A comparison of four sustainable manufacturing strategies

Abstract

Effective use of materials is one possible component of a sustainable manufacturing strategy. There are many such strategies proposed in the literature and used in practice, with confusion over what they are, what the differences among them may be and how they can be used by practitioners in design and manufacture to improve the sustainability of their product and processes. This paper reviews the literature on sustainable manufacturing strategies that deliver improved material performance. Four primary strategies were found: waste minimisation; material efficiency; resource efficiency; and eco‐efficiency. The literature was analysed to determine the key characteristics of these sustainable manufacturing strategies and 17 characteristics were found. The four strategies were then compared and contrasted against all the characteristics. While current literature often uses these strategy titles in a confusing, occasionally inter‐changeable manner, this study attempts to create clear separation between them. Definition, scope and practicality of measurement are shown to be key characteristics that impact upon the ability of manufacturing companies to make effective use of the proposed strategy. It is observed that the most actionable strategies may not include all of the dimensions of interest to a manufacturer wishing to become more sustainable, creating a dilemma between ease of implementation and breadth of impact.

Keywords:

• material efficiency
• waste minimisation
• resource efficiency
• eco‐efficiency
• sustainable manufacturing
• sustainability

1. Introduction

Centuries ago, when natural resources were abundant and labour was scarce, industries strived to find ways to increase labour efficiency through introducing diverse manufacturing strategies and technologies. Strategies ranged from job flexibility, shift‐work, time‐and‐motion study and mass production to lean production, while technologies ranged from machine tools, engines, and automated devices to robots and automated lines; all these were designed and used to increase labour productivity in order to meet customer demand. Machines needed to be faster, cheaper, more reliable and always available. More recently, the theme of ‘doing more with less’, normally meaning less labour effort per unit of production, was re‐directed away from increasing batch sizes, hence improving machine utilisation, toward the revolutionary approach of ‘lean’ production, which emphasised making what was needed when asked for by the customer. While the lean concept attracted initial concern over its impact on decreasing machine utilisation, the many benefits of improved lead times, lower inventory, etc. has shown the value of this radical re‐think.

That radical re‐thinking of the system of manufacturing may be occurring once more, propelled by a changing world where energy and materials are becoming less abundant and labour more abundant. Environmental changes, globalisation and access to cheap labour through cheap transport is altering this balance. This paper is particularly concerned with materials and how manufacturing may be changing in response to increasing scarcity of materials. While a strategy of using less material has an obvious and direct economic efficiency of paying less per product, it also helps to make a manufacturer more robust to supply shortages and contributes positively to the limits placed on humanity by the physical limits of the planet – noting that human resources are renewable for as long as natural resources remain available but not the other way around.

Efforts made by researchers from as early as the 1960s promoted ‘pollution prevention’ (Dales 1968) and the IPAT equation [the multiplicative contribution of population {P}, affluence {A} and technology {T} to environmental impact {I}] (Ehrlich and Holdren 1971, Commoner 1972, Holdren and Ehrlich 1974 as cited by Fischer‐Kowalski and Amman 2001). In 1987, the Brundtland report popularised the concept of sustainable development which it defined as ‘meets the needs of the present without compromising the ability for future generations to meet their own needs’. However, it was not until the ‘wake‐up call’ in 1992 at the Earth Summit in Rio de Janeiro, when nations met to discuss problems due to pollution, that they agreed to the need for actions toward sustainable development. While no agreement between nations was reached at the summit on the issue of pollution, the consensus on there being limits to what we could put into nature (in the form of pollution) as well as what we could take out of nature (in the form of raw materials) did result in industries and organisations starting to work towards practicing sustainable material/resource strategies such as resource efficiency, eco‐efficiency and sustainable development. This also has made governments more active in imposing regulations and rules related to waste management and pollution.

For industry, a widely‐used and basic strategy to increase the efficiency with which we use available resources is to concentrate efforts on recovery of products or materials at the end of their useful life [which includes re‐use, re‐manufacturing, re‐cycling and energy recovery and is termed the waste hierarchy (Jackson 1996)]. Sometimes referred to under the generic name of re‐cycling, the effectiveness of these strategies in tackling waste and pollution problems is questioned in the literature. Schmidt‐Bleek (1995) pointed out that less than 20% of all materials originally moved (disturbed and extracted) end up in products and infrastructure. This makes the overall recycling capacity very limited. Lovins (2003) suggests that from the 100% of natural capital extracted to make a product in the United States, commonly only 7% of materials become products that we end users see or use, meaning 93% becomes waste within industrial processes (this includes extractive and manufacturing waste). Out of the 7%, 1% becomes durable and 6% becomes waste from customer first use. Going further, of these 1% consumer durables, only 0.02% is recycled or re‐manufactured and the balance of 0.98% becomes persistent waste from disposal (typically landfill). Waste recovery activities often concentrate on the 7% of waste that occurs after use; being a small percentage of the natural resources extracted it is obvious that waste recovery should also be focused earlier in resource flows within the industrialised supply chain. This view puts emphasis on the role of the production system rather than the waste management system, and this paper seeks to explore published strategies that are proposed to mitigate against these lost material resources.

There are many techniques and concepts that are proposed to support a move toward sustainable manufacturing (such as local manufacturing, low carbon manufacturing, low temperature processing, etc.), but the authors focus here on those published strategies which are reported to tackle the issue of resource use and waste in the industrial system, namely, waste minimisation; material efficiency; resource efficiency; and eco‐efficiency. There are similarities and distinctions between these strategies, but one thing they have in common is that they strive to prevent and reduce waste by increasing natural resource productivity. Given that these concepts are now reaching into industrial practice it is a concern that a proliferation of terms, definitions, tools, explanations and scope could act to confuse practitioners and so delay implementation of sensible industrial strategies to do more with less. This paper seeks to structure, compare and contrast the four identified primary strategies of waste minimisation; material efficiency; resource efficiency and eco‐efficiency. Given the variety of terms and ideas presented in literature and other media, the quality of debate and learning among and between practitioners and researchers may be negatively impacted. The issue of common language, clear definitions and scope, and shared mental models are regular themes in the literature on change management and knowledge management [for example, Moss Kanter (2007) and Senge (2006)]. This paper seeks to juxtapose the primary strategies to enable a more precise debate; it is not the intention to select or propose one strategy as ‘superior’.

