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Urban areas have a considerable impact on the environment. Among the sectors contributing to the environmental impacts is plastic product usage, resulting in urban plastic waste accumulation. There exists a need to determine and evaluate plastic flows and their environmental impacts in urban areas. Our research comprehended the modelling of the eight most commonly used plastic polymers in a system of a European city with 10^5 inhabitants for the year 2020. A scenario analysis was conducted, considering the European Union's policy of achieving a 65 % recycling rate by 2035. Plastic production contributes to most environmental impacts during the life cycle, where polyurethane, polystyrene and other plastic types are at the forefront. The results per waste management options revealed that recycling is still preferable for plastic waste, followed by incineration and landfill. Recycling potential was further noted during the scenario analysis, where an increased recycling fraction following the EU's policy could decrease the environmental impacts of global warming by a margin of 20 %–45 % and fossil resource scarcity by a margin of 20 %–52 % per individual plastic polymer. While the established model indicates potential benefits, improved data collecting, and further research are needed to improve the model and establish a plastic nexus within urban areas. [Display omitted] [ABSTRACT FROM AUTHOR]

This work presents a flowsheet superstructure and integration possibilities for simultaneous optimization of the maximum share of attainable direct and indirect solar utilization through heat storage in industrial operations. Multi-period Mixed Integer Non-Linear Programming (MINLP) models were developed for this purpose and account for the dynamics in the profile of heat supply and demand using discrete time intervals/periods. The resulting models are applied to an industrial case study of a dairy plant for the two distinct integration alternatives of targeting one and multiple (two) cold stream utility requirements. The design and optimization of the integrated system is implemented and solved in GAMS. The results show good prospect for solar thermal utilization in industries with low temperature applications. Sensitivity analysis shows linear increase in the average attainable heat load up to certain collector area (on case-by-case basis), after which a break point is obtained where it is observed that additional increase in collector area does not result to much increase in the obtained heat load. For the selected case study of a dairy plant, average solar output of about 75 W/m2 of collector is obtained. Image 1 • Model for integration of solar thermal for industrial applications is proposed. • Dynamic model includes periodic heat storage and backup utility. • Design parameters and operating conditions are optimised by maximizing total heat output. • Sensitivity analysis shows attainable heat load versus collector area. • Two integration patterns involving one and multiple cold streams are considered. [ABSTRACT FROM AUTHOR]

Abstract Sustainable management in the biogas production via anaerobic digestion process intents the use of alternative biomass sources that are not competitive with food production. The aim of this study is to investigate the application of the abundant-quantity residue in more sustainable production of heat and electricity along with the production of the digested substrate as a fertiliser. The study has been divided into several sequential steps. First, the grass samples have been collected at the following locations: uncultivated land, river embankment and highway verge. The greatest grass yield has been determined for the riverbank grass, with an average value of 19 t/ha of fresh mass and 2.6 t/ha of dry mass. Next, the chemical characterisation of the collected residue grass and the laboratory batch mono and co-digestion tests with maize silage and cattle slurry have been conducted. The results show that all grass samples have satisfying digestive parameters (C/N ratio between 16.6:1 to 22.8:1) with the low presence of impurities, which makes them suitable for biogas production. The following biochemical methane potential in mono-digestion of residue grass has been recorded: uncultivated land (0.275 Nm3/kgTS), riverbank (0.192 Nm3/kgTS) and highway verge (0.255 Nm3/kgTS). The control of the process has been improved in co-digestion tests, by avoiding acidification in the first days of the operation. The estimation of kinetic parameters in mathematical modelling has shown that the degradation of residue grass shows some different parameters compared to the previous study. The model results for the gas phase show some small deviations compared to the experimental data. Based on the life cycle analysis results it can be concluded that there are perspectives in the use of residual grass compared to maize silage in the production of heat and electricity, especially in the improvement of ecosystem quality. Graphical abstract Image 107654 Highlights • Utilisation of residue grass in anaerobic mono- and co-digestions is analysed. • Grass mowed on uncultivated land, on river embarkment and on highway verge is studied. • Characterisation of grass types, anaerobic digestion, kinetic modelling and LCA are performed. • Position of grassland influences the grass properties and anaerobic digestion. • Residue grasses show potential to serve as feedstocks for mono- and co-digestion. [ABSTRACT FROM AUTHOR]

• Economic optimization model and application to biogas supply network is presented. • Biogas supply network from various optional feedstocks is optimized. • Poultry manure, poultry bedding and corn silage are optimal raw materials. • Most profitable solution shows 13% dry matter and 59.44% methane content. • Sensitivity analysis includes variations in prices, dry matter content and production of food. This contribution presents a developed generic mixed integer linear programming (MILP) model for optimizing biogas supply network to generate electricity over monthly time-periods by maximizing the economic performance. Dry matter content and methane yield for each feedstock are included, which more accurately represents a realistic network. The model is applied to an illustrative case study of an agricultural biogas production plant in Slovenia. Optimal results show poultry manure and bedding and corn silage as the selected feedstocks to meet the production of 999 kW of electricity. Technologies selected include anaerobic digester, press-based dewatering and combined heat and power plant (CHP), while water, and heat required for the anaerobic digestion plant itself are "recycled". A profit after tax of about 254,625 $/y is obtained. Furthermore, sensitivity analysis in terms of prices of electricity and digestate, dry matter content and utilization of crop residues is performed. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract This paper describes an upgraded concept of the sustainability metric named Sustainability Profit (SP) from various micro- and macroeconomic perspectives and how it can be used for the synthesis of production systems in order to increase their circularity. An upgraded concept of SP is presented from three different perspectives: a microeconomic one, representing the company level, a macroeconomic perspective, combining the company and country (government) levels, and a wider macroeconomic one, with the addition of individuals (employees). Basic indicators of circularity, which measure the share of materials and energy reuse, are incorporated in order to synthesize more sustainable systems involving reuse of materials and energy. The concept is demonstrated on two case studies of supply network synthesis. The first case study is a supply network of fossil and renewable electricity production from various energy sources with fixed electricity demand, and the second case study is a larger-scale, renewable-based supply network for producing food, biofuels and electricity, and is applied to Central Europe. The results indicate that, by maximizing SP using the upgraded concept, overall circularity is favoured, and trade-offs between different sustainability pillars are obtained. The study could further be extended to account for uncertainty and more detailed Eco- and Social profit analysis and circularity measures as a good decision support tool in evaluating sustainable production systems. Graphical abstract Image 1 Highlights • Sustainability Profit has been upgraded for a wider macroeconomic perspective. • Employee perspective is added to the company and government perspectives. • Sustainability Profit is studied in relation to energy and mass circularity indicators. • It is applied to the synthesis of a large scale, renewable energy supply network. • Sustainable solutions exhibit high sustainability profits and high circularity indicators. [ABSTRACT FROM AUTHOR]

