Search

The present communication reports the development of reliable building bricks with improved thermal insulation behavior through substitution of the water mixed with the standard ceramic clayey raw materials with olive-mill wastewater (OMWW). This endeavor will contribute to circular economy and environmental protection as well as possible energy savings and CO2 emission reductions. OMWW is an aqueous by-product generated in large amounts during olive oil production processes. It is characterized by high COD values, low biodegradability, high toxicity, acidic pH, a high concentration of potassium and high solid matter content. Therefore, finding eco-friendly and economically viable solutions for OMWW treatment and valorization represents a significant challenge in the oilproducing countries, in order to avoid severe environmental problems from the uncontrolled disposal of this effluent. For that purpose, a series of ceramic brick specimens are fabricated with the introduction of either olive-mill wastewater or water employing a pilot-plant simulation of the industrial brick manufacturing procedures. The brick thermal conductivity and the mechanical performance are evaluated. According to the results obtained the replacement of fresh water by olive-mill wastewater in the ceramic manufacturing provides a production of lighter building bricks of a decreased thermal conductivity (hence increased thermal insulation capability) as well as an acceptable and a reliable mechanical strength. Furthermore, the energy consumption measurements reveal energy savings of as much as 30% attained during the brick firing. [ABSTRACT FROM AUTHOR]

The present research work introduces a novel mixture optimization methodology for biodiesel fuels using an Evolutionary Computation method inspired by biological evolution. Specifically, the optimal biodiesel composition is deduced from the application of a nature-inspired adaptive genetic algorithm that first examines percentages of the ingredients in the optimal mixtures. The innovative approach's effectiveness lies in problem simulation with improvements in the evaluation of the specific function and the way to define and tune the genetic algorithm. Environmental imperatives in the era of climate change currently impose the optimized production of alternative environmentally friendly biofuels to replace fossil fuels. Biodiesel in particular, appears to be more attractive in recent years, as it originates from renewable bio-derived resources. The main ingredients of the specific biofuel mixture investigated in this research are diesel and biodiesel (100% from bioresources). The assessment of the new biodiesel examined was performed using a fitness function that estimated both the density and cost of the fuel. Beyond the evaluation criterion of cost, density also influences the suitability of this biofuel for commercial use and market sale. The outcomes from the modeling process can be beneficial in saving cost and time for new biodiesel production by using this novel decision-making tool in comparison with randomized laboratory experimentations. [ABSTRACT FROM AUTHOR]

Governments efforts to reduce future emissions and change the trajectory of fossil fuel consumption must include widespread adoption of the Hydrogen (H 2) promise. However, from a long-term viewpoint, inherent uncertainties drive the strategic vision of H 2 development, usage and establishment. The future trends created by a variety of exogenous and endogenous elements, including Political, Economic, Social, Technological, Environmental, and Legal factors (PESTEL) are significantly influenced by these unpredictable volatilities as they come into play. The objective of this study is to recognize, define, and analyze significant PESTEL aspects influencing the dynamics of H 2 energy in an unpredictably changing environment. Fuzzy Inference systems (FIS) and Fuzzy Cognitive Maps (FCM) methodologies were used for the case scenario of Greece to analyze how interrelated criteria from the previous categories interact dynamically and behave in a holistic approach. With the help of diverse quadruple helix stakeholders, a survey and three workshops were conducted to establish a participatory modeling framework with multi-level scenario analysis phases for the Greek use case. Initially, an FCM model was determined as an amalgamation of qualitative and quantitative valued concepts. This model was augmented by four more concepts related to Greek H 2 production plants projecting future trends of this industry. We run several scenarios (including best and worst case) to analyze the influence of politics and regional economy to the growth of H 2 production industry. The scenario of energy crisis depicts a limited positive trend of the hydrogen production. While the economy grows, and the crisis diminishes results show a stronger turn to the hydrogen production. Societal factors affect the process in all phases and scenarios. Results span from deterioration trends to slight improvements depending on the starting values of key criteria. [Display omitted] • A Decision Support System is designed to evaluate the potential for sustainable Hydrogen clean energy production in Greece. • The model utilizes a PESTEL analysis and a Fuzzy Cognitive Map. • Multiple scenario analysis is performed based on various PESTEL criteria. • All results coincide with relevant research findings. [ABSTRACT FROM AUTHOR]

