If a motor vehicle uses less fuel and produces lower tailpipe emissions it’s classed as being ‘green’. But what if the manufacture of each of those vehicles involves a much larger carbon footprint?

“Too much of the focus on the evolution to green technologies is on the ‘use’ phase of products,” says Mark Jolly, Director of Manufacturing and Professor of Sustainable Manufacturing. “It’s been all about whether those products are low energy; their ability to be recycled. To be responsible consumers, we have to be looking at the full picture in terms of materials used and the environmental cost of manufacture. Because the reality is that by the time the recycling stage has been reached, the heavy energy use and carbon footprint has already been made; scarce materials have been wasted.”

Research by the Sustainable Manufacturing Systems Centre - a detailed ‘cradle-to-grave’ study of the total energy and CO2 impact of passenger vehicle engine production - has demonstrated how the manufacture of more lightweight ‘green’ vehicles with aluminium engines actually means the use of up to four times more energy. A typical aluminium car would need to be driven for between 185,000 km and 560,000 km before there were environmental benefits from lower fuel use. The waste from the production of aluminium, what’s known as ‘red mud’ is highly toxic.

“Manufacturers aren’t in charge of all the materials they use - but they do need to be look back to the full extent of supply chain, unpicking the provenance of what is actually going into products. With the growing scarcity of natural resources, materials taken from the Eath, there needs to be more attention to alternatives: organic materials, that can be grown, and in themselves have carbon-reducing effects.”

Key Facts

Impact of our research

The University’s ‘Small is Beautiful’ programme has created models and guidelines for manufacturing companies on how to improve their use of materials and identify ‘hotspots’ in manufacturing processes that need to be avoided. This has included a focus on energy use in foundries and methods of casting, setting out savings from changes in processes.

Another project with a business partner has provided evidence in support of the refurbishment of IT over cycles of replacement every 3-4 years, setting a precedent for re-use over the sometimes haphazard re-cycling of scarce materials (in a typical laptop: copper from Chile, gold from Mali, iron ore from Brazil, nickel from the Congo, bauxite from Peru).

Cranfield is a member of the new Decarbonising Transport Network+ programme to identify the synergies between the aerospace, automotive and railway sectors and their systems of manufacture and use of materials.