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Abstract We have investigated, for the first time, the alkaline pre-treatment of microalgal biomass, from the species Chlorococcum infusionum , using NaOH for bioethanol production. This pre-treatment step aims to release and breakdown entrapped polysaccharides in the microalgae cell walls into fermentable subunits. Three parameters were examined here; the concentration of NaOH, temperature and the pre-treatment time. The bioethanol concentration, glucose concentration and the cell size were studied in order to determine the effectiveness of the pre-treatment process. Microscopic analysis was performed to confirm cell rupturing, the highest glucose yield was determined to be 350 mg/g, and the maximum bioethanol yield obtained was 0.26 g ethanol/g algae using 0.75% (w/v) of NaOH and 120 °C for 30 min. Overall, the alkaline pre-treatment method proved to be promising option to pre-treat microalgal biomass for bioethanol production.

A graphical pinch approach for analysis of water footprint constraints on biofuel production systems is presented. The technique is based on the composite curve method which was originally developed for carbon-constrained energy planning, which is extended in this paper based on the underlying similarities of source-sink allocation problems. The pinch analysis approach enables limiting water footprint conditions to be identified, and provides insights that are useful for planning the large-scale cultivation of biofuel crops. An illustrative case study based on the bioethanol program of the Philippines is solved using the proposed approach.

This study aims at developing a low cost technique to be used in rural and coastal areas for converting saline water into potable water using solar energy. A triangular solar still (TrSS) was, therefore, designed and developed with cheap, lightweight, local and available materials. A number of field experiments were carried out to evaluate the effects of solar radiation intensity, ambient air temperature and the initial water depth on the daily water production of the TrSS. A time lag of about and hour between the hourly peaks of solar radiation and water production is observed. Finally, a few essential relationships were attained, e.g. between the daily production and the initial water depth, between the daily production and daily solar radiation, and between the daily production and the average ambient temperature. The effect of the initial water depth in the basin on the daily water productivity was evaluated by varying the water depths (1.5, 2.5 and 5 cm) with the climatic condition of Malaysia and an inverse proportional relationship was revealed between them. However, the daily water productivity is nearly proportional to the daily solar radiation. In addition, some important water quality parameters were tested in the laboratory to evaluate the distillate quality and were then compared with the drinking water standards.

