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).

Markevičius 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 (Markevičius 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). Böhringer 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) (Böhringer 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), multi-objective 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).

3.2.2 Technologies and their interaction with the environment

The interaction of a technology with its environment is very complex. In general it can be stated that a technology may have impacts on the natural or physical as well as on the economic and sociocultural environment. The ways in which this interaction takes place may be diverse, depending on the kind of technology. However, every technology has a reason for its application, which ultimately is to deliver either a product or a service to society. This function – if it meets the demands of the final consumer – is what makes a new technology enter the market and consequently drives its impact on the environment. This idea of the interaction of technology with its environment through a function that needs to be fulfilled is shown in Fig. 3.1 (Balkema et al., 2002).

Consequently, the impact of a technology is always assessed taking into account its function. This is what makes it possible to compare a novel technology to ‘old’ technologies or to compare different alternatives for shaping a technology to each other. It is even possible to compare different technologies to services provided that the function for the user remains the same. Although the motivation to compare is very important, if not the most widespread one for sustainability assessment, it may also be interesting to assess one technology on its own. This motivation is encountered mostly in cases where the term technology designates not a single device, process or service, but rather a far reaching change in the sense of systems innovation which usually encompasses technology as well as organizational and social innovation; a well-known example of this is the internet. Here, often the term technology assessment (TA) is used, which covers a wide procedural approach encompassing many methodological tools in order to explore and assess a multitude of possible and maybe interacting consequences on the natural or social environment (van den Ende, 1998; Bütschi et al., 2004).

In contrast, the term sustainability assessment of technologies in the literature is rather used for a more focused assessment and comparison of specific technologies and their interaction with their environment. Keeping in mind that the impact of a technology is always connected to its function, one generic approach of assessment has become most popular: the methodology of life cycle assessment (LCA). It mirrors the view of the function as driving force for the use of a technology and as a point of reference for assessment. Most approaches to sustainability assessment of technologies are based on this method, either exclusively or by incorporating it in a wider framework. This notion is also true when looking at the assessment of technologies for energetic or material use of biomass (Dewulf and van Langenhove, 2006). Consequently, in order to reduce the plethora of names and single approaches, this chapter will be restricted to life cycle assessment as the most widespread concept for sustainability assessment of technologies.

3.2.3 Basics of life cycle assessment (LCA)

Life cycle assessment (LCA) is a systematic approach to analyze and examine the impacts of products or services on the environment. Not only these impacts, but their whole life cycle (i.e., from resource extraction to end-of-life) is analyzed. LCA is based on the modeling of interconnections between the single processes of a product system, in order to identify the material and energy flows within the system. From this model, the so-called ‘elementary flows’ – i.e., material flows between the product system as a whole and the natural environment – can be derived. Finally, the impacts or damage to the environment can be assessed. The core methodology of LCA was developed during the 1990s, with the SETAC ‘Code of Practice’ as a first milestone (Consoli et al., 1993), and today is described in two international standards, ISO 14040 and 14044, which are part of the ISO 14000 family of standards on environmental management.

According to ISO 14040, a life cycle assessment study consists of four phases: goal and scope definition, inventory analysis, impact assessment, and finally interpretation (Fig. 3.2). The double arrows in Fig. 3.2 indicate that an LCA is seen as an iterative process; additional information gained during a study can require a backshift to a previous stage to include further aspects. The first phase of an LCA study, goal and scope definition, defines and specifies the objects and the research questions. It also defines the system boundaries of the product system, e.g. as to space and time. A central task of LCA is the comparison of different products with the same function to extract particularly environmentally friendly goods or services. To fulfill this target, a clearly defined functional unit has to be determined. According to ISO 14040: ‘the functional unit defines the quantification of the identified functions of the product’, which means that the function has to be specified in terms of a quantity of a product or service, e.g. per kg of a product or per km of a transport service.

The second phase, life cycle inventory analysis (LCI), consists of three parts: creation of a flow model, data collection and calculation of the results. In a flow model, processes of the product system and their connections are described. The product system itself is defined by ISO 14040 as a ‘collection of unit processes with elementary and product flows, performing one or more defined functions and which models the life cycle of a product.’ For each unit process, data for input and output flows have to be gathered, together with other important information as to the process itself. The result of the LCI analysis is the quantification of the elementary flows resulting from the delivery of the functional unit, i.e. the product or service. The third step – the life cycle impact assessment, LCIA – transfers the results of the inventory analysis in a quantification of potential damage to the environment. To do so, the concept of impact categories is used. An impact category represents a certain environmental problem, e.g. climate change. It is quantified by a category indicator, which is based on an understanding of the underlying causes of an environmental problem as described in a respective scientific model (‘characterization model’). As the last phase of LCA, the interpretation transfers the results from the LCI analysis and LCIA to a clearly understandable message for the intended audience of an LCA study. The phase of interpretation also includes procedures of quality assurance and sensitivity analysis.

Details of the methodology of life cycle assessment can be found in textbooks as well as on internet platforms (Baumann and Tillmann, 2004).