2. Methodology

The four strategies were chosen because they are the most commonly represented in academic and practitioner literature and are self‐reported to act at the level of manufacturing strategies; terms used by single authors were ignored as were terms which were assessed to be tools or to be of a limited scope or to be phrases to capture all other strategies (such as material selection techniques, design for dis‐assembly and green manufacturing). Each strategy appeared to have its own audience: waste minimisation is more commonly used in the UK; resource efficiency is popular among UK authorities, and especially in the literature: eco‐efficiency is popular world‐wide, and especially in Europe (where resource efficiency is less common); and material efficiency is emerging as a related strategy.

The literature search strategy for this research was developed by first identifying the likely relevant databases, conferences and journals and using key words (such as material efficiency, sustainability, waste minimisation, cleaner production and factor X). This generated hundreds of potential papers whose abstracts were analysed and the promising papers were read. Snowballing using paper references, authors, conferences and journals generated a second long list. The authors found many publications such as theses, journal articles, conference proceedings, newsletters, books, government reports in the UK and abroad. Each new search brought more authors, journals, conferences and companies to our attention, as well as a growing set of potential keywords. It is clear that the topic of sustainable manufacturing, and efficient use of materials have been described in many different ways over past decades. Using the new keywords, new authors, new journals, etc., it was possible to search further. Based on title and/or abstract, all papers indicating the topic of material efficiency were collated, read through and their references added to the search. When new searches brought no new material, the initial searching was ended. Regular searches have been used since then to update with new material as it becomes available. The majority of the papers found did not relate directly to the topic of material efficiency and were discarded; the remainder formed a core set of some 60 papers which were used within this study.

Through the literature review, and the authors' analysis, four main strategies were chosen as representing the main body of knowledge. Although other labels existed for strategies they could reasonably be categorised within one of the four selected strategies. The authors then sought for key characteristics noted as important by one or more papers, importance here was conceptualised as relating to sustainable manufacturing or strategy or guidance for action, (for example, importance claimed through novelty alone was ignored). These characteristics identified from the literature review formed the structure for a second reading of each paper, seeking for evidence of comment against the key characteristic. Characteristics that generated low or no data were then discarded, followed by analysis of each characteristic across the four previously identified strategies which improved the detail understanding of each characteristic.

At this point the characteristics were then fixed and a table (Table 6 in the sequence of tables provided) created of the characteristics and all relevant papers, categorised under the four strategies (17 characteristics were identified, ranging from ‘system boundaries’ through ‘data availability’ to ‘measurement and target’). Further analysis studied all papers related to a single characteristic for any pattern that could elaborate on similarities or differences between the four strategies. Finally all the papers related to each strategy were re‐visited to throw light on the relative importance of each characteristic to that strategy. The academic papers used are international in source, while the policy documents relate primarily to European Union and UK situations. This paper now explains a variety of perspectives on that literature, beginning with explanations on what each strategy is.

3. Defining and analysing the four strategies

3.1 Waste minimisation

Waste minimisation is frequently mentioned in sustainability strategies. Committing to minimise waste is recognised as desirable in managing resources. Waste minimisation is described as ‘the reduction of waste’ at source recognising that is cheaper not to produce waste in the first place. Waste minimisation covers activities aimed at reducing wastes from: raw material and ingredient use; product loss; water consumption and effluent generation; paper and packaging; factory and office consumables; energy consumption; all other solid; liquid and gaseous wastes; and wasted effort (Department of the Environment 1998).

The waste hierarchy provides a framework within which the most desirable waste management options are set out. Waste management policy in the UK is created with reference to the waste directive of the European Council (75/442/EEC, amended by 91/156/EEC), with further development through national directives such as the Waste Strategy for England 2007 (DEFRA 2007). This sets out the requirements for countries in managing their waste. The hierarchy of waste management principles has been agreed by European Council Directive, 1991 as: waste prevention; recovery; and then safe disposal. In the UK, the present national strategy in dealing with waste is based upon a hierarchy of preferred options (Phillips et al. 1999) described as: reduction (previously known as waste minimisation), reuse, recovery (including recycling, composting and energy recover) and disposal (landfill and incineration without energy recovery). Waste minimisation is now being referred to as an out‐dated option compared to waste prevention (waste prevention, recovery and safe disposal) [House of Lords (2008) and Kirkpatrick, as cited in Pongrácz et al. (2004)]. Although there are different versions of the waste hierarchy it is widely accepted that waste minimisation, reduction or prevention is the first priority, while recycling has a higher priority than incineration, and land filling has the lowest priority (Moberg et al. 2005).

The primary definition of waste minimisation is ‘the reduction in quantity and hazardousness of waste produced at source’ (OECD 1998). In this definition, re‐use, recycling and recovery are not included. Although this waste minimisation definition is only confined to hazardous related waste, the Waste Minimisation Act 1998 states that waste minimisation is a top priority of UK government in managing waste. Waste minimisation is claimed as the top priority of the waste management hierarchy, but it is not being prioritised or given necessary support by the UK authorities [according to the House of Commons All Party Environmental Audit Committee, 5th Report, Waste‐Audit, as cited in Hawkins and Shaw (2004), Read et al. (1998)]. Selected definitions referring to these ideas in literature, including those commonly used by organisations in the UK are listed in Table 1.

The term ‘waste minimisation’ can be argued to be the clearest among the four strategies, emphasising the reduction of the worst types of polluting waste. However, some authors do refer to waste minimisation as a different version of waste prevention, indicating the level of challenge in creating a common language for the emerging fields of sustainable manufacturing and sustainable engineering. The term ‘waste minimisation’ is preferred and used in the UK while in the US, the term ‘waste minimisation’ is most often replaced by ‘pollution prevention’ (Levin 1990, Freeman et al. 1992). Waste minimisation, due to its simple and direct goal of minimising waste has been seen as a first step for organisations implementing a broader and more sophisticated environmental strategy (Clelland et al. 2000). van Weenen (1990) grouped the terms waste prevention, waste avoidance, waste reduction, waste minimisation, pollution reduction, pollution prevention and recycling as similar in terms of strategies. All these strategies are concerned with waste (cause) and pollution (problems or effect), although using different names they have the same underlying aim of minimising impact on the environment from human activities.

