Emerging trends in research and development on earth abundant materials for ammonia degradation coupled with H2 generation.

Ammonia, as an essential and economical fuel, is a key intermediate for the production of innumerable nitrogen-based compounds. Such compounds have found vast applications in the agricultural world, biological world (amino acids, proteins, and DNA), and various other chemical transformations. However, unlike other compounds, the decomposition of ammonia is widely recognized as an important step towards a safe and sustainable environment. Ammonia has been popularly recommended as a viable candidate for chemical storage because of its high hydrogen content. Although ruthenium (Ru) is considered an excellent catalyst for ammonia oxidation; however, its high cost and low abundance demand the utilization of cheaper, robust, and earth abundant catalyst. The present review article underlines the various ammonia decomposition methods with emphasis on the use of non-noble metals, such as iron, nickel, cobalt, molybdenum, and several other carbides as well as nitride species. In this review, we have highlighted various advances in ammonia decomposition catalysts. The major challenges that persist in designing such catalysts and the future developments in the production of efficient materials for ammonia decomposition are also discussed.

In this dynamic area, ammonia degradation to hydrogen fuel provides a valuable contribution in the carbon neutral economy. Ammonia has been used extensively in several industries and is considered an ideal candidate for hydrogen generation and storage due to its high hydrogen content. Consequently, the ammonia decomposition to yield green hydrogen has become a hot topic in research. Although numerous studies on ammonia decomposition have been conducted over the last few decades, still very few review articles on the most recent advances in this field of catalysis have been published. Through this review, systematic information on the types of decomposition catalysts including both noble (Ru) and non-noble earth abundant metals such as iron, nickel, cobalt, molybdenum, their carbides and nitrides, catalytic routes, as well as the reactivity and mechanism can be comprehended. The literature on newly discovered catalysts, specifically from the last five years, is well documented and explained in this review article. Furthermore, the effect of catalyst supports, their reaction kinetics and mechanistic insights have also been discussed. The challenges and opportunities associated with the decomposition catalysts are comprehensively explicated in the end.

Ammonia decomposition reaction (ADR) is a viable method for hydrogen storage in the form of chemical bonds.Catalysts composed of noble, non-noble metals, amides, imides, carbides, nitrides, and their combinations have been widely explored towards the ADR.Challenges and opportunities in the ammonia oxidation are pointed out.

Hydrogen from sewage sludge: Production methods, influencing factors, challenges, and prospects.

The rising global population and rapid industrialization have frequently resulted in a significant escalation in energy requirements. Hydrogen, renowned for its eco-friendly and renewable characteristics, has garnered substantial interest as a fuel alternative to address the energy needs currently fulfilled by fossil fuels. Embracing such energy substitutes holds pivotal importance in advancing environmental sustainability, aiding in the reduction of greenhouse gas emissions - the primary catalysts of global warming and climate fluctuations. This study elucidates recent trends in sewage sludge (SS)-derived hydrogen through diverse production pathways and critically evaluates the impact of varying parameters on hydrogen yield. Furthermore, a detailed analysis of the breakdown of the hydrogen generation process from SS is provided, along with an assessment of its economic dimensions. The review culminates by illuminating key obstacles in the adoption of this innovative technology, accompanied by practical recommendations to surmount these challenges. This comprehensive analysis is expected to attract considerable interest from stakeholders within the hydrogen production domain, fostering substantial engagement.

Harnessing Nanomaterials for Enhanced Biohydrogen Generation from Wastewater.

Biohydrogen is considered a green fuel due to its eco-friendly nature since it only produces water and energy on combustion. However, their lower yield and production rate is one of the foremost challenges that need an instant sustainable approach. The use of nanotechnology is a potential approach for the enhanced generation of biohydrogen, owing to the significant characteristics of the nanomaterials such as greater specificity, high surface-area-to-volume ratio, better reactivity and dispersibility, enhanced catalytic activity, superb selectivity, greater electron transfer, and better anaerobic microbiota activity. This article explores the recent trends and innovations in the production of biohydrogen from wastewater through the applications of different nanomaterials. The potential of various nanomaterials employed for biohydrogen production from wastewater is evaluated and the impacts of important parameters such as the concentration and size of the nanomaterials, temperature, and pH on the production and yield of biohydrogen are explained in detail. Several pathways involved in the mechanistic approach of biohydrogen generation from wastewater are critically assessed. Lastly, numerous technological challenges are highlighted and recommendations regarding future research are also provided.

