Material flow analysis for Europe: An exergoecological approach

Material flow analysis is a key tool to quantify and monitor the use of natural resources. A very visual way to undertake such analyses representing the mineral trade is through 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 not effective resource policies. A way to overcome this deficiency is representing the flows in exergy replacement cost (ERC) terms instead of tonnage. Exergy replacement cost is a concept derived from the second law of thermodynamics and assesses the exergy cost required to return with available technologies a given mineral to its initial conditions of composition and concentration in the mines where it was found, once it has been dispersed after use. Using this methodology, minerals are physically valued in terms of their respective scarcities and the effort (in exergy cost terms) required to produce them. Accordingly, in this paper the so-called exergoecology method is used to evaluate mineral trade and foreign mineral dependency in the EU-28 for 1995 to 2012. Using the year 2011 as a case study, it can be seen using this novel approach that 45.8% of the total input of minerals are imported resulting in lower values of self-sufficiency than if a traditional MFA were applied (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 deemed critical by the European Commission, of the total internal production, 0.88% corresponded to critical minerals when data were expressed in tonnes and 3.19% when expressed in exergy replacement costs, highlighting their relevance respect to other minerals. This external dependency leaves Europe in a delicate situation regarding fossil fuels and non-fuel minerals supply highlighting the importance of recycling especially scarce minerals and searching for alternative sources.     

Life cycle assessment in the minerals and metals sector: a critical review of selected issues and challenges

Background, aim and scope

The mining sector provides materials that are essential elements in a wide range of goods and services, which create value by meeting human needs. Mining and processing activities are an integral part of most complex material cycles so that the application of life cycle assessment (LCA) to minerals and metals has therefore gained prominence. In the past decade, increased use of LCA in the mineral and metal sector has advanced the scientific knowledge through the development of scientifically valid life cycle inventory databases. Though scientifically valid, LCA still needs to depend on several technical assumptions. In particular, measuring the environmental burden issues related to abiotic resource depletion, land use impacts and open-loop recycling within the LCA are widely debated issues. Also, incorporating spatial and temporal sensitivities in LCA, to make it a consistent scientific tool, is yet to be resolved. This article discusses existing LCA methods and proposed models on different issues in relation to minerals and metals sector.

Main features

A critical review was conducted of existing LCA methods in the minerals and metals sector in relation to allocation issues related to indicators of land use impacts, abiotic resource depletion, allocation in open-loop recycling and the system expansions and accounting of spatial and temporal dimension in LCA practice.

Results

Evolving a holistic view about these contentious issues will be presented with view for future LCA research in the minerals and metals industry. This extensive literature search uncovers many of the issues that require immediate attention from the LCA scientific community.

Discussion

The methodological drawbacks, mainly problems with inconsistencies in LCA results for the same situation under different assumptions and issues related to data quality, are considered to be the shortcomings of current LCA. In the minerals and metals sector, it is important to increase the objectivity of LCA by way of fixing those uncertainties, for example, in the LCA of the minerals and metals sector, whether the land use has to be considered in detail or at a coarse level. In regard to abiotic resource characterisation, the weighting and time scales to be considered become a very critical issue of judgement. And, in the case of open-loop recycling, which model will best satisfy all the stake holders? How the temporal and spatial dimensions should be incorporated into LCA is one of the biggest challenges ahead of all those who are concerned. Addressing these issues shall enable LCA to be used as a policy tool in environmental decision-making. There has been enormous debate with respect to on land use impacts, abiotic resource depletion, open-loop recycling and spatial and temporal dimensions, and these debates remain unresolved. Discussions aimed at bringing consensus amongst all the stake holders involved in LCA (i.e. industry, academia, consulting organisations and government) will be presented and discussed. In addition, a commentary of different points of view on these issues will be presented.

Conclusions

This review shall bring into perspective some of those contentious issues that are widely debated by many researchers. The possible future directions proposed by researchers across the globe shall be presented. Finally, authors conclude with their views on the prospects of LCA for future research endeavours.