Table 1. Selected definitions of waste minimisation.

Author(s)	Waste minimisation
US Environment Protection Agency (EPA) (1986)	As the reduction, to the extent feasible, of hazardous waste that is generated or subsequently treated, sorted or disposed. It includes any source reduction or recycling activity undertaken by a generator that results in either (1) the reduction of total volume or quantity of hazardous waste, or (2) the reduction of toxicity of hazardous waste, or both, so long as such reduction is consistent with the goal of minimising recent and future threats to human health and the environment.
Bates and Philips (1998)	Waste minimisation is the reduction of waste at source, recognising that is cheaper not to produce waste in the first place.
The UK Chartered Institution of Waste Management (formerly IWM), 1996 (as cited in Read et al. 1998)	Prevention and/or reducing the generation of waste, improving the quality of waste generated, including reduction of hazard and encouraging re‐use, recycling and recovery.
OECD, 1996 (Riemer and Kristoffersen, as cited in Pongrácz et al. 2004)	According to which it encompasses these three elements in the following order or priority: preventing and/or reducing the generation of waste at source; improving the quality of the waste generated, such as reducing the hazard; and encouraging re‐use, recycling and recovery.
ETC/W (Riemer and Kristoffersen, as cited in Pongrácz et al. 2004)	Waste minimisation/cleaner production is only related to preventive measures. Waste minimisation includes: waste prevention, i.e. reduction of waste by application of more efficient production technologies; internal recycling of production waste.
	Source‐oriented improvement of waste quality, e.g. substitution of hazardous substances; re‐use of products or parts of products, for the same purpose.
The UK Environment Agency, 1997 (as cited in Phillips et al. 1999)	‘…describes waste minimisation as: the reduction at source, by understanding and changing processes to reduce and prevent waste. This is also known as process or resource efficiency. Waste minimisation also includes the substitution of less environmentally harmful materials in the production process.

Pongrácz (2002) pointed out that although waste minimisation is not yet considered equally everywhere because many activities of waste prevention are concentrated in ‘on‐site recycling’ activities (recovery, or diversion of waste from landfill). Thus, Pongrácz suggested that waste minimisation includes four rather different options:

1. using less material to produce the product, so that when it is thrown away, there is less waste created;

2. creating durable products;

3. waste evasion: the effort to avoid waste creation;

4. substitution: by using less harmful substances.

The first three options suggested by Pongrácz are broader than most other authors offer for waste minimisation and are considered by the authors to indicate the level of definition confusion in this field. These three options are not considered part of waste minimisation in this paper and can be more commonly found among the techniques referenced in papers related to the three strategies discussed in later sections.

Measurements and indicators for assessing success in waste minimisation are direct in nature as many of them are based on recovery and recycling targets (Hanssen et al. 2003). In the UK, where businesses are going to be increasingly responsible for the waste they produce, waste minimisation is proposed as the best way for companies to reduce their impact on the environment (Cheeseman and Phillips, 2001) and to cut cost associated with waste. Based on the definitions listed in Table 1, most authors agreed that waste should be prevented at the source rather than after the waste is brought into existence; while congruent with the concept of waste minimisation the need to reduce waste at source emphasises the role of prior decisions (such as product and process design) which is commonly viewed by the relevant papers as outside the scope of waste minimisation.

3.2 Material efficiency

Efficiency is the ratio of an output to the input of any system. Thus, material efficiency can be stated as ‘the ratio of the output of products to input of raw materials’. Worrell et al. (1997) explained material efficiency as analogous to energy efficiency where material efficiency improvement is described as reducing the consumption of primary material without substantially affecting the service or function of a product. In a broader definition this is expanded by Worrell et al. as ‘reducing the consumption of primary materials without affecting the level of human activities qualitatively’.

von Weizsäcker et al. (1997) in their book ‘Factor four: doubling wealth, halving resource use’ suggested that we could use resources at least four times as effectively as we currently do. Hawken et al. (2000) in their book ‘Natural capitalism: the next industrial revolution’ suggests that we will observe the birth of a new type of industrial revolution which emphasises the use of resources efficiently including material resources. Young et al. (1994) suggested the need for an efficient material economy as the next efficiency revolution, claiming that it will require more than technological improvements alone, and calls for a shift of culture and ethics. Material efficiency as explained here is echoed in later sections and can be said to be a core element of other sustainability strategies such as resource efficiency and eco‐efficiency.

In the literature, the authors found relatively few studies on material efficiency or material productivity; most studies mentioning material efficiency did so as part of other strategies such as energy efficiency, resource efficiency and eco‐efficiency. The closest concept to material efficiency is dematerialisation. The concept of dematerialisation is presented as being concerned with the reduction of the quantity of material used to achieve a functional performance, which can be contrasted with the concept of material efficiency introduced by Worrell (1995) which is concerned with the maximum usage of input material. To achieve material efficiency, it is clear that dematerialisation should be practiced, as well as other actions. Some definitions of material efficiency and dematerialisation are shown in Tables 2 and 3 respectively.

Table 2. Selected definitions of material efficiency.

Author(s)	Material E\efficiency
Worrell (Worrell et al. 1997)	The definition of material efficiency as ‘the amount of primary material that is needed to fulfil a specific function’. Material efficiency improvement allows the same function to be fulfilled but with a reduced amount of material.
Glossary of EEA (EEA 2006)	Material productivity is an indicator of the output or value added generated per unit of material used.

Table 3. Selected definitions of dematerialisation.

Authors	Dematerialisation
van der Voet et al. (2004)	Dematerialisation is the reduction of the throughput of materials in human societies.
De Bruyn (1998)	The concept of dematerialisation refers to the decline of material use per unit of service output.
Herman et al. (1990)	‘…the word dematerialisation is often broadly used to characterise the decline over time in weight of the material used in industrial end products.’
Wernick et al. (1996)	More broadly, dematerialisation refers to the absolute or relative reduction in the quantity of materials required to serve economic functions.
Bernardini and Galli (1993)	‘…as the reduction of raw material (energy band material) intensity of economic activities, measured as the ratio of material (or energy) consumption in physical terms to gross domestic product (GDP) in deflated constant terms.’

