Alicia Valero

Application of Thermoeconomics to Industrial Ecology

Industrial Ecology involves the transformation of industrial processes from linear to closed loop systems: matter and energy flows which were initially considered as wastes become now resources for existing or new processes. In this paper, Thermoeconomics, commonly used for the optimization and diagnosis of energy systems, is proposed as a tool for the characterization of Industrial Ecology. Thermoeconomics is based on the exergy analysis (Thermodynamics) but goes further by introducing the concepts of purpose and cost (Economics). It is presented in this study as a systematic and general approach for the analysis of waste flow integration. The formulation is based on extending the thermoeconomic process of the cost formation of wastes in order to consider their use as input for other processes. Consequently, it can be applied to important Industrial Ecology issues such as identification of integration possibilities and efficiency improvement, quantification of benefits obtained by integration, or determination of fair prices based on physical roots. The capability of the methodology is demonstrated by means of a case study based on the integration of a power plant, a cement kiln and a gas-fired boiler.

From Grave to Cradle

Life cycle assessment (LCA) is a promising tool in the pursuit of sustainable mining. However, the accounting methodologies used in LCA for abiotic resource depletion still have some shortcomings and need to be improved. In this article a new thermodynamic approach is presented for the evaluation of the depletion of nonfuel minerals. The method is based on quantifying the exergy costs required to replace the extracted minerals with current available technologies, from a completely degraded state in what we term “Thanatia�? to the conditions currently found in nature. Thanatia is an estimated reference model of a commercial end of the planet, where all resources have been extracted and dispersed, and all fossil fuels have been burned. Mineral deposits constitute an exergy bonus that nature gives us for free by providing minerals in a concentrated state and not dispersed in the crust. The exergy replacement costs provide a measure of the bonus lost through extraction. This approach allows performing an LCA by including a new stage in the analysis: namely the grave to cradle path. The methodology is explained through the case study of nickel depletion.

Decreasing ore grades in global metallic mining: A theoretical issue or a global reality?

Mining industry requires high amounts of energy to extract and process resources, including a variety of concentration and refining processes. Using energy consumption information, different sustainability issues can be addressed, such as the relationship with ore grade over the years, energy variations in electricity or fossil fuel use. A rigorous analysis and understanding of the energy intensity use in mining is the first step towards a more sustainable mining industry and, globally, better resource management. Numerous studies have focused on the energy consumption of mining projects, with analysis carried out primarily in one single country or one single region. This paper quantifies, on a global level, the relationship between ore grade and energy intensity. With the case of copper, the study has shown that the average copper ore grade is decreasing over time, while the energy consumption and the total material production in the mine increases. Analyzing only copper mines, the average ore grade has decreased approximately by 25% in just ten years. In that same period, the total energy consumption has increased at a higher rate than production (46% energy increase over 30% production increase).

GLOBAL GOLD MINING: Is technological learning overcoming the declining in ore grades?

Abstract: Future availability of mineral resources is influenced by two opposed facts. On the one hand, general trends suggest a long-term decline in ore grade, which increases energy consumption in mining industry. But on the other hand there have been technological transitions that might avert rises in energy consumption. The aim of this paper is to become acquainted if technological breakthroughs that have occurred can preclude the rising energy demand for the gold mining industry. As experience is acquired, material and energy efficiency increase and technical changes can be expressed through the so called learning curves. For this purpose, the learning curve approach is applied to several data sets of 17 major gold producing countries. Our results show that technological learning is as dependent on ore grade as it is on mining operation and recovery processes. Applying the learning curve method we obtain average progress ratios varying from +20% to -22%. This survey allows us to have a better understanding of the mining sector and the outcomes of technology evolution together with ore grade declining by means of identifying best mining practices around the world.

Thermodynamic Approach to Evaluate the Criticality of Raw Materials and Its Application through a Material Flow Analysis in Europe

Summary This paper makes a review of current raw material criticality assessment methodologies and proposes a new approach based on the second law of thermodynamics. This is because conventional methods mostly focus on supply risk and economic importance leaving behind relevant factors, such as the physical quality of substances. The new approach is proposed as an additional dimension for the criticality assessment of raw materials through a variable denoted “thermodynamic rarity,” which accounts for the exergy cost required to obtain a mineral commodity from bare rock, using prevailing technology. Accordingly, a given raw material will be thermodynamically rare if it is: (1) currently energy intensive to obtain and (2) scarce in nature. If a given commodity presents a high risk in two of the three dimensions (economic importance, supply risk, and thermodynamic rarity), it is proposed to be critical. As a result, a new critical material list is presented, adding to the 2014 criticality list of the European Commission (EC) Li, Ta, Te, V, and Mo. With this new list and using Sankey diagrams, a material flow analysis has been carried out for Europe (EU-28) for 2014, comparing the results when using tonnage and thermodynamic rarity as units of measure. Through the latter, one can put emphasis on the quality and not only on the quantity of minerals traded and domestically produced in the region, thereby providing a tool for improving resource management.

