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Abstract A novel approach was used as support for synthesis of fly ash derived catalyst from waste fly ashes from the energy sector was used as support in the preparation of Ni-catalysts for CO2 methanation. The catalysts were characterized by XRD, H2 -TPR, CO2 -TPD and N2 low-temperature nitrogen sorption. As a result of application of new approach using a ball-mill mechanical energy, carbon dioxide conversion to methane of 58% was obtained at 350 °C. The conversion long with economical aspects of catalyst preparation, including waste material reuse, leads to highly promising results. The results indicate that the catalyst for the methanation process can be easily obtained by the mechanical activation of waste from the energy sector. The chemical modification is more complicated and does not give significantly better results. This approach to waste transformation is innovative, ecological, and economical. It meets the assumptions of the circular economy concept and allows to reuse of waste materials.

Abstract The transition to a low-Carbon Hydrogen production will unavoidably follow a path where fossil fuels are going to play a fundamental role in the short term. The technological development of Hydrogen production based on sustainable, renewable energies (wind, solar, biomass) will most likely characterize the gradual substitution of fossil-based Hydrogen production in the long term. In this transition, the environmental concerns regarding greenhouse gas emissions to the atmosphere are a crucial issue, fostering the development of Hydrogen production scenarios in which either carbon capture and sequestration or decarburation could be implemented as mitigation or adaptation measures in order to avoid CO 2 release from the utilization of fossil fuels. Therefore, the development of CO 2 -free technologies enabling fossil fuels exploitation is a must to make compatible their utilization with emission reductions. New innovative solutions should be put into practice. In this regard, methane cracking is a promising alternative and its potentials are highlighted and analyzed in this paper.

Abstract Renewable energy is believed to be the central issue in sustainable development. Literatures on renewables׳ costs are rather sparse, especially on costs of integration and system balancing. The objective of this paper is to fill the research gap by providing an assessment for the cost of China׳s grid-connected renewable energy development and analyze its sharing between different stakeholders. Due to China׳s pricing mechanism of renewable energy and their cost decreasing potential, the pricing model of feed-in tariff and dynamic technological learning processes are employed. In the estimation of purchasing cost, the positive bias is overcome by considering China׳s energy-saving dispatching policy. The results suggest that purchasing cost would be 32.57–40.80 billion Yuan over 2012–2020, and peak in 2017. Grid integration costs which further involve costs of grid infrastructure and system balancing are also investigated. We find that grid infrastructure will cost 27.88 billion Yuan by 2015 and soar to 45.32 billion by 2020, while system balancing will cost 31.49 billion Yuan in 2015 and 63.97 billion Yuan in 2020 among which a substantial part (over 60%) comes from electricity loss in energy transfer. The different parts of these costs are underwritten by disparate participants due to China׳s renewable energy policies and its institutional arrangement. Purchasing cost is shared by power consumers through RES; the cost of grid infrastructure is mainly covered by grid enterprises; and there is no mechanism to specify how to share the cost electricity loss during system balancing which might become a major obstacle for system balancing.

Cellulose nanocrystals (CNC) have been extensively used in various fields due to their renewability, excellent biocompatibility, large specific surface area, and high tensile strength. Most biomass wastes contain significant amounts of cellulose, which forms the basis of CNC. Biomass wastes are generally made up of agricultural waste, and forest residues, etc. CNC can be produced from biomass wastes by removing the non-cellulosic components through acid hydrolysis, enzymatic hydrolysis, oxidation hydrolysis, and other mechanical methods. However, biomass wastes are generally disposed of or burned in a random manner, resulting in adverse environmental consequences. Hence, using biomass wastes to develop CNC-based carrier materials is an effective strategy to promote the high value-added application of biomass wastes. This review summarizes the advantages of CNC applications, the extraction process, and recent advances in CNC-based composites, such as aerogels, hydrogels, films, and metal complexes. Furthermore, the drug release characteristics of CNC-based material are discussed in detail. Additionally, we discuss some gaps in our understanding of the current state of knowledge and potential future directions of CNC-based materials.

Low carbon transitions of urban energy systems have been on urban research and policy agendas for several years now. While the spatialities of infrastructure transitions have been widely discussed, their temporalities have attracted much less attention. This is surprising, since the transition of urban infrastructures in the course of system integration and decarbonisation reveal strong temporal dynamics: new temporalities or temporal requirements not only emerge as a result of technological change (e.g. by integrating fluctuating renewables or storage technologies) but also of changing social practices (e.g. in urban load management or energy use). We argue that aligning urban and infrastructure temporalities involves negotiations between the various energy providers, regulators and users involved and is a highly political process. As we know little about such temporal dynamics so far, this study uses an explorative methodology to elaborate on a conceptual framework of urban and infrastructural temporalities. This framework has been developed in an iterative way by going back and forth between conceptual contributions and empirical findings drawn from expert interviews regarding low carbon transitions in Rotterdam. Our case study of Rotterdam indicates that unsolved challenges in aligning urban and infrastructural temporalities can be seen as a major restriction to realise low carbon energy solutions.

