LCA entails the analysis of flows exchanged between a product system and the environment, resources consumed, and emissions in its supply, use, and end-of-life. The impact assessment in LCA of resources is generally limited to the depletion potential of abiotic resources. However, also other aspects related to resources can be useful in eco-design contexts and in policy making, e.g., the material efficiency of alternative products as well as the use and recovery of critical resources. This latter information would support and guide the minimization of use of critical resources, recovery in waste management, and/or their substitution. A further potential use of LCA consists in the evaluation of the environmental performance of possible substitutes of CRMs. Considering the criticality of materials within the LCA may require, however, a methodological advancement that could include both a better definition of the meaning of the resource impact category and the analysis of potential mismatching or inconsistencies that could exist between LCA and criticality assessments.
The potential of LCA in integrating considerations related to resource security is explored here in terms of the following:
Availability of information on CRM flows used in the supply chain, at inventory level
Suitability of the current LC impact assessment methods for including criticality criteria (i.e., aspects like supply risk, substitution and recycling potential, etc.) within the current conceptual definition of the “natural resources” area of protection
Potential to analyze the flows of CRM at macroeconomic scale and at sectorial level within the framework of resource life cycle indicators
In each section, the main research gaps and open issues regarding the role of LCA in supporting a resource policy are addressed.
Life cycle inventory (LCI) analysis involves data collection and calculation procedures to quantify relevant inputs and outputs of a product system (its supply, use, and end-of-life). In principle, LCI should include all relevant flows related to unit processes within the system boundaries. This refers to all kind of resources, including CRMs. However, LCI is performed in line with the goal definition and meeting the requirements derived in the scope phase (EC 2010d). Some flows could be not accounted due to applied cutoff rules or allocation rules and system boundary definition. This could be the case of critical materials, which are usually used in very small amounts in a product’s life cycle. This may result in a lack of information on the issue of resource criticality.
Therefore, criticality should be specifically addressed during the goal and scope definition, at least for those products belonging to sectors where such materials are relevant. Relevance of sectors is related to geopolitical, economic, social, and environmental considerations. EU relevant sectors have been recently identified by the European Commission (EC 2010c, Annex V) (see Table 3). These sectors cannot be considered a general priority and might differ from market to market.
LCI data quality is related to completeness, which is usually evaluated against selected impact categories (EC 2010e). Current resource depletion impact assessment methods do not consider several criticality aspects and could therefore not capture CRM-related flows that are relevant. Having a clear impact category related to such issues, hence requiring explicit consideration of CRMs when assessing product life cycles, would ensure CRMs to be considered while evaluating data quality and completeness.
A further issue to take into account when analyzing the use of critical resources in supply chains is the nature of criticality indicators. In the EU study, the “supply risk” aggregated indicator includes country-dependent indexes, i.e., HII and WGI (see Sect. 3.1). This suggests the need for a spatially differentiated LCI, unless just listed totals of critical raw material inventory irrespective of their origin.
The concept of spatial differentiated resources inventory has been already introduced (e.g., Strauss et al. 2006; Gao et al. 2009), but only a very limited number of examples can be found in literature at this time. Although only at a country resolution and assuming this would be the appropriate resolution where no more detailed supplier insights exist, spatially differentiating resources inventory could increase drastically both the number of flows to be accounted and LCI database management and update operations. For foreground data, such information may be more readily available and result in no additional burden. For background data, this may be more complex and reliance may have to be on the total inventory of CRMs irrespective of their source/supplier.
The European Commission has developed methodologies and tools for spreading the life cycle thinking (LCT) and facilitating a broad application of LCA. The European Platform on LCA (http://eplca.jrc.ec.europa.eu/) has been created with the aim of improving the quality and reliability of life cycle data and assessment, increasing the availability of quality ensured data and facilitating the knowledge exchange. This has facilitated the development of the European Life Cycle Database (ELCD), the International Reference Life Cycle Data System (ILCD) handbook, and the Life Cycle Data Network amongst other outputs.
The ELCD provides reference data on life cycle inventories of selected processes of material production, energy carriers and technologies, transport services, systems like packaging and construction, end-of-life treatments. As far as currently feasible, these reference data are aligned with the entry-level criteria of the Life Cycle Data Network. These criteria include a format and nomenclature developed as part of the ILCD handbook.
CRMs are currently listed as elementary flows in the ILCD reference nomenclature list. REE and PGM flows are not aggregated, and inventory of single resources is required. The ILCD data format allows running spatial differentiated LCI for the CRM resources.
The ELCD datasets provide an insight on the use of CRMs within the supply chains of some products widely taken into account in LCAs, both as production inputs and as by-products/emissions/waste. Displaying the amounts of materials used in products and processes, these datasets can expedite the implementation of resource efficiency strategies focused on the use of CRMs, within or in parallel with the LC practice. Table 3 summarizes the availability of information on CRMs in the ELCD database, with reference to the main end-use markets and mega-sectors, as defined by the EU study on CRMs (EC 2010b).