This study presents an extension of a recently proposed concept and metric by the authors named “Sustainability profit” to “Sustainability net present value” for the purpose of synthesizing more sustainable large-scale energy supply networks. The concept and metric are based on a composite sustainability measurement considering economic, environmental and social pillars and expressed in monetary terms from a wider macro-economic perspective that combines both the governmental and the industrial view. By using the proposed metric, it is possible to obtain answers regarding the advisability of a particular investment in terms of sustainability. The concept is illustrated by two examples: (i) a smaller case study presenting an electricity supply network consuming fossil and/or renewable energy sources, and (ii) a larger-scale renewable energy supply network considering biomass, waste, solar, wind and geothermal energies on an EU continental scale. Solutions obtained to problems regarding maximizing Sustainability net present value occur at the trade-off between economic profitability, environmental (un)burdening, and new jobs created, considering the time value of the money involved. [ABSTRACT FROM AUTHOR]

The recognition of the humans, vehicles or any other objects in the outdoor environment, such as roads, streets, pedestrian ways, car parking and public parks, is only possible with illumination after dark. The outdoor lighting consumes significant amounts of electricity. The best short-term payout period for reduction in energy consumption is implementation of energy efficiency solutions. A shift from traditional illumination technology to the advanced lighting solutions has the ability for significant energy savings. The main focus of this study is to find out the most suitable, environmentally friendly and “green” solution(s) to fulfill the outdoor lighting requirements. It includes ecological impact assessment of commonly available lighting technologies for outdoor illumination, such as high pressure sodium, compact fluorescent and light emitting diode, by using Sustainable Process Index methodology. The effects of different alternative energy resources and the impacts of geographical locations due to variations in energy provision system (i.e. energy mix) are also considered in this study. The obtained results show that Sustainable Process Index ranges from 258 km 2 to 7760 km 2 and carbon footprint from 930 t CO 2 eq. to 48,496 t CO 2 eq. to fulfill lighting requirement for 100,000 h of lighting. These results are compared with Sustainable Process Index and Carbon Footprint caused by high pressure sodium and light emitting diode luminaires providing electricity from Saudi Arabian electricity network. [ABSTRACT FROM AUTHOR]

This study proposes a new concept and a new metric for multi-criteria evaluation of sustainable systems. The new metric, termed “sustainability profit”, is composed of economic, environmental and social indicators. Since all of these are expressed by monetary terms, the different criteria are now merged, and a multi-objective optimization problem can be reduced to a single-objective one. The new concept for measuring sustainability is based on micro-economic (company’s viewpoint) and on wider macro-economic perspectives (combined government’s and company’s viewpoint). The concept and metric presented are illustrated by three examples of supply networks including a large-scale biorefinery supply network. The obtained results give the insights into sustainable technologies from the overall sustainability viewpoint, and also evaluate the stimulations from governments in the form of subsidies and taxes for deployment of (un-)sustainable systems. The results also indicate that this metric provides good compromise solutions between economic, environmental and social pillars of sustainability. [ABSTRACT FROM AUTHOR]

This contribution presents a multi-objective Mixed-Integer Linear Programming (MILP) synthesis of a dynamic supply-network under uncertainty applied to food industry. The previously-developed multi-objective model for achieving energy self-sufficiency by integrating renewables into companies' supply-networks has now been extended to account for the dynamic consideration of variable supply and demand over the year, for uncertainties related to products' demand and sun radiation, and for multi-objective optimisation, in order to obtain the most sustainable company's supply-network. The sustainable synthesis of a company's network is performed regarding the integration of renewables such as biomass and other wastes, and solar energy. The obtained solutions are those reflecting maximal profit, reflecting constantly-changing dynamic market conditions, accounting for several uncertain parameters, and protecting the environment. [ABSTRACT FROM AUTHOR]

Abstract: This contribution addresses the multi-period synthesis of an optimally integrated regional biomass and bioenergy supply network through a mixed-integer linear programing (MILP) approach. The production processes from different sources of biomass include first, second, and third generations of biofuels like bioethanol, biodiesel, hydrogen, Fischer Tropsch diesel, and green gasoline. The aim is to maximize the sustainably viable utilization of resources by accounting for the competition between fuels and food production. An MILP model for efficient bioenergy network optimization based on four layers is extended to include several features, such as seasonality and availability of resources, enabling recycles of products and total site heat integration in order to address real-world applications with a systematic decision-making approach. The multi-period optimization of a heat-integrated biorefinery's supply network is performed through maximization of the economic performance. Economically efficient solutions are obtained with optimal selection of raw materials, technologies, intermediate and final product flows, and reduced greenhouse-gas emissions. [Copyright &y& Elsevier]

Abstract: This contribution presents a simplified and more practical version of an objective dimensionality reduction method within multi-objective optimisation – a Representative Objectives Method. This method is based on similarities between several objectives in order to reduce the number of objectives to a minimum number of representative objectives. This method can be applied to different direct and total objectives. In this contribution the selected objectives are annual profit and total footprints. Total footprints are the sum of direct and indirect footprints where the direct footprints only consider the burdening of the environment, whilst the total footprints consider both the burdening and unburdening of the environment. This dimensionality reduction method is applied during a demonstration case study of regional supply chains regarding the evaluations of different total environmental footprints. This case study indicates that this simplified version of the Representative Objectives Method is easy to apply and enables the user to more easily understand multi-objective optimisation solutions. It represents a practical tool for performing the dimensionality reduction of criteria during the economic and environmental optimisation of different problems when considering total environmental footprints. [Copyright &y& Elsevier]

Abstract: This contribution presents and discusses two multi-objective optimisation approaches considering total (direct and indirect) effects on the environment. Sustainability metrics, conventionally measuring direct harmful effects on the environment, are now upgraded with indirect effects in order to measure the unburdening the environment, e.g. due to the substitution of harmful with benign products. The first approach, based on a relative direct sustainability index, is now upgraded to a total sustainability index, and the second one, based on a concept of eco-cost and net profit, is extended to a recently introduced concept of eco- and total profit. These approaches are illustrated through a case study of the supply chain synthesis for producing biogas from organic and animal wastes. The results indicate that considering total effects enables obtaining more realistic solutions, than in those cases when only direct effects are considered. An appropriate trade-off between economic and environmental criteria can be established when performing a maximisation of total profit. [Copyright &y& Elsevier]

Abstract: This study presents an overview of footprints as defined indicators that can be used to measure sustainability. An overview of the definitions and units of measurement associated with environmental, social, and economic footprints is important because the definitions of footprints vary and are often expressed unclearly. Composite footprints combining two or more individual footprints are also assessed. These combinations produce multi-objective optimisation problems. Several tools for footprint(s)'' evaluation are presented, including some of the numerous carbon footprint calculators, available calculators for other footprints, some ecological footprints-based, graph-based, and mathematical programming tools. A comprehensive overview is offered of footprint-based sustainability assessment. [Copyright &y& Elsevier]

Abstract: This paper presents a MCO (multi-criteria optimisation) of regional biomass supply chains for the conversion of biomass to energy through the simultaneous maximisation of economic performance and minimisation of the environmental and social FPs (footprints). The energy supply-chain model contains agricultural, pre-processing, processing, and distribution layers. An integrated model, previously developed by the authors, for regional biomass energy network optimisation is used as a basis, and now extended for simultaneous assessment of the supply-chain performance based on LCA (Life cycle assessment). Several total FPs are introduced for “cradle” to “grave” evaluation, which, besides direct, comprises also indirect effects caused by products’ substitutions. In the MCO approach, the annual profit is maximised against each FP generating different sets of Pareto optimal solutions, one for each FP. With this approach the aggregation of different environmental and/or social pressures is thus avoided. The results indicate that total FPs enable the obtaining of more realistic solutions, than in those cases when only direct FPs are considered. More profitable and less environmentally harmful solutions can be gained with significant reduction in total carbon and total energy FPs. [Copyright &y& Elsevier]

