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15 December 2012

Sustainable Materials: With Both Eyes Open

Tag(s): Sustainability

One third of the world’s carbon emissions are emitted by industry. Most industrial emissions relate to producing materials, and steel and cement are by far the most important contributors. The industries that make materials are energy intensive, so have always been motivated to be efficient, and have now reached a fantastic level of performance. However, the world’s demand for materials is growing and likely to double by 2050. By default, industrial emissions will also double unless we do something differently.

About three years ago I met Professor David MacKay who had just published an excellent book called Sustainable Energy- without the Hot Air.[i]I blogged on the book (see Sustainability 14th November 2009). David later became Chief Scientific Adviser to the Department for Energy and Climate Change. Recently I was invited to the Royal Society where David introduced a fellow Cambridge scientist Dr Julian Allwood who is leader of the Low Carbon Materials Processing Group in the Department of Engineering. The group focuses on the technologies and systems of energy, material and resource efficiency. Current projects include exploration of material efficiency in metals, development of novel metal-forming processes and investigating options for future carbon emissions reductions in consumer goods. In 2008 he was awarded a 5-year EPSRC Leadership Fellowship to lead a major project on the global carbon emissions targets for steel and aluminium in collaboration with a consortium of 20 global companies.

Dr Allwood and his team have just published a book summarising this work called Sustainable Materials: with both eyes open.[ii]  The project has led to six ‘material efficiency’ options which allow for the same services, such as housing or transport, with significantly less material. Dr Allwood sought to demonstrate how these strategies can be applied in practice and set out an agenda for making a big difference to global emissions.

He began by poking fun at some of our attempts to reduce material usage. Back in 2007 Gordon Brown had encouraged us all to stop using disposable carrier bags when we go shopping. Well the effect of one household following this advice for a year is the equivalent of reducing its use of the car by just one mile.  Jaguar LandRover has launched the Evoque which apparently is selling well. In the zeitgeist of the moment it offers carbon offsets for 14,000 miles but then it has a 4.2 litre engine which achieves just 12 mpg.

Dr Allwood is a member of the Mitigation Group of the IPCC. Emissions since its last report are worse than the worst of the six scenarios they had projected. All options are not additive. Energy sources of electricity generation combined with conversion devices can produce results. Worldwide renewables account for just 3% of all energy, most of which is hydroelectric. They will have to increase by a factor of 50 in the next 38 years to replace carbon energy sources and meet projected demand. Alternatively nuclear could increase by a factor of 25 but it’s in decline after the tsunami in Japan and the German reaction to that. Therefore the answer has to be in greater efficiency. But then when you consider that a company like Rolls-Royce has employed thousands of the world’s best engineers for the past 50 years trying to optimise the aircraft engine it might be reasonable to suppose that it is close to being fully optimised. Dr Allwood thinks the answer is in passive systems. Logically a low carbon car is a small car. Rather than focussing on the gas boiler in a house architects should concentrate on the building itself. A passive house has an ultra-low carbon footprint. In Europe some 25000 to 30000 passive houses have been built to date, mainly in Germany and Scandinavia, but then in the US it’s just 13!

Turning to industry much of the energy consumption goes in producing intermediate goods i.e. materials not products. Excluding agriculture industry accounts for 35% of CO2 emissions, building 31% and transport 27%. The most energy intensive material production is steel accounting for 25% followed by cement 19%, paper and plastic 4% each and aluminium 3%. 42% of steel use is in building, 14% in infrastructure and 13% in mechanical equipment.  24% of aluminium goes in building, 18% in cars and 13% in packaging. Steel continues to be in greater demand. While steel production in the UK has halved in the last 35 years its usage has continued to grow. In the EU, the US and Japan the stock of steel averages 10 tonnes per person. This lasts about 20 years, as long as 40 in buildings and 10 in cars. So annual consumption of steel in the developed West is ½ tonne per person per year or about 9 times body weight. In China the average consumption is just 3 tonnes per person but in the cities has already reached the western level of 10 tonnes.

Steel can easily be recycled because of its magnetic quality and this halves energy consumption. This currently meets one third of needs and by 2050 could be ½. But a ¼ of liquid steel never reaches final products but is scrapped in production. End of life scrap is less than half of the scrap input. Thus out of 200 kg of steel that is produced for every person on the planet 50kg is permanently recycled but never actually used!

Both steel and aluminium have reduced their use of energy consistently but the rate of reduction is now plateauing. Indeed with aluminium it is going up again because we’ve used all the best sites of bauxite.  With just one eye open with the most optimistic assumptions we can’t halve emissions by 2050 if demand doubles. So what happens with both eyes open?

We can reduce the return loops, design lighter products and create longer life goods that last 40 years on average rather than 20.

1.       Use less by design e.g. I-beams used in construction are of constant thickness but should be thicker in the middle. They could be designed to use one third less material though this would cost more because it would use more labour.

2.       Yield losses. These cannot be reduced in I-beams but certainly can be in sheet metal where as much as ½ can be lost. It takes 2 tonnes of steel to make a Prius but only 1 tonne is in the final product. The steel where the window is cut out is wasted. There are now good examples of imaginative use of materials to reduce losses. The Olympic stadium used unwanted North Sea gas pipes.

3.       Reuse without melting. The reuse of steel in construction has started. Steel does not degrade in use, unless there is fire. Buildings are often unoccupied for up to two years pending contract negotiations and this needs to be resolved.

4.       Longer life products. Most products are thrown away for other reasons than they’re broken. Only infrastructure gets replaced because it’s worn out.  Nearly all the rolling mills which are open structures are still going after many decades of constant use.

5.       Reduce final demand. This comes down to the sociology of consumption. On average cars are used for just 4.5 hours per week carrying 1.5 people.

In questions Dr Allwood agreed that regulation works in changing behaviour, that there is a trade off in optimisation vs. reuse and that the role of standardisation is important. But to those who believed that a carbon price was the answer he pointed out that while steel had replaced wood and cement had replaced stone that nothing had yet emerged to replace steel or cement. He also poured cold water on those who looked to 3D printing as an answer as he thought its use would be very limited. While some products can no doubt be formed from powder steel goes though heating processes etc.

In conversation afterwards I brought him back to the sociology of consumption. I had read that the average electric screwdriver is used for less than 20 minutes in its lifetime. Was there not a new ownership model where such products could be shared? In my cul-de-sac everyone has his own lawn mower which he uses at a different time in the week. Why don’t we all share one? With the money saved we could even pay someone to mow our lawns for us.

Copyright David C Pearson 2012 All rights reserved

[i]Sustainable Energy – without the hot air Professor David MacKay

[ii]It’s free to download at I recommend you buy it because it’s full of marvellous diagrams which are not so easy to appreciate online.

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