Recommendations and outlook

Specific LCA issues of minerals and metals need to be investigated further to gain more understanding. To facilitate the future use of LCA as a policy tool in the minerals and metals sector, it is important to increase the objectivity with more scientific validity. Therefore, it is essential that the issues discussed in this paper are addressed to a great detail.     

Applying cumulative exergy demand (CExD) indicators to the ecoinvent database

Goal, Scope and Background Exergy has been put forward as an indicator for the energetic quality of resources. The exergy of a resource accounts for the minimal work necessary to form the resource or for the maximally obtainable amount of work when bringing the resource’s components to their most common state in the natural environment. Exergy measures are traditionally applied to assess energy efficiency, regarding the exergy losses in a process system. However, the measure can be utilised as an indicator of resource quality demand when considering the specific resources that contain the exergy. Such an exergy measure indicates the required resources and assesses the total exergy removal from nature in order to provide a product, process or service. In the current work, the exergy concept is combined with a large number of life cycle inventory datasets available with ecoinvent data v1.2. The goal was, first, to provide an additional impact category indicator to Life-Cycle Assessment practitioners. Second, this work aims at making a large source of exergy scores available to scientific communities that apply exergy as a primary indicator for energy efficiency and resource quality demand. Methods The indicator Cumulative Exergy Demand (CExD) is introduced to depict total exergy removal from nature to provide a product, summing up the exergy of all resources required. CExD assesses the quality of energy demand and includes the exergy of energy carriers as well as of non-energetic materials. In the current paper, the exergy concept was applied to the resources contained in the ecoinvent database, considering chemical, kinetic, hydro-potential, nuclear, solar-radiative and thermal exergies. The impact category indicator is grouped into the eight resource categories fossil, nuclear, hydropower, biomass, other renewables, water, minerals, and metals. Exergy characterization factors for 112 different resources were included in the calculations. Results CExD was calculated for 2630 ecoinvent product and process systems. The results are presented as average values and for 26 specific groups containing 1197 products, processes and infrastructure units. Depending on the process/product group considered, energetic resources make up between 9% and 100% of the total CExD, with an average contribution of 88%. The exergy of water contributes on the average to 8% the total exergy demand, but to more than 90% in specific process groups. The average contribution of minerals and metal ores is 4%, but shows an average value as high as 38% and 13%, in metallic products and in building materials, respectively. Looking at individual processes, the contribution of the resource categories varies substantially from these average product group values. In comparison to Cumulative Energy Demand (CED) and the abiotic-resource-depletion category of CML 2001 (CML’01), non-energetic resources tend to be weighted more strongly by the CExD method. Discussion Energy and matter used in a society are not destroyed but only transformed. What is consumed and eventually depleted is usable energy and usable matter. Exergy is a measure of such useful energy. Therefore, CExD is a suitable energy based indicator for the quality of resources that are removed from nature. Similar to CED, CExD assesses energy use, but regards the quality of the energy and incorporates non-energetic materials like minerals and metals. However, it can be observed for non-renewable energy-intensive products that CExD is very similar to CED. Since CExD considers energetic and non-energetic resources on the basis of exhaustible exergy, the measure is comparable to resource indicators like the resource use category of Eco-indicator 99 and the resource depletion category of CML 2001. An advantage of CExD in comparison to these methods is that exergy is an inherent property of the resource. Therefore less assumptions and subjective choices need to be made in setting up characterization factors. However, CExD does not coversocietal demand (distinguishing between basic demand and luxury), availability or scarcity of the resource. As a consequence of the different weighting approach, CExD may differ considerably from the resource category indicators in Eco-indicator 99 and CML 2001. Conclusions The current work shows that the exergy concept can be operationalised in product life cycle assessments. CExD is a suitable indicator to assess energy and resource demand. Due to the consideration of the quality of energy and the integration of non-energetic resources, CExD is a more comprehensive indicator than the widely used CED. All of the eight CExD categories proposed are significant contributors to Cumulative Exergy Demand in at least one of the product groups analysed. In product or service assessments and comparative assertions, a careful and concious selection of the appropriate CExD-categories is required based on the energy and resource quality demand concept to be expressed by CExD. Recommendations and Perspectives A differentiation between the exergy of fossil, nuclear, hydro-potential, biomass, other renewables, water and mineral/metal resources is recommended in order to obtain a more detailed picture of resource quality demand and to recognise trade-offs between resource use, for instance energetic and non-energetic raw materials, or nonrenewable and renewable energies. ESS-Submission Editor: Dr. Gerald Rebitzer (Gerald.Rebitzer@alcan.com)     

