Within the context of diminishing natural resources, global warming, ozone depletion, acidification, and pollution of land, rivers and oceans, manufacturing companies are increasingly adopting policies that take the environment into account. Design for the Environment (DfE) and design for Sustainability (DfS) are two approaches, and

life-cycle assessment (LCA) is another. Because of the complexities involved in these, it is no wonder that various software packages have been developed for use by design engineers, design managers and other individuals with responsibility for these matters in manufacturing companies.

Creating efficient products is a step in the right direction, and software packages such as those for computer-aided design (CAD) and finite element analysis (FEA) can help in this respect. For example, an alloy wheel for a car may be designed to be lightweight yet strong and stiff. This reduces the use of material (and energy to some extent) during production, and also helps to cut energy consumption during the car’s useful life. However, CAD, FEA and related design and analysis tools only enable limited aspects of a product’s environmental impact to be addressed.

Life-cycle assessment (LCA) was first used in the late 1960s when it was realised that individual production operations were being improved by displacing pollution elsewhere, resulting in no net benefit. Another reason for the interest in LCA was that, while individual production processes were being improved, it was becoming apparent that looking at the production process as a whole could result in result in greater gains overall.

In the 1970s, LCAs were not software-based, and they focused mainly on raw materials and energy usage. Today LCA analyses tend to be performed using dedicated software packages, and in conformance with a series of international standards:

• ISO14040:2006 Environmental management – Life cycle assessment – Principles and framework
• ISO14044:2006 Environmental management – Life cycle assessment – Requirements and guidelines.
• ISO/TS14048:2002 Environmental management – Life cycle assessment – Data documentation format.

Proprietary software packages enable users to analyse materials, energy, emissions and solid wastes throughout a product's entire life-cycle, including raw material production, component manufacture, assembly, packaging, transportation, use by the consumer, and end-of-life disposal. One of the longest-established providers of LCA services, and the company behind one of the most comprehensive LCA software packages, is Boustead Consulting Ltd of the UK. Its Boustead Model LCA software is now at version 5.0.

This high-end package enables exhaustive analyses to be performed, but some people may prefer to start with a simpler, entry-level package. The Eco-Indicator Tool (ECO-it) for environmentally friendly design, from PRé Consultants of the Netherlands, is claimed to enable users to model a complex product and its life cycle in a few minutes. ECO-it calculates the environmental load and shows which phases of the product’s life cycle contribute most – so the designer can concentrate on this in order to improve the product’s overall environmental footprint. A 10-day evaluation version of the software is available for download from the company's website, and a single-user license costs just E99.

Design decisions

However, the full benefits of LCA lie in its rigorous approach, but that this calls for a comprehensive set of accurate data that can only be collated after a product has been designed, manufactured and used by consumers. In other words, lessons learnt can only be implemented on the next generation of product, which is not as beneficial as having access to tools that enable environmentally beneficial decisions to be made early in the design phase.

This is the view shared by Professor Mike Ashby of the University of Cambridge and his colleagues at Granta Design Ltd. This company, based in Cambridge, UK, has developed the CES Selector materials selection software package and the CES Eco Selector, a specialist edition combining powerful selection tools with data tailored towards eco-design and analysis.

Ashby’s design-led approach to materials selection is not on the basis of simple properties such as stiffness, density or price, but on combinations of two or more – such as stiffness per unit weight. By plotting material properties on a graph and drawing lines that correspond with the end product's loading conditions, the optimum material can be readily identified (Fig.1).

Now, with the CES Eco Selector, designers can analyse environmental impact per unit of function. Of course, environmental impact covers not just energy, but also emissions. Nevertheless, with the Kyoto Protocol calling specifically for reductions in carbon dioxide (CO2), most eco-design steers towards minimising life-cycle energy consumption, as this is closely related to carbon dioxide emissions.

As with other approaches to eco-design, the CES Eco Selector helps the user to consider the energy consumption during different phases in the life cycle – so that the biggest impact can be made by concentrating on the appropriate phase. For example, most of the energy consumed by a wooden chair will be accounted for in its production; in contrast, an electric kettle will consume by far the majority of its energy during use.

In addition, the CES Eco Selector takes into account three separate types of energy: production energy – the fossil fuel energy consumed in making one kilogram of the material; intrinsic energy – which is the energy stored within one kilogram of the material; and recycling energy – the energy required to recycle one kilogram of the material. However, it needs to be remembered that the energy-efficiency of recycling is not the same as the cost-efficiency, as dispersed materials can be costly to remove from complex assemblies, sort, clean and transport. Furthermore, some materials cannot be recycled, though they can be down-cycled for use in another way (perhaps as a filler in a polymer matrix).

Granta Design says that full eco-data only exists for around 100 engineering materials out of a total in excess of 60000. Consequently the 3000-record database built into the CES Eco Selector contains estimates – though great care has been taken to ensure that these are as realistic as possible, and lower-bound estimates are used for alloys, polymer blends and composites when no direct data is available.

Product life-cycle phases

The CES Eco Selector can either be used as a way to browse the built-in materials database, or it can be used as a tool to aid materials selection when working from a ‘blank sheet of paper’. If the latter, the first step is to decide which product life-cycle phase to target: material production, product manufacture, product use or product disposal. Depending on which of these is selected, the user is guided through the materials selection process with the aim of minimising the impact of the phase on the environment:

• Material production: minimise energy per unit of function; minimise CO2 per unit of function; and minimise the indicator per unit of function.
• Product manufacture: seek minimum-energy process; seek minimum-emissions process; and seek
• minimum-waste process.
• Product use: design to minimise weight; design to minimise heat loss; and design to minimise electrical losses.
• Product disposal: choose recyclable materials; choose biodegradable materials; and exclude toxic materials.

While the CES Eco Selector offers huge benefits for new product designs and developments of existing products, Granta Design is also experiencing increasing demand for its Granta MI software package for managing and applying proprietary materials data within organisations. This can help with eco-design because companies wanting to improve the environmental performance of their products must first know what materials are currently used and what the materials’ properties are. They can then compare these materials and properties against references – for example, lists of materials restricted by environmental regulations – to inform design or procurement decisions.

Achieving this while accounting for all material types (plastics, metals, ceramics, composites, etc) and their variants (different grades, compositions, heat treatments, surface coatings, etc) is a significant, specialist, data management problem. Granta and its customers have been working on solutions to this problem, and the latest version (GrantaMI1.3) accesses new or enhanced reference data for: aerospace alloys, nuclear and chemical engineering materials, thermoplastic elastomers (TPEs), medical plastics, and eco-design (Fig.2). Price data for over 3000 materials has been updated using an improved price model.

Within the complex subject of sustainable design, there are many areas that require attention. However, materials selection is one of the most important, and one where designers are continually making decisions that can make a real difference.