Environmental Materials

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by Cris Arnold

Background and Context

Issues of environmental protection and sustainable development are gaining an increasing importance in everyday life, and nowhere is this more so than in the field of Materials Science and Engineering. Almost every aspect of materials usage, from extraction and production, through product design and ultimately disposal issues, is now subject to environmental considerations. Furthermore there are many cases where the development of novel 'environmentally-friendly' materials are providing new challenges for materials scientists and engineers.

The growing awareness of environmental issues has increased the attention focussed on the materials industry. There is a danger that this could give a negative picture, highlighting examples where materials production and use has led to environmental problems. In many of these cases, materials, additives and production methods were used for very good materials engineering reasons before environmental concerns were established. The more positive image of materials engineering that can be portrayed is one where the industry is at the forefront of technical advances - not only to 'deal with past mistakes', but also to drive sustainable and safe use of materials for the future.

The topic of 'Environmental Materials' is broad and can touch on some relatively in-depth aspects of materials structure, chemical and physical properties, processing and design as well as more general areas such as legislative, economic and social aspects. Interesting topics within this area can be presented at a range of levels: for instance the sustainable use of materials in the IT sector can be discussed by 11 year olds with as much enthusiasm as by post-graduate students - although the latter would be expected to grasp the chemical details of identifying brominated flame-retardants, whereas the former would consider much simpler aspects, that are nonetheless important.

This guide aims to provide information on what can be taught under the broad title of Environmental Materials; how it can be most effectively delivered to students; and how it might be assessed. The next section gives details of the subject areas that should be covered within this theme and provides some suggestions about how these different areas can be linked together. Effective teaching and assessment methods are then discussed, reflecting the fact that as this subject is a rapidly-changing one, there is perhaps less reliance on factual information and a greater need to encourage individual interpretation of more subjective information. The guide concludes with two case studies which show how these ideas can be put into practice.

Overview

The figure below schematically shows how the disparate areas under the heading of 'environmental materials' can be linked via a life cycle analysis approach.

Life cycle analysis figure

What to Teach

Life Cycle Analysis

Life Cycle Analysis is essentially a method of considering the entire environmental impact, energy and resource usage of a material or product. It is often known as a 'cradle-to-grave' analysis and can encompass the entire lifetime from extraction to end-of-life disposal. Life cycle analysis can be an extremely effective way of linking many different aspects of the environmental impacts of materials usage. The scope of a life cycle analysis can be adjusted to suit a particular case. For instance it could cover the environmental impact of the global aluminium industry or simply that of one single plastic injection moulding machine. In order to gain most learning benefit from this area, students would be expected to have a good grasp of the necessary underlying technical areas, which could be quite complex and so this ideally suits more advanced degree level students. The most conventional way of approaching a life cycle analysis is to follow a particular material or product through its lifetime. Therefore the first consideration would be the impact of materials extraction, and then production and manufacture, product use and finally end-of-life considerations. This approach is followed below. Various aspects, such as energy usage, economic and legislative issues occur throughout the cycle.

Materials Extraction and Resource Implications

The environmental impact of raw materials extraction and processing together with global resource issues provides a good place to start consideration of environmental aspects of materials. Indeed taking this approach can provide a more interesting way of dealing with subjects such as extraction metallurgy that can otherwise come across as very dry factual subjects. This can be taken at quite a basic level covering materials abundance and the energy required for extraction, up to a detailed consideration of environmental impacts of extraction processes. For example, the production of aluminium requires large amounts of energy and produces a significant contribution to overall greenhouse gas emission. By comparing energy usage for extraction of new aluminium compared to recycling of used aluminium, students will see the large benefit to recycling in this case.

Environmental Impacts of Processing

This area often overlaps with the above, and again can provide an interesting slant to the teaching of materials processing. Topics that would come under this subject area include the specific environmental problems associated with processing of metals, polymers, ceramics, composites etc, and how these problems can be overcome.

Design for Sustainability

This area takes the conventional subjects of materials and process selection and product design and adds the sustainability criterion. It will therefore cover issues such as design for successful recycling, waste minimisation, energy efficiency and increased lifetime.