Abstract: The objective of this contribution is to perform the sustainable mixed-integer linear programming (MILP) synthesis of biogas processes based on life cycle assessment (LCA). An aggregated model previously developed by authors for the efficient optimisation of biogas processes has been upgraded with LCA, using the novel concept of eco-profit. Eco-profit is defined as the difference between burdening (eco-cost) and unburdening (eco-benefit) the environment, where eco-cost and eco-benefit calculations are based on LCA. The advantage of eco-profit is that it is expressed as a monetary value. Therefore, eco-profit and economic profit can be merged together and the preferred solutions are those with maximal total profit. The single-and multi-objective optimisations were performed on a model of the biogas production processes. Within the former, economic, eco- and total profit were maximised separately and, within the latter, maximisation of economic profit vs. eco-profit was introduced. All the results obtained from single- and multi-criteria optimisation show that biogas production is a sustainable alternative that provides an important eco-profit. [Copyright &y& Elsevier]

Abstract: This paper presents simultaneous integration of different technologies such as the traditional dry-grind process to obtain ethanol from grain with the gasification of the corn stover followed by either syngas fermentation or catalytic mixed alcohols synthesis. The optimal integrated process when using the entire corn plant (18kg/s of grain and 10.8kg/s of stover) is the one in which the dry-grind technology to process corn grain is integrated with the catalytic path for the corn stover due to the improved integration of energy, requiring only 17MW of energy, 50MW of cooling and 1.56gal/gal of freshwater, for an ethanol production cost of 1.22$/gal. However, the production cost decreases as we only use stover to produce ethanol, while the grain is used for food due to the lower cost of the stover and the more favorable energy balance of the ethanol production process from gasification. [Copyright &y& Elsevier]

A large fraction of anthropogenic CO 2 emissions comes from large point sources such as power plants, petroleum refineries, and large industrial facilities. A significant decrease of these CO 2 emissions can be achieved with CO 2 capture, utilization, and storage (CCUS) technologies. This study proposes a conceptually simplified model for the optimization of combined CO 2 supply networks and capture and utilization technologies by the mixed-integer non-linear programming (MINLP) approach. The objective is to maximize the profit of CCUS technologies, considering chemisorption using methyl-diethanolamine (MDEA) as a capture technology and conversion of CO 2 to CH 3 OH as a utilization technology. Additionally, avoided tax from reduced CO 2 emissions is considered as a revenue. A hypothetical case study of five larger point sources of CO 2 was investigated, namely coal power plants, biogas plant, aluminium production plant and two cement plants. Two scenarios were considered: i) Scenario A considering different values of the CO 2 tax, and ii) Scenario B considering different flue gas flowrates at different values of the CO 2 tax. The results show the potential of model-based optimization in reducing the amount of CO 2 in the atmosphere by CCUS technology. Furthermore, the results in Scenario A show that CCUS technology is only profitable if the price of CO 2 emissions is higher than 110 €/t emitted CO 2. Moreover, the results in Scenario B show that both the profit and the production of CH 3 OH depend to a large extent on the flue gas flow. [Display omitted] • An improved CO 2 network model for Carbon Capture, Utilization and Storage (CCUS). • Introduction of the MINLP approach with detailed capture and utilization flowsheets. • Locations, routes and transport modes optimally determined with operating conditions. • Investigation of CO 2 taxation influence and flue gas effluents on an annual profit. • CCUS technology currently profitable at CO 2 emission prices above 110 €/t. [ABSTRACT FROM AUTHOR]

In order to achieve the goal of a carbon neutral EU by 2050 and meet the climate targets of the Paris Agreement, a sustainable, efficient, competitive and secure energy system needs to be developed. This paper presents the synthesis of sustainable renewable energy supply networks within the EU-27, proposing a stepwise energy transition in the transport and power sectors, achieving a carbon net neutral target by 2050. A multi-period mixed-integer programming model is developed, with the objective of maximizing sustainability net present value, considering different biomass and waste resources for the production of biofuels, renewable electricity, hydrogen, food and bioproducts, employing different types of technologies. The results show that, with further development of existing technologies, the goal of a carbon-neutral EU can be achieved without compromising food production. Wind farms have proven to be the most promising solution at present for the rapid expansion of electricity generation from renewable energy sources, while the importance of solar photovoltaics is increasing over the years, reaching the 43% share of electricity generation from RES in 2050. Moreover, the energy transition within the EU could have a significant positive impact on the economic, environmental and also social aspects of sustainability, with more than 1.5 million new job opportunities created across the EU over the next 30 years. [Display omitted] • Mathematical programming approach for the transition to carbon-neutral EU by 2050. • Critical review of technologies and synthesis of renewable energy supply networks. • Sustainable multi-period selection of locations, products and types of technologies. • Large economic, eco and social benefits if optimization is carried out at EU level. • Carbon-neutral EU can be achieved through further development of technologies. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells have emerged as a promising alternative to conventional solar cells due to their cost-effectiveness and ease of fabrication. In recent years, the integration of nanomaterials into dye-sensitized solar cells has garnered substantial attention, offering new avenues to enhance their photoelectric performance. This review comprehensively examines the role of nanomaterials in elevating the efficiency and functionality of dye-sensitized solar cells. The fundamental principles of dye-sensitized solar cells are introduced, emphasizing the intricate interplay between crucial components that enable light absorption, charge separation, and electron transport. Nanomaterials play important roles across the entire spectrum of photoelectric conversion of dye-sensitized solar cells, e.g., constructing light-trapping architectures, creating interlayer transmission bridges, and facilitating charge carrier transport pathways, thus offering cost-effective alternatives to precious metals. Furthermore, this review concludes the central role of nanomaterials in shaping the landscape of flexible optoelectronic materials, highlighting their paramount importance in this area. The extensive scientific insights presented herein not only showcase the cutting-edge achievements in solar energy conversion efficiency but also serve as a comprehensive guide for the proper selection of nanomaterials. Finally, this work outlines the forthcoming challenges and offers insights into promising research avenues based on a comprehensive examination of various scholarly pursuits. Unlike other reviews that focus on the analyses of structures or components, this review concentrates on the impact of nanomaterials on the overall photoelectric performance of dye-sensitized solar cells. By fostering cross-disciplinary collaboration and advancing relevant research, dye-sensitized solar cells hold promise as a significant contributor to the global transition toward clean and renewable energy sources. [Display omitted] • Sensitizer and electrolyte are the keys to enhancing the performance of DSSCs. • Ultra-thin nanolayer improves cell stability and charge transport characteristics. • Nanomaterials promote cross-linked network formation in quasi-solid electrolytes. • Using nanomaterials in solar cells can extend their lifespan by 40%–60%. • Nano-textured structure leads to ∼30% increase in power conversion efficiency. [ABSTRACT FROM AUTHOR]