Today's waste regulation in the EU comprises stringent material recovery targets and calls for comprehensive programs in order to achieve them. A similar movement is seen in the US where more and more states and communities commit to high diversion rates from landfills. The present paper reviews scientific literature, case studies and results from pilot projects, on the topic of central sorting of recyclable materials commonly found in waste from households. The study contributes, inter alia, with background understanding on the development of materials recovery, both in a historical and geographical perspective. Physical processing and sorting technology has reached a high level of maturity, and many quality issues linked to cross-contamination by commingling have been successfully addressed to date. New sorting plants tend to benefit from economies of scale, and innovations in automation and process control, which are targeted at curtailing process inefficiencies shown by operational practice. Technology developed for the sorting of commingled recyclables from separate collection is also being successfully used to upgrade residual MSW processing plants. The strongest motivation for central sorting of residual MSW is found for areas where source separation and separate collection is difficult, such as urban agglomerations, and can in such areas contribute to increasing recycling rates, either complementary to- or as a substitute for source separation of certain materials, such as plastics and metals.

High contents of chlorine and alkalies restrict the use of biomass in energy production. Alkali chlorides vaporize during combustion. Chlorine tends to produce corrosive deposits and unacceptably high emissions of HCl and dioxins. Chlorine recovery and enrichment of Cl, Na, K, Ca, Al, and Si in coarse and fine fly ash were studied experimentally with two electrically stabilized bubbling fluidized bed (BFB) reactors capable of reproducing the particle residence times existing in full-scale BFB plants. Feedstocks were fir (mixture of heartwood and bark), paper sludge, and blends of fir with agricultural waste or plastic waste. Sulfur concentrations of feed components were low (<0.5 wt %), while chlorine and potassium concentrations ranged widely (0.02−3.2 wt % for Cl and 0.07−3.1 wt % for K). Aluminum-containing additives (kaolin, bauxite and fly ash from a pulverized coal plant) and limestone were added to the feedstocks at various dosages to evaluate their influence on Cl behavior and enrichment of the elements of interest. HCl was measured by FTIR and wet-absorption methods. Different ash samples (bed, cyclone and filter ash) were characterized for their Cl content and the major ash-forming constituents. Cl was completely volatilized from bed ash and recovered only in coarse (cyclone) and fine (filter) fly ash fractions. Al-containing additives increased HCl formation and decreased Cl concentration in the fly ash. In the case of Al−Si based additives, evidence was found of the formation of alkali aluminum silicates from alkali chlorides. The aluminum silicates were transferred mainly to the coarse fly ash fraction. Al-based additives also seemed to liberate Cl from alkali chlorides with reactions forming water-soluble alkali compounds. Limestone had the opposite effect to the Al-containing additives by binding Cl from gas phase to fly ash, but mainly to the coarse fly ash fraction. The results will be useful in optimizing the behavior of chlorine in bubbling bed combustion of Cl- and alkali-containing biomass.

Abstract Highly efficient insulating systems help reduce heat losses and promote building energy efficiency due to their very low thermal conductivity. However, when applied to outdoor surfaces, climate conditions exposure might deteriorate the material's properties, compromising the building's energy performance over its lifetime. In the framework of a European research project (Horizon2020 - Wall-ACE), a novel aerogel-based insulating external render was developed, characterized, and submitted to a large-scale weathering test to assess its durability. The test rig was equipped with hygrothermal, impedance, and heat flux sensors, used as reference data to create and calibrate a 2D heat and moisture transfer (HMT) model that compared impedance readings and predicted water content. Before and after the test, thermal properties, e.g., U-Value, were measured to assess the weather impact on the exterior render performance, which were also investigated through building energy simulation (BES). In this article, both experimental and numerical procedures are described. Results show high water absorption in the analyzed render systems during weathering, especially at the innermost layer, demonstrated by both impedance and simulation outputs. An adjusted base coat and attention at the execution phase can avoid such intrusion of water. Nevertheless, a low thermal conductivity degradation was measured after the large-scale test, showing that the aerogel-based insulating system's effectiveness is not harshly compromised throughout its life-cycle.

In this paper, we investigate the cogency of the “sustainability or collapse” narrative, that is, the notion that the current global civilization risks ecological overshoot-induced collapse. Combining different strands of literature, we put forward three arguments: First, for many empirical cases of past societies that purportedly “collapsed”, alternative interpretations, emphasizing resilience, transformation and reorganization are equally if not more plausible. Second, the “sustainability or collapse” narrative tends to be misleading insofar as it suggests that resource input constraints are the main sustainability challenge global civilization faces today. Instead, we argue that a stronger focus on system outputs and pollution is needed. Third, collapse-warnings are psychologically ineffective because they might induce fear and guilt, which leads to apathy not action. In consequence, we suggest that the sustainability agenda relies on positive framings that highlight the benefits from institutional and behavioral changes for human well-being. We illustrate our argument with two examples, water scarcity in Cape Town, South Africa and the German energy transition.