• Energy Research

Biological production of second generation biofuels such as biohydrogen (H2) or methane (CH4) represents a promising alternative to fossils fuels. Alkaline pretreatments of lignocellulosic biomass are known to enhance the accessibility and the bioconversion of hollocelluloses during anaerobic digestion and dark fermentation processes. In the present study, four different configurations were investigated: one-stage CH4 continuous and two-stage H2 batch/CH4 continuous process with and without alkaline pretreatment of sunflower stalks (55 °C, 24 h, 4 g NaOH/100 g TS). The results showed that two stage H2/CH4 (150 ± 3.5 mL CH4 g−1 VS) did not improve methane yields compared to one stage CH4 (152 ± 4 mL CH4 g−1 VS). Although alkaline pretreatment was shown to be inefficient in improving the H2 yields in the two-stage H2/CH4 process, an increase in methane yields by 26% and 29% were observed with one-stage CH4 and two-stage H2/CH4 production compared to one-stage CH4 process without alkaline pretreatment, respectively. Chemical analysis of the solid digestate showed that hemicelluloses were the most preferred substrates compared to cellulose whereas lignin remained undegraded in all four studied configurations. Finally, energy balance showed that a positive energy balance and economic sustainability can be achieved when the alkaline pretreatment is applied at a high substrate concentration and/or when heat is recovered at a maximum efficiency during the pretreatment step.

In this study, iron oxide- and copper oxide-decorated reduced graphene oxide has been synthesized via a simple wet chemical oxidation-reduction method. The effectiveness of the aforementioned composite as an electrode for supercapacitors (SCs) has been explored via cyclic voltammetry. Raman spectroscopic measurement shows the appearance of a 2D band at 2670 cm-1 and fitting of the 2D band with multiple Lorentzian functions highlights the formation of a few layers of graphenes. Reduced graphene oxide (RGO) formation and the presence of iron and copper oxides on the RGO surface were evident from both X-ray diffraction and energy dispersive spectroscopy results. The thermogravimetric analysis of the synthesized nanocomposite demonstrated superior thermal stability compared to graphene oxide (GO) with almost 60% retention of initial weight after 500 °C. Both the Brunauer-Emmett-Teller test and scanning electron microscopy images established the formation of pores. Average pore diameters of RGO and nanocomposite were observed to be 1.76 and 1.32 nm, respectively. The as-developed nanocomposite exhibited an admirable specific capacitance (Csp) of 626 F/g at a current density of 1.0 A/g. The bimetallic composite demonstrated an excellent energy density of 86.94 Wh/kg. ; No Full Text

Abstract The effect of organic loading on process performance and methane yields during anaerobic mono-digestion of sugarcane trash (ST) and sugarcane bagasse (SB) with and without dilute sulphuric acid impregnated steam explosion was investigated. At first, biochemical methane potential (BMP) of ST and SB was performed at 37 °C in batch assays with an inoculum to substrate (ISR) ratio of 2 on VS basis. Methane yields of 161.8 ± 4 and 187.9 ± 2.4 N mL g−1 VSadded were obtained for ST and SB, respectively. These yields were 55.6 and 53.8 % of the theoretical methane potentials for ST and SB respectively. Later, semi-continuous reactor experiments were conducted using four stainless steel reactors with working volume of 10 L and hydraulic retention time (HRT) of 35 d at 37 °C. Reactors were fed with untreated ST, untreated SB, steam exploded trash (TT) and steam exploded bagasse (TB). In all four reactors, methane production increased with increase in organic loading rate (OLR) from 1.5 to 2.5 gVS L-1 d-1. However, higher methane yields were noticed in TT (226 ± 37 NmL g-1VSfed) and TB (236 ± 22 NmL g-1VSfed) than for ST (121 ± 24 mL g-1VSfed) and SB (148 ± 25 mL g-1VSfed). Increase in OLR from 2.5 to 3.5 gVS L-1d-1 resulted in decreased methane yields and pseudo state stable conditions. Thus, steam explosion with dilute H2SO4 catalyst can improve the methane yields of both ST and SB.

