Material, energy and environmental performance of technological and social systems under a Life Cycle Assessment perspective
Introduction
A platform on Life Cycle Assessment (http://lct.jrc.ec.europa.eu/eplca) has been established by the European Commission in support of the implementation of the EU Thematic Strategies on the Prevention and Recycling of Waste and on the Sustainable Use of Natural Resources, the Integrated Product Policy (IPP) Communication and Sustainable Consumption and Production (SCP) Action Plan. The purpose is to improve the credibility, acceptance and practice of Life Cycle Assessment (LCA) in business and public authorities, by providing reference data and recommended methods for LCA studies. The concept itself of LCA stems from the awareness that processes generate impacts in all steps of their lifetime. Upstream impacts relate to a process contribution to deplete the reservoirs of resources (mineral, energy, biotic) while downstream impacts are concerned with emissions and waste generation. LCA techniques are used worldwide to assess material and energy flows to and from a production process. These methodologies are aimed at assessing the environmental impacts of a product (or service) from ‘cradle to grave’ or better ‘from cradle to cradle’, including recycling and reclamation of degraded environmental resources. More than a specific methodology, LCA is a cooperative effort performed by many investigators throughout the world (many of which involved in the industrial sectors) to follow the fate of resources from initial extraction and processing of raw materials to final disposal. This effort is day-by-day converging towards standard procedures and common frameworks, in order to make results comparable and reliable. SETAC (the International Society for Environmental Toxicology and Chemistry) developed a “code of practice” to be adopted as a commonly agreed procedure for reliable LCAs (SETAC, 1993). The SETAC standardization has been followed by a robust effort of the International Organization for Standardization (ISO) to develop a very detailed investigation procedure for environmental management based on LCT, namely Life Cycle Assessment (International Standards ISO 14040/2006–LCA Principles and framework and 14044/2006 – Requirements and guidelines, www.iso.org). The ISO documents suggest clear and standard procedures for the description of data categories, definitions of goals and scope, statements of functions and functional units, assessments of system boundaries, criteria for inclusions of inputs and outputs, data quality requirements, data collection, calculation procedures, validation of data, allocation of flows and releases, reuse and recycling, reporting of results. Nowhere in the ISO documents is preference given to a particular impact assessment method. In the opinion of the authors, LCA can be looked at as a standardized (and still to be improved) framework, where most of the methodologies already developed for technical and environmental investigations may be included and usefully contribute.
In order to take into proper account the different methodological, spatial and time-scale perspectives, we developed an integrated assessment framework named SUMMA (Sustainability Multi-scale Multi-method Assessment) (Ulgiati et al., 2006). Several case-studies where the SUMMA approach is applied, tested and improved are discussed in this paper.
It is self-evident that each evaluation can be carried out at different space and time scales. In general, the local scale only includes direct energy and mass inputs flows (that include a system's assets and infrastructures, discounted over the plant lifetime). As the scale is expanded to the regional level, it includes the production processes for all system components (machinery, building materials like concrete and steel, etc.) so that additional mass and energy inputs must be accounted for. If the scale is further expanded, the mass of raw minerals that must be excavated to manufacture the pure metals for plant components also contribute to all of the calculated performance indicators. At this larger scale, raw oil used up in the extraction and refining of minerals and fuel oil itself must also be accounted for. Finally, the large-scale evaluation should also include the ecosystem services that contribute to a process sustainability, such as wind for dilution of emissions, solar radiation and rain water for photosynthesis, the cycling of nutrients and so on. The evaluation may therefore be carried out at three different scales (local, regional and global), each one characterized by well-specified processes (resource final use, manufacturing and transport of components, resource extraction and refining, respectively), so that inefficiencies (poor performance, bottlenecks, generation of undesired co-products, etc.) at each scale may be easily identified and dealt with.
The larger the spatial scale, the larger the cost in terms of material and energy flows, i.e. the worse the related conversion efficiency and other impact indicators. In fact, if a process evaluation is performed at a small scale, its actual performance may not be well understood and may be overestimated due to a lack of inclusion of some large-scale impacts. Depending upon the goal of the investigation, a small-scale analysis may be sufficient to shed light on the process performance for technical or economic optimization purposes, while a large-scale overview is needed to investigate how the process interacts with other upstream and downstream processes as well as the biosphere as a whole. Defining the system boundary and clarifying at what time scale an assessment is performed is therefore of paramount importance, even if the scale of the assessment is sometimes implicit in the context of the investigation. It is very important to be aware that a ‘true’ value of net energy return or other performance indicators does not exist. Each value of a given indicator is only ‘true’ at the scale at which it is calculated. When the same value is used at a different scale, it does not necessarily become false. It is, however, out of the right context, and therefore most often useless.
Time is an important, although most often neglected, issue in any kind of evaluation. The simplest case is when we have inputs, whose lifetime exceeds the time frame of the analysis. It is easy to transform extended-lifetime inputs into annual flows by dividing by their lifetime (in years). Another and perhaps more important time scale is hidden in the resources used, i.e. the time nature takes to concentrate or produce a given resource (e.g. oil). A resource turnover time is often a good measure of its renewability. An effort to go beyond the concept of turnover time in resource evaluations is the introduction of emergy accounting procedures (Odum, 1988, Odum, 1996, Brown and Ulgiati, 2004) that is also included in our extended LCA approach and is discussed later on in this paper.
Section snippets
Methods: towards and integrated evaluation approach
Environmental and socio-economic accounting procedures so far proposed by many authors were applied to different space–time windows of interest and were aimed at different investigations and policy goals (Szargut et al., 1988, Odum, 1996, Herendeen, 1998, Ayres and Masini, 1998, Giampietro et al., 1998, Lozano and Valero, 1993, Foran and Crane, 1998, Finnveden and Moberg, 2005, Gasparatos et al., 2008). These authors offered valuable insight towards understanding and describing important
Results from selected case studies
The case studies presented in this section are the results of specific assessments performed by the authors directly or from literature cases. The joint use of complementary methods, points of view and numeraires allows the generation of a large set of performance indicators that can be used for technological improvement, informed investment choices, comprehensive resource and environmental policy.
The ‘upstream’ methods are concerned with the inputs, and account for the depletion or appropriate
Discussion
Quantifying direct and indirect flows of matter and energy to and from a system permits the construction of a detailed picture of the process itself as well as of its relationship with the surrounding environment. Processing these data in order to calculate performance indicators as well as material and energetic intensities makes it possible to compare the process output to other products of competing processes. Results may differ depending on the goal, the boundaries, the time scale, and the
Conclusion
We presented in this paper a framework for a comprehensive investigation of complex systems. The joint application of several different methods to the analysis of technical and social systems based on the same set of inventory data allows a consistent reading of a system's performance and the comparability of calculated indicators. Some of the methods used are specific for local scale evaluation, while others are more suited for larger regional or biosphere scales. Moreover, the inclusion of
Acknowledgements
The authors at Parthenope University gratefully acknowledge the financial support received from the European Commission within the 7th Framework Programme, Project no. 217213, SMILE – Synergies in Multi-scale Inter-Linkages of Eco-social systems and Socioeconomic Sciences and Humanities (SSH) Collaborative Project FP7-SSH-2007-1.
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