Material efficiency and energy efficiency are always linked together, first as similar concepts applied to different objects – material and energy; and second it is commonly argued that actions to reduce one resource will also reduce the other. Improvement in material efficiency typically saves energy in not producing and transporting that material; while improvement in energy efficiency reduces the consumption of materials and other primary resources (Worrell 1995, Worrell et al. 1997). Again it is argued that material efficiency is a core strategy in all sustainable strategies. Energy efficiency is a field attracting much research, while less attention is given to material efficiency as a strategy. The authors argue that there is a need to study material efficiency as a whole and in depth, including upstream and downstream material flows that include everything from material extraction to landfill and from production up to national level, an argument that is explored in more depth in House of Lords (2008). Material efficiency problems if tackled intensively have a great potential to contribute to sustainability and can make it easier for other strategies, such as resource efficiency and eco‐efficiency, to be executed successfully. Material efficiency as a strategy is argued to benefit from having a very clear measure of performance (material out of versus material into the system), which makes it easier to implement in practice.

The definition of material efficiency by Worrell (1997) however is limited in scope due to his prior concerns with increasing energy efficiency through improving material efficiency. A thorough study should be conducted on material efficiency. The strategy for achieving sustainability by reducing the amount of material alone could be ineffective because a smaller amount of material used is not necessarily safer in terms of its toxicity and its environmental impacts compared to larger amounts of other types of material. Different materials give different environmental impact (Weaver et al. 1996, Pearce 2001). Therefore, the toxicity and not only conversion efficiency and recyclability of the material should be prioritised due to its great influence on the environment. Deep investigations on various material impacts are often missing in resource efficiency and eco‐efficiency strategies, leading to Geiser (2002) arguing that we have spent several decades focusing on the consequences of materials use but not addressing the materials directly.

3.3 Resource efficiency

Resource efficiency is actively being promoted by the UK government as part of its government policy for sustainable development (Foxon 2000). Resource efficiency is the strategy that ‘strives for the efficient use, reduction of flow and consumption of resources drawn from nature’ (Schmidt‐Bleek 1996). Resource efficiency, also called resource productivity, has received much attention recently because it is focused on managing resources as a whole rather than being limited to one stage of the resource's life, such as waste minimisation and pollution prevention which centred the focus on waste (cause) and its polluting effect. The strategy of resource efficiency defines itself as concerned with a wider scope of impacts on environment including reducing the generation of waste, using fewer resources and using resources, production processes and extracting processes that have less impact towards the environment. Schmidt‐Bleek (1996) points out that resource extraction is the most significant cause, since all materials taken into an economy end up sooner or later as emissions and wastes. Thus reducing the costs of environmental damage requires both bringing down emissions and reducing the flow of resources drawn from nature.

Resource productivity and resource efficiency are among the terms used and are often proposed as specific indicators of the efficiency of the entire economy [OECD as cited in (EEA 1998)]. Emphasising national resources consumed versus economic value added can give a very rough calculation of conversion efficiency at the level of the nation state, but is seen as more challenging for single businesses or manufacturers. While the measurement of resource efficiency and resource productivity is presented at the nation level the concepts are still advocated as pertinent and useful to industrial organisations. The authors' analysis (Table 6) shows that many authors consider the ability to easily and accurately measure something as being important in ‘operationalising’ the concept or strategy into practice, which the concept of resource efficiency finds difficult. Some of the authors or organisations were selective in their terminology and used either resource efficiency (e.g. Foxon 2000, Wuppertal Institute 2002) or resource productivity (e.g. Pearce 2001, Schmidt‐Bleek 1995), while some refer to both resource efficiency and resource productivity and sometimes use them interchangeably (e.g. von Weizsäcker et al. 1997, Hawken et al. 2000, Commission of the European Communities 2003) and yet others use both terms and do differentiate between them [e.g. Dahlström and Ekins (2005)]. Refer to Table 4 for definitions of resource efficiency and resource productivity.

Table 4. Selected definitions of resource efficiency.

Author(s)	Resource efficiency
UK policy (Environmental agency, R&D technical report, 2004) (Thomas and Iles 2004)	At a national policy level, resource efficiency and resource productivity can be defined as the efficiency with which energy and materials are used throughout the economy, i.e. the value added per unit of resource input.
	At the installation level this means ‘making more with same quantity of raw materials’.
Commission of the European Communities (2003)	Resource efficiency or resource productivity can be defined as the efficiency with which we use energy and materials throughout the economy, i.e. the value added per unit of resource input.
Cabinet Office, UK (2001)	Resource productivity measures the efficiency of the economy in generating added value from the use of natural resources.
Pearce (2001)	Suggested the ratio of ‘output’ (Y) to natural resource ‘input’ (R). Where is Y could be GNP and R may be materials or energy input.

Among the authors who promote a resource efficiency strategy for industry are those promoting Factor X: Amory Lovins and his co‐authors in Factor 4 (von Weizsäcker et al. 1997) and Natural Capitalism (Hawken et al. 2000) plus Schmidt‐Bleek with Factor 10 with its MIPS and ecological rucksacks as measurement tools (Schmidt‐Bleek 1996). Factor X is a quantitative goal for resource productivity and also eco‐efficiency (Reijnders 1998). Lovins and co‐authors in their book ‘Factor four: doubling wealth, halving resource use’ suggested that we could use resources at least four times as effectively as we do now. Hawken in his book ‘Natural capitalism: the next industrial revolution’ envisions a new industrial revolution by combining the principle of radical resource productivity improvements with principles of bio‐mimicry (reducing waste through closing cycles), encouraging a services and flow economy and increasing natural capital. Schdmit‐Bleek suggested that a Factor 10 level of resource efficiency improvement is both necessary and attainable for industrialised countries if sustainability is to be reached. He suggested that within one generation, nations can achieve a tenfold increase in the efficiency with which they use energy, natural resources and other materials.

The European Environment Agency pointed to differences between the Factor 4 and Factor 10 concepts; suggesting that Factor 10 addresses absolute use of nature, where global use of nature should be halved and that the use of, or access to, natural resources should be distributed equally all over the world. Meanwhile, Factor 4 addresses the relative concepts of eco‐efficiency or resource productivity, with assumptions that global use should be halved and at the same time, global welfare should be doubled (EEA 1998). Some authors commented that achieving Factor 10 is much more challenging by comparison with Factor 4 and would require very significant technological innovation to implement (Reijnders 1998, Moffatt et al. 2001, Hawkins and Shaw 2004).