Exergetic life cycle assessment of a grid-connected,polycrystalline silicon photovoltaic system

Purpose

Nowadays, the intensive use of natural resources in order to satisfy the increasing energy demand suggests a threat to the implementation of the principles of sustainable development. The present study attempts to approach thermodynamically the depletion of natural resources in the methodological framework and the principles of life cycle assessment (LCA).

Methods

An environmental decision support tool is studied, the exergetic life cycle assessment (ELCA). It arises from the convergence of the LCA and exergy analysis (EA) methodologies and attempts to identify the exergetic parameters that are related to the life cycle of the examined system or process. The ELCA methodology, beside the fact that it locates the system parts which involve greater exergy losses, examines the depletion of natural resources (biotic and abiotic) and the sustainable prospective of the examined system or process, under the scope of exergy. In order to obtain concrete results, the ELCA methodology is applied to a large-scale, grid-connected, photovoltaic (PV) system with energy storage that is designed to entirely electrify the Greek island of Nisyros.

Results and discussion

Four discerned cases were studied that reflect the present state and the future development of the PV technology. The exergy flows and balance for the life cycle of the PV system, as they were formed in the ELCA study, showed that the incoming exergy (solar radiation, energy sources, and materials) is not efficiently utilized. The greater exergy losses appear at the stage of the operation of the PV installation. Due to the fact that contribution of the renewable exergy (solar radiation) to the formation of the total incoming exergy of Life Cycle is significant, it emerges that satisfaction of electric power needs with a PV system appears to be exergetic sustainable. The increase of the Life Cycle exergetic efficiency supported by the future technological scenario in contrast to present scenarios emerges from the increased electricity output of the PV system. Consequently, the increased exergetic efficiency involves decreased irreversibility (exergy losses) of the PV system’s life cycle.

Conclusions

The application of ELCA in electricity production technologies exceeds the proven sustainable prospective of the PV systems; however, it aims to show the essence of the application of ELCA methodology in the environmental decision making process. ELCA can be a useful tool for the support and formation of the environmental decision making that can illustrate in terms of exergetic sustainability the examined energy system or process.     

The anthropogenic stock extended abiotic depletion potential (AADP) as a new parameterisation to model the depletion of abiotic resources

Purpose  

Raw material availability is a cause of concern for many industrial sectors. When addressing resource consumption in life cycle assessment (LCA), current characterisation models for depletion of abiotic resources provide characterisation factors based on (surplus) energy, exergy, or extraction–reserve ratios. However, all indicators presently available share a shortcoming as they neglect the fact that large amounts of raw materials can be stored in material cycles within the technosphere. These “anthropogenic stocks” represent a significant source and can change the material availability significantly. With new characterisation factors, resource consumption in LCA will be assessed by taking into account anthropogenic material stocks in addition to the lithospheric stocks. With these characterisation factors, the scarcity of resources should be reflected more realistically.     

Impact assessment for LCAs involving agricultural production

LCA has been developed primarily for industrial production systems. Application to agricultural systems requires systematic application of existing methodology and new methodological developments. Conventional approaches can obscure potential options for improving the environmental performance of systems involving agricultural production due to use of restricted system boundaries, incomplete assessment of impacts, and exclusion of ancillaries from the analysis. For use of nutrients such as phosphorus, it is proposed that Impact Assessment should be based on the quantity dispersed after use rather than on the input to the productive system. Eventually, the impacts associated with depletion should be based on technological or thermodynamic assessment of concentration for reuse, but this approach requires further theoretical development.     

