Summary
Evaluating the sustainability of the urban water cycle is not straightforward, although a variety of methods have been proposed. Given the lack of integrated data about sewers, we applied the ...eco‐efficiency approach to two case studies located in Spain with contrasting climate, population, and urban and sewer configurations. Our goal was to determine critical variables and life cycle stages and provide results for decision making. We used life cycle assessment and life cycle costing to evaluate their environmental and economic impacts. Results showed that both cities have a similar profile, albeit their contrasting features, that is, operation and maintenance, was the main environmental issue (50% to 70% of the impacts) and pipe installation registered the greatest economic capital expenditure (70% to 75%) due to labor. The location of the wastewater treatment plant (WWTP) is an essential factor in our analysis mainly due to the topography effects (e.g., the annual pump energy was 13 times greater in Calafell). Using the eco‐efficiency portfolio, we observed that sewers might be less eco‐efficient than WWTPs and that we need to envision their design in the context of an integrated WWTP‐sewer management to improve sewer performance. In terms of methodological approach, the bidimensional nature of eco‐efficiency enables the benchmarking of product systems and might be more easily interpreted by the general public. However, there are still some constraints that should be addressed to improve communication, such as the selection of indicators discussed in the article.
Many industrial processes and conventional fossil fuel energy production systems used in small-medium industries, such as internal combustion engines and gas turbines, provide low or medium ...temperature (i.e., 200–500
°C) heat fluxes as a by-product, which are typically wasted in the environment. The possibility of exploiting this wasted heat, converting it into electric energy by means of different energy systems, is investigated in this article, by extending the usual range of operation of existing technologies or introducing novel concepts. In particular, among the small size bottoming cycle technologies, the identified solutions which could allow to improve the energy saving performance of an existing plant by generating a certain amount of electric energy are: the Organic Rankine Cycle, the Stirling engine and the Inverted Brayton Cycle; this last is an original thermodynamic concept included in the performed comparative analysis.
Moreover, this paper provides a parametric investigation of the thermodynamic performance of the different systems; in particular, for the Inverted Brayton Cycle, the effects of the heat source characteristics and of the cycle design parameters on the achievable efficiency and specific power are shown. Furthermore, a comparison with other existing energy recovery solutions is performed, in order to assess the market potential. The analysis shows that the highest electric efficiency values, more than 20% with reference to the input heat content, are obtained with the Organic Rankine Cycle, while not negligible values of efficiency (up to 10%) are achievable with the Inverted Brayton Cycle, if the available temperature is higher than 400
°C.
This paper presents a review of the organic Rankine cycle and supercritical Rankine cycle for the conversion of low-grade heat into electrical power, as well as selection criteria of potential ...working fluids, screening of 35 working fluids for the two cycles and analyses of the influence of fluid properties on cycle performance. The thermodynamic and physical properties, stability, environmental impacts, safety and compatibility, and availability and cost are among the important considerations when selecting a working fluid. The paper discusses the types of working fluids, influence of latent heat, density and specific heat, and the effectiveness of superheating. A discussion of the 35 screened working fluids is also presented.
Mammalian tissues are fuelled by circulating nutrients, including glucose, amino acids, and various intermediary metabolites. Under aerobic conditions, glucose is generally assumed to be burned fully ...by tissues via the tricarboxylic acid cycle (TCA cycle) to carbon dioxide. Alternatively, glucose can be catabolized anaerobically via glycolysis to lactate, which is itself also a potential nutrient for tissues and tumours. The quantitative relevance of circulating lactate or other metabolic intermediates as fuels remains unclear. Here we systematically examine the fluxes of circulating metabolites in mice, and find that lactate can be a primary source of carbon for the TCA cycle and thus of energy. Intravenous infusions of
C-labelled nutrients reveal that, on a molar basis, the circulatory turnover flux of lactate is the highest of all metabolites and exceeds that of glucose by 1.1-fold in fed mice and 2.5-fold in fasting mice; lactate is made primarily from glucose but also from other sources. In both fed and fasted mice,
C-lactate extensively labels TCA cycle intermediates in all tissues. Quantitative analysis reveals that during the fasted state, the contribution of glucose to tissue TCA metabolism is primarily indirect (via circulating lactate) in all tissues except the brain. In genetically engineered lung and pancreatic cancer tumours in fasted mice, the contribution of circulating lactate to TCA cycle intermediates exceeds that of glucose, with glutamine making a larger contribution than lactate in pancreatic cancer. Thus, glycolysis and the TCA cycle are uncoupled at the level of lactate, which is a primary circulating TCA substrate in most tissues and tumours.