Eggshells are an inorganic waste, and their accumulation rate is increasing globally, complicating waste management. However, the European Union defines eggshells as low-risk material that can be recycled and reused safely in other applications. Their chemical composition renders them an attractive precursor of calcium phosphate materials (CaPs). Because of their remarkable biocompatibility and capacity for natural degradation, CaPs are frequently employed in biomedical engineering applications. In this research, the wet precipitation method was employed for fabricating CaP powder. Initially, the eggshells were processed into CaCO3 powder and then reacted with HCl to obtain CaCl2 (aq). This reacted with Na2HPO4 to obtain a precipitate that was filtered and dried. The precipitate in powder form underwent X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis to evaluate its microstructure, and elemental and phase composition. The results indicated that the recovered powder was brushite. [ABSTRACT FROM AUTHOR]

The deployment of low-carbon energy (LCE) technologies and management of installations represents an imperative to face climate change. LCE planning is an interminable process affected by a multitude of social, economic, environmental, and health factors. A major challenge for policy makers is to select a future clean energy strategy that maximizes sustainability. Thus, policy formulation and evaluation need to be addressed in an analytical manner including multidisciplinary knowledge emanating from diverse social stakeholders. In the current work, a comparative analysis of LCE planning is provided, evaluating different multicriteria decision-making (MCDM) methodologies. Initially, by applying strengths, weaknesses, opportunities, and threats (SWOT) analysis, the available energy alternative technologies are prioritized. A variety of stakeholders is surveyed for that reason. To deal with the ambiguity that occurred in their judgements, fuzzy goal programming (FGP) is used for the translation into fuzzy numbers. Then, the stochastic fuzzy analytic hierarchical process (SF-AHP) and fuzzy technique for order performance by similarity to ideal solution (F-TOPSIS) are applied to evaluate a repertoire of energy alternative forms including biofuel, solar, hydro, and wind power. The methodologies are estimated based on the same set of tangible and intangible criteria for the case study of Thessaly Region, Greece. The application of FGP ranked the four energy types in terms of feasibility and positioned solar-generated energy as first, with a membership function of 0.99. Among the criteria repertoire used by the stakeholders, the SF-AHP evaluated all the criteria categories separately and selected the most significant category representative. Finally, F-TOPSIS assessed these criteria ordering the energy forms, in terms of descending order of ideal solution, as follows: solar, biofuel, hydro, and wind. [ABSTRACT FROM AUTHOR]

Several energy transition plans attempt to establish low-carbon practices towards a circular bio-economy in order to reduce greenhouse gas emissions. However, most actions only try to assuage the impacts of climate change without improving the resource flows generated by human activities. In this paper, we propose a semi-quantitative assessment of the impacts of biowaste-based energy transition by engaging all relevant social stakeholders' evaluation in the strategic plan. This holistic approach models a Decision Support System (DSS) to effectively evaluate the interplay of local and sectoral low-carbon actions. Regional energy alliances and stakeholders are used for participatory modeling to promote the buildup of the learning base of this DSS. The core pillar of the DSS involves the application of advanced features of soft computing for the development of a Fuzzy Cognitive Map (FCM) that elicits the inter-causalities of the critical factors affecting the energy transitions towards bio-economy options. The concepts participating in the map are established by experts, and their interrelations via a learning process that utilizes survey statistics. The strands of research include scenarios to highlight the effect of energy provision to urbanization and the increase of urban actors (social, technological, political) in influencing the decision making related to low-carbon policies. Particularly, we study a use case of a Greek region that, despite its munificent agricultural production, also disclosures a stimulated manufacturing economy sector. The proposed decision making tool uses analytics and optimization algorithms to guide competent authorities and decision makers to sustainable energy transitioning towards decarbonization. Unlabelled Image • Holistic assessment of bio-based energy transition to circular economy • Fuzzy Cognitive Map-based DSS for the influential actors towards decarbonization • Case study of the impacts from biowaste-based transition to biofuel energy • Drying and biowaste technologies increase the shift to bioethanol by 5%. [ABSTRACT FROM AUTHOR]