• Robust approach for MINLP process synthesis under uncertainty is proposed. • Decomposition to optimization of first- and second-stage variables is used. • Flexible solutions are obtained by solving one- or two-scenario problems. • Sizes of mathematical models do not grow with the number of uncertain parameters. • The procedure is applied to synthesis of flexible agricultural biogas supply network. This contribution presents the application of a systematic tool for the synthesis of flexible supply networks under uncertain conditions. The proposed methodology consists of four steps during which an inflexible supply network constructed under nominal conditions progressively develops into a flexible network. First-stage variables are determined by a two-scenario mixed integer linear programming (MILP) model in which uncertain parameters deviate through specified ranges from their nominal values. The second-stage variables are determined by one-scenario Monte Carlo stochastic optimization. The approach is demonstrated on an illustrative case study of an agricultural biogas supply network with the objective being to maximize economic, eco- and viability profits. Flexible biogas supply networks with 28 uncertain parameters were achieved with acceptable computational effort. The expected economic and viability profits decreased compared to nominal profits by around 8%, while the eco-profit increased slightly as a result of higher utilization of less burdensome raw materials. [ABSTRACT FROM AUTHOR]

Formalin is among the most important commodity chemicals, used mainly as a precursor to a wide range of value-added products. Currently, formalin is widely produced from methanol derived from natural gas, however a transition from fossil-based production to sustainable feedstocks and pathways is crucial. This study evaluates the environmental impacts of selected promising formalin production technologies to shape a pathway towards more sustainable production of key chemicals. Among the investigated production routes are through methane steam reforming of other fossil and renewable sources, hydrogenation of CO 2 , and direct conversion of methane, syngas or CO 2. to formalin. A comparative Life Cycle Assessment (LCA) is performed for seven different formalin synthesis routes with higher readiness levels. Technologies utilizing waste CO 2 and biogas from manure as feedstocks show the most promising results, reducing greenhouse gas footprint by roughly 60% compared to the conventional pathway. Results show that a key contribution to the environmental impact mitigation was the unburdening effect due to the use of waste and product's substitution. With this study, a more comprehensive outlook focusing on the environmental sustainability of formalin production is provided. Environmental performance and readiness levels of formalin production technologies utilizing renewable or waste feedstocks indicate that such pathways could be applied to industrial scale in the future. • Formalin production routes with higher Technology Readiness Levels are studied. • Environmental impacts for selected formalin production technologies are evaluated. • Technologies utilizing waste CO 2 and biogas from manure show promising results. • Greenhouse gas footprint is reduced by up to 60% compared to conventional pathway. • A key mitigation is unburdening effect due to waste use and product substitution. [ABSTRACT FROM AUTHOR]

In this study, the hydrothermal co-carbonization (co-HTC) of residues from the vegetable oil industry (pumpkin oil cake – PC, hemp oil cake – HC) and sewage sludge (SS) was investigated for the first time. The co-HTC was performed at 250 °C and a treatment time of 5 h. The effects of the mass ratio of the feedstocks (1:1, 1:3 and 3:1) on the properties of the HTC products were investigated using various analytical methods (NMR, XRD, 3D-EEM, FTIR, etc.). The co-HTC of SS with oil cakes resulted in improved fuel properties of the hydrochar and an increase in C content from 36.9 to 53.7 wt%, and an increase in the higher heating value (HHV) from 14.8 to 23.6 MJ/kg. The combination with HC gave hydrochars with a higher HHV and higher C content than the combination with PC. The hydrochar yield varied in the range of 39.4–55.3 wt%. NMR analysis revealed a higher proportion of aliphatic (∼60 %) than aromatic compounds (∼35 %) in the hydrochars, as well as a high content of orthophosphate and unsaturated fatty acids. The liquid fractions were rich in nutrients and organic compounds, but toxic to aquatic organisms. The hydrochars and liquid fractions performed well in the germination test with plant species. [Display omitted] • Sewage sludge was hydrothermally co-carbonized with hemp/pumpkin oil cake. • Hydrothermal co-carbonization increases C content of hydrochar from 37 to 54 wt%. • The higher the content of oil cake the higher the calorific value of hydrochar. • NMR showed significant differences in C, P speciation and lipid distribution. • The process liquids were rich in phenolic compounds and volatile fatty acids. [ABSTRACT FROM AUTHOR]

The bionic fins inspired by the shark are proposed to enhance the thermal-hydraulic performance of the intercoolers in this work. The geometric parameters of the fins are investigated to examine the effects on thermal-hydraulic performance. The height and width of protrusions are chosen as optimization parameters based on the results of the geometric parameter analysis. Non-dominated genetic algorithms are combined with artificial neural networks to obtain the optimal solution for the geometry parameters. The artificial neural networks used in this study exhibit a reliable accuracy with errors below 10 % (with mostly remaining below 5 %). The optimal values for the height and width of the protrusions are determined to be 1.01 mm and 0.82 mm, which results in a Colburn factor of 0.01923 and a comprehensive index of 0.04305. Compared with the original design, the optimized structure yields 17.69 % and 4.77 % increments for the Colburn factor and comprehensive index. Compared with the original model, the intercooler with the optimal structure exhibits a 9.9 % increase in entropy generation and a 20.2 % enhancement in the exergy difference between the inlet and outlet. • Bionic fins are designed to enhance the thermal performance of intercoolers. • Globally optimal results are obtained by non-dominated genetic algorithms. • Optimal fin is proposed with a protrusion height of 1.01 mm and width of 0.82 mm. • A 17.69 % increment in Colburn factor is obtained for the optimized intercooler. • Comprehensive index of the intercooler increases by 4.77 % with the optimized fin. [ABSTRACT FROM AUTHOR]