La gazéification des déchets solides municipaux (DSM) avec l'utilisation ultérieure de gaz de synthèse dans les moteurs à gaz/turbines et les piles à combustible à oxyde solide peut augmenter considérablement la production d'énergie des installations de valorisation énergétique des déchets et optimiser l'utilisation des déchets en tant que ressources énergétiques durables. Cependant, la purification du gaz de synthèse pour éliminer les impuretés multiples telles que les particules, le goudron, le HCl, les chlorures alcalins et les espèces soufrées est nécessaire. Cette étude étudie la faisabilité de la purification à haute température du gaz de synthèse issu de la gazéification des DSM en mettant l'accent sur le reformage catalytique du goudron et la désulfuration. Le gaz de synthèse produit à partir d'un gazéificateur à lit fixe à courant descendant est purifié par un système à plusieurs étages. Le système comprend un reformeur de goudron catalytique à lit fluidisé, un filtre pour les particules et un réacteur à lit fixe pour la déchloration puis la désulfuration avec une cascade globale vers le bas des températures de fonctionnement dans tout le système. Un nouveau catalyseur au nickel nanostructuré supporté sur alumine et un sorbant de désulfuration Ni-Zn régénérable chargé sur nid d'abeilles sont synthétisés. Des méthodes complémentaires d'échantillonnage et d'analyse sont appliquées pour quantifier les impuretés et déterminer leur répartition à différents stades. Les résultats de modélisation expérimentale et thermodynamique sont comparés pour déterminer les contraintes cinétiques dans le système intégré. Le système de purification à chaud démontre jusqu'à 90 % d'efficacité d'élimination du goudron et du soufre, une augmentation du rendement total du gaz de synthèse (14 %) et une amélioration de l'efficacité du gaz froid (12 %). Le gaz de synthèse traité est potentiellement applicable dans les moteurs/turbines à gaz et les piles à combustible à oxyde solide en fonction des points de rosée et des limites de concentration des composés de goudron restants. Le reformage du gaz de synthèse brut par catalyseur au nickel pendant plus de 20 h en flux montre une forte résistance à la désactivation. La désulfuration du gaz de synthèse provenant de la gazéification des DSM contenant une proportion significativement plus élevée de sulfure de carbonyle que de sulfure d'hydrogène, des traces de goudron et de chlorure d'hydrogène démontre une haute performance des sorbants Ni-Zn. La gasificación de residuos sólidos municipales (RSU) con la posterior utilización de gas de síntesis en motores/turbinas de gas y pilas de combustible de óxido sólido puede aumentar sustancialmente la generación de energía de las instalaciones de conversión de residuos en energía y optimizar la utilización de residuos como recursos energéticos sostenibles. Sin embargo, se requiere la purificación del gas de síntesis para eliminar múltiples impurezas como partículas, alquitrán, HCl, cloruros alcalinos y especies de azufre. Este estudio investiga la viabilidad de la purificación a alta temperatura del gas de síntesis de la gasificación de RSU con el enfoque en la reforma catalítica del alquitrán y la desulfuración. El gas de síntesis producido a partir de un gasificador de lecho fijo de corriente descendente se purifica mediante un sistema de múltiples etapas. El sistema comprende un reformador de alquitrán catalítico de lecho fluidizado, un filtro para partículas y un reactor de lecho fijo para la decloración y luego la desulfuración con una cascada descendente general de las temperaturas de operación en todo el sistema. Se sintetizan nuevos catalizadores de níquel nanoestructurados soportados sobre alúmina y sorbente de desulfuración de Ni-Zn regenerable cargado en panal. Se aplican métodos complementarios de muestreo y análisis para cuantificar las impurezas y determinar su distribución en diferentes etapas. Los resultados del modelado experimental y termodinámico se comparan para determinar las restricciones cinéticas en el sistema integrado. El sistema de purificación en caliente demuestra hasta un 90% de eficiencia en la eliminación de alquitrán y azufre, aumento del rendimiento total de gas de síntesis (14%) y mejora de la eficiencia del gas frío (12%). El gas de síntesis tratado es potencialmente aplicable