Economic, Social and Legislative Issues

Although this subject area takes things outside the normal realm of a Materials specialist, there are many important aspects that have a significant influence on the more technical issues. For example, materials selection within the automotive industry is now heavily influenced by 'end-of-life vehicle' and 'hazardous material' regulations.

Use of Sustainable Materials

The design, production and use of 'sustainable materials' are at the heart of this subject, and yet the definition of such a material is hard to specify. It could easily be argued that steel is a very sustainable material; it is abundant, takes relatively little energy to extract and is easy to recycle, however people living near a steelworks would argue against this. It is probably sensible to define such materials as those that have distinct differences that achieve environmental benefit compared to conventional materials. With this definition, the list would include:

Materials of a significantly plant-based nature, including wood, natural fibre composites, natural polymers.
Materials produced using a large proportion of waste material, including recycled polymers, composites made from waste mineral powders, and arguably also much steel and aluminium.

Materials for Green Energy

The most exciting developments in Materials Science are in the realm of functional materials, and many of these serve an environmentally-beneficial purpose, particularly in the production of green energy.
These include:
- Solar-cell materials
- Fuel-cell technology
- Catalytic pollution control

End-of-Life Issues

The treatment of materials at the end of their lifetime is a significant subject area and encompasses aspects such as recycling techniques and materials limitations, biodegradabilty and composting, chemical recovery and energy recovery.

How to Teach

For students to gain maximum learning outcomes from this area, there is a requirement for a certain amount of basic knowledge. This includes:

Details of environmental legislation and economic factors
Processing methods
Materials composition, structure and behaviour
Details of environmental impacts (eg the detailed chemical mechanism by which CFC's deplete the ozone layer)

The methods by which students obtain this information can vary, depending on the level of initiative expected from the students. It could be presented via conventional lectures, with supporting multi-media material. If students are given more time and responsibility for their learning, they could be required to undertake a literature/information survey, however with this method it is quite common for important information to be missed or not understood.

The area of environmental materials presents an exceptionally good opportunity for other teaching and learning methods that are much more suited to the quite subjective and rapidly changing nature of the subject such as:

Group discussion
Self-directed information review
Market research
Case-study work

One example of where group discussion has proved to be an effective learning tool is the consideration of new environmental legislation. Once students have become familiar with regulations dealing with packaging, automotive and electrical sectors, they could be asked to consider what should be in legislation aimed at other sectors, for example construction and agriculture.Self-directed information reviews are used most effectively to gather factual information and details of new materials/ technologies being used to address environmental concerns. An example might be for students to collect information on how the major automotive companies are planning to deal with forthcoming end-of-life vehicle regulations.

Market research is an interesting way for students to gain information on more subjective issues such as public perceptions, marketability of products and so on. In project work, there is scope for students to undertake surveys via questionnaires or door to door surveys. Case studies can be used to bring many important aspects together. For instance, an interesting case study might be to consider the environmental impact of PVC use. In order to do this effectively, students would need to have access to factual information on PVC production methods, additive technology including plasticiser chemistry, recycling methods, dioxin chemistry and the associated health risks.
With this information, students could then consider the more subjective issues of the overall environmental risks posed by PVC, the optimum disposal routes and the benefits of long outdoor lifetimes when replacing other materials that require paint or preservative treatments.

The significant learning objective in such a case would be the consideration of the full lifetime environmental impact in order to make reasoned comparisons with alternative materials. For students to be able to do this, a distinction must be made between the factual information presented, about which there is little argument and the subjective issues, where students should be encouraged to take a range of standpoints and argue their advantages/disadvantages.

How to Assess

Aside from exams of course, it is envisaged that a range of assessment methods would be used, linked to the different types of learning outcomes.

Reports/dissertations allow a greater assessment of student's understanding as they allow greater depth and interpretation of particular subjects. However the issues of plagiarism need to be addressed.
Project work can be an even better method for assessing a student's in-depth understanding and also allow assessment of the student's ability to devise investigative methods that go beyond the review of published information.
Other methods are also possible within the field of environmental materials, that can mimic real-life situations. For instance, to assess understanding of the legislative issues associated with this subject, mock advocacy case studies could be performed. The development of marketing plans for an environmental material, product or process could also be undertaken.