To keep temperature rise well below 2 °C, production systems should be synthesised in a way that are regenerative, climate-resilient, and equitable, and to maintain biodiversity to preserve life and meet future human needs with the integrity of nature. In line with this approach, this paper presents a stepwise transition to a regenerative energy system in the EU by 2050, with the aim of going beyond carbon neutrality and achieving annual net negative emissions. A mixed-integer linear programming model is developed with the goal of maximising the Sustainability Net Present Value while achieving a balanced solution between all the three basic sustainability pillars. In order to obtain a regenerative system design, the annual self-sequestration of CO 2 by the Earth was evaluated based on the amount of CO 2 released into the atmosphere and the change in atmospheric CO 2 concentration. The impact of different CO 2 emission reduction scenarios on the atmospheric CO 2 concentration until 2050 was evaluated. The results show that carbon neutrality at the global level could be achieved by 2050 with a 1.63% annual reduction in anthropogenic CO 2 emissions. Moreover, the results indicate that if carbon emission neutrality is achieved at the global level in 2050, it could be achieved in the EU as early as 2039, given the Earth's self-sequestration capacity. To go beyond carbon emissions neutrality at the EU level, electricity demand is expected to nearly double, particularly due to the electrification of road transport, the use of heat pumps for heating residential and the tertiary sectors, 6G and IoT widespread out etc. • A critical review of sustainable heat production technologies. • A MILP model to achieve carbon emissions neutrality or negative net emissions in the EU by 2050. • Cross-sectoral synthesis of regenerative energy systems – beyond sustainability. • Assessment and prediction of Earth's self-sequestration in the synthesis of regenerative energy systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pumpkin and hemp oilseed cake were treated by hydrothermal carbonization. • Hydrothermal treatment significantly improved fuel properties of hydrochars. • Hemp cake gave higher hydrochar yields and carbon content than pumpkin cake. • Co-carbonisation with cheese whey increased calorific value of hydrochar. • Process liquids showed potential for recovery of volatile fatty acids and phenols. The conversion of residues from the vegetable oil industry into energy and valuable products is crucial for solving the disposal issues associated with these wastes. In this study, the hydrothermal carbonization of hemp cake (HC) and pumpkin cake (PC) to produce hydrochar was investigated for the first time. In addition, the effects of co-carbonization (co-HTC) of oil cakes with whey (instead of water as process liquid) on the product properties were investigated by various analyses (FTIR, TGA, XPS, SEM-EDS and 3D-EEM fluorescence spectroscopy). High-quality hydrochars with a high C content (47.4–59.8 wt%) and a high calorific value (20.6–26.2 MJ/kg) were obtained from the mono-carbonization of oil cakes. HC provided higher hydrochar yields (42–66 %) than HC (33–63 %). PC hydrochars were richer in N, P, Mg and K, while HC hydrochars had a higher C content. The HC process liquids contained a high proportion of volatile fatty acids, while the PC fluids were rich in N and phenolic compounds. The operating conditions strongly influence the physico-chemical properties of the products; increasing the operating temperature and duration increased the C content and calorific value of the hydrochars as well as the N, volatile fatty acids and humic acids content of the process liquids. Co-HTC improved the yield of hydrochar and the fuel properties of the hydrochars as whey acts as a catalyst; the calorific value increased to ∼31 MJ/kg and the C content to ∼62 wt%. Co-HTC retained P in the hydrochars and increased the content of phenols, NH 4 -N and K in the process liquids. Hydrochars and process liquids showed encouraging results in the germination test and exhibited high root length indexes. Cheese whey proved to be an excellent co-substrate for oil cakes and made the process more sustainable and cost-effective. [ABSTRACT FROM AUTHOR]

The hydrothermal degradation of different polyolefins (virgin and recycled HDPE, recycled LLDPE, metallocene LLDPE, LDPE waste, virgin and recycled PP, PP waste) and their blends in different forms (granulate, foil) was investigated with supercritical water at 450 °C. The degradation of HDPE was investigated in a time range from 15 min to 240 min. The maximum yield of the oil phase was obtained at a degradation time of 60 min and was over 90 %, therefore all further experiments were carried out at a reaction time of 60 min. It was found that the composition of the oil obtained, and its calorific value depend on the type of material degraded. The oils obtained from PE materials contained between 65.3 % and 69.5 % saturated hydrocarbons, 11.4 %–17 % olefins and 8.9 %–20 % aromatics, while the oils from PP materials contained 40.8 %–45.9 % aromatics, 28.4 %–33.4 % saturated hydrocarbons and 10.6 % to 19.2% olefins. The main compounds in the oils from PP materials were the C 9 compounds and from PE materials the C 16 compounds. An exception were the oils from rLLDPE-1-g and LDPE-b, in which C 8 compounds were most abundant and which contained the highest proportion of C 17 – C 31 hydrocarbons (approx. 17 %) compared to oils from other PE and PP materials (1.3 %–7.1 %). The HHV of the oils was between 29.4 and 45.7 MJ/kg and was highest for the oils where the gasoline/heavy oil ratio was less than 1, while the HHV of the gas phase was between 48.4 MJ/kg and 50.7 MJ/kg. [Display omitted] [ABSTRACT FROM AUTHOR]

• Battery thermal management is studied with phase-change materials and heat pipes; • Phase change materials improve the temperature uniformity of the battery pack; • Phase change-heat pipe cooling reduces by 22.3% battery temperature than using air; • Phase change material RT31 reduces by 11.8 % battery temperature at 5–50 W·m−2·K−1; • Short circuit of combination cooling reduces by 29.9% temperature than air cooling. Lithium-ion battery packs generate high-level heat under harsh and rigorous conditions. The inadequate heat dissipation results in high pack temperature above the safe operating range. This study investigates an efficient and cost-effective battery thermal management system based on phase change materials and a micro heat pipe array. The battery is treated as a single domain. A battery pack with six series stacked batteries is analyzed using the Newman-Tiedemann-Gu-Kim model. The thermal performance of a battery thermal management system is analyzed using phase change materials with various melting temperature values, ambient temperature, and convective heat transfer coefficients of micro heat pipe arrays. Results show that the maximum temperature of the cooling system with micro heat pipe arrays and phase change materials is 33.8 °C, which is reduced by 22.3 % and 7.8 % compared to the air-cooled and cooling system with micro heat pipe arrays. At forced convection of 50 W·m−2·K−1, the maximum battery temperature values for the phase change material RT31, RT35, and RT42 are reduced by 11.8 %, 8.9 %, and 5.4 % compared to those at forced convection of 5 W·m−2·K−1. Under short-circuit conditions, the cooling system with micro heat pipe arrays and cooling system with micro heat pipe arrays − phase change materials reduce the maximum battery temperature by 12.4 % and 29.9 % compared to the air-cooled system. Results show that the developed model for the battery thermal management system provides a reference for designing phase change materials with micro heat pipe arrays. [ABSTRACT FROM AUTHOR]

Abstract: Effectively implementing various energy and environmental policies contributes to the acceleration of energy performance, a reduction in negative environmental impacts, and increased deployment of renewable resources. The MEEMS (municipal energy and environmental management system) performs the almost inconceivable role of accomplishing prerequisite targets at the national level and, consequently, the European and World levels also. Therefore, a proper infrastructure for MEEMS needs to be effectively applied in order to implement policy initiatives. A novel organisational framework of MEEMS is proposed and is constituted upon three pillars: integration of the municipal metabolism approach, the KBS (knowledge-based system), and the MTIS (municipal technology innovation system). By properly addressing the dynamics of the MEES (municipal energy and environmental system), and the new conceptual organisation of MEEMS, a need for the inclusion of innovative elements can be defined regarding support mechanisms. Integration of the end-user approach defines the fundamental orientation of modern MEEMS. This new concept paves a pathway towards an intelligent energy and environmental system. This paper describes an implementation of the new conceptual design of MEEMS within the urban municipality energy system of Ptuj, Slovenia. [Copyright &y& Elsevier]

This study presents an integrated design and optimization of an Organic Rankine Cycle (ORC) for the recovery of waste heat from aluminium production. Non-Linear Programming (NLP) models were developed, with the objectives of maximizing electricity production and the Net Present Value (NPV) of the system. The models account for optimizing the operating conditions and changes in thermodynamic features of the system. The developed models are applied to a case study of Slovenian aluminium company where the performance of three different working fluids (R245fa, R1234yf and R1234ze) are compared. The optimization is performed considering different temperatures and prices of produced hot water and electricity, minimum approach temperature (Δ T min), concentration of CO 2 in flue gas and temperature and flowrate of flue gas. Results show that the selected working fluids for the proposed waste heat-based ORC system have the potential to substitute up to about 830 kW of electricity in a sustainable and economic manner. Out of the three working fluids considered, R245fa showed up to 7.9% efficiency of the ORC cycle and was identified as the best performing working fluid considering both economic viability and the amount of electricity produced by the system, however the refrigerant inherently has higher GHG footprint. [Display omitted] • Optimization of Organic Rankine Cycle is performed for waste heat recovery. •Correlations developed for thermodynamic data, operating conditions are variables. •Optimisaton of power output and net present value on aluminium smelter's flue gas. •System shows up to 7.9 % (R245fa), 6.5 % (R1234yf) and 6.9 % (R1234ze) efficiency. •Solution with maximal NPV shows 5.4 % efficiency and payback time of about 1.9 y. [ABSTRACT FROM AUTHOR]