Effect of green fuel and green lubricant with metallic nanoparticles on emissions of HC, CO, NOx, and smoke for a compression ignition engine.

The United Nations Sustainable Development Goals (SDGs) are imperative from the point of view of protecting the environment by employing sustainable options. Considerable research has been carried out in the transportation sector to meet this objective. Here, the influence is assessed of epoxidised gingelly oil methyl ester biolubricant with alumina (Al2O3) nanoparticles on the performance and emissions of a single cylinder 0.66-L capacity direct injection compression ignition engine driven by gingelly B20 biodiesel. Engine tests are carried out with gingelly B20 biodiesel as a fuel, and gingelly methyl ester (B100), epoxidised gingelly methyl ester (B100E), and epoxidised gingelly methyl ester (B100E) mixed with 0.5%, 1.0%, and 1.5% w/w alumina (Al2O3) nanoparticles as the lubricant combinations. The results are compared with baseline B20 biodiesel fuel-mineral lubricant operation. The findings indicate that brake thermal efficiency increases by 8.64% for epoxidised gingelly methyl ester (B100E) with 1.0% w/w alumina (Al2O3) nanoparticle biolubricant in comparison to baseline operation. Considerable reductions in emissions are detected; specifically, reductions of 52.4%, 22.0%, 20.0%, and 34.9%, respectively, are observed for CO, NOx, and HC concentrations and smoke opacity for the abovementioned combination as compared to baseline operation. The present work suggests that further research is merited on green fuel-green lubricant combinations. The findings of this study address the United Nations Sustainable Development Goals (SDGs) 7 and 13.

Bioethanol Production from Lignocellulosic Biomass-Challenges and Solutions.

Regarding the limited resources for fossil fuels and increasing global energy demands, greenhouse gas emissions, and climate change, there is a need to find alternative energy sources that are sustainable, environmentally friendly, renewable, and economically viable. In the last several decades, interest in second-generation bioethanol production from non-food lignocellulosic biomass in the form of organic residues rapidly increased because of its abundance, renewability, and low cost. Bioethanol production fits into the strategy of a circular economy and zero waste plans, and using ethanol as an alternative fuel gives the world economy a chance to become independent of the petrochemical industry, providing energy security and environmental safety. However, the conversion of biomass into ethanol is a challenging and multi-stage process because of the variation in the biochemical composition of biomass and the recalcitrance of lignin, the aromatic component of lignocellulose. Therefore, the commercial production of cellulosic ethanol has not yet become well-received commercially, being hampered by high research and production costs, and substantial effort is needed to make it more widespread and profitable. This review summarises the state of the art in bioethanol production from lignocellulosic biomass, highlights the most challenging steps of the process, including pretreatment stages required to fragment biomass components and further enzymatic hydrolysis and fermentation, presents the most recent technological advances to overcome the challenges and high costs, and discusses future perspectives of second-generation biorefineries.

Designing Nanoengineered Photocatalysts for Hydrogen Generation by Water Splitting and Conversion of Carbon Dioxide to Clean Fuels.

Semiconductor photocatalysis has received tremendous attention in the past decade as it has shown great promise in the context of clean energy harvesting for environmental remediation. Sunlight is an inexhaustible source of energy available to us throughout the year, although it is rather dilutely dispersed. Semiconductor based photocatalysis presents one of the best ways to harness this source of energy to carry out chemical reactions of interest that require external energy input. Photocatalytic hydrogen generation by splitting of water, CO2 mitigation, and CO2 conversion to green fuel have therefore become the highly desirable clean and sustainable processes for a better tomorrow. Although numerous efforts have been made and continue to be expended to search and develop new classes of photocatalyst materials in recent years, several significant challenges still remain to be resolved before photocatalysis can reach its commercial potential. Therefore, major attention is required towards improving the efficiencies of the existing photocatalysts by further manipulating them and parallelly employing newer strategies for novel photocatalyst designs. This personal account aims to provide a broad overview of the field primarily invoking examples of our own research contributions in the field, which include photocatalytic hydrogen generation and CO2 reduction to value added chemicals. This account reviews the state-of-the-art research activities and scientific possibilities which a functional material can offer if its properties are put to best use through goal-oriented design by combining with other compatible materials. We have addressed fundamental principles of photocatalysis, different kind of functional photocatalysts, critical issues associated with them and various strategies to overcome the related hurdles. It is our hope that this current personal account will provide a platform for young researchers to address the bottleneck issues in the field of photocatalysis and photocatalysts with a sense of clarity, and to find innovative solutions to resolve them by a prudent choice of materials, synthesis protocols, and approaches to boost the photocatalysis output. We emphasize that a targeted or goal-directed photocatalyst nanoengineering as perhaps the only way to realize an early success in this multiparametric domain.