Pearce (2001) suggested a variety of means for making natural resource use more efficient through:

	reducing the wasteful use of resources;
	adopting technological change which raises the efficiency of a given unit of resources;
	substituting other inputs, such as labour, for natural resources, so that output stays the same but resource use is reduced;
	recycling materials so that that the ‘same’ unit of resources is used several times;
	substituting one resource for another. If the focus is on environmental pollution, one tonne of one material may be less polluting than one tonne of another.

There are several calculation methods proposed for measuring resource efficiency. An example of resource efficiency calculation at national level is dividing the total economic activity of a country (expressed in GDP) by the total energy use or total material use (Bringezu 1993, Commission of the European Communities 2003). The material intensity per unit service [or function] (MIPS) was proposed by Schdmit‐Bleek in 1992 as an initial measure of resource efficiency of product and services. He suggested that resource productivity is the inverse of MIPS (Schmidt‐Bleek 1995).

MIPS = material input per service init = MI/S

resource productivity = service or function delivered/material used = reciprocal of MIPS = S/MI

Dahlström and Ekins (2005) have sought to elaborate on the two related strategies and have differentiated between the meaning of resource efficiency and resource productivity. Resource efficiency was defined as a basic ratio of two resource variables of the same kind; that is, the ratio is dimensionless. Resource productivity is not dimensionless and introduces economic output as a purposeful objective, assessing the amount of natural resource input needed to achieve a level of economic activity.

Resource efficiency:

Resource productivity

where M _o is material output, M _i is material input, E _o is energy output, E _i is energy input and Y _o is economic output (the welfare output is seen to be measured by economic output).

Moffatt et al. (2001) listed several more resource efficiency measurements:

1. Factor 10 and Factor 4 (including MIPS and Rucksacks);

2. environmental space;

3. ecological footprints;

4. human appropriated net primary production (HANPP);

5. assimilative capacity;

6. asset balances for environmental capital;

7. safe minimum standards;

8. cost‐effectiveness in pollution control;

9. comparing resource utilisation rates with economic optima;

10. ‘Y/e’ measure.

A criticism of resource efficiency is that although the strategy may be technologically possible, it requires economic and political action (such as incentives and regulatory regimes) (Reijnders 1998, Foxon 2000, Pearce 2001, Hawkins and Shaw 2004). This makes resource efficiency difficult to implement by a single organisation and acts as a barrier to its practicality for industry. The report by the Commission of European Communities (2003) commented that the system boundary covered by resource efficiency is still limited.

‘…the given definition of resource efficiency deals solely with the use to which resources are put. This implies that it does not consider the way resources are extracted or harvested [upstream of the economic activity] nor how they are disposed to air, water and soil [downstream of the economic activity]. In order to fully understand the environmental implications of resource use, it is necessary to include both upstream and downstream activities [including the use of infrastructure, transport, dispersive losses, etc.]’ (Commission of European Communities 2003).

3.4 Eco‐efficiency

The strategy of eco‐efficiency is explained as ‘having the business link to sustainability’. The concept of eco‐efficiency was used by Schaltegger and Sturm in 1990 (Schaltegger and Burrit 2000). The strategy is concerned with increasing economic development while aiming to lower environmental impact, and is not a new strategy since it has been around since the 1970s (Ehrenfeld 2005, Cote et al. 2006). The concept was mainly popularised at the United Nations Conference on Environment and Development (UNCED) summit in Rio in 1992 through Changing Course, the book written by Stephen Schmidheiny and published by BCSD [since 1995, called the World Business Council for Sustainable Development (WBCSD)]. WBCSD then took up the strategy and launched it world‐wide and has since marketed eco‐efficiency as its central business strategy for bringing about corporate progress towards sustainability and has helped it become adopted by numerous companies, firstly in Europe and Latin America, then in other countries (WBCSD 2000a). The WBCSD describes eco‐efficiency as ‘being achieved by the delivery of competitively priced goods and services that satisfy human needs and bring quality to life, while progressively reducing ecological impacts and resource intensity throughout the life cycle, to a level at least in line with the earth's estimated carrying capacity’. More definitions by various authors are listed in Table 5 for reference.

Table 5. Selected definitions of eco‐efficiency.

Author(s)	Eco‐efficiency
Stephen Schmidheiny, Chairman of the Business Council for Sustainable Development, 1992 (as cited in WBCSD 2000a).	Coined the term ‘eco‐efficiency’ to describe ever more useful goods and services while continuously reducing resource consumption and pollution.
The World Business Council for Sustainable Development (2000a)	Eco‐efficiency is achieved by the delivery of competitively priced goods and services that satisfy human needs and bring quality to life, while progressively reducing ecological impacts and resource intensity throughout the life cycle, to a level at least in line with the earth's estimated carrying capacity.
President's Council on Sustainable Development (1996)	Eco‐efficiency can broadly define as the production, delivery, and use of competitively priced goods and services, coupled with the achievements of environmental and social goals.
Welford (1997)	Improvement in ‘eco‐efficiency’ defined as ‘adding maximum value with minimum resource use and minimum pollution’.

Compared to the first three strategies discussed, eco‐efficiency is the broadest strategy, because it not only aims to prevent waste and increase resource productivity but also to ensure minimal impact towards ecology while improving the quality of life all without exceeding Earth's limits. Thus, it is bigger in scope, covering economic, social and ecological dimensions, and is not limited to the company itself. Eco‐efficiency is a management philosophy, which encourages business to search for environmental improvement while at the same time giving social and economic benefits by fostering innovation, growth and competitiveness. Eco‐efficiency can be viewed from many levels, including the macro‐economic (national economy), the meso‐economic (region) and the micro‐economic (company) levels (Mickwitz et al. 2005). Basically, eco‐efficiency is a call to achieve more value added from resources input with reduced emissions and waste.

The ‘efficiency’ measures in eco‐efficiency are said to hold more than one perspective. ‘The cross‐efficiency between the economic and the ecological dimension – economic‐ecological efficiency – is the ratio between the changes in value in environmental impact added and economic value added. Economic‐ecological efficiency is often referred to as eco‐efficiency” (Schaltegger and Burrit 2000). Schaltegger and Burrit proposed the following equation for measuring eco‐efficiency:

The WBCSD represents eco‐efficiency as a ratio of ‘product or service value’ over ‘environmental influence’, and argues that eco‐efficiency brings together the two eco‐dimensions of economy and ecology to relate product or service value to environmental influence (WBCSD 2000a).