A Consistent Framework for Assessing the Impacts from Resource Use - A focus on resource functionality (8 pp)

Background The quantification of resource depletion in Life Cycle Assessment has been the topic of much debate; to date no definitive approach for quantifying effects in this impact category has been developed. In this paper we argue that the main reason for this extensive debate is because all methods for quantifying resource depletion impacts have focussed on resource extraction. - Aim and Scope. To further the state of the debate we present a general framework for assessing the impacts of resource use across the entire suite of biotic and abiotic resources. The main aim of this framework is to define the necessary and sufficient set of information required to quantify the effects of resources use. Method logy. Our method is based on a generic concept of the quality state of resource inputs and outputs to and from a production system. Using this approach we show that it is not the extraction of materials which is of concern, but rather the dissipative use and disposal of materials. Using this as a point of departure we develop and define two key variables for use in the modelling of impacts of resource use, namely the ultimate quality limit, which is related to the functionality of the material, and backup technology. Existing methodologies for determining the effects of resource depletion are discussed in the context of this framework. Results We demonstrate the ability of the general framework to describe impacts related to all resource categories: metallic and non-metallic minerals, energy minerals, water, soil, and biotic resources (wild or domesticated plants and animals). Recommendation focus on suggestions for a functionality measure for each of these categories; and how best the two modelling variables derived can be determined.     

Global Supply Chains of Coltan

The spot price for tantalum, a metal used in high‐performance consumer electronics, spiked in 2000, triggering a boom in artisanal mining of surface deposits in the Democratic Republic of Congo (DRC). The profit from columbite‐tantalite ore, or coltan, is alleged to have funded militants during that country's civil war. One warlord famously claimed that in 2000, coltan delivered a million dollars per month. While coltan mining was neither a necessary nor sufficient cause for the civil war, there is nevertheless a clear association between mining and conflict. In order to trace global flows of coltan out of the DRC, we used a high‐resolution multiregion input‐output (MRIO) table and a hybrid life cycle assessment (LCA) approach to trace exports through international supply chains in order to estimate a “coltan footprint” for various products. In this case study, our aim is to highlight the power and utility of hybrid LCA analysis using high‐resolution global MRIO accounts. We estimate which supply chains, nations, and consumer goods carry the largest loads of embodied coltan. This hybrid LCA case study provides estimates on illicit flows of coltan, estimates a coltan footprint of consumption, and highlights the advantages and challenges of using hybrid monetary‐physical input‐output/LCA approaches to study and quantify a negative social impact as an input to production. If successful, the hybrid LCA approach could be a useful and expedient measurement tool for understanding flows of conflict minerals embodied in supply chains.     

Extending effectiveness to efficiency: Comparing energy and environmental assessment methods for a wet cooling tower

Improving the environmental performance and energy efficiency of cooling towers requires systematic evaluation. However, methodological challenges emerge when applying typical environmental assessment methods to cooling towers. Hence, this paper compares the methods, analyzes their strengths and weaknesses, and proposes adaptions for evaluating cooling towers. As a case study, we applied five methods for assessing the wet cooling system of the high-performance data center in Stuttgart. These are material flow analysis (MFA), life cycle inventory, life cycle assessment (LCA), exergy analysis, and life cycle exergy analysis (LCEA). The comparison highlights that the LCA provides the most comprehensive environmental evaluation of cooling systems by considering several environmental impact dimensions. In the case of the wet cooling tower, however, electricity and water consumption cause more than 97% of the environmental impacts in all considered impact categories. Therefore, MFA containing energy flows suffices in many cases. Using exergy efficiency is controversially debated because exergy destruction is part of the technical principle applied in cooling towers and, therefore, difficult to interpret. The LCEA appears inappropriate because construction and disposal barely affect the exergy balance and are associated with transiting exergy. The method comparison demonstrates the need for further methodological development, such as dynamic extensions or the efficiency definition of cooling towers. The paper highlights that the methodological needs depend on the specific application.     

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

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.     