ABSTRACTSugarcane is the most traded crop in the world, with Brazil being the world's largest producer. Sugarcane processing generates up to 28% of sugarcane bagasse (SB) from the entire plant, with only 50% of it used for energy generation. SB is a lignocellulosic biomass that can be converted into biogas. However, the optimization of pretreatment process parameters is essential for its successful scaling up. This study evaluated the effect of mild alkaline pretreatment of SB using NaOH and KOH at concentrations of 1-10% and exposure time of 1-12 hours) on the biochemical methane potential (BMP) under mesophilic temperature. The central composite rotatable design (CCRD) was applied as statistical tool to generate optimal operating pretreatment conditions. The tests were performed in triplicates totalizing 84 batch bottles. The BMP of the untreated SB varied between 297-306 LN CH4 kg VS-1 while the BMP of the pretreated samples with NaOH and KOH were 19% and 20% higher. The optimized conditions were NaOH at 7.7% and KOH at 8.3% KOH for 12 hours. However, the range indicated by the statistical design with CCRD revealed that there was no statistical difference in terms of methane yield when concentrations between 4-10% NaOH and 6-10% KOH during 12 hours were applied, when compared to the specific optimized points. The optimization of the pretreatment parameters demonstrated to be a key-factor to improve the anaerobic digestion of lignocellulosic substrates, leading to a less chemically dependent and more sustainable approach, while allowing a more profitable process.

