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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]

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]

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]

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: 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]

Solar energy is a renewable energy source that can be utilized for different applications in today's world. The effective use of solar energy requires a storage medium that can facilitate the storage of excess energy, and then supply this stored energy when it is needed. An effective method of storing thermal energy from solar is through the use of phase change materials (PCMs). PCMs are isothermal in nature, and thus offer higher density energy storage and the ability to operate in a variable range of temperature conditions. This article provides a comprehensive review of the application of PCMs for solar energy use and storage such as for solar power generation, water heating systems, solar cookers, and solar dryers. This paper will benefit the researcher in conducting further research on solar power generation, water heating system, solar cookers, and solar dryers using PCMs for commercial development. [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]

• Implications for efficient pyrolysis processes using municipal green waste. • Potential for increased process economics and sustainability. • Optimal parameters boost bio-oil yield (52.8%) and energy efficiency (72.9%). • Holding time enhances bio-oil and syngas yields, while decreases biochar yields. • Smaller feedstock particle size leads to higher energy and exergy efficiency. This study aims to determine how different operating conditions for a fast pyrolysis process employing municipal green waste (MGW) in an auger reactor affect product yields, overall energy efficiency, and total exergy efficiency. In this study, a range of pyrolysis conditions, including temperatures from 400 to 600 °C (in 50 °C increments), holding times from 1 to 5 min (in 1-minute increments), and feedstock particle sizes from 2 to 10 mm (in 2-mm increments) were used. MGW and pyrolysis products were characterised using separate pieces of equipment and in accordance with applicable ASTM standards. The results demonstrate that a yield of 52.8% for bio-oil and a yield of 23.7% for syngas can be achieved at temperatures of 500 and 600 °C, respectively. At 400 °C, the biochar production was highest as 21.5%. Bio-oil and syngas yields improved with holding times, whereas biochar yields declined. At a feedstock particle size of 2 mm, the overall energy efficiency was at its maximum (72.9%), while the total exergy efficiency was also at its highest (68.4%). As feedstock particle size increased, overall energy efficiency and total exergy efficiency dropped. In conclusion, this study provides valuable insights into the effects of different operating parameters on the pyrolysis process using MGW, which can be used to optimize the process and increase its efficiency. [ABSTRACT FROM AUTHOR]

Increasing population and urbanization call for smarter cities where the cycles of matter and energy are optimized, notably in buildings which are actually a source of pollution consuming a lot of energy. The efficiency of building energy has been improved by modelling earth-air heat exchangers, yet selecting the suitable models is challenging. Here we review data-driven earth-air heat exchanger models used for buildings. We discuss issues brought about by assumptions, unmeasured disruptions, and uncertainties in numerical and experimental works. We found that high accuracy can be reached if sufficient data is available. Models are appropriate for real-time activity due to their structure simplicity, yet they display a poor generalization capacity. Model development is limited by the constrained parameters and the complex boundary conditions of the heat exchangers. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rice bran biodiesel is produced using ultrasound and infrared radiation. • ANN-GWO is a reliable tool to optimize the transesterification process. • The predicted rice bran yield is 98.16%. • The optimum yield obtained from the experiment is 97.74%. • The FAME content of the optimized biodiesel is 95%. A system combining ultrasound and infrared radiation was used to increase the chemical reactions between incompressible reactants by enhancing their mass transfers with the aim to reduce the energy usage and reaction time. In this study, biodiesel from RBO was produced via transesterification, and the process variables were optimized using the combination of ANN and GWO algorithm. Process parameters considered in this study are ratio of methanol to oil, catalyst concentration, and reaction time. Based on the ANN-GWO algoritm used, the optimum conditions for the process parameters were (1) methanol to oil ratio: 60%, (2) concentration of catalyst: 1 wt%, (3) time: 7.76 min, leading to the metyl ester yield of 98.16 wt%. The algoritm was verified by conducting a triplicate independent experiments using the suggested optimum values, resulting in an average methyl ester yield of 97.74 wt%. Subsequently, properties of rice bran biodiesel were compared to ASTM D6751 and EN 14214 standards, and the obtained values met both the standards. [ABSTRACT FROM AUTHOR]

The transportation, agricultural, and power sector of Bangladesh is largely dependent on fossil fuels that decrease day by day. The government has to import large volumes of fuel from foreign sources to meet the fuel demand for power production, causing a negative impact on the country’s economy. Finding an alternative to fossil fuels is becoming the most urgent issue. Biodiesel can thus be a destined source to future energy demands. Increasing the usage of biodiesel will also decrease the global problem of environmental pollution, as fossil fuels are considered to be the major source of harmful emissions. Biodiesel is renewable, bio-degradable, non-toxic, technologically feasible, and can be used as a bio-lubricant. In this study, the current energy scenario of Bangladesh, available potential biodiesel feedstocks, production process and engine fuel property, environmental impact, performance and emission characteristics on diesel engines, comparison of cost analysis, and future direction are discussed. Various research related to these feedstocks are performed in Bangladesh, which include an overview of biodiesel properties, engine performance, and emission parameters used in diesel engines. All types of biodiesel have similar functional properties compared with diesel fuel and can be successfully used in compression ignition engines. Biodiesel can thus serve as a subsequent replacement of non-renewable fossil fuels. Compared with diesel fuel, CO and HC emission were also low, but a slight increase in NO x was observed in some cases. One of the major advantages is that Bangladesh is a country with plenty of biodiesel feedstock sources, such as mustered, Jatropha curcas , rapeseed, sesame, castor, cottonseed, neem, algae, coconut, and groundnut. In conclusion, producing biodiesel from different feedstocks is greatly possible and can thus assist in future energy needs. [ABSTRACT FROM AUTHOR]