Based on the above equation, eco‐efficiency is improved by reducing the environmental impact while maintaining or increasing the monetary value added. Due to its greater scope, this strategy is argued to appeal to higher levels of management and government in policy and decision‐making. Similar to the resource efficiency strategy, Factor X is among the eco‐efficiency goals. Thus MIPS calculations for Factor 10 appear in measurements of resource productivity and in eco‐efficiency. Resource productivity can also be included as one of a set of eco‐efficiency indicators. WBCSD outlined two types of indicators that are suited to measure eco‐efficiency at a business level, being ‘generally applicable’ indicators which can be used by virtually all businesses and ‘business specific indicators’ which are likely to be individually defined from one to another business or sector. For a list of generally applicable and business specific indicators proposed by WBCSD, see WBCSD (2000b). For the highest level of measurement, see Seppälä et al. (2005) which listed four types of indicators that can be used to measure eco‐efficiency at macro‐economy levels such as at the regional level.

While eco‐efficiency is a popular concept, evidenced by the frequency of citation, many authors voice concerns over the eco‐efficiency strategy. As the definition (refer to Table 5) from WBCSD suggests, eco‐efficiency will be achieved when competitively priced goods or services can satisfy human needs and bring quality of life, while reducing ecological impacts and resources intensity throughout the life cycle, to a level at least in line with the earth's estimated capacity. From the eco‐efficiency measurement and list of indicators proposed by WBCSD, there is no means for society to determine that eco‐efficiency can satisfy human needs, quality of life, reduce ecological impact and far more, importantly, to guarantee that earth's carrying capacity would not be exceeded (Ehrenfeld 2005). It is not clear how earth's carrying capacity can be related to the practical measurement of eco‐efficiency. Ehrenfeld noted that ‘…carrying capacity simply does not enter the economic calculus’. It is still possible for the earth's carrying capacity to be exceeded although eco‐efficiency has been implemented widely.

To deal with this challenge of having meaningful measures at the level of an individual organisation, while recognising impacts on the wider world, a measurement of eco‐efficiency is proposed by WBCSD which is very much limited to the boundaries of a single company. Warhust (2002) comments that Eco‐Efficiency…‘only includes indicators for quantity and value of company products and does not consider indicators of product use downstream in the supply chain’. Hukinnen (2001) pointed out that ‘…by expressing environmental impact simply in terms of mass consumption of natural resources, eco‐efficiency creates the illusion that environmental impacts are universally commensurable, regardless of where the impact takes place, and can, therefore, be managed through globally applicable governance systems’. Ehrenfeld (2005) has joined the argument on measurement of eco‐efficiency, stating that, as with other environmental management systems, eco‐efficiency has a problem with quantification when both the numerator and denominator are problematic. It is argued that the eco‐efficiency indicators, proposed by WBCSD, can dangerously show false eco‐efficiency positives due to relative measurements being used because increases in eco‐efficiency may not necessarily mean improved eco‐effectiveness (Day, Dyllick and Hockerts; Gray and Bebbington; Stahlmann and Clausen; and Ullman, as cited in Figge and Hahn, 2004). The eco‐efficiency ratio achieved could give a false indication, for example when eco‐efficiency fails to differentiate between kinds of material (Hukinnen 2001) and its impact towards the environment. It is also suggested that its broader aim and relative measurement can make eco‐efficiency an implicit and general goal (McDonough and Braungart 1998, Honkasalo 2001, Ehrenfeld 2005,).

4. Comparison of strategies and discussion

Table 6. Comparison of four sustainable manufacturing strategies.

Strategies		Waste minimisation	Material efficiency	Resource efficiency	Eco‐efficiency
Characteristic
Definition	Type	Concrete (1,2)	Concrete	Concrete	Philosophical (3,4,5)
	Orientation	Goal oriented	Action oriented	Action oriented (9)	Measurement oriented
	Focus	Effect‐waste (1)	Cause‐material	Cause‐resources	Cause/effect–resources/pollution
	Main goal	Reduce waste and pollution	Efficient use of resources (both material and energy)	Efficient use of resources	Efficient use of resources, reduce waste and pollution, quality of life
		Reduce cost (1,6)	Reduce waste and pollution (7)	Reduce waste and pollution	Earth carrying capacity (8)
Scope	Systems boundaries	Limited‐downstream	Upstream–downstream (7)	(i) Do not cover upstream and downstream activities (9)	Claimed to cover upstream–downstream by addressing all stages of product life‐cycle (11) but seen as debateable (12)
				(ii) Cover upstream and down stream by measuring MIPS (10)
	Influence over externalities	Limited	Yes	Yes	Yes – supposedly big influence
	Level usually used	Process, company and national	Process, product (7)	Product, company and national (13)	Product, company and national (3,4,5)
	Depth of issues to be tackled to achieve goal	Relatively easy	Potentially difficult	Difficult	Very difficult (3)
	Concerns (e.g. economy, ecology, social)	Limited	Limited (14)	Broad	Broad (3,4,5)
	Utility being assessed	Weight, volume, cost	Functionality/services	Unit of value added	Unit of value added (8,15)
Practicality	Measurement and target	Direct/simple (1,16)	Potentially complicated quantitative	Complicated quantitative (17)	Complicated (3)
		Quantitative (1,6)			Quantitative (17) and Qualitative
	Indicator effectiveness	Yes	Potentially difficult	Difficult	Very difficult (20)
	Technical feasibility	Yes	Potentially difficult	Difficult (17,18,19,20,21)	Difficult
	Data availability	Easy (1)	Potentially yes	Difficult	Difficult
	Easy of communication	Yes	Potentially yes	Potentially yes	Difficult
	Does it guide actions	Yes	Potentially yes	Potentially yes	Debateable (3,4,20,22,23)
Compatibility	Between goal and measurement	Yes	Potentially yes	Potentially yes	No – difficult to determine on earth's carrying capacity (3)
Authors:
(1) Bates and Philips (1998); (2) Clelland et al. (2000); (3) Ehrenfeld (2005); (4) McDonough and Braungart (1998); (5) Honkasolo (2007); (6) Cheeseman and Philips (2001); (7) Worrel (1997); (8) WBCSD (2000a); (9) Commission of European communities (2003); (10) Schmidt‐Bleek (1995); (11) Mosovsky et al. (2000); (12) Warhust (2002); (13) Cramer and van Lochem (2001); (14) Worrell (1995); (15) OECD (1997); (16) Hanssen et al. (2003); (17) Reijnders (1998); (18) Hawkins and Shaw (2004); (19) Pearce (2001); (20) Foxon (2000); (21) Figge and Hahn (2004); (22) Huesemann (2004); (23) Jansen (2003)

This section describes various characteristics of each strategy, enabling more direct comparisons to be made across a broad literature. The aim is not to identify the superior strategy but to improve understanding.