Evaluation

In addition to teaching and assessment of learning outcomes, it is important to evaluate the degree to which the learning outcomes have been achieved. For the more factual elements, this is quite simple, based on student's performance in formal assessments. Project work and extended reports/dissertations give a better indication of how students can gather, assimilate and combine new information. The most important general learning outcome in this area is the ability to generate a complete overview of the inter-relating environmental aspects of a material or process. Assessment and evaluation of such a learning outcome is best made from the more open-ended types of assignments, where students have the freedom to show initiative and their own interpretations.

Case Study Examples

The following two case studies illustrate how several aspects of environmental issues of materials use can be covered within a single context. Case studies such as these provide excellent methods of combining advanced technical knowledge and commercial/legal/social issues in an interesting manner.

1 Environmental Materials Use in the Automotive Industry

Graph Environmental Materials Use in the Automotive Industry

The main challenges facing the automotive industry at present include:

End-of-life Vehicle (ELV) regulations
Restriction of hazardous materials regulations
Requirements for greater fuel efficiency
Emission reductions
Improved safety
Aesthetic design
Cost competitiveness

Several of these are beginning to have a significant impact on the materials selection and design issues within the automotive industry. For instance, the ELV regulations will specify recovery and recycling rates at the end of a vehicle's lifetime, the responsibility for which will rest with the producer. They will also require the use of a minimum amount of recycled material to be used in new vehicles. The hazardous materials regulations will impose further restrictions on materials use and how they can be treated at the end of their life. The requirements for improved fuel efficiency tend to drive materials usage towards reductions in vehicle weight.

The two most significant requirements for materials selection and design are becoming the need for low weight and the requirement for recyclability. Lightweighting tends to favour greater use of polymers and polymer composites, although designers with steel have responded to this via initiatives such as the Ultra Light Steel Auto Body (ULSAB) project. Weight reductions can also be achieved by the greater use of multi-material components and adhesive bonding.

Recyclability tends to favour the more traditional metallic materials (steel and aluminium), with fewer different materials used in a vehicle, in larger single components that are joined by more mechanical means. The two requirements (both with environmental protection justifications) tend to drive materials selection and design in different directions. The relative importance of these requirements, and hence the most environmentally-friendly design route, provides a very good subjective discussion point for students.

An interesting new use of materials in this sector is found with natural composites (with plant fibres such as hemp and flax replacing glass nd carbon). With suitable degradable polymer matrices, these materials can provide low weight together with recyclability via composting.

2 Waste Electrical and Electronic Equipment (WEEE)

The second case study also relates to forthcoming waste legislation, the WEEE directive, which will specify minimum collection and recycling rates for waste electrical and electronic equipment. In this case, the most interesting materials issues arise when this legislation is taken in conjunction with that dealing with hazardous waste, e.g. the ROHS directive. Many components within WEEE contain materials that will be designated as hazardous and will require special treatment. Examples include:

Lead solders
Phosphorus coated monitor and TV screens
Mercury switches
Batteries
Brominated flame retardants in plastics
Refrigerants

Consideration of these allows in-depth study of the materials issues (for instance what is the physical mechanism that requires a phosphorus coating on a TV screen), to consider alternatives that can be used in future (eg what other low melting point metal alloys could be used as solders) and also what problems they are likely to pose in waste treatment. One of the most important examples of the latter issue is that of flame retardant identification with plastics.

An estimated 30% of waste plastics from IT contain brominated flame retardants, which are to be designated as hazardous. The WEEE directive will require minimum levels of recycling of plastics from IT (expected to be about 60%). Unless the brominated flame retardants can be accurately identified and separated, it will be impossible to recycle any. At present, identification methods are yet to be proven as 100% effective, and so there is a potentially huge technical problem awaiting us. Detailed consideration of this issue is an excellent way for students to learn about polymer additive technology and chemical identification methods.