3.4.1 Broadening the concept of LCA

Due to the widespread acceptance and use of the LCA methodology for environmental assessment of products and technologies during the last decade, efforts have been made to include the aspects of economy and social issues in LCA in order to derive a full sustainability assessment (Klöpffer, 2008). The aim is, similar to environmental LCA, to study the economic and social impacts of a product or technology, respectively, throughout its full lifetime, from manufacture through use to disposal or recycling. As a result of these efforts, methodological approaches to ‘life cycle costing’ (LCC) as well as ‘social life cycle assessment’ (SLCA) have been proposed. The currently most well-known approaches are the Code of Practice on LCC published by SETAC (Hunkeler et al., 2008; Swarr et al., 2011) and the Guidelines for Social Life Cycle Assessment, published the UNEP-SETAC Life Cycle Intitiative (UNEP, 2009; Benoît et al., 2010). However, no standardized methodology exists, and due to the complex nature of assessment of economic as well as social issues, diverging approaches can be encountered in the literature.

Klöpffer states the conceptual ‘equation’ of life cycle sustainability assessment: LCSA = LCA + LCC + SLCA (Klöpffer, 2008). Prerequisite of this ‘equation’ is that the system boundaries and functional units of LCA, LCC and SLCA are similar. However, this, is not self-evident for approaches to economic and social assessment. The term of ‘life cycle costing’ was introduced during the 1970s; for a short history, see Sherif and Kolarik (1981). It originally denotes a formal analysis tool which is applied in business management. Here, the life cycle of a product is seen to cover the stages from invention, research, commercialization and end-of-life of a product, which is different from the idea of a ‘physical life cycle’ in LCA that covers material flows from research extraction to disposal. The idea of life cycle costing as a summary of all costs caused by a product during its entire life cycle, however, can be transferred also to the notion of a ‘physical life cycle’. In this sense, LCC has also been proposed as a tool of sustainability assessment in recent years, postulating that the life cycle shall be congruent between LCC and LCA (UNEP, 2009). Even if systems boundaries are congruent, major methodological choices for LCC still exist. Notably, the question whether LCC covers monetization of externalities, i.e. environmental burdens, is crucial for any findings from this approach.

As to the method of SLCA, in the first place the question of adequate social indicators arises. Here indicators and indices are taken from different contexts mentioned in Section 3.2.1. However, given the large number of indices and indicator systems, the choice of proper indicators is often a highly controversial issue. Looking at system boundaries and matching to the phases of an environmental LCA, the methodological problem arises that indicators may not be directly related to processes, but rather to the level of companies or organizations (Jørgensen et al., 2008). In addition, for some fields of interest, qualitative rather than quantitative indicators may be adequate. The emerging methodology for SLCA consequently comprises elaborate schemes for the choice of indicators which are operated by use of check-lists (Benoît-Norris et al., 2011). However, it has to be emphasized again that other approaches also exist, which either use only environmental LCA, but combine it with other methods to account for economic and social aspects, or which use different methodological approaches to sustainability assessment. Examples for the variety of methods can be found in, for example, Assefa and Frostell (2007), Sugiyama et al. (2008) and Othman et al. (2010).

3.4.2 Results from economic and social asssessment of biorefineries

Given the far-reaching implications of the concept of biorefinery, economic and social aspects seem most important in addition to environmental assessment. However, the on-going scientific discussion on sustainability assessment methodology, combined with the open definition of the concept of ‘biorefinery’, results in the literature on sustainability assessments of biorefineries being scarce. Moreover, findings from the literature are often snapshots of single aspects rather than an overall sustainability assessment of the concept of ‘biorefinery’.

One general finding stressed by several authors is that environmental and economic optimization go hand in hand. Several publications stress the importance of integration for efficiency improvement and consequently enhancing sustainability as well as environmental issues and costs (e.g., Mateos-Espejel et al., 2011; Gassner and Maréchal, 2013). Generally speaking, the more efficient the chemistry, the lower the energy consumption during the production, and investment costs. A specific aspect is treated by Lange (2007) who points out that in fossil-based chemistry the goal of synthesis is often to add oxygen to hydrocarbons, which requires expensive oxidation processes. This causes a general increase of costs along with increasing the oxygen content in the production (see Fig. 3.7) (Lange, 2007). The generic advantage of renewable resources is that they are often rich in oxygen functionalities. This is why renewable resources can be used best when highly functional intermediates and polymer need to be obtained. Other authors point out that the selective deoxygenation of carbohydrates is more effective and therefore cheaper than the selective oxygenation of hydrocarbonates (Alles and Jenkins, 2010).

Luo et al. dealt with the economic and environmental analysis as well as with technical design of a lignocellulosic biorefinery (LCF), which produces ethanol, succinic acid, acetic acid and electricity. The economic analysis shows that the designed biorefinery has great potential in comparison with a sole ethanol biorefinery even if the price of succinic acid drops or the investment costs double (Luo et al., 2010).

Various studies address the costs of production across the value chain. One important aspect here is transport. Several studies use mathematical models to assess the complete costs of energy use of biomass while considering the whole supply chain (biomass production, harvest, farm and road transport and conversion plant). On the basis of the assessment results, strategies have been proposed to reduce costs. In general the transport of biomass is an important aspect, so processing biomass in the vicinity of agricultural production areas has economic advantages (Yu and Tao, 2009; Akgul et al., 2012; Giarola et al., 2011).