A proposal for accounting for biodiversity in life cycle assessment

Life cycle assessment (LCA) is a methodology for assessing the environmental impacts associated with products throughout their lifecycle. Many impacts are accounted for within the LCA framework, but to date biodiversity impacts have received little attention. There are a number of existing direct and indirect measures of biodiversity within the ecological field, some of which have the potential to be developed into a useable method for LCA. However, our assessment is that considerable development would be required and their implementation for LCA is not likely in the foreseeable future. Here an alternative approach is proposed for rapidly incorporating biodiversity impacts into LCA. The approach relies on expert opinions through a series of questions which aim to encapsulate the main issues relating to biodiversity within a disturbance impact framework. While the technique is in its infancy we outline a foundation for the approach and identify the steps required to develop this method for implementation into LCA.     

Towards harmonizing natural resources as an area of protection in life cycle impact assessment

Purpose

In this paper, we summarize the discussion and present the findings of an expert group effort under the umbrella of the United Nations Environment Programme (UNEP)/Society of Environmental Toxicology and Chemistry (SETAC) Life Cycle Initiative proposing natural resources as an Area of Protection (AoP) in Life Cycle Impact Assessment (LCIA).

Methods

As a first step, natural resources have been defined for the LCA context with reference to the overall UNEP/SETAC Life Cycle Impact Assessment (LCIA) framework. Second, existing LCIA methods have been reviewed and discussed. The reviewed methods have been evaluated according to the considered type of natural resources and their underlying principles followed (use-to-availability ratios, backup technology approaches, or thermodynamic accounting methods).

Results and discussion

There is currently no single LCIA method available that addresses impacts for all natural resource categories, nor do existing methods and models addressing different natural resource categories do so in a consistent way across categories. Exceptions are exergy and solar energy-related methods, which cover the widest range of resource categories. However, these methods do not link exergy consumption to changes in availability or provisioning capacity of a specific natural resource (e.g., mineral, water, land etc.). So far, there is no agreement in the scientific community on the most relevant type of future resource indicators (depletion, increased energy use or cost due to resource extraction, etc.). To address this challenge, a framework based on the concept of stock/fund/flow resources is proposed to identify, across natural resource categories, whether depletion/dissipation (of stocks and funds) or competition (for flows) is the main relevant aspect.

Conclusions

An LCIA method—or a set of methods—that consistently address all natural resource categories is needed in order to avoid burden shifting from the impact associated with one resource to the impact associated with another resource. This paper is an important basis for a step forward in the direction of consistently integrating the various natural resources as an Area of Protection into LCA.

     

Thermodynamic rarity of electrical and electronic waste: Assessment and policy implications for critical materials

The strategic relevance of extracting raw materials from waste from electrical and electronic equipment (WEEE) in the EU is increasing due to value chain risks caused by geopolitical instability, accessibility of specific minerals, and decreasing reserves due to growing extraction rates. This article examines the quantities of so-called critical raw materials (CRMs) originating within WEEE streams from a depletion perspective. Presently, current recycling targets are based solely on mass collection and recycling rates. We examine the potential limitations of this approach using an exergy-based indicator named thermodynamic rarity. This indicator represents the exergy costs needed for producing materials from the bare rock to market. The case of Italy is used to explore the application of the indicator at the macro (national) and micro (company) level for the product categories “small electronics” and “screens and monitors.” Our estimations show significant differences between the mass and rarity of materials within Italian WEEE streams. While iron accounts for more than 70% of the weight of the product categories analyzed, it accounts for less than 15% of the rarity. Similarly, several CRMs with a small mass have a higher rarity value, for example, tungsten with less than 0.1% of the mass and over 6% of the rarity. The policy context is reflected upon, where it is argued that thermodynamic rarity can provide novel insights to support end-of-life WEEE decision-making processes, for example, target development and recycling standards setting to help prioritize material monitoring and recovery options.     