Biogas is an instrument of synergy between responsible waste management and renewable energy production in the overall transition to sustainability. The aim of this research is to assess the integration of the power-to-gas concept into a food waste-based biogas plant with the goal to produce renewable methane. A robust optimisation was studied, using linear programming with the objective of minimising total costs, while considering the market price of electricity. The mathematical model was tested at an existing biogas power plant with the installed capacity of 1 MW el. It was determined that the integration of power-to-gas in this biogas plant requires the installation of ca. 18 MW el of wind and 9 MW el of photovoltaics, while importing an additional ca. 16 GWh el from the grid to produce 36 GWh of renewable methane. The economic analysis showed that the feedstock gate fee contributes significantly to the economic viability of renewable methane: a change in the feedstock gate fee by 100 €/tonne results in a decrease of production costs by ca. 20–60%. The robust nature of the model showed that uncertainties related to electricity production from wind and photovoltaics at the location increased the cost of gas production by ca. 10–30%. • Robust optimisation of power-to-gas integration in biogas plant was studied. • Hourly level operation was investigated with regard to electricity market prices. • Capacities of units for production and demand of electricity were assessed. • Gate fee significantly contributes to viability of renewable methane production. • Uncertainties in electricity production decrease system's economic benefits. [ABSTRACT FROM AUTHOR]

Plastic waste pollution is a challenging and complex issue caused mainly by high consumption of single-use plastics and the linear economy of "extract-make-use-throw". Improvements in recycling efficiency, behaviour changes, circular business models, and a more precise waste management system are essential to reduce the volume of plastic waste. This paper proposes a simplified conceptual model for a smart plastic waste separation system based on sensor technology and deep learning (DL) to facilitate recovery and recycling. The proposed system could be applied either at the source (in a smart waste bins) or in a centralised sorting facility. Two smart separation systems have been investigated: i) the one utilising 6 sensors (near-infrared (NIR), humidity, temperature, CO 2 , CH 4 , and a laser profile sensor) and ii) the one with an RGB camera to separate packaging materials based on their composition, size, cleanliness, and appearance. Simulations with a case study showed that for a camera-based sorting, Inception-v3, a DL model based on convolution neural networks (CNN), achieved the best overall accuracy (78%) compared to ResNet-50, MobileNet-v2, and DenseNet-201. In addition, the separation resulted in a higher number of misclassified items in bins, as it focused solely on appearance rather than material composition. Sensor-based sorting faced limitations, particularly with dark colouration and organic matter entrapment. Combining the information from sensors and cameras could potentially mitigate the limitations of each individual method, thus resulting in higher purity of the separated fractions. [Display omitted] • Plastic packaging waste is separated using sensors and deep learning algorithms. • The Separation is based on plastic type and cleanliness. • Inseption-V3 yielded the best classification results (78.34 %). • Sensors resulted in a better identification of dirty packaging items then camera. • Both methods minimised the number of items in the mixed waste bin. [ABSTRACT FROM AUTHOR]

Step towards resilience and sustainability through exploring renewable biomass and waste streams to produce higher-added value products and energy is among key aspects for closing the loops, saving resources, and reducing the resource and emission footprints. In that respective, crustacean shells waste can offer rich spectre of valuable compounds such as proteins, chitin, carotenoids. This waste is produced in large quantities worldwide, thus allowing for commercial valorisation. An overview of technologies is undertaken for more sustainable and environmentally friendly chitosan production via chitin isolation and conversion and compared to the conventional processes. Furthermore, an assessment of the environmental burden and energy demand distribution for conventional and more sustainable alternative processes was performed, based on lab-scale experimental data. Three different chitin extraction routes and three distinct chitosan conversion processes were considered and compared for their greenhouse gas footprint, abiotic depletion, acidification, eutrophication and other potentials. Finally, the energy demand distribution was analysed considering electricity production patterns from three European countries, Slovenia, Portugal and Norway. The results showed that alternatives 3-A and 3-B (conventional eco-solvents - conventional deacetylation with 40 % and 50 % NaOH) generate the lowest environmental burden (184 g CO 2 eq./g chitosan). Electricity was the main hotspot of the processes, used either for extraction, plasma treatment or deacetylation. The sensitivity analysis proved that the Norwegian electricity mix has the lowest environmental impact (4.2 g CO 2 eq./g chitosan). This study highlights the impact of blue biorefineries by transforming marine waste to valuable biopolymers such as chitin and chitosan. [Display omitted] • A review of three chitin extraction and three chitosan production pathways. • A performed comparative analysis of environmental impact and energy distribution. • Besides the burdening, unburdening considers the valorisation of waste shrimp shells. • Conventional eco-solvents-based chitin extraction has the lowest environmental burden. • The greenhouse gas footprint ranged between 184 and 1891 g CO 2 eq./g chitosan. [ABSTRACT FROM AUTHOR]

The optimisation of Rankine cycle systems is mainly influenced by the type of heat source, working fluid selection, process components, control strategy, component layout and sizing, and has been recognised as a promising way to contribute to the development of renewable and sustainable energy systems. In this study, a combined steam-organic Rankine system is proposed to recover waste heat from aluminium production at various temperature levels and heat from solar, geothermal and biomass renewable sources. Based on a case study in a Slovenian city, the operating conditions of two different configurations are optimised for individually positioned cycles and for a cascade design of these cycles. The process design and its characteristics are captured in a flowsheet structure formulated with a non-linear programming model and solved in GAMS. The comparison of the optimal performance of the studied systems shows the better performance of the separate design, generating a total power of more than 1.6 MW, while in cascade design 11.4% less power is produced. The flexibility and adaptability of the system to different energy sources are investigated and the trade-offs associated with different system configurations are discussed. • Separate and cascade Rankine cycle system designs are presented • Multiple heat sources at high, medium and low temperatures are utilised • Operating conditions of the systems are set as variables to be optimised • Optimal performance is determined with respect to the highest electricity yield • Separate design produces 187.3 kW more power than cascade design (1430.4 kW) [ABSTRACT FROM AUTHOR]