Membrane-Assisted Methanol Synthesis Processes and the Required Permselectivity.

Water-selective membrane reactors are proposed in the literature to improve methanol yield for a standalone reactor. However, the methanol productivity is not a precise metric to show the system improvement since, with this approach, we do not consider the amount of energy loss through the undesirable co-permeation of H2, which could otherwise remain on the reaction side at high pressure. In other words, the effectiveness of this new technology should be evaluated at a process flowsheet level to assess its advantages and disadvantages on the overall system performance and, more importantly, to identify the minimum required properties of the membrane. Therefore, an equation-based model for a membrane reactor, developed in Aspen Custom Modeler, was incorporated within the process flowsheet of the methanol plant to develop an integrated process framework to conduct the investigation. We determined the upper limit of the power-saving at 32% by exploring the favorable conditions wherein a conceptual water selective membrane reactor proves more effective. Using these suboptimal conditions, we realized that the minimum required H2O/H2 selectivity is 190 and 970 based on the exergy analysis and overall power requirement, respectively. According to our results, the permselectivity of membranes synthesized for this application in the literature, showing improvements in the one-pass conversion, is well below the minimum requirement when the overall methanol synthesis process flowsheet comes into consideration.

Appropriateness of waste jasmine flower for bioethanol conversion with enzymatic hydrolysis: sustainable development on green fuel production.

Utilized and waste jasmine flower contains a high portion of organic carbohydrate and other organic acids, making it a suitable substrate for bioethanol production. This study was designed to estimate the prospective of waste jasmine flower biomass applied with chemical (alkaline) and thermal pretreatment applied on samples through bioethanol production efficiencies. Therefore, pretreatment and enzymatic hydrolysis are directed to disrupt the complex cell wall layer and improve the accessibility towards polysaccharide fraction. Also, applying response surface methodology tools during fermentative bioethanol production to study the interactive effects of different bioprocess variables for higher bioethanol yield in batch small and large scale model is discussed. The immobilized yeast between jasmine found that jasmine sugar utilization was 50%. The jasmine flower's ethanol production was 6.54 g/L and after distillation of jasmine was 31.40 g/L at pH 4.5. Results showed that this immobilized yeast method could be successfully used for bioethanol production from waste jasmine flower.

Technical insights into the production of green fuel from CO2 sequestered algal biomass: A conceptual review on green energy.

Algae a promising energy reserve due to its adaptability, cheap source, sustainability and it's growth ability in wastewater with efficient sequestration of industrial carbon dioxide. This review summarizes the pathways available for biofuel production from carbon sequestered algae biomass. In this regard, this review focuses on microalgae and its cultivation in wastewater with CO2 sequestration. Conversion of carbon sequestered biomass into bio-fuels via thermo-chemical routes and its engine emission properties. Energy perspective of green gaseous biofuels in near future. This review revealed that algae was the pre-dominant CO2 sequester than terrestrial plants in an eco-friendly and economical way with simultaneous wastewater remediation. Hydrothermal liquefaction of algae biomass was the most preferred mode for biofuel generation than pyrolysis due to high moisture content. The algae based fuels exhibit less greenhouse gases emission and higher energy value. This review helps the researchers, environmentalists and industrialists to evaluate the impact of algae based bio-energy towards green energy and environment.

Current scenario of CNG vehicular pollution and their possible abatement technologies: an overview.