La transition du système énergétique actuel à base de combustibles fossiles vers un système durable nécessite une technologie d'énergie renouvelable. Bien que l'énergie géothermique présente ses propres défis particuliers par rapport à d'autres technologies d'énergie renouvelable, l'énergie géothermique a montré un potentiel important pour réduire l'impact environnemental et les émissions de gaz à effet de serre provenant de la production d'électricité. Les avantages de la géothermie ne sont pas seulement la production d'électricité dans différentes configurations de centrales, mais aussi l'application directe de chaleur dans l'industrie et les usages domestiques, quelles que soient les conditions météorologiques. Dans cette étude, une revue de recherche est réalisée sur l'aspect du développement de l'énergie géothermique, en évaluant la technologie des centrales électriques et les applications de chaleur directe. Cinq configurations de centrales électriques sont étudiées : simple flash, double flash, vapeur sèche, binaire et avancée. Les aspects thermodynamiques sont abordés afin de les prendre en compte pour les futures analyses de centrales géothermiques. En outre, les utilisations directes les plus courantes de la chaleur géothermique sont discutées. Les résultats illustrent que les centrales électriques à cycle de classement binaire – organique pourraient jouer un rôle vital dans l'exploitation des ressources géothermiques à basse température. En outre, il est identifié un besoin de recherche dans les configurations hybrides géothermie-solaire-biomasse à des fins de poly-génération. Ces configurations augmentent la production d'énergie, augmentant l'efficacité thermique et augmentant la durée de vie du réservoir géothermique. De même, les applications directes de la chaleur géothermique présentent de bonnes opportunités pour augmenter les revenus d'un projet géothermique. Selon la zone géographique, les configurations en cascade contribuent à maximiser l'utilisation des ressources géothermiques. Les futurs examens de recherche devraient prendre en compte les aspects financiers, économiques et politiques des développements géothermiques ainsi que les aspects géologiques, géophysiques, géochimiques, de forage, d'ingénierie des réservoirs et environnementaux. L'objectif principal de ces sujets est de fournir l'état de l'art du développement géothermique pour les développeurs, les décideurs, les chercheurs et les communautés intéressées par l'énergie géothermique. La transición del actual sistema energético basado en combustibles fósiles a uno sostenible requiere tecnología de energía renovable. Aunque la energía geotérmica presenta sus propios desafíos particulares en comparación con otras tecnologías de energía renovable, la energía geotérmica ha mostrado un potencial significativo para reducir el impacto ambiental y las emisiones de gases de efecto invernadero de la producción de electricidad. Las ventajas de la energía geotérmica no son solo la generación de electricidad en diferentes configuraciones de planta, sino también la aplicación directa de calor en usos industriales y domésticos, independientemente de las condiciones meteorológicas. En este estudio, se lleva a cabo una revisión de la investigación sobre el aspecto del desarrollo de la energía geotérmica, evaluando la tecnología de las centrales eléctricas y las aplicaciones de calor directo. Se estudian cinco configuraciones de centrales: single-flash, double-flash, dry-steam, binary y advanced. Se abordan los aspectos termodinámicos con el fin de considerarlos para el análisis de futuras centrales geotérmicas. Además, se discuten los usos directos más comunes del calor geotérmico. Los resultados ilustran que las centrales eléctricas de ciclo de clasificación binario – orgánico podrían desempeñar un papel vital en la explotación de los recursos geotérmicos de baja temperatura. Además, se identifica una necesidad de investigación en configuraciones híbridas geotérmica-solar-biomasa para fines de poligeneración. Estas configuraciones aumentan la producción de energía, aumentando la eficiencia térmica y aumentando la vida útil del depósito geotérmico. Del mismo modo, las aplicaciones directas del calor geotérmico presentan buenas oportunidades para aumentar los ingresos de un proyecto geotérmico. Dependiendo de la zona geográfica, las configuraciones en cascada contribuyen a maximizar el uso de los recursos geotérmicos. Las futuras revisiones de investigación deben considerar los aspectos financieros, económicos y políticos de los desarrollos geotérmicos junto con los aspectos geológicos, geofísicos, geoquímicos, de perforación, de ingeniería de yacimientos y ambientales. El objetivo principal de abordar estos temas es proporcionar el estado del arte del desarrollo geotérmico para desarrolladores, responsables políticos, investigadores y comunidades interesadas en la energía geotérmica. The transition from current fossil-fuel energy system towards a sustainable one-based requires renewable energy technology. Although geothermal energy presents its own particular challenges in comparison with other renewable energy technologies, geothermal energy has showed significant potential to reduce environmental impact and greenhouse gas emissions from electricity production. Advantages of geothermal energy are not only the generation of electricity in different plant configurations but also the direct application of heat in industry and household uses regardless of meteorological conditions. In this study, a research review is carried out on the aspect of geothermal energy development, assessing power plant technology and direct heat applications. Five power plant configurations are studied: single-flash, double-flash, dry-steam, binary and advanced. The thermodynamic aspects are addressed in order to consider them for future geothermal power plant analysis. Furthermore, the most common direct uses of geothermal heat are discussed. Results illustrate that Binary – Organic Ranking Cycle Power Plants might play a vital role in the exploitation of low temperature geothermal resources. Furthermore, it is identified a need for research in hybrid geothermal-solar-biomass configurations for poly-generation purposes. These configurations increase the energy output, increasing the thermal efficiency and increasing the life of the geothermal reservoir. Similarly, direct applications of geothermal heat present good opportunities for increasing the revenue of a geothermal project. Depending of the geographic zone, cascade configurations contributes to maximise the use of geothermal resources. Future research reviews should consider the financial, economic and policy aspects of geothermal developments along with the geology, geophysics, geochemistry, drilling, reservoir engineering and environmental aspects. The main goal of addressing these topics is to provide the state-of-the-art of geothermal development for developers, policy makers, researchers and communities interested in geothermal energy. يتطلب الانتقال من نظام طاقة الوقود الأحفوري الحالي إلى نظام مستدام قائم على أساس واحد تكنولوجيا الطاقة المتجددة. على الرغم من أن الطاقة الحرارية الأرضية تمثل تحديات خاصة بها مقارنة بتقنيات الطاقة المتجددة الأخرى، فقد أظهرت الطاقة الحرارية الأرضية إمكانات كبيرة للحد من التأثير البيئي وانبعاثات غازات الدفيئة الناتجة عن إنتاج الكهرباء. مزايا الطاقة الحرارية الأرضية ليست فقط توليد الكهرباء في تكوينات المصنع المختلفة ولكن أيضا التطبيق المباشر للحرارة في الصناعة والاستخدامات المنزلية بغض النظر عن ظروف الأرصاد الجوية. في هذه الدراسة، يتم إجراء مراجعة بحثية حول جانب تطوير الطاقة الحرارية الأرضية، وتقييم تكنولوجيا محطة الطاقة وتطبيقات الحرارة المباشرة. يتم دراسة خمسة تكوينات لمحطة توليد الطاقة: فلاش واحد، وميض مزدوج، بخار جاف، ثنائي ومتقدم. يتم تناول الجوانب الديناميكية الحرارية من أجل النظر فيها لتحليل محطة توليد الطاقة الحرارية الأرضية في المستقبل. علاوة على ذلك، تتم مناقشة الاستخدامات المباشرة الأكثر شيوعًا للحرارة الأرضية. توضح النتائج أن محطات توليد الطاقة الثنائية – دورة التصنيف العضوي قد تلعب دورًا حيويًا في استغلال موارد الطاقة الحرارية الأرضية ذات درجة الحرارة المنخفضة. علاوة على ذلك، تم تحديد الحاجة إلى البحث في تكوينات الكتلة الحيوية الشمسية الحرارية الأرضية الهجينة لأغراض التوليد المتعدد. تزيد هذه التكوينات من خرج الطاقة، مما يزيد من الكفاءة الحرارية ويزيد من عمر خزان الطاقة الحرارية الأرضية. وبالمثل، توفر التطبيقات المباشرة للحرارة الأرضية فرصًا جيدة لزيادة إيرادات مشروع الطاقة الحرارية الأرضية. اعتمادًا على المنطقة الجغرافية، تساهم التكوينات التعاقبية في تعظيم استخدام موارد الطاقة الحرارية الأرضية. يجب أن تأخذ المراجعات البحثية المستقبلية في الاعتبار الجوانب المالية والاقتصادية والسياسية للتطورات الحرارية الأرضية جنبًا إلى جنب مع الجيولوجيا والجيوفيزياء والكيمياء الجيولوجية والحفر وهندسة المكامن والجوانب البيئية. الهدف الرئيسي من معالجة هذه الموضوعات هو توفير أحدث تطوير للطاقة الحرارية الأرضية للمطورين وصانعي السياسات والباحثين والمجتمعات المهتمة بالطاقة الحرارية الأرضية.