4.1 Challenges in making comparisons

The broader the strategies, the more complex the measurements involved. Indicators used in measurement should have a metric or combination of metrics that reflect the real state of the product or processes as defined by the strategy. Some strategies have clear definitions but having measurements that do not cover all the areas as defined. Effective measurements and indicators are important for operational success, and should be understandable, implying the correct situation and based on accessible data. Problems arise when products or processes achieve a good score while not meeting the aim of the strategy. For example making packaging lighter but using more toxic and more scarce materials would ‘improve’ a waste minimisation score. Thus it is important to have a set of indicators that are feasible to measure and which can be acted upon, for ‘what gets measured gets improved’. Difficulties in measurement can lead to difficulties in communicating the strategy.

4.2 Comparing the strategies

There is no doubt that all the strategies compared can contribute to sustainable development. They are all practiced in a variety of industries and some of them implemented under different names. But how much each of them is facilitating action towards sustainability and how effective they are remains debateable. As shown in Table 6, they have various similarities and differences. Criteria chosen to compare the strategies are divided into: definition, scope, practicality and compatibility as described below.

4.2.1 Definition – what is the strategy and its aim

	Type – the clarity of the definition. Is the strategy clear (concrete) versus ambiguous and is it testable versus complex (philosophical)?
	Orientation – what is the strategy defined around? Is it defined around goal, action or its measurement?
	Focus – what is the definition centred on? Is it on cause (e.g. resources and material) or effect (e.g. pollution, emissions and waste).
	Main goal – what is the priority goal that practitioners are expected to deliver against, extracted from the strategy's definition.

4.2.2 Scope – what is included in the strategy

	System boundaries – the horizontal limit of ‘elemental’ (e.g. waste, material or resources) flows that the strategy is intended to influence.
	Influence over externalities – does the strategy influence externalities? Note: externalities arise when actions by producers or consumers cause unintended effects on others. Externalities could be positive or negative.
	Level usually used – what level the strategy is usually used at, as cited in the literature, e.g. product/process/company/regional/ national.
	Depth of issues to be tackled to achieve goal – the depth of investigation needed on the ‘element’ which the strategy is intended to cover.
	Concerns – which dimensions of sustainability are covered, e.g. ecology, economy, and/or social.
	Utility being assessed – the ‘output’ which is expected or desired when practicing the strategy.

4.2.3 Practicality – how difficult or easy the strategy is to implement

	Measurement and target – how simple or difficult the measurement would be to use in practice. Qualitative and quantitative aspects of strategies can contribute to levels of difficulty in setting targets and measuring against them.
	Indicator effectiveness – how well does the measure indicate effectiveness (that a better score is a better outcome and indicates direction of improvement).
	Technical feasibility – the ease of implementing the strategy and achieving its goal.
	Data availability – the availability and cost effectiveness of obtaining and processing the data to measure and manage progress.
	Ease of communication – how easy it is for the strategy and its indicators to be understood by the stakeholders.
	Does it guide action – how well does the strategy provide a clear guide to generate actions for change.

4.2.4 Compatibility

Between goal and measurement – does the measurement cover the dimensions, scope and system boundaries stated by the definition?

As can be seen in Table 6, using the criteria chosen as a comparison tool, the authors concluded that waste minimisation is the most direct and simple of the strategies. Its goal is to reduce waste in order to save money and reduce pollution. The definition of waste minimisation is around its goal and focused on minimising waste, using the waste hierarchy to remove waste at source as a preference. Due to its simplicity, it is somewhat limited in scope although it can be implemented at various levels of a company. In terms of practicality, and due to the quantitative nature of its utility assessment, it makes the measurement relatively easy to implement. Data collection is usually available inside the company. The waste minimisation strategy can be a very effective strategy in reducing waste to landfill if every waste producer practices it and is committed to the strategy. There are few externalities to deal with, and this makes the strategy meaningful to individual manufacturers; unfortunately singular action may not impact an entire supply chain and have limited effect on the amount of waste produced by the whole system. The strategy is attractive to companies as it helps reduce cost. Waste minimisation activities are often a first step taken by industry in response to the call for sustainability. Waste minimisation activities are also priorities in other sustainable strategies. Thus, efforts to implement a waste minimisation strategy can be a first step towards implementing bigger and more complex sustainable manufacturing strategies by manufacturing companies.

Among the four strategies, material efficiency is given less attention in the literature although it is referred to in all the other strategies. The concept, compared with others, is more inclusive of upstream and downstream processes (and impacts), while it remains quite direct and relatively easy to measure and turn into action. Material efficiency has the potential to reduce impacts on the environment by using material efficiently upstream and downstream of factory material flows. The strategy is defined around its aim to achieve efficiency in material use.

Resource efficiency is concerned with the productivity of natural resources. This strategy has been viewed from multiple disciplinary perspectives: what is efficient, value adding and effective from one view is not necessarily viewed the same by others. Resource efficiency embraces broader dimensions, while the reduced depth that the strategy covered also contributes to difficulties in ‘operationalising’ the strategy into effective action, nevertheless it remains attractive to policy makers. Utility assessment is based on a ‘unit of value added per unit resource input’ which is very difficult to measure because value added is qualitative and differs from one customer to another. Difficulty in measurement impacts on the utility of the indicator for sustainable manufacturing practice. Resource efficiency does allow for the inclusion of energy inputs, while choosing not to embrace toxicity, earth carrying capacity or social dimensions. This makes it a good tool to indicate and monitor the consumption of a national or regional economy. Due to the movement of resources around the globe, resulting from global manufacturing, it is difficult to gain a true indication of national resource efficiency (for example, do you become more resource efficient simply by deciding to buy a component from overseas rather than make it in‐house?).