en motores/turbinas de gas y pilas de combustible de óxido sólido en función de los puntos de rocío y los límites de concentración de los compuestos de alquitrán restantes. El reformado del gas de síntesis bruto mediante catalizador de níquel durante más de 20 h en la corriente muestra una fuerte resistencia a la desactivación. La desulfuración del gas de síntesis de la gasificación de RSU que contiene una proporción significativamente mayor de sulfuro de carbonilo que de sulfuro de hidrógeno, trazas de alquitrán y cloruro de hidrógeno demuestra un alto rendimiento de los sorbentes de Ni-Zn. Gasification of municipal solid waste (MSW) with subsequent utilization of syngas in gas engines/turbines and solid oxide fuel cells can substantially increase the power generation of waste-to-energy facilities and optimize the utilization of wastes as a sustainable energy resources. However, purification of syngas to remove multiple impurities such as particulates, tar, HCl, alkali chlorides and sulfur species is required. This study investigates the feasibility of high temperature purification of syngas from MSW gasification with the focus on catalytic tar reforming and desulfurization. Syngas produced from a downdraft fixed-bed gasifier is purified by a multi-stage system. The system comprises of a fluidized-bed catalytic tar reformer, a filter for particulates and a fixed-bed reactor for dechlorination and then desulfurization with overall downward cascading of the operating temperatures throughout the system. Novel nano-structured nickel catalyst supported on alumina and regenerable Ni-Zn desulfurization sorbent loaded on honeycomb are synthesized. Complementary sampling and analysis methods are applied to quantify the impurities and determine their distribution at different stages. Experimental and thermodynamic modeling results are compared to determine the kinetic constraints in the integrated system. The hot purification system demonstrates up to 90% of tar and sulfur removal efficiency, increased total syngas yield (14%) and improved cold gas efficiency (12%). The treated syngas is potentially applicable in gas engines/turbines and solid oxide fuel cells based on the dew points and concentration limits of the remaining tar compounds. Reforming of raw syngas by nickel catalyst for over 20 h on stream shows strong resistance to deactivation. Desulfurization of syngas from MSW gasification containing significantly higher proportion of carbonyl sulfide than hydrogen sulfide, traces of tar and hydrogen chloride demonstrates high performance of Ni-Zn sorbents. يمكن أن يؤدي تغويز النفايات الصلبة البلدية (MSW) مع الاستخدام اللاحق للغاز الاصطناعي في محركات/توربينات الغاز وخلايا وقود الأكسيد الصلب إلى زيادة كبيرة في توليد الطاقة لمرافق تحويل النفايات إلى طاقة وتحسين استخدام النفايات كمصادر طاقة مستدامة. ومع ذلك، يلزم تنقية غاز التخليق لإزالة الشوائب المتعددة مثل الجسيمات والقطران و HCl والكلوريدات القلوية وأنواع الكبريت. تبحث هذه الدراسة في جدوى تنقية الغاز الاصطناعي بدرجة حرارة عالية من تغويز النفايات الصلبة البلدية مع التركيز على إصلاح القطران التحفيزي وإزالة الكبريت. يتم تنقية الغاز المركب المنتج من جهاز التغويز ذو الطبقة الثابتة بنظام متعدد المراحل. يتكون النظام من مصلح القار الحفاز ذو الطبقة المميعة، ومرشح للجسيمات ومفاعل ذو طبقة ثابتة لإزالة الكلور ثم إزالة الكبريت مع التسلسل الهابط الكلي لدرجات حرارة التشغيل في جميع أنحاء النظام. يتم تصنيع محفز النيكل الجديد ذو البنية النانوية المدعوم بالألومينا والمواد الماصة القابلة للتجديد لإزالة الكبريت من Ni - Zn المحملة على قرص العسل. يتم تطبيق طرق أخذ العينات والتحليل التكميلية لتحديد كمية الشوائب وتحديد توزيعها في مراحل مختلفة. تتم مقارنة نتائج النمذجة التجريبية والديناميكية الحرارية لتحديد القيود الحركية في النظام المتكامل. يوضح نظام التنقية الساخنة ما يصل إلى 90 ٪ من كفاءة إزالة القطران والكبريت، وزيادة إجمالي إنتاج غاز التخليق (14 ٪) وتحسين كفاءة الغاز البارد (12 ٪). من المحتمل أن يكون غاز التخليق المعالج قابلاً للتطبيق في محركات/توربينات الغاز وخلايا وقود الأكسيد الصلب بناءً على نقاط الندى وحدود تركيز مركبات القار المتبقية. يُظهر إصلاح غاز التخليق الخام بواسطة محفز النيكل لأكثر من 20 ساعة على التيار مقاومة قوية للتعطيل. إن إزالة الكبريت من غاز التخليق من تغويز النفايات الصلبة البلدية الذي يحتوي على نسبة أعلى بكثير من كبريتيد الكربونيل من كبريتيد الهيدروجين، وآثار القطران وكلوريد الهيدروجين توضح الأداء العالي للمواد الماصة Ni - Zn.