• Roadside grass (RG) and roadside grass digestate (RGD) were utilized for pyrolysis. • Degradability of RG determined via thermogravimetric analysis is from 44 to 50% • Anaerobic digestion decreased the values of kinetic parameters of pyrolysis. • RGD shows higher residue (mainly biochar) yield compared to RG. The aim of this research is to evaluate the thermogravimetric behaviour of roadside grass and its digestate obtained from mesophilic anaerobic mono-digestion by quantifying its impacts on biomass composition and properties. Thermogravimetric measurements were conducted in a laboratory furnace under nitrogen flowrate of 100 mL/min in the temperature range from 35 to 800 °C at five different heating rates of 2.5, 5, 10, 15 and 20 °C/min. Friedman and Kissinger-Akahira-Sunose differential and integral isoconversional models were applied to determine the distributions of activation energies and modified pre-exponential factors per reacted mass (degree of conversion). The investigation demonstrated that anaerobic digestion of roadside grass can be used to generate biochar-richer material (with significantly greater yield of final residues after pyrolysis) with less energy required for subsequent pyrolysis in comparison with raw roadside grass. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrothermal co-carbonization of sewage sludge and cheese whey was performed. • Co-carbonization improved the hydrochar properties (HHV, carbon content). • Thermogravimetric analysis of hydrochar revealed its potential for use as a fuel. • Germination tests showed that HTC products can be used for agricultural purposes. • Undiluted process liquids were toxic to Daphnia magna organisms. The impacts of operating conditions on hydrothermal carbonization of sewage sludge (SS) in water media were investigated in this study. Hydrothermal co-carbonization (co-HTC) of SS and cheese whey was also carried out under selected conditions (T = 250 °C, t = 5 h), to investigate the effects of replacing water with whey on product properties. Besides, the potential application was also tested of HTC products for agricultural use. The HTC treatment increased the content of nutrients (P, Ca, and Mg) in hydrochars compared to untreated SS, but fuel properties were not improved. Increasing the operating temperature and time increased the contents of nitrogen and volatile fatty acids in the process liquids. The replacement of water with whey resulted in remarkable improvement of the fuel properties of hydrochar, as the hydrochar yield increased from 57.10 to 64.14 wt%, the calorific value from 14.75 to 18.29 MJ/kg, and carbon content from 36.89 to 45.24 wt%. The ash content decreased from 46.55 to 40.06 wt%. The content of N, P, Ca, Mg and K increased significantly. SEM-EDS, FTIR and thermogravimetric analysis revealed the strong influence of the co-carbonization on the thermogravimetric behaviour of the hydrochars and their chemical properties. The HTC products proved efficient as fertiliser in a germination test with plants. Process liquids can be used as an N fertiliser, while hydrochars as a P fertiliser. Undiluted process liquids were toxic to the freshwater organisms Daphnia magna. [ABSTRACT FROM AUTHOR]

The (bio)degradation of plastics in soil is a complex process that depends on several factors, such as the type of plastic, environmental conditions, microbial activity, and the presence of other organic matter in the soil. Ageing in soil thus also influences the physicochemical properties of plastic materials. To understand the mechanisms and investigate the changes in plastic properties in soil due to decomposition and followed by fragmentation, the gravimetric, morphological, surface, and thermal properties of plastics were studied, some of them for the first time. The study was performed for three different plastics materials, polyethylene terephthalate (PET-fib) and melamine etherified resin (MER-fib) in the form of nonwoven fabrics and polylactic acid (PLA) in the form of foils. The materials were exposed to soil for one, three and six months, only in the case of PLA foil for final four months. The results show that remarkable changes were observed especially for MER-fib and PLA after exposure to soil, which is related to the bio and chemical degradation proceses. The biodegradation process was indicated with the soil microorganisms used in the study (lactic acid bacteria, photosynthetic organisms, yeasts, actinomycetes, and enzymatically active fungi), while chemical degradation showed that it may occur at the surface of the material with changes in elemental composition and chemical functionality. The microbial end products of biodegradation of MER-fib are presumably NH 3 and CO 2 , while for PET-fib it is CO 2 and for PLA it is CO 2 and H 2 O, including several proposed conversion products in partial pathways. The study represent an important contribution to understanding the behaviour of the analysed (bio)plastics and the changes in their properties after exposure to natural systems for pollution countermeasures and cleaner production. [Display omitted] • PET-fib, MER-fib and PLA plastic degradation was studied in soil. • Morphology, thermal and surface properties of aged plastics were investigated. • PET-fib and MER-fib showed little degradation, while PLA degraded after 4 M. • XPS was used for the first time to identify the chemical surface of aged plastics. • Zeta potential revealed changes in surface functional groups due to fragmentation. [ABSTRACT FROM AUTHOR]

This paper proposes a general superstructure and a Mixed-Integer Nonlinear Programming (MINLP) model for the synthesis and simultaneous optimisation and Heat Integration (HI) of Single- and Multiple-Effect Evaporation (SEE/MEE) systems including Mechanical Vapour Recompression (MVR) and the background process. The proposed superstructure also includes different flow patterns (forward feed, backward feed, parallel feed and mixed feed), Flashing of Condensates (FCs), single- and multi-stage MVR systems and various HI opportunities for preheating of feed stream (e.g. with condensates, bled vapours, and hot streams from the background process). The newly proposed SEE/MEE-FC-MVR superstructure is combined with a Heat Exchanger Network (HEN) superstructure for performing simultaneous optimisation and HI. On the basis of this combined superstructure, an MINLP model with tight bounds on the variables is developed and implemented for its solution in the General Algebraic Modeling System (GAMS). The model is solved using a two-step solution strategy. The proposed model enables to explore simultaneously all interconnections within the proposed superstructure in order to find the configuration with the optimal trade-offs between capital and energy costs as demonstrated in this paper for different cases of a milk concentration process. [ABSTRACT FROM AUTHOR]

In the globalised world greenhouse gas (GHG) emissions and water consumption are becoming increasingly important indicators for policy and decision making. Development of footprint assessment techniques over the last decade has provided a set of tools for monitoring CO 2 emissions and water flows in the world. An overview of the virtual CO 2 emissions and virtual water flow trends in the international trade based on consumption perspective is performed in the current work. The review of the recent literature indicates that: (1) Producers and consumers are located at various places in different parts of the world, and consequently they are significant differences in virtual GHG (Greenhouse gases) emissions. (2) The US and the EU have high absolute net CO 2 imports. (3) China and some other fast developing countries as India, Brazil, and others are exporting countries and increasingly carry the load of exports of virtual GHG including CO 2 emissions and virtual water that are triggered due to consumption of the related goods in the importing countries. (4) By importing products produced with lower carbon emission intensity and less water consumption than in the domestic industry, international trade can reduce global environmental pressure. Results from analysis indicate that future actions should be focused onto two main areas: (i) To steer regions towards self-sufficiency based on more efficient processes and by combining production of surrounding countries. (ii) To develop a mechanism with shared market of virtual carbon and virtual water between trading partners regionally and internationally. [ABSTRACT FROM AUTHOR]

Hydrogen applications range from an energy carrier to a feedstock producing bulk and other chemicals and as an essential reactant in various industrial applications. However, the sustainability of hydrogen production, storage and transport are neither unquestionable nor equal. Hydrogen is produced from natural gas, biogas, aluminium, acid gas, biomass, electrolytic water splitting and others; a total of eleven sources were investigated in this work. The environmental impact of hydrogen production, storage and transport is evaluated in terms of greenhouse gas and energy footprints, acidification, eutrophication, human toxicity potential, and eco-cost. Different electricity mixes and energy footprint accounting approaches, supported by sensitivity analysis, are conducted for a comprehensive overview. H 2 produced from acid gas is identified as the production route with the highest eco-benefit (−41,188 €/t H 2), while the biomass gasification method incurred the highest eco-cost (11,259 €/t H 2). The water electrolysis method shows a net positive energy footprint (60.32 GJ/t H 2), suggesting that more energy is used than produced. Considering the operating footprint of storage, and transportation, gaseous hydrogen transported via a pipeline is a better alternative from an environmental point of view, and with a lower energy footprint (38 %–85%) than the other options. Storage and transport (without construction) could have accounted for around 35.5% of the total GHG footprint of a hydrogen value chain (production, storage, transportation and losses) if liquefied and transported via road transport instead of a pipeline. The identified results propose which technologies are less burdensome to the environment. [Display omitted] • A review of eleven hydrogen production and various storage and transport options. • Comparative energy, environmental footprint and eco-cost analysis of technologies. • Different electricity mixes and energy footprint accounting are considered. • Sensitivity analysis for hydrogen production via gasification and acid gas. • Storage and transport could comprise 35% of the overall greenhouse gas footprint. [ABSTRACT FROM AUTHOR]