Integrating the Thermo-ecological and Exergy Replacement Costs to Assess Mineral Processing

Depletion of non-renewable natural resources is one of the factors leading mining industry to reach sustainability. Meeting this challenge entails the assessment of mineral resources as well as the mining operations needed to produce commodities. In this chapter, an exergy analysis of six minerals (aluminium, copper, chromium, gold, iron and manganesum) processing is accomplished through the application of two complementary methodologies: Thermo-ecological Cost (TEC) and Exergy Replacement Cost (ERC). The coalescence of both methodologies allows to have an absolute assessment of non-fuel mineral processing. The TEC evaluates the cumulative consumption of non-renewable exergy required to produce a unit of useful product from the raw materials contained in natural deposits, i.e. from cradle to market. Whilst, the ERC accounts for the exergy required to produce minerals from a completely dispersed state to the original conditions in which they were originally found in nature, i.e. from grave to cradle.

Exergy Evaluation of the Mineral Capital on Earth: Influence of the Reference Environment

The mineral capital on Earth is assessed from a 2nd law of thermodynamics approach. This requires to define precisely the Reference Environment (R.E.). Therefore, the exergy difference of the mineral capital generated from different R.E. is calculated. A sensitivity analysis is done to measure the influence of the element chemical exergy and other physical parameters of the R.E. on the mineral’s exergy. The exergy of the world mineral reserves, base reserves and world resources is obtained: 0.75, 1.08 and 6.59 Gtoe, respectively.Copyright

Sankey and Grassmann Diagrams for Mineral Trade in the EU-28

Material flow analysis is a key tool to quantify and monitor natural resource use. A very visual way to undertake such analyses representing the mineral trade of a certain nation or continent is through the well-known Sankey diagrams, in which the mineral resources that are extracted, imported, exported, recycled and consumed within the given boundaries are represented with the arrows proportional to their respective quantities. Yet Sankey diagrams alone are not sensitive to the quality of the resources as they only reflect tonnage. This issue can lead to misleading conclusions and thereby ineffective resource policies. A way to overcome this deficiency is using Grassmann diagrams instead, in which instead of tonnage the flows are represented in exergy terms, thereby accounting for the physical value of minerals. In this chapter we use the exergoecology method to evaluate mineral trade and foreign dependency in EU-28 for the 1995–2012 period. Using the year 2011 as a case study, we can see that 45.8% of the total input tonnes of minerals are imported resulting in low values of self-sufficiency (Domestic Extraction to Domestic Material Consumption ratio). With data expressed in exergy replacement costs we can better reflect the real material dependency, 0.45 for minerals and 0.41 for fossil fuels, in contrast to 0.79 and 0.52 obtained respectively when using tonnes. Analyzing 10 of the 20 minerals considered critical by the European Commission, imports represent 6.74% of the total imports while extraction represents only 3.19% of the total extraction. This external dependency leaves Europe in a delicate situation regarding fossil fuels and non-fuel mineral supply and highlights the importance of recycling and the search for alternative sources.

Thermodynamic Methods to Evaluate Resources

Natural resources can be evaluated from different points of view. One of them, and perhaps the most commonly known is the economic point of view. Nevertheless, the price-fixing mechanisms, rarely take into account the concrete physical characteristics which make them valuable. But natural resources have at least two physical features which make minerals or fresh water for example unusual: a particular composition which differentiates them from the surrounding environment and a distribution which places them in a specific concentration. These intrinsic properties can be in fact evaluated from a thermodynamic point of view in terms of exergy. Chapter 6 presents in details how to evaluate resources quality applying exergy.

Resources. Production. Depletion

Any activity around the world as well as further development of humankind relies on natural resources. The primary deposits, which represent the work that nature offers us, are essential for current and future civilizations. There are several examples of ancient civilizations that collapsed due to the depletion of local natural resources; the most significant include depletion of the forests in Easter Islands, the depletion of fresh water in Central America or the depletion of the agricultural areas in South-East Asia [1]. Nowadays, these examples should not be underestimated and a rational resource management should be enhanced.