Most nations are shifting towards renewable energy sources to reduce energy-related emissions and achieve their net zero emissions targets by mid-century. Consequently, many attempts have been made to invest in clean, accessible, inexpensive, sustainable and reliable renewable energy sources while reducing dependency on fossil fuels. Recently, the production of biogas and upgrading it to produce biomethane is considered a sustainable way to reduce emissions from natural gas consumption. However, uncertainties in the biomass supply chain and less attention to decarbonising the natural gas grid have led to fewer investors in biomethane injection projects. Thus, researchers have applied Geographic Information System (GIS) as the best decision-making tool with spatial analytical and optimisation capabilities to address this issue. This study aims to review GIS-based applications on planning and optimising the biomass supply chain. Accordingly, this review covers different GIS-based biomass assessment methods with the evaluation of feedstock types, GIS-based approaches on selecting and optimising bioenergy plant locations and GIS-based applications on facilitating biomethane injection projects. This review identified four major biomass assessment approaches: Administrative division-based, location-based, cluster-based and grid-based. Sustainability criteria involved in site selection were also discussed, along with suitability and optimality techniques. Most of the optimising studies investigated cost optimisation based on a single objective. However, optimising the whole supply chain, including all operational components of the biomass supply chain, is still seldom investigated. Furthermore, it was found that most studies focus on site selection and logistics, neglecting biomethane process optimisation.

Solution-state two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy of plant cell walls is a powerful tool for characterizing changes in cell wall chemistry during the hydrothermal pretreatment process of wheat straw for second-generation bioethanol production. One-bond 13C–1H NMR correlation spectroscopy, via an heteronuclear single quantum coherence experiment, revealed substantial lignin β-aryl ether cleavage, deacetylation via cleavage of the natural acetates at the 2-O- and 3-O-positions of xylan, and uronic acid depletion via cleavage of the (1 → 2)-linked 4-O-methyl-α-d-glucuronic acid of xylan. In the polysaccharide anomeric region, decreases in the minor β-d-mannopyranosyl, and α-l-arabinofuranosyl units were observed in the NMR spectra from hydrothermally pretreated wheat straw. The aromatic region indicated only minor changes to the aromatic structures during the process (e.g., further deacylation revealed by the depletion in ferulate and p-coumarate structures). Supplementary chemical analyses showed that the hydrothermal pretreatment increased the cellulose and lignin concentration with partial removal of extractives and hemicelluloses. The subsequent enzymatic hydrolysis incurred further deacetylation of the xylan, leaving approximately 10 % of acetate intact based on the weight of original wheat straw.