Compressed natural gas is an alternative green fuel for automobile industry. Recently, the Indian government is targeting to replace all the conventional fuel vehicles by compressed natural gas (CNG) automobiles due to its several merits. Still, the presence of a significant amount of CO, CH4, and NOx gases in the CNG vehicle exhaust are quiet a matter of concern. Thus, to control the emissions from CNG engines, the major advances are under development of and oxidation is one of them in catalytic converter. In literature, the catalysts such as noble and non-noble metals have been reported for separate oxidation of CO and CH4.. Experimentally, it was found that non-noble metal catalysts are preferred due to its low cost, good thermal stability, and molding tractability. In literature, several articles have been published for CO and CH4 oxidation but no review paper is still available. Thus, the present review provides a comprehensive overview of separate as well as simultaneous CO and CH4 oxidation reactions for CNG vehicular emission control.

Modalities for conversion of waste to energy - Challenges and perspectives.

The United Nation is achieving its sustainable development objectives by focusing on the greener technologies for waste to energy (WTE) conversion. This necessitates the exploration of every conceivable sustainable route in different sectors. Among these, sustainable bio-economy, electricity, and waste management are the most dynamic areas. However, till now sustainability judgments for the generation of electricity from waste-to-energy supply chain (WTE-SC) technologies have been restricted in scale with respect to the three-dimensional sustainability structure (social, environmental, and economic). In most of the cases, the assessments were controlled by various environmental factors/indicators, via overlooking the economic and social indicators. In this review, we have tried to summarize a variety of state-of-the-art WTE technologies including biological and thermal treatment, landfill gas utilization and biorefineries technologies etc. These technologies can be implemented by various policy makers and agencies to deal with the communities fear before spreading and executing the relevant rules and regulations. The implementation of these rules and regulations for WTE-SC were scheduled to decide the barriers and challenges from the perspective of finance, institution, technology, and regulation.

An excellent heterojunction nanocomposite solar-energy material for photocatalytic transformation of hydrogen sulfide pollutant to hydrogen fuel and elemental sulfur: A mechanistic insight.

Hydrogen sulfide (H2S) is a noxious gas for living organisms and devastating/corrosive agent for metallic structures, which is generated in large scale through natural [geothermal/bacterial] activities or industrial processes, particularly by petroleum and gas industries. Photocatalytic elimination of this plentiful-perilous pollutant and its transformation into hydrogen green fuel and elemental sulfur is a novel/sustainable strategy, which is intriguing from energy and environmental science as well as technological viewpoints. To this end, the design and synthesis of low-price, environmentally friendly, effective photocatalyst/solar-energy materials are highly in demand. Herein, through a facile hydrothermal route, a set of new pn junction xBi2S3·yMnS nanocomposite photocatalysts were synthesized and employed in an alkaline H2S medium (pH = 11) to generate hydrogen fuel and elemental sulfur under atmospheric pressure at room temperature conditions. The maximum conversion yield was attained at the molar ratio xy=2, where the photocatalyst exhibited the lowest charge recombination, strong photon absorption, and the greatest surface area among the synthesized nanocomposite materials. Furthermore, it was witnessed that disulfide (S22-) was the only oxidation product in the reaction medium, which could be effortlessly precipitated as elemental sulfur by acidification of the medium and lowering the pH to about 5.

Production of gasoline range hydrocarbons from catalytic cracking of linoleic acid over various acidic zeolite catalysts.

Employment of edible oils as alternative green fuel for vehicles had raised debates on the sustainability of food supply especially in the third-world countries. The non-edible oil obtained from the abundantly available rubber seeds could mitigate this issue and at the same time reduce the environmental impact. Therefore, this paper investigates the catalytic cracking reaction of a model compound named linoleic acid that is enormously present in the rubber seed oil. Batch-scale experiments were conducted using 8.8 mL Inconel batch reactor having a cyclic horizontal swing span of 2 cm with a frequency of 60 cycles per minute at 450 °C under atmospheric condition for 90 min. The performance of HZSM-5, HBeta, HFerrierite, HMordenite and HY catalysts was tested for their efficiency in favouring gasoline range hydrocarbons. The compounds present in the organic liquid product were then analysed using GC-MS and classified based on PIONA which stands for paraffin, isoparaffin, olefin, naphthenes and aromatics respectively. The results obtained show that HZSM-5 catalyst favoured gasoline range hydrocarbons that were rich in aromatics compounds and promoted the production of desired isoparaffin. It also gave a higher cracking activity; however, large gaseous as by-products were produced at the same time.

