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The accumulation of plastic debris has been a consistently alarming global issue. Plastic recycling is a viable option, but the sustainability of the recycling network is directly linked with environmental performance, which is mainly dependent on energy consumption. This work aims to provide a sustainability assessment tool by determining the ideal minimum energy requirements for a circular system, with the main driven constraint to be the thermodynamic Energy Quality Factor (exergy fraction within the energy flow). The energy quality represents the extractible energy fraction from either a material or an energy stream. The Energy Quality Pinch Analysis serves as an assessment tool for a symbiosis network, as an indication of the existing system performance from the perspective of energy. The analysis considers cascades of the energy requirements released by recycling or symbiosis processes, evaluating the minimal external energy flows: high-quality energy input and waste energy output. The method is applied for a plastic waste recycling network case study, where the energy products can be reused or recycled for various recycling pathways. The case study shows that the maximum recyclable energy is 28 %. However, if the exergy destruction rate is taken into account for fuel conversion processes, the energy quality of the sources or sinks could be reduced. Various renewable fuels with different energy quality factors can be incorporated into the system tool to evaluate the energy requirements for the plastic system. [ABSTRACT FROM AUTHOR]

Process Integration provides an excellent engineering toolbox for optimising industrial systems to achieve sustainability gains. However, effective large-scale use of such tools depends on effective education of new generations of engineers with the correct training and mind-set. Learning strategies refer to the different combinations of activities the learners utilise in their process of learning. Chemical engineering students often face the challenges in processing key concepts integral in the understanding of Process Integration, optimisation and sustainability. A preliminary survey of students from the undergraduate program from the Philippines identifies learning strategies they employ in better understanding Process Integration, optimisation and sustainability. These strategies help learners in analysing concepts, monitoring the learning process, linking concepts with one another, inferring meanings from context, and managing their behaviour towards learning. Educational best practices are suggested based on insights drawn from the responses. [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]

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]

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]

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]

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]

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]