•The main differences are the extent of the refurbishment and the system boundaries.•The reference of the expected service life needs to be established to facilitate comparison.•Process Analysis is ...the most used LCI method, instead of Input–Output or Hybrid.•Most refurbishment LCAs focus on building energy retrofits: increasing insulation.•The environmental impacts of structure or finishing reparations were not studied.
This review organises and summarises the recent contributions related to the environmental evaluation of building refurbishment and renovation using the lifecycle assessment (LCA) methodology. This paper classifies the recent contributions in this field and selects the primary methodology options. The review shows that most LCAs focus on energy refurbishment, comparing the environmental impacts before and after refurbishment. In contrast, almost none of the LCAs study the environmental impact of building system reparations, such as structure or finishing. The more frequently studied life cycle stages are those related to the manufacturing and use phases. Similarly, the most considered impact categories are the global warming potential and embodied energy. The main barriers found for disseminations are discussed: system boundaries interpretation of EN 15978, functional unit, LCI methods, operational stage and the end-of-life stage definition.
•The best performing system among pure ammonia, steam Rankine and Kalina cycles were decided at same working condition.•Performance optimisation results were compared for pure ammonia, steam Rankine ...and Kalina cycles.•To show a wide vision for all real working cases, steam content at turbine outlet were considered.•Economic parameters for the case of using the best performing sub-cycle was calculated.•Impact of using best performing sub-cycle on CO2 emission reduction was investigated.•The best cycle configurations in terms of performance and emission were decided.
There are many studies on the Kalina cycle and steam Rankine cycles. However, there are not enough comparative and descriptive studies on why the Kalina cycle or steam Rankine cycle should be selected. In addition to that, almost there are no papers on why Kalina cycle and steam Rankine cycle are commonly used systems rather than the pure ammonia cycle. For these reasons, the present paper was designed, analysed and compared comprehensively the Kalina, steam Rankine and pure ammonia cycles as a subsystem for use in a cogeneration cycle. Moreover, the pure ammonia cycle system was analysed for both simple and regenerative designs to comprehensively present all cases. After deciding the best cogeneration system configuration for the present system, the economic and environmental analyses of the best performing system were performed. In addition to all these, during the study, the condensing temperature remained constant to be able to analyse systems in line with real working conditions. As a result of the comprehensive analyses, the Kalina cycle showed the best performance. The maximum net power, thermal and exergy efficiencies of the Kalina cycle were calculated at ammonia-water concertation of X = 25% and a turbine inlet temperature of t = 340 °C as 365.92 kW, 25.52%, 57.96% respectively. Thanks to the power generated by integrating the Kalina cycle into the system, 244.53 kg-CO2/h carbon dioxide was reduced and the total cost of the Kalina cycle and the payback period was found as 343,975.26$ and 2.2 years. The maximum thermal and exergy efficiencies of the Kalina cycle-based cogeneration system were calculated as 72.13% and 78.60%.
PURPOSE: Sustainability of a material-based product mainly depends on the materials used for the product itself or during its lifetime. A material selection decision should not only capture the ...functional performance required but should also consider the economical, social, and environmental impacts originated during the product life cycle. There is a need to assess social impacts of materials along the full life cycle, not only to be able to address the “social dimension” in sustainable material selection but also for potentially improving the circumstances of affected stakeholders. This paper presents the method and a case study of social life cycle assessment (S-LCA) specialized for comparative studies. Although the authors’ focus is on material selection, the proposed methodology can be used for comparative assessment of products in general. METHODS: The method is based on UNEP/SETAC “guidelines for social life-cycle assessment of products” and includes four main phases: goal and scope definition, life cycle inventory analysis, life cycle impact assessment, and life cycle interpretation. However, some special features are presented to adjust the framework for materials comparison purpose. In life cycle inventory analysis phase, a hot spot assessment is carried out using material flow analysis and stakeholder and experts’ interviews. Based on the results of that, a pairwise comparison method is proposed for life cycle impact assessment applying analytic hierarchy process. A case study was conducted to perform a comparative assessment of the social and socio-economic impacts in life cycle of concrete and steel as building materials in Iran. For hot spot analysis, generic and national level data were gathered, and for impact assessment phase, site-specific data were used. RESULT AND DISCUSSION: The unique feature of the proposed method compared with other works in S-LCA is its specialty to materials and products comparison. This leads to some differences in methodological issues of S-LCA that are explained in the paper in detail. The case study results assert that “steel/iron” in the north of Iran