Produção de biodiesel usando blend de óleo de abacate e de soja / Production of biodiesel using blend of avocado oil and soybean oil

A crescente preocupação com questões ambientais vem criando a busca por fontes alternativas de combustíveis que sejam renováveis e não agridam o meio-ambiente. Com este pensamento, a elaboração de biodiesel com misturas de óleos vegetais (blend) é um processo que apresenta todos os requisitos necessários para a fabricação de um biocombustível seguro e dentro dos parâmetros estabelecidos pela legislação. O objetivo deste trabalho foi estudar a fabricação de biodiesel de óleo de soja misturado com óleo de abacate. Elaboraram se duas formulações de biodiesel com misturas de óleos vegetais: 50% de óleo de soja refinado e 50% de óleo de abacate refinado (F1) e 80% de óleo de soja refinado e 20% de óleo de abacate refinado (F2). Para comparação com o biodiesel derivado da mistura de óleos vegetais, foi efetuada a elaboração de biodiesel de óleo de soja (100%) (R1, R2 e R3). Os resultados das análises físico-químicas apresentaram-se dentro dos padrões especificados, com pequenas diferenças nas viscosidades analisadas. O biodiesel blend referente à formulação (F1) não apresentou separação de fases. A formulação (F2) apresentou um rendimento de 49,65%, próximo do biodiesel de soja, que foi de 53,79%, o que justifica sua elaboração, desde que o álcool anidro em excesso seja recuperado e a glicerina obtida purificada, reduzindo as perdas e os custos, viabilizando o processo de obtenção do biodiesel blend de soja e abacate.

The growing concern about environmental issues has created a search for alternative sources of fuel which are renewable and do not harm the environment. The elaboration of biodiesel with mixtures of vegetable oils (blend) is a process that possibly presents all the necessary requirements for the manufacture of a safe biofuel and within the parameters established by the legislation. The objective of this work was to study the of biodiesel production of soybean oil mixed with avocado oil. Two formulations of biodiesel were prepared with mixtures of vegetable oils: 50% refined soybean oil and 50% refined avocado oil (F1) and 80% refined soybean oil and 20% refined avocado oil (F2). In order to compare biodiesel derived from the blend of vegetable oils, soybean oil biodiesel was produced (100%) (R1, R2 and R3). The results of the physical chemical analyzes were within the specified standards, with small differences in the analyzed viscosities. The biodiesel blend (F1) did not show phase separation. The formulation (F2) presented a yield of 49.65%, close to soybean biodiesel, which was 53.79%, which justifies its elaboration, as long as the excess anhydrous alcohol is recovered and the obtained glycerin purified, reducing losses and the costs, enabling the process of obtaining of biodiesel blend of soy and avocado.

Transporter-mediated biofuel secretion.

Engineering microorganisms to produce biofuels is currently among the most promising strategies in renewable energy. However, harvesting these organisms for extracting biofuels is energy- and cost-intensive, limiting the commercial feasibility of large-scale production. Here, we demonstrate the use of a class of transport proteins of pharmacological interest to circumvent the need to harvest biomass during biofuel production. We show that membrane-embedded transporters, better known to efflux lipids and drugs, can be used to mediate the secretion of intracellularly synthesized model isoprenoid biofuel compounds to the extracellular milieu. Transporter-mediated biofuel secretion sustainably maintained an approximate three- to fivefold boost in biofuel production in our Escherichia coli test system. Because the transporters used in this study belong to the ubiquitous ATP-binding cassette protein family, we propose their use as "plug-and-play" biofuel-secreting systems in a variety of bacteria, cyanobacteria, diatoms, yeast, and algae used for biofuel production. This investigation showcases the potential of expressing desired membrane transport proteins in cell factories to achieve the export or import of substances of economic, environmental, or therapeutic importance.