Non-traditional tools for lca and sustainability

LCA practice focuses on impacts resulting from the release of chemicals into the environment, but consideration of ‘non-chemical impacts’ is as important for LCA, particularly as it relates to sustainability. Methodologies and philosophies exist for addressing non-chemical impacts, particularly in the area of resource depletion and land use, but the problem of comparing or integrating chemical and non-chemical impacts remains. A new approach for identifying and integrating impacts involves the use of an object-oriented modeling and simulation platform, such as Department of Energy Argonne National Laboratory’s Dynamic Information Architecture System (DIAS). LCA and impact categories can be described as ‘objects’ (at any level of detail or specificity) and any combination of objects and behaviors can be brought into a DIAS analysis frame. Related models that address objects’ behavior characteristics are linked only to their respective objects, not to each other. Thus, maximum flexibility and speed is possible. The process of dividing LCA and impact assessment into a hierarchy of objects provides new insights into the complex mixture of dynamic things, activities, and relationships inherent in LCA and sustainability. Ultimately, embracing the complexity of LCA may be the way to simplify it.     

Possibility Theory: A New Approach to Uncertainty Analysis? (3 pp)

Background, Aims and Scope The problem of the evaluation of practitioner's belief and belief-related uncertainties on LCA results obtained from different methodological choices has been addressed so far by scenario modeling, Cultural Theory perspectives and probabilistic simulation. The direct evaluation of belief and related uncertainties could be of interest, e.g. when the information available (resulting from classical uncertainty analysis or the application of the precautionary principle) do not allow one to choose between methodological alternatives leading to different LCA results and conclusions. The difficulty of modeling belief arises from the additive nature of classical measures, e.g. probabilities. Since the 1960s, non-additive measures (e.g. possibilities) have been developed and applied to model belief in real world problems. The aim of this paper is to discuss the application of possibility measures in LCA for uncertainty analysis in complement to classical approaches. Methods The nature and the meaning of possibilities are briefly introduced by comparison with probabilities (subjective or not) in order to enlighten strengths, drawbacks and complementarities. A tentative possibilistic approach based on the evaluation of a posteriori possibilities of final LCA results depending on a priori possibilities of the methodological choices behind the calculations is described, also by means of an application example. Results and Outlook. A new approach for the modeling of practitioner's belief and belief-related uncertainties in complement of classical methods of uncertainty analysis has been proposed for discussion. Uncertainty can be characterized by confidence intervals and indexes that could help practitioners in making methodological choices and could improve the interpretation and reliability of LCA results, still increasing its sophistication.     

Life cycle assessment of construction materials: the influence of assumptions in end-of-life modelling

Purpose

The nature of end-of-life (EoL) processes is highly uncertain for constructions built today. This uncertainty is often neglected in life cycle assessments (LCAs) of construction materials. This paper tests how EoL assumptions influence LCA comparisons of two alternative roof construction elements: glue-laminated wooden beams and steel frames. The assumptions tested include the type of technology and the use of attributional or consequential modelling approaches.

Methods

The study covers impact categories often considered in the construction industry: total and non-renewable primary energy demand, water depletion, global warming, eutrophication and photo-chemical oxidant creation. The following elements of the EoL processes are tested: energy source used in demolition, fuel type used for transportation to the disposal site, means of disposal and method for handling allocation problems of the EoL modelling. Two assumptions regarding technology development are tested: no development from today’s technologies and that today’s low-impact technologies have become representative for the average future technologies. For allocating environmental impacts of the waste handling to by-products (heat or recycled material), an attributional cut-off approach is compared with a consequential substitution approach. A scenario excluding all EoL processes is also considered.

Results and discussion

In all comparable scenarios, glulam beams have clear environmental benefits compared to steel frames, except for in a scenario in which steel frames are recycled and today’s average steel production is substituted, in which impacts are similar. The choice of methodological approach (attributional, consequential or fully disregarding EoL processes) does not seem to influence the relative performance of the compared construction elements. In absolute terms, four factors are shown to be critical for the results: whether EoL phases are considered at all, whether recycling or incineration is assumed in the disposal of glulam beams, whether a consequential or attributional approach is used in modelling the disposal processes and whether today’s average technology or a low-impact technology is assumed for the substituted technology.