The aim of the current research was to investigate and compare the total phenolic content and antioxidant capacity of sweet pepper cultivars at different development and maturation stages, in order to optimize the beneficial effects. For that purpose, three important sweet pepper cultivars, namely Dolmy-F1, Yahoo-F1 and Florinis-NS-700, were cultivated in a greenhouse. Their total phenolic content, ascorbic acid content and antioxidant properties were assessed at different development and maturation stages. In the aforementioned cultivars, the total phenolic content ranged from 345.2 to 602.1, 404.9 to 794.5, and 795.7 to 2220.3 μg GAE g-1 FW respectively. The ascorbic acid content ranged from 236 to 957, 258 to 1157, and 410 to 1550 μg AA g-1 FW respectively. The highest antioxidant activity was noted at the red maturity stage. Particularly the cultivar Florinis NS 700 was found to possess higher total phenolic, flavonoid phenol, non-flavonoid phenol, ascorbic acid contents, and greater antioxidant capacity, compared to the other cultivars. The results of our study recommend the consumption of the sweet peppers at red maturity stage, for achieving the maximum health-beneficial effects. [ABSTRACT FROM AUTHOR]

The transformation of both calcareous and siliceous Greek power station by-products (lignite ashes) into novel composite materials with photocatalytic properties for environmental application was investigated. Particularly, a comparison between the development of coated ceramic substrates and the modification of ash surfaces is attempted. Specifically, a) the sintering process (1000 °C, 2 h) of both fly and bottom ash (either calcareous or siliceous) for their conversion into compacted ceramic substrates coated with TiO2 slurry and then further thermally treated (500 °C, 1 h) to acquire TiO2 film consistency onto the ceramic substrate and b) the process of TiO2 precipitation on lignite ash surfaces in acidic solution after neutralization, and estimation of the TiO2 percentage, are compared. The microstructures obtained were examined by XRD and SEM-EDX analysis. Vickers microhardness was also determined for the ceramic microstructures, with satisfactory results (up to 356HV). The energy gap measurements of the coatings were found to be between 3.02eV and 3.17eV, which is located between the energy gap of anatase (3.23eV) and rutile (3.02eV). The coating mass was about 0.059 g/cm2. The photocatalytic activity under visible and UV irradiation was investigated in aqueous solutions of methylene blue and methyl orange organic dyes, with encouraging results. A main advantage of the processes proposed is the immobilization of TiO2 onto largely available secondary resources, which can lead to production of value-added 'green' photocatalysts for the treatment of industrial effluents in the framework of circular economy. [ABSTRACT FROM AUTHOR]

In the current study, the production of novel antioxidants for hygienic disinfection against common pathogenic bacteria, based on the incorporation of bioextractant oils/waters from either lavender or oregano distillates is proposed in the framework of circular economy. For the first time, the main compounds found in distillation products (oils/waters), specifically of lavender Lavandula angustifolia (lynalyl acetate and linalool) and of oregano Oreganum vulgare (carvacrol, thymol, and p-cymene) are presented. The analyses of both the lavender and oregano essential oils/waters indicate excellent physicochemical properties and microbial absence. Moreover, the antioxidant activity of all distillates as DPPH radical scavengers is assessed. The results confirm that the essential oils of both oregano and lavender possess superior antioxidant activity to their corresponding waters, while the oregano oil exhibited far better antioxidant activity than the lavender oil, as 1 mL of oregano oil was able to consume 45 μmoles of DPPH radicals. Overall, our research findings suggest that the particular lavender and oregano bioextractants produced possess important potential to address the resistance of bacteria from the perspective of their wider exploitation in therapeutic or preventive medicine, thus contributing to enhancing public health. [ABSTRACT FROM AUTHOR]