generally has the better social performance than “concrete/cement.” However, steel is associated with many negative social effects in some subcategories, e.g., freedom of association, fair salary, and occupational health in extraction phase. Against, social profile of concrete and cement industry is damaged mainly due to the negative impact of cement production on safe and healthy living condition. The case study presented in this article shows that the evaluation of social impacts is possible, even if the assessment is always affected by subjective value systems. CONCLUSIONS: Application of the UNEP/SETAC guidelines in comparative studies can be encouraged based on the results of this paper. It enables a hotspot assessment of the social and socio-economic impacts in life cycle of alternative materials. This research showed that the development of a specialized S-LCA approach for materials and products comparison is well underway although many challenges still persist. Particularly characterization method in life cycle impact assessment phase is challenging. The findings of this case study pointed out that social impacts are primarily connected to the conduct of companies and less with processes and materials in general. These findings confirm the results of Dreyer et al. (Int J Life Cycle Assess 11(2):88–97, 2006). The proposed approach aims not only to identify the best socially sustainable alternative but also to reveal product/process improvement potentials to facilitate companies to act socially compatible. It will be interesting to apply the UNEP/SETAC approach of S-LCA to other materials and products; materials with a more complex life cycle will be a special challenge. As with any new method, getting experience on data collection and evaluation, building a data base, integrating the method in software tools, and finding ways for effective communication of results are important steps until integrating S-LCA in routine decision support.
EOMES and T-BET are related T-box transcription factors that control natural killer (NK) cell development. Here we demonstrate that EOMES and T-BET regulate largely distinct gene sets during this ...process. EOMES is dominantly expressed in immature NK cells and drives early lineage specification by inducing hallmark receptors and functions. By contrast, T-BET is dominant in mature NK cells, where it induces responsiveness to IL-12 and represses the cell cycle, likely through transcriptional repressors. Regardless, many genes with distinct functions are co-regulated by the two transcription factors. By generating two gene-modified mice facilitating chromatin immunoprecipitation of endogenous EOMES and T-BET, we show a strong overlap in their DNA binding targets, as well as extensive epigenetic changes during NK cell differentiation. Our data thus suggest that EOMES and T-BET may distinctly govern, via differential expression and co-factors recruitment, NK cell maturation by inserting partially overlapping epigenetic regulations.
•An approach is proposed for structures under progressive and sudden deterioration.•The proposed approach is based on the renewal theory of renewal-reward processes.•The lifetime resilience losses ...are proposed to consider resilience to lifetime hazards.•Multi-objective optimization is used for life-cycle management.•The optimization considers intervention costs, failure risks and resilience losses.
Civil infrastructure during its service life is subject to progressive deterioration due to aggressive environments and sudden deterioration due to natural and/or manmade hazards. This paper presents a general approach to perform life-cycle management considering both types of deterioration. As an important aspect of life-cycle asset management under hazards, the present study introduces a novel concept, referred to as lifetime resilience. The lifetime resilience of a deteriorating structure is characterized by its cumulative losses to lifetime hazards. By modeling lifetime hazards and life-cycle performance as renewal-reward processes, the proposed approach resorts to the renewal theory to formulate analytical expressions of expected values of lifetime intervention costs, lifetime failure risks, and lifetime resilience losses. Owing to the efficiency in evaluating these expressions, a generic life-cycle management framework is proposed using multi-objective optimization. This proposed framework is applicable to a wide range of civil infrastructure systems under various types of hazards. The proposed approach is illustrated by using a numerical example.
This study aims to assess the comprehensive energy, environmental and economic performance of a retrofit zero energy building (ZEB). Three life cycle assessments were conducted: life cycle energy ...(LCE), life cycle carbon emissions (LCCE) and life cycle cost (LCC). Actual building construction cost data and energy use data were used in the assessments. The analysis results indicated that during the whole building life span, the operational life stage (B6) was a major contributor to LCE (82%) and LCCE (77%), but not to LCC (18%). Within the life cycle embodied carbon (LCEC), A3 was the life stage with the highest contribution (56%), which is mainly related to the manufacturing of building assemblies. This case study provides new empirical evidence of ZEB performance in the United States. The findings suggest that to achieve the carbon neutrality goal, current ZEB certifications or designations are not adequate to measure actual building performance. A further reduction of operational energy, in addition to reducing the embodied carbon released during manufacturing, should be the focus.
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