3.2.1 Methods and indicators of sustainable development

Given the broad concept of sustainability outlined above, it is obvious that sustainability assessment does not mean one single method, but that different types of methodologies and assessment procedures may be applied. This calls for the structuring or a typology of approaches, and indeed such typologies can be found in the literature. Before presenting them, at the most simple, three structuring criteria shall be discussed: first, what indicators are used for the assessment, second, how the object of assessment is defined, and third, how the quantitative or qualitative values for the chosen indicators as to the defined object of assessment are generated.

As to the issue of indicators, these can be defined from the three dimensions of sustainability and on different levels; these levels have to be adequate for the object to be assessed. Many indicator systems have been defined at the country level, e. g. the United Nations Commission for Sustainable Development (UNCSD) Theme Indicator Framework (UN, 2001). Some of these indicators may be meaningful also at the company, product or technology level (e. g., the amount of greenhouse gases), but some may be not (e. g., the national debt).

The task to define the object of investigation is not as trivial as it may seem. Every object has a structure — for example, a product has its components, a technology has auxiliary processes and a demand for material and energy — so each object can be seen as a system and the definition of the objects is equal to the definition of the system boundaries. This system can be specified by technological components, but also by geographical or temporal aspects. One idea of a system boundary is specifically prominent in sustainability assessment which is the so-called life cycle of a product. ‘Life cyle thinking’ means looking at the full process chain from extraction of raw materials through production of a product or technology, its use by the consumer and also its end of life, where materials are transferred back to nature.

These two structuring criteria are decisive for the third one, the meth­odology, with which quantitative or qualitative values for the chosen indi­cators and the system boundary are generated. Here, usually two types of procedures are encountered: either information is gathered directly via measurement or statistics (or taken from databases which contain respective data), or a model is built in order to generate new data from a set of data fed in. The choice of methodology makes up the tools that are used for assessment.

Typologies found in the literature make use of these criteria in different ways. Singh et al. report on a broad literature overview of sustainability assessment methods, structured by sustainability indicators, classification and evaluation of methodologies. They address guidelines for the construction of indices; in addition, they give a comprehensive survey and description of existing sustainability indices (Singh et al., 2009). Hacking and Guthrie propose a framework and a consistent terminology for approaches to sustainability assessment found in the literature, which uses three axes: ‘the comprehensiveness of the SD coverage; the degree of ‘integration’ of the techniques and themes; and the extent to which a strategic perspective is adopted’ (Hacking and Guthrie, 2008). Ness et al. present a proposal for assessment tools and arrange them into three main categories: indicators/indices, product-related assessment, and integrated assessment tools. There is a ‘parent category’ (monetary valuation tools), which acts in all categories (Ness et al., 2007).

Markevicius et al. use 35 criteria for a so-called Emerging Sustainability Assessment Framework. The majority of indicators focus on environmental issues (12 indicators), while four social indicators and one economic indicator are added (Markevicius et al., 2010). Hueting and Reijnders report on the construction of sustainability indicators. They make the general criticism that so far suggested economic and social elements for inclusion in indicators do not have plausible causal relation to nature conservation, i. e. ‘sustainability defined as a production level that does not threaten the living conditions of future generations’ (Hueting and Reijnders, 2004). Bohringer and Jochem select 11 indices from 500 Sustainable Develop­ment Indicators, that are suggested to researchers and policy makers, including the Living Planet Index (LPI), Ecological Footprint (EF), City Development Index (CDI), and Human Development Index (HDI) (Bohringer and Jochem, 2007). Assefa and Frostell discuss an approach for the evaluation of indicators for social sustainability of technical systems (e. g., waste management and energy systems). Three indicators are reviewed: knowledge, perception and fear (Assefa and Frostell, 2007). Finnveden et al. mention the strategic environmental assessment (SEA), the environmental impact assessment (EIA), the environmental risk assessment (ERA), the cost-benefit analysis (CBA), the material flow analysis (MFA), the ecological footprint, and notably life cycle assesment (LCA) as most frequently used methods (Finnveden et al., 2009). Balkema et al. propose a methodology of sustainability assessment structured in three steps following the approach of life cycle assessment: (1) Goal and definition, (2) inventory analysis, and (3) optimization and results. The last step is essential for assessing sustainability (Balkema et al., 2002).

Sustainability assessment also has to be seen as a decision-making process where the interests of many stakeholders have to be taken into account. The various players have their environmental, social and economic criteria and interests for the development of a sustainable system. To support these decision-making processes and take into account different goals and interests, methods such as multi-criteria decision analysis (MCDA), multi­objective decision making (MODM), operations research and management science are proposed. These methods are used to review the assessment of various decisions and political strategies as well as to include the competing interests of various stakeholders and experts (Halog and Manik, 2011). When quantitative sustainability indicators are used, multi-objective optimization can be integrated to identify a group of favorable options for sustainable solutions (Balkema et al., 2002). Such methodology has to be included in a procedural framework of stakeholder participation (see, e. g., Stoll-Kleemann and Welp, 2006).