Abstract Biodiesel production by non-catalytic supercritical methyl acetate (SCMA) reaction has been developed and optimized in previous study using Jatropha oil as oil feedstock. The reaction produces fatty methyl acid esters (FAME) as well as triacetin as the co-product. Due to the requirement of high reaction temperatures in SCMA treatment, thus the thermal stability of methyl oleate and methyl linoleate which are the major FAME in SCMA was investigated at temperature ranging from 330 °C to 420 °C. In addition, thermal stability of triacetin which was utilized as fuel additive in biodiesel was also investigated. The results revealed that the thermal stability of poly-unsaturated methyl linoleate decreases dramatically as temperature is increased from 330 °C to 420 °C while degradation of methyl oleate was only significant at 390 °C and above. Similar behaviour was also observed for triacetin which was found to degrade at high temperatures, resulting in low yield of biodiesel fuel even at optimum conditions.

Ineffective waste management that involves dumping of waste in landfills may degrade valuable land resources and emit methane gas (CH4), a more potent greenhouse gas than carbon dioxide (CO2). The incineration of waste also emits polluted chemicals such as dioxin and particle. Therefore, from a solid waste management perspective, both landfilling and incineration practices pose challenges to the development of a green and sustainable future. Waste-to-energy (WtE) has become a promising strategy catering to these issues because the utilisation of waste reduces the amount of landfilled waste (overcoming land resource issues) while increasing renewable energy production. The goal of this paper is to evaluate the energy and carbon reduction potential in Malaysia for various WtE strategies for municipal solid waste (MSW). The material properties of the MSW, its energy conversion potential and subsequent greenhouse gases (GHG) emissions are analysed based on the chemical compositions and biogenic carbon fractions of the waste. The GHG emission reduction potential is also calculated by considering fossil fuel displacement and CH4 avoidance from landfilling. In this paper, five different scenarios are analysed with results indicating a integration of landfill gas (LFG) recovery systems and waste incinerator as the major and minor WtE strategies shows the highest economical benefit with optimal GHG mitigation and energy potential. Sensitivity analysis on the effect of moisture content of MSW towards energy potential and GHG emissions are performed. These evaluations of WtE strategies provides valuable insights for policy decision in MSW management practices with cost effective, energy benefit, environmental protection.

Abstract Green roofs have been proposed for sustainable buildings in many countries with different climatic conditions. A state-of-the-art review of green roofs emphasizing current implementations, technologies, and benefits is presented in this paper. Technical and construction aspects of green roofs are used to classify different systems. Environmental benefits are then discussed mainly by examining measured performances. By reviewing the benefits related to the reduction of building energy consumption, mitigation of urban heat island effect, improvement of air pollution, water management, increase of sound insulation, and ecological preservation, this paper shows how green roofs may contribute to more sustainable buildings and cities. However, an efficient integration of green roofs needs to take into account both the specific climatic conditions and the characteristics of the buildings. Economic considerations related to the life-cycle cost of green roofs are presented together with policies promoting green roofs worldwide. Findings indicate the undeniable environmental benefits of green roofs and their economic feasibility. Likewise, new policies for promoting green roofs show the necessity for incentivizing programs. Future research lines are recommended and the necessity of cross-disciplinary studies is stressed.

Sediment microbial fuel cells (SMFCs) are an innovative, green technology with great potential, and they utilize a voltage drop of redox potential between aerobes and anaerobes to produce electricity and degrade organic wastewater. However, the power performance and degradation rate in SMFCs are limited by the low concentration of dissolved oxygen on the cathode. Therefore, in this study, SMFCs with comb-type cathode electrodes with carbon cloths exposed partly to air and embedded partly in the reactor substrate were designed and operated. They were utilized for enhancing the power density and the effect of three different exposed areas of cathode electrode for improving transfer of oxygen. Results showed that the power density reached 3.77 × 10−2 mW/m2 for 75% of the (MA75) exposed area, which was 1.93 times than that of 50% of the (MA50) exposed area and 6.44 times than that of 0% (i.e., completely immersed; MA0) exposed area. These results indicated that the exposed area of the cathode electrode had a positive effect on the power performance of SMFCs and would reduce the impedance of the cathode. These findings would apparently offer useful information on the feasibility of SMFCs for wastewater treatment applications in the future.