adopting the most appropriate EAHE modelling technique for their climates. [ABSTRACT FROM AUTHOR]

The application of waste oils as pyrolysis feedstocks to produce high-grade biofuels is receiving extensive attention, which will diversify energy supplies and address environmental challenges caused by waste oils treatment and fossil fuel combustion. Waste oils are the optimal raw materials to produce biofuels due to their high hydrogen and volatile matter content. However, traditional disposal methods such as gasification, transesterification, hydrotreating, solvent extraction, and membrane technology are difficult to achieve satisfactory effects owing to shortcomings like enormous energy demand, long process time, high operational cost, and hazardous material pollution. The usage of clean and safe pyrolysis technology can break through the current predicament. The bio-oil produced by the conventional pyrolysis of waste oils has a high yield and HHV with great potential to replace fossil fuel, but contains a high acid value of about 120 mg KOH/g. Nevertheless, the application of CaO and NaOH can significantly decrease the acid value of bio-oil to close to zero. Additionally, the addition of coexisting bifunctional catalyst, SBA-15@MgO@Zn in particular, can simultaneously reduce the acid value and positively influence the yield and quality of bio-oil. Moreover, co-pyrolysis with plastic waste can effectively save energy and time, and improve bio-oil yield and quality. Consequently, this paper presents a critical and comprehensive review of the production of biofuels using conventional and advanced pyrolysis of waste oils. [Display omitted] • The advance in the pyrolysis of waste oils is discussed in detail. • Waste oils are excellent materials for the production of biofuels. • Plastic wastes are the optimal co-feedstocks for the pyrolysis with waste oils. • SBA-15@MgO@Zn is the best catalyst for the pyrolysis of waste cooking oil. • Catalytic co-pyrolysis of hazardous waste oils is economical and feasible. [ABSTRACT FROM AUTHOR]

[Display omitted] • Continuous algae growth could be achieved by MPR using sludge centrate. • Nutrient loading had indiscernible impact on biomass growth. • Nutrient removal efficiency increased as nutrient loading rate decreased. • Nutrient removal efficiency increased as HRT increased. • Backwashing completely restored water flux decline caused by microalgae deposition. This study aims to evaluate the performance of C. vulgaris microalgae to simultaneously recover nutrients from sludge centrate and produce biomass in a membrane photobioreactor (MPR). Microalgae growth and nutrient removal were evaluated at two different nutrient loading rates (sludge centrate). The results show that C. vulgaris microalgae could thrive in sludge centrate. Nutrient loading has an indiscernible impact on biomass growth and a notable impact on nutrient removal efficiency. Nutrient removal increased as the nutrient loading rate decreased and hydraulic retention time increased. There was no membrane fouling observed in the MPR and the membrane water flux was fully restored by backwashing using only water. However, the membrane permeability varies with the hydraulic retention time (HRT) and biomass concentration in the reactor. Longer HRT offers higher permeability. Therefore, it is recommended to operate the MPR system in lower HRT to improve the membrane resistance and energy consumption. [ABSTRACT FROM AUTHOR]