The effect of the algal species Chlorella vulgaris at six different ratios (0, 1, 2, 3, 4, 5 g) of air dried algae biomass, mixed with 10.18 g of sheep manure, added to 50 g of soil, and incubated for a period of 15 weeks was studied in a laboratory in order to detect the role of adding small amounts of admixed algal biomass to soil in biodegradation of soil organic carbon. The obtained data showed that mineralization of soil organic carbon increased by 16.2-35.9% at all rates of algae addition compared to the control, while the highest increase was observed at the highest rates of algae addition. There was a 40-50% increase in the available form of potassium, while the highest increase was also observed at the highest rates of algae addition. The four times higher rates of added algae increased the corresponding content of nitrate nitrogen by 20-30%, while ammonium nitrogen contents decreased by 9.5-35.7% for all amounts of added algae in comparison with the control. The available forms of copper, manganese, and zinc were also increased for all amounts of added algae by 56.8-61.9%, 55.8-67.3%, and 34.1-40.6%, respectively. On the contrary, the addition of algae did not indicate significant differences among treatments as concerns organic or available phosphorus contents. The results proved the effect of the algae Chlorella vulgaris as an accelerator agent in biodegradation of soil organic matter, without any significant negative impact on soil chemical properties. [ABSTRACT FROM AUTHOR]

This research aims at the utilization of both calcareous and siliceous lignite ashes, by-products of lignite combustion in power plants, toward a development of new materials of an environmental benefit. The possibility of fly and bottom ash surface modification by anatase and rutile (titanium dioxide structures) is investigated. The precipitation of TiO2 from an acidic solution on lignite ash surface is studied and the percentage of TiO2 coating obtained is found ranging from 11 to 55%. The latter microstructure is examined by XRD and SEM-EDX taking into consideration the ashes particle size (as received and < 45 µm), the solution pH (5.5 - 7.5), the ageing time (1 and 3 h) and the sintering temperature (300°C, 500°C, 700°C) applied. Anatase and rutile crystalline structures are observed within the whole heat treatment range. The main advantage of the process reported refers to titania immobilization onto a cheap porous substrate providing an additional solution to liquid wastes treatment by photocatalysis. [ABSTRACT FROM AUTHOR]

The cogeneration of power and heat was investigated for Biomass Boiler–Organic Rankine Cycle (BB–ORC) plants with the characteristics of typical units, such as the 1 MWel Turboden ORC 10 CHP. The thermodynamic analysis of the ORC unit was undertaken considering forty-two (42) dry and isentropic candidate pure working fluids. Only subcritical Rankine cycles were considered, and the pinch point temperature differences for the evaporation and condensation heat exchangers were kept constant at 10 °C in all cases. The study provides an original and unique screening of almost all pure working fluids that are considered appropriate in the literature under the same operation and optimization conditions and compiles them into a single reference. In its conclusions, the study provides useful fluid selection and design guidelines, which may be easily followed depending on the optimization objective of the ORC designer or operator. In general, hydrocarbons are found to lie in the optimum middle range of the fluid spectrum, between the siloxanes that maximize the production of mechanical power and the refrigerants that maximize the production of heat. Specific hydrocarbon fluids, such as cyclopentane, heptane, hexane, benzene, and toluene, are found as rational options for maximum mechanical efficiency when operating with practically feasible condensation pressures between 10 and 200 kPa. At condensation pressures below 10 kPa, ethylbenzene, o-xylene, m-xylene, p-xylene, and nonane are also found to be feasible options. Finally, cyclopentane, hexane, and MM (hexamethyldisiloxane) are selected as the most appropriate options for cogeneration plants aiming simultaneously at high mechanical power and maximum temperature water production. [ABSTRACT FROM AUTHOR]