This paper presents a method for integrating the periodic heat demand of sets of co-located process plants with a biomass-based utility supply chain network. The methodology adopted involves generating a composite superstructure, which combines the supply chain model and the multi-period interplant stage-wise superstructure model. Supply nodes in the supply chain are linked to the central utility hub through a set of transportation/energy transmission options, while the utility hub is linked to a set of co-located process plants through fluid transmission pipelines. The developed model was applied to a hypothetical case study involving three co-located process plants. The solution generated involves the use of biomass, transported by truck. For hot utility generation at the utility hub, corn stover is used in all seasons (63.4% of the total feedstock), glycerol in seasons 1 and 3 (27.1% of the total feedstock) and wood only in season 1 (9.5% of the total feedstock). In terms of hot utilities generated from the selected feedstocks, only high- and low-pressure steam were selected. Of the 14 heat exchangers selected, 3 involve interplant heat exchange at the utility hub, 2 are hot utility heat exchangers, 1 is cold utility exchanger and 8 are intra-plant heat exchangers. The developed method illustrates how seasonality in availability of bio-based renewable energy sources and the periodicity of process plants operating parameters influence the heat demand of co-located process plants. [ABSTRACT FROM AUTHOR]

Increasing global plastic consumption and its related plastic waste have become a major concern in the world. Achieving sustainable development in the plastics industry requires a systematic insight into all the relevant life cycle phases of plastic products and their environmental impacts. This paper utilises the concepts of industrial ecology and the circular economy to evaluate the three key aspects of thermoset plastic materials and their overall life cycle comprehensively: i) Sustainable production, ii) Recycling to obtain secondary products, and iii) End-of-life behaviour. For all three aspects, their environmental impacts are evaluated additionally using the conceptual Life Cycle Assessment (LCA) approach. The industrial ecology approach, together with LCA is performed on a case study of melamine etherified resin (MER) fibre, which is a high value-added thermoset plastic, difficult to recycle, and, at the end-of-life, potentially emits hazardous compounds. The potential to sustainably produce MER fibre exclusively from renewable and waste sources is explored, closing the loop on the manufacturing and disposal phases. The hydrothermal decomposition of MER fibres into valuable compounds is investigated as a recycling technology. Regarding the end-of-life, a systematic assessment is conducted of the environmental impacts of discharging such material into soil and water bodies. Cleaner production of MER fibres shows the potential to reduce greenhouse gas footprint up to 67%, while analysis of sustainable recycling and disposal highlights important environmental hotspots. [Display omitted] • Industrial Ecology concept is applied to melamine etherified resin fibres. • Sustainable production, chemical recycling, and end-of-life phases are investigated. • Environmental burden is evaluated for each phase based on simulations and experiments. • Sustainable production pathways could reduce environmental burden by up to 67%. • Important hotspots are highlighted for more sustainable recycling and disposal. [ABSTRACT FROM AUTHOR]

Present day energy policies are increasingly being focused towards local energy systems. Local communities may be more effective when implementing energy objectives due to the lower losses of energy during transmissions, closer contact with the end-users, and also greater support from local decision makers. Different tools, approaches and concepts are available for achieving greater energy efficiency within local energy systems. One of them is the Locally Integrated Energy Sectors (LIES) concept that provides energy integration with end-users from various sectors such as the industry, service, household, agriculture, transport and public sectors within a particular geographical area. LIES could well contribute towards lower energy consumption, novel opportunities for sustainable energy supply, decreased negative impact on the environment and consequently towards the amplification of sustainable development (SD) regarding local communities. The presented research focused on developing suitable metrics for evaluating the sustainability of LIES. These metrics are comprised of general sustainability indicators grouped into four major categories: energy, environmental, economic, and social. The applicability of the proposed metrics for LIES evaluation is illustrated by a case study of the district heating system within the Ormož municipality in Slovenia. [ABSTRACT FROM AUTHOR]

Large amounts of food waste and sewage sludge exert a hazardous environmental impact in several countries. Producing biogas and digestate from food and industrial waste is one of the solutions for waste management, stabilization of sludge, resource and energy recovery and reductions in the amount of waste. However, biogas production from such substrates has challenges in degradation efficiency, inhibitory effects and other challenges, and thus co-digestion and pretreatment techniques could be applied to enhance biogas production. The aim of this study is to explore the effects of co-digestion of food waste, meat and bone meal and rendering wastewater sludge. First, thermal pretreatment was performed (35°C, 5 days) by adding the rendering-industry streams to food waste in the amounts of 0, 5, 10 and 15% on a total solid basis, and further anaerobic digestion (40.5°C, ca. 40 days) was then performed. Both experimental and kinetic analysis were conducted, and the major factors regarding opportunities and challenges in the two-stage process are discussed. Results have shown that both co-substrates from rendering industry decreased the biogas yield of food waste. When 5% of them was added to food waste, meat and bone meal decreased biogas production by 12%, and wastewater sludge decreased it by 23%. Both co-substrates, on the other side, increased the rate of reaction of food waste digestion when applying different common kinetic models. • Rendering streams were studied as co-substrates to food waste for biogas production. • Experimental study of thermal pretreatment and anaerobic digestion was performed. • Food waste could cause inhibition of the anaerobic digestion process. • Kinetic parameters were estimated for anaerobic digestion of selected mixtures. • Rendering streams decrease biogas production, while increase the rate of reaction. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the operation of biogas plants in advanced energy markets after energy crops become limited in their use and biogas plants exit subsidy schemes for electricity production. Continuous biogas combined heat and power production and sale of electricity on the day-ahead market could be a viable operation strategy only in the case of low-cost substrates. When the break-even cost of electricity production in biogas power plants reaches 100 €/MWh el , selling electricity on the day-ahead market does not create profit. The study shown that a more profitable operation strategy involves coupling biogas power plant operation on the electricity balancing market with biomethane production or combining a small-scale sugar beet processing facility with a biogas upgrading plant to cover heat demand for sugar beet processing. Techno-economic analysis showed that the viability of both alternative operation strategies is severely impacted by the selling price of biomethane. In the given market conditions, a selling price of biomethane below 50 €/MWh is not viable for a biogas plant. The model developed could be used as a guideline for biogas plant operators on how to proceed after significant changes appear in both biogas production and biogas utilisation. • The operation of a biogas plant in advanced energy markets was studied. • Low-cost substrates become significant once a biogas plant exits subsidy schemes. • Biogas plants gain profit while operating on the electricity balancing market. • The biomethane selling price has a significant impact on the project's viability. [ABSTRACT FROM AUTHOR]