This study explores the role of renewable energy (RE) penetration in Malaysia's energy security (ES) and its implications for the country's target of 20% capacity in the energy mix by 2025. Renewable energy (RE) is a critical driver of long-term energy security. In 2018, the share of renewable energy in Malaysia's energy mix was 9%, falling far short of the national target of 20% penetration by 2025. This study employs a system dynamics approach to investigate the relationship between RE penetration and correlated indicators from energy security (ES) dimensions: energy availability, environmental sustainability, and socio-economics. The causal relationships between the three-dimensional indicators of ES have been established using causal and stock and flow logic. Simulated results show that energy consumption has increased sharply, while energy efficiency and economic growth have only increased by a small margin with an increase in RE from 2015 to 2020. The energy intensity is expected to rise slightly by the end of the fifth year. As a result, the overall impact is positive for Malaysia's environmental sustainability while reducing its reliance on energy imports and meeting national economic growth demands. • 1. Increase in RE share improves pollution remediation. • 2. RE improves the short and long-term ES of a nation. • 3. Energy intensity, energy efficiency and growth in economic health is noticed. • 4. Reduces dependency on fossil fuels and promotes the use of alternatives such as biofuels. [ABSTRACT FROM AUTHOR]

Abstract: Increasing energy demand and environment concerns have prompted an evolution of alternative fuel sources. As an alternative fuel source, biodiesel is attractive because it reduces engine emissions. However, biodiesel produces higher NO x emissions compared to ordinary diesel fuel. Previous researches have established many factors that cause biodiesel to produce elevated NO x emissions. This study reviews the impacts of biodiesel combustion on NO x emissions and their reduction approaches in diesel engines. The first part of this study recaps the NO x formation mechanisms for understanding the kinetics behind the NO x forming reactions. The second part describes the factors affecting on NO x emissions. This paper established that higher NO x emissions are produced for biodiesel combustion which influenced by several factors such as physicochemical properties and molecular structure of biodiesel, adiabatic flame temperature, ignition delay time, injection timing and engine load conditions etc. The final section discusses on the reduction of NO x emissions from biodiesel fuelled engines for both pre and post combustion techniques. The results of reduction approaches of the NO x emissions implies, exhaust gas recirculation (EGR) and retarded injection timing are effective as well as low cost techniques than others. Between these two techniques, EGR reduces the NO x emissions at 5–25% EGR rate adequately in biofuelled engine by controlling oxygen content and combustion peak temperature with slightly decreasing HC and CO emissions. However this technique shows few penalties on smoke and PM emissions as well as brake specific fuel consumption if not perfectly optimized. [Copyright &y& Elsevier]

• Impact of water – biodiesel – diesel nano-emulsion fuel on diesel engine parameters investigated. • Nano-emulsion fuel generated less power and torque than diesel. • NO emission of nano-emulsion fuel decreased 9.06% than diesel. • Diesel nano-emulsion fuel is a satisfactory alternative to fossil diesel fuel in diesel engines. The use of emulsion fuel in the engine has been reported as an effective solution to reduce the harmful emission. This experimental study examined the effects of nano-emulsion biodiesel fuel on engine efficiency, gas emission parameters and combustion parameters of a single-cylinder air-cooled diesel engine. Nano-emulsion fuel made of 5% waste cooking oil biodiesel and 5% distilled water were used to test the performance of the diesel engine. This fuel was produced using ultrasonic waves by stabilizing 5% by volume tween 80 and spans 80 surfactants in HLB8 (Hydrophilic-Lipophilic Balance). Performance parameters and pollutants emission of a diesel engine using nano-emulsion fuel were compared with emulsion fuel. This test was performed on four different engine loads (25%, 50%, 75%, and 100%) at different speeds of 1700, 2000, 2300, and 2600 rpm. Power, torque, cylinder pressure levels, and emissions including soot opacity, carbon monoxide (CO), unburned hydrocarbon (UHC), carbon dioxide (CO 2), and nitrogen oxides (NO X) were measured. The test results show that diesel engine power and torque using nano-emulsion fuel improved by about 4.84% and 4.65% compared to emulsion fuel, respectively. The use of nano-emulsion fuel significantly decreased CO (~11%), UHCs (~6%), NOx (~9%) and soot opacity (~10%) emission. However, a small rise in CO 2 (~7%) emission was observed. The combustion result shows that nano-emulsion fuel creates more cylinder pressure (CP) than emulsion fuel during combustion. The highest CP was recorded at 10° crank angle after the top dead centre with diesel fuel. Finally, nano-emulsion fuel can be a satisfactory alternative to diesel fuel in a diesel engine without having to change the engine. [ABSTRACT FROM AUTHOR]