Mineral resource assessment: Compliance between Emergy and Exergy respecting Odum's hierarchy concept

International audienceIn this paper, authors suggest to combine the exergoecology and the emergy concept in order to evaluate mineral resources, taking into account their abundance, their chemical and physical properties and the impact of their extraction. The first proposition of this work is to consider that every group of mineral, dispersed in the Earth's crust, is a co-product of the latter. The specific emergies of dispersed minerals are, then, inversely proportional to their abundance. The results comply with the material hierarchy as the specific emergy of a dispersed mineral rise with its scarcity. The second is an emergy evaluation model based on the chemical and concentration exergy of the mineral, its condition in the mine and its abundance. This model permits to assess the decline of mineral reserves and its impact on the ecosystem. The dispersed specific emergy of 42 main commercially used minerals has been calculated. Furthermore, the emergy decrease of some Australian mineral reserves has been studied, as well as the land degradation of US copper mines

Analyse du recyclage par la méthode émergétique

International audienceLe recyclage matière est a priori considéré comme éco-favorable par rapport à l'exploitation de minerais provenant de mines, par nature en quantité finie et donc s'épuisant. Néanmoins, une vision holistique du recyclage requiert l'analyse de l'ensemble des ressources mobilisées pour effectuer cette opération. De plus, en suivant le déplacement/cheminement de la matière dans le temps, il devient alors nécessaire de connaître l'ensemble de l'historique de la matière considérée. Les auteurs établissent une équation théorique décrivant l'évolution à temps discret de l'émergie d'un produit : le pas d'échantillonnage est le temps du cycle. L'équation peut se réduire à une suite géométrique de raison, la fraction à recycler, sous certaines hypothèses. L'aluminium est ensuite proposé comme exemple d'application

Impact of building material recycle or reuse on selected emergy ratios

cited By (since 1996)1International audienceWhile the emergy evaluation method has been used successfully in recycling processes, this area of application still requires further development. One of such is developing emergy ratios or indices that reflect changes depending on the number of times a material is recycled. Some of these materials may either have been recycled or reused continuously as inputs to a building, for example, and thus could have various impacts on the emergy evaluation of the building. The paper focuses on reuse building materials in the context of environmental protection and sustainable development. It presents the results of an emergy evaluation of a low-energy building (LEB) in which a percentage of input materials are from recycled sources. The corresponding impacts on the emergy yield ratio (EYR B) and the environmental loading ratio (ELR B) are studied. The EYR which is the total emergy used up per unit of emergy invested, is a measure of how much an investment enables a process to exploit local resources in order to further contribute to the economy. The ELR however, is the total nonrenewable and imported emergy used up per unit of local renewable resource and indicates the stress a process exhibits on the environment. The evaluation provides values for the selected ratios based on different recycle times. Results show that values of the emergy indices vary, even more, when greater amounts of material is recycled with higher amount of additional emergy required for recycling. This provides relevant information prioritizing the selection of materials for recycling or reuse in a building, and the optimum number of reuse or recycle times of a specific material. © 2012 Elsevier B.V. All rights reserved

Carbon footprint and emergy combination for eco-environmental assessment of cleaner heat production

cited By (since 1996)0; Article in PressInternational audienceThe aim of this paper is to study via environmental indicators to which extent, replacing fossil fuel with biomass for heating is an environmentally friendly solution. The environmental impact of using biomass depends mostly on the transportation process. Authors define the notion of maximum supply distance, beyond which biomass transportation becomes too environmentally intensive compared to a fossil fuel fired heating system. In this work a carbon footprint analysis and an emergy evaluation, has been chosen to study the substitution of wood for natural gas. The comparative study seeks to examine, via the two approaches, two heating systems: one is fired with wood, transported by trucks and the other one is fired with natural gas transported by pipelines. The results are expressed in terms of maximum supply distance of wood. In the emergy evaluation it represents the maximum supply distance permitting wood to be more emergy saving than natural gas. In the carbon footprint analysis, it represents the maximum supply distance permitting wood to be a carbon saving alternative to natural gas. Furthermore, the unification of carbon footprint and emergy evaluation permits to define, for both approaches, the minimum theoretical wood burner first law efficiency that allows, CO 2 or emergy to be saved, when there is no wood transport. In order to identify the impacts of the main parameters of the study a sensitivity analysis has been carried out. The case study investigated in this paper shows that there is a large gap between the results. The maximum supply distances calculated via carbon footprint and emergy evaluation are about 5000 km and 1000 km, respectively, anthe minimum theoretical wood burner efficiencies are about 5% and 54%, respectively. © 2012 Elsevier Ltd. All rights reserved

Metallurgical recycling processes: Sustainability ratios and environmental performance assessment

International audienceRecycling is considered as core element of the sustainable development. In reality, however, due to the physical and chemical limits of current recycling technologies, material and quality losses occur that affect the efficiency of recycling. This paper aims to assess the environmental performance of metallurgical recycling, from both a donor and user-side perspective, by using the emergy evaluation combined with exergetic life cycle assessment (ELCA). The developed evaluation model is based on Ulgiati's proposition to erase the memory of the recovered material and to account only for the current recycling cycle. The use of an average transformity is proposed to measure the environmental performance of recycled materials. Contrary to classical transformities, it evaluates the material based on all previous processes that generated the material while avoiding the ``double counting''. Finally, three sustainability ratios have been defined to further assess the benefits and limits of consecutive metallurgical recycling processes: the resource efficiency ratio alpha, the performance ratio beta and the eco-design ratio chi. Their functions have been.described and clarified with provided examples. (C) 2015 Elsevier B.V. All rights reserved

Emergy assessment of the benefits of closed-loop recycling accounting for material losses

WOS:000363352200009International audienceEmergy analysis is applied to closed-loop recycling processes. The emergy balance is written under the form of a discrete-time equation following a comparable approach to the Lagrangian particle tracking in fluid mechanics. Two material losses were taken into consideration, the first one at the level of treatment (collection, dismantling, recycling etc.) and the second one at the transformation level. As expected, the emergy of a product increases with the number of cycles (after the transformation processes). To assess the environmental stress at each recycling stage, relative emergy of the product Delta E-p(n) was used after discussing the limitation of others solutions like the environmental loading ratio (ELR) or the recycle benefit ratio (RBR) which are not suitable for use in the cases of multiple recycling analysis. The values obtained showed that the Delta E-p(n) has an increasing trend for successive recycles. Additionally, this approach allowed the study of different cases of theoretical closed-loop recycling and an application on aluminum. The results indicated that the several cycles in the first stage of recycling have a significant impact, and an asymptotic behavior of Delta E-p(n) can be noted. In any cases recycling remains a better option compared to raw material use to compensate the material losses. Furthermore, the presented equations illustrate the impact of the material recycle rate and the percentage of losses during the both recycling and transformation processes. (C) 2015 Elsevier B.V. All rights reserved