Eco‐efficiency is the broadest of the four dominant sustainable manufacturing strategies identified and incorporates many more dimensions than the previous three. Although resource efficiency and eco‐efficiency have similarities, eco‐efficiency is further extended to address earth carrying capacity and quality of life. While this works to include concerns that the other strategies fail to encompass, these two dimensions cannot be measured directly thus making the measurement and management of eco‐efficiency difficult and its effectiveness debateable. The current use of eco‐efficiency is largely supported by the World Business Council on Sustainable Development (WBCSD), who recognises its value in explaining the broad interactions between a business and the planet and its people. The WBCSD also recognises that a single measure is incapable of capturing the richness of the concept of eco‐efficiency and they provide a set of possible measures for business to select from, in the hope that the measures can guide action. In practice, the relative measurement used by eco‐efficiency is problematic because its indicator can be manipulated and can give false indications. The goal is broad, tends to be general and elusive and lacks depth and is limited in implementation. For example the measurement proposed by WBCSD does not easily include upstream and downstream activities; which is of the utmost importance. The eco‐efficiency measurement is used as set of indicators but the literature is sparse on the achievement of manufacturers in using these to become more sustainable.

Figure 1 The hierarchy of sustainable strategy.

Figure 1 shows the relative scope of these sustainable manufacturing strategies and suggests a hierarchy between them. The more concrete the strategy the simpler the measurement and therefore management of its implementation would be. The figure shows the simplest strategy is only concerned with reducing waste, which is a narrow view of sustainable resource use in manufacturing. However the more dimensions of sustainable resource use that are embraced, the more difficult it becomes to measure and the more philosophical the definition becomes.

5. Concluding remarks

This paper has presented a review and comparison of the four most popular sustainable manufacturing strategies mentioned in the academic and practitioner literature. These strategies range from the simple strategy of waste minimisation, which is direct and easy to achieve, to eco‐efficiency, which embraces many more concerns but poses challenges to implement and measure. The sustainable manufacturing resource strategy hierarchy in Figure 1 shows that the lower the strategy in the hierarchy the more concrete the definition is and the higher the strategy in hierarchy, the more philosophical the definition becomes. The lower strategy also has simpler measurements compared to the higher strategy. The concern at the lowest level of the hierarchy is to reduce waste, the highest level concern being to improve social, economic and environmental sustainability. The literature emphasised various characteristics of a successful sustainable manufacturing strategy – for example, that an excellent strategy would have a clear definition, that the scope of the strategy would have clear and appropriate boundaries that handled externalities appropriately, that the strategy was practicable to implement, including having dimensions that were amenable to measurement, and being easy to understand and communicate, and that the goals of the strategy were compatible with the measurements used. Some 17 characteristics were observed in the literature and a comparison of the four primary sustainable manufacturing strategies was undertaken using the characteristics; such a comprehensive comparison is not available in the existing literature.

Each of the four strategies of waste minimisation, material efficiency, resource efficiency and eco‐efficiency has different performance against each characteristic, with no strategy being superior. It is concluded through this research that waste minimisation is much simpler in definition and measurements but limited in coverage compared to eco‐efficiency which is the most philosophical and complex in measurements due to it intention to cover wider concerns. However, the data suggest that all these strategies are currently contributing to sustainable manufacturing and overall sustainability. The similarity is that all of them are aiming for sustainability, whether the goal is to reduce waste and to achieve better utilisation or to reduce resources. The differences between the strategies are various, but it is argued that the four strategies form a continuum from the simplest, most easily adopted, but narrow strategy of waste minimisation, through material efficiency then resource efficiency to eco‐efficiency. The existence of intermediate strategies, operating between the four, is possible, but the literature does not point to them, and the authors argue that this is due to the challenge of measurement and its impact on definition and scope. The four strategies have emerged as those that have some compatibility between the definition and its measurement. By including a new variable the previous strategy is changed into a new one, and with few variables there are few strategies.

To choose among the four, practitioners from different manufacturing backgrounds may prefer different strategies. There is no evidence that specific strategies suit a specific manufacturing situation or product or process or sector. Those practitioners who prefer simpler measurement and visible achievement might choose waste minimisation or even material efficiency. For those who are willing to deal with a broad scope of effect and causes that potentially go beyond their own production plant boundaries, the concepts, tools and measures of material efficiency and resources efficiency strategies may be useful and appropriate, while generalists who would like to include many indicators might prefer eco‐efficiency (Pearce 2001). For higher level decision‐makers eco‐efficiency has a broader scope allowing for a variety of actions and an improved ability to communicate green initiatives and to motivate actions. Care must be taken however in assessing and measuring eco‐efficiency.

This paper has highlighted that material efficiency is at the core of every sustainable manufacturing strategy. It is important that the debate on sustainable manufacturing does not get reduced to energy only. Given the primacy of the issue of global warming an emphasis on energy efficiency is reasonable, yet material efficiency can help directly with energy efficiency and material scarcity and equity remains an important and separate issue. Many manufacturers are either implementing or considering an energy efficiency strategy, and will be faced with some similarities to the issues raised in this paper for material efficiency, in particular the challenge of selecting the scope of the strategy (do we include the energy in the parts supplied to our factory, do we include the energy used in transporting our staff to work, etc.). Material efficiency has the potential to sit alongside energy efficiency strategies and initiatives; indeed without such a dual approach many opportunities for energy reduction may be missed.

Across a variety of manufacturing sectors these different strategies have been shown to deliver significant benefits, both environmentally and economically. These results can be compelling; however the data are often piece‐meal and anecdotal, measuring different aspects of material and environmental performance in different manufacturers. Research is needed into existing practice and results, assessing the benefits achieved and the conditions under which they were achieved, both at the level of individual factories and the level of the product life cycle. This will help guide future manufacturing practice as well as future research into those tools and techniques that may support sustainable manufacturing strategies. In addition to observation of practice of these four strategies it is evident that more research is needed in understanding the interaction between goal, scope and measurement for sustainable manufacturing strategies, with the aim of developing measurement techniques and tools that work to ease the implementation of the strategies.