Conclusions

The results suggest that EoL assumptions can be highly important for LCA comparisons of construction materials, particularly in absolute terms. Therefore, we recommend that EoL uncertainties are taken into consideration in any LCA of long-lived products. For the studied product type, LCA practitioners should particularly consider EoL assumptions regarding the means of disposal, the expected technology development of disposal processes and any substituted technology and the choice between attributional and consequential approaches.     

Improved exergetic life cycle assessment through matrix reduction technique

Purpose

The concept of exergy can be used in LCA to quantify the value of natural resources consumed in production processes, as well as to assess the environmental impacts of waste streams. Prior studies noted the complexity of exergy accounting for wastes due to the diversity and complexity of waste streams. We develop an improved method to allow for rigorous exergy accounting of both resources and wastes.

Methods

The exergy content of a mass stream depends on many physical characteristics, including temperature, pressure, and chemical composition. We develop a novel matrix reduction technique to reduce data gathering requirements by multiple orders of magnitude. This method predivides the impact matrix into key rows and processes and “rest of economy” flows. Thermodynamic data can then be gathered for key flows emitted by key processes, and all other flows can be modeled using default values with little loss of accuracy.

Results and discussion

Our method is applied to an example LCA of electricity production via a natural gas combined cycle (NGCC) system. The case study finds that life cycle (economy-wide) exergetic efficiency of NGCC electricity production is ≈43 %, compared to a plant-level (local) exergetic efficiency of ≈54 %. The exergy content of life cycle waste flows is contained primarily in chemical exergy and physical exergy of flue gases, with nearly equal contributions. These waste exergy fluxes represent ≈3 % each of total input exergy.

Conclusions

The matrix reduction technique is found to be robust to assumptions about flows that are not directly modeled. By examining ranges of reasonable assumptions about mass flows not specifically modeled, we show that key rows and processes account for the vast majority of exergy content of interventions.

     

Impact assessment of abiotic resource consumption conceptual considerations

The impact assessment of the consumption of abiotic resources, such as fossil fuels or minerals, is usually part of the Life Cycle Impact Assessment (LCIA) in LCA studies. The problem with the consumption of such resources is their decreasing availability for future generations. In currently available LCA methods (e.g. Eco-indicator’ 99/Goedkoop and Spriensma 1999, CML/Guinée 2001), the consumption of various abiotic resources is aggregated into one summarizing indicator within the characterization phase of the LCIA. This neglects that many resources are used for different purposes and are not equivalent to each other. Therefore, the depletion of reserves of functionally non-equivalent resources should be treated as separate environmental problems, i.e. as separate impact sub-categories. Consequently, this study proposes assigning the consumption of abiotic resources to separate impact sub-categories and, if possible, integrating them into indicators only according to their primary function (e.g. coal, natural gas, oil → consumption of fossil fuels; phosphate rock → consumption of phosphate). Since this approach has been developed in the context of LCA studies on agricultural production systems, the impact assessment of the consumption of fossil fuels, phosphate rock, potash salt and lime is of particular interest and serves as an example. Following the general LCA framework (Consoli et al. 1993, ISO 1998), a normalization step is proposed separately for each of the subcategories. Finally, specific weighting factors have been calculated for the sub-categories based on the ’distance-to-target’ principle. The weighting step allows for further interpretation and enables the aggregation of the consumption of different abiotic resources to one summarizing indicator, called the Resource Depletion Index (RDI). The proposed method has been applied to a wheat production system in order to illustrate the conceptual considerations and to compare the approach to an established impact assessment method for abiotic resources (CML method, Guinée 2001).     

LCA experiences in Danish industry

A study has been performed on Danish industry’s experiences with LCA. Twenty-six enterprises from different sectors conpleted a questionnaire. The enterprises are still in an adoption and learning phase, and experiences with full-blown LCA’s are sparse. Expectations of future market pressure to supply more environmentally friendly products is the most important incentive for the enterprises to engage in LCA activities. This pressure, however, has not yet emerged and the enterprises have not achieved the expected competitive advantages. LCA work has revealed new environmental aspects of the products with subsequent new priorities in the environmental efforts. Only a few enterprises have built up in-house LCA competence, whereas consultants are heavily involved in LCA work. In large enterprises, LCA work is predominantly carried out by environmental staff members, but the product development staff is also involved. The nature of the co-operation and distribution of roles between these two actors is not clear, and should therefore be studied further.     