There is a lack of consensus on how resources should be addressed in LCA. The existing impact category refers to resource depletion or scarcity only; security of supply is so far not explicitly included in the impact assessment methodologies.
Considering criticality of raw materials in LC impact assessment (LCIA) entails the inclusion of aspects that can constrain the access to resources. These aspects have different natures: political (e.g., the stability of producing countries), economic (e.g., concentration of supply, demand dynamics, or trade barriers), and regulatory (e.g., the level of environmental legislation in the producing countries). The meaning of an impact category for resources and its inclusion in the LCA framework are, however, still open issues.
The debate whether or not natural resources should be considered an area of protection in the context of LCA started in at least the 1990s and is still unresolved (Weidema et al. 2005). Resource use is appraised in LCA with an anthropocentric approach, according to which the assessment focus on the impacts on human welfare derived by reduced resource availability. The conceptual definition of the natural resources area of protection is, however, unclear: in the assessment of the impacts related to resource depletion, many doubts rise concerning the boundaries between environmental and socioeconomic spheres. Indeed, a considerable range of methodologies for assessing resource depletion in LCA have been proposed, with different theoretical underpinnings (Klinglmair et al. 2013). Currently, in most of the LCIA methods, use of resources is accounted, at midpoint level, in the impact category “resource depletion,” taking into account the decreased availability caused by the resource use both for abiotic and biotic resources.
Presently, LCIA methods have as their modeling basis different definitions of the depletion problem (Steen 2006), that could be summarized as follows: (1) assuming that mining cost will be a limiting factor, (2) assuming that collecting metals or other substances from low-grade sources is mainly an issue of energy, (3) assuming that scarcity is a major threat, and (4) assuming that environmental impacts from mining and processing of mineral resources are the main problem.
These four problem definitions reflect mainly a socioeconomic orientation in the resource depletion assessment. In all the four problem definitions, extraction of a resource from the natural environment leads to a decrease in its future availability for human use. This, in turn, is expressed either in relation to the available amount of a resource at a given point in time (e.g., ore deposits or fossil fuel reserves) or the future consequences (e.g., higher economic and/or energetic costs) of the extraction of a certain amount of a resource in the present. Environmental and human health impacts related to extraction or use, such as toxic emissions, are taken into account under separate environmental impact categories, and scarcity or criticality impacting directly ecosystem health is not taken into account.
Focusing on abiotic resources, many impact assessment methodologies exist. These are based on the property of the materials (e.g., exergy), the resource scarcity (thus considering use/extraction and availability), or at an endpoint level, the consequences of resource depletion for society. The different methodologies provide very diverse estimations and different coverage of CRMs (Table 4), while there is no consensus on the basis underpinning this impact category.
Currently, the methods for impact assessment in LCA recommended by the ILCD handbook (EC 2011d) cover only scarcity-related issues and not all CRMs. The selected method for midpoint is the abiotic depletion potential (ADP) (Guinée 2002), which assesses fossil fuels and mineral resources in terms of resource scarcity by including the extraction rate and its reserve. Instead, none of the endpoint methods were considered robust at the time of the related analysis, hence were not recommended.
The consideration of aspects that can constrain the access to resources (in addition to the geological availability) in the impact assessment of resources is currently debated, and some methods have been developed with this aim.
In the context of the European project LC impact, a stakeholder consultation has been organized on the impact assessment of resources. The conclusion of this process was that an indicator for mineral resource depletion in a short-term perspective should be based on political factors limiting resource availability (Vieira et al. 2011). In Schneider et al. (2011, 2013) factors, e.g., concentration of supply (at country and company levels), availability of secondary production and substitutes, trade barriers, and anthropogenic reserves have been included in an “economic resource scarcity potential (ESP)” indicator.
The consideration of aspects related to supply risk in the impact assessment of resources faces, however, methodological hurdles. Some open issues have to be addressed before implementing such development, e.g.,
How to bring in a characterization model indicators and/or concepts used for assessing criticality?
Since CRMs result from a relative ranking and their assessment has some degree of subjectivity (given by, e.g., the setting of thresholds), how could they be considered in the LCIA, which is based on measured and absolute figures?
How to deal with the fact that CRMs are assessed relatively to a certain country/region and do not have an absolute validity?
How to differentiate the geographic origin (and the risk related to different geographic areas) of resource supply in the LCIA?
Should the aspect related to supply risk be taken into account in the environmental LCA or in the social LCA?
Addressing the abovementioned questions implies, however, a common understanding of the resource category and also of the whole LCA methodology. We advocate that the assessment of impacts related to resource use should take into account both environmental, social, and economic issues and that a common understanding of the area of protection Natural Resources is needed. Moreover, LCA should not be considered only an environmental assessment methodology since it already has a broader scope, e.g., in the assessment of resource depletion. Rather more, other socioeconomic and geopolitical issues, e.g., supply risk, could be taken into account. As stated by Schneider et al. (2013), the consideration of economic and social dimensions related to resources could complement existing scarcity-based models and would represent a contribution toward life cycle sustainability assessment (LCSA) (UNEP 2011).