Efficient information visualization in LCA: Application and practice

Aim, Scope and Background  Acquisition and analysis of huge amounts of data still pose a challenge, with few options available for solutions and support. Life cycle assessment (LCA) experts face such problems on a daily basis. However, data do not become useful until some of the information they carry is extracted, and most important, represented in a way humans can both recognize efficiently and understand and interpret as quickly as possible. Unfortunately, information representation techniques as used in this field are still based on traditional low-dimensional information spaces, featuring only a few basic choices to represent life cycle (LC) related data. We must part from those traditional techniques and shift to visual representations that are easier for us to understand due to the human capability for detecting spatial structures and shapes represented in different colors and textures. Then all the advantages of modern, advanced information visualization can be applied and exploited. Main Features  With the introduction of a new glyph-based information representation and visualization approach to LCA, current issues of representing LC-related information efficiently at a glance are being tackled. These new techniques support reduction of information load by providing tools to select and summarize data, assist in making explicit and transparent data feature propagation, and provide a means of representing data errors and uncertainty. In this approach the human perceptual capability for easily and quickly recognizing and understanding graphical objects in different colors and textures is exploited for the design and application of highly structured and advanced forms of multi-dimensional information representation. Results  Now in the example presented in this paper, OM-glyphs were used to represent LCA-related information for an industrial product and its compiled life cycle inventory under conditions normal for LCA. To demonstrate the application and benefits of the approach introduced, several different visualization scenarios were computed and presented. These were illustrated with a selection of generated glyph-based displays containing spherical glyph clusters for environmental items such as air pollutants and water pollutants, and inventory glyph matrices related to components and to LC phases. Where appropriate, to further aid understanding and clarity, displays were additionally shown with various orientations and in enlarged form. This is a functional feature of interactive 3D OM-glyph based information visualization that can be used in practice to efficiently navigate through displays while at the same time adjusting rendered scenes to the needs of the user at any given time. Due to the huge amount of data acquired and compiled, only a small fraction of the glyph-based displays could be shown, and, in consequence, only a fraction of the data properties, patterns and features available could be discussed in detail. However, it is believed that the basic principles and methods of this approach, as shown in a real application, could be clearly conveyed, and, most important, that the benefits and potential could be displayed in a convincing manner. This technology will support a marked increase in efficiency, speed and quality in LC information analysis. Conclusions  This paper concludes our short series on efficient information visualization in LCA. A new approach to efficient information visualization has been introduced, together with its basic principles. This background was enriched with discussions on and further insights into technical details of the approach and the framework developed. The first practical examples were provided in the previous paper, demonstrating the mapping of LCA-related data and their contexts to glyph parameters. In this paper the application of the approach was presented using data for an actual industrial product. During the discussions, and with the various glyph-based displays shown, it could be convincingly demonstrated that all data features, trends, patterns, relationships, and data imperfections detected and examined, and sometimes traced, could be quickly and efficiently recognized in a short time. Even basic data features, such as small gaps in the data propagation of related values, could be easily seen using OM-glyphs. In the case of traditional data representation, using for example LCI tables, this would require the identification and comparison of several thousand numerical entries. As is the case with all new technology, however, it is still difficult to obtain the interest of the experts, and to convince them that such new ideas will eventually change the face of industry. Outlook  A new, advanced and efficient information representation and visualization approach has been introduced to the LCA community. Hopefully, through this small series of papers, some interest will have been generated in the field of advanced information visualization. For the first time this area has been related to LCA, and some seeds for interdisciplinary research may have been sown. Now it is up to individuals, the experts in the various fields elated to those issues, to respond. The desired results will be stimulating discussions, an exchange of ideas, further initiated multilateral, interdisciplinary efforts, and improved collaboration between partners from academia and industry. At that point, efficient information visualization will finally have arrived at, and received, its deserved place within LCA.