The role of metal forming in a world with zero emissions

Plenary Lecture by Professor Julian Allwood, given at ICTP 2023, Cannes, 27th September 2023

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In 2011 I gave a keynote paper at ICTP in Aachen, to introduce our book “Sustainable Materials: with both eyes open” and we gave a copy of it to all delegates. The title refers to the fact that if you look with only one eye at reducing emissions in industry, you will focus on Energy Efficiency. But there isn't much room for further improvement as it has already had so much attention. We therefore introduced the idea of looking at industrial emissions with both eyes open to champion the strategy of Material Efficiency: living well while using much less material. That idea was radical at the time but has become widely accepted and has penetrated into international policy. In their 5th assessment report the Intergovernmental Panel on Climate Change (IPCC) included a sub-chapter on Material Efficiency, and the International Energy Agency now anticipates that it will deliver one third of future industrial decarbonisation.

Climate policy

The most famous of the United Nations Conference of the Parties Meetings led to the Paris Agreement in December 2015, which aimed to hold the global temperature rise due to climate change to 1.5 degrees. That meeting was a milestone, largely ending climate scepticism, except in American right-wing politics. However, the message of the rest of the Paris meeting was all about new technology. Immediately afterwards, I wrote a letter which appeared in Nature in February 2016 to point out that unreasonable optimism about new energy technologies was now as big a barrier to climate mitigation as climate scepticism had been before the Paris Agreement. That statement remains true, and it sets the agenda for what I want to talk about today.

If we want to secure a safe climate, we must be realistic about the rate at which new technologies can be deployed. Doing something for the first time in a lab is irrelevant when we have so little time left to make changes that are big and global. So, as we think about our role in metal forming, the key question is, what can we do that can scale sufficiently in the remaining time that we have left to act?

We have talked a lot about climate change since the 1992 Rio de Janeiro Summit, but global emissions now are 50% higher than they were then. In the last three years many countries have also made pledges to reach what is now called net-zero emissions. We are talking, but we're not delivering - and the problem is getting worse every year.

The problem is not about annual emissions. The atmosphere acts as a tank in which emissions accumulate. In 2011, a paper in Nature anticipated that the total carrying capacity of the atmosphere was a trillion tonnes of carbon or 3.7 trillion tonnes of carbon dioxide. The authors estimated that we had emitted half of this amount by about 2011. If our emissions continue growing at current rates, the tank will be full before 2050.

Thinking about climate mitigation is not an academic exercise. It is urgent and, in my eyes, it takes priority over every other goal that we might share in this room. The obvious consequence of our inaction is rising temperatures. Often people talk about climate change leading to a one degree rise since pre-industrial times. But in fact, temperatures have risen by one degree since about 1980.

If you look at their most recent report, the IPCC predicts that temperatures are likely to rise at the same rate or even higher unless we act radically. Even if we act collectively to reduce emissions, temperatures will continue to rise due to the accumulation of emissions in the atmospheric tank.

My life expectancy is around about 2050 or 2055, but my children will be alive for most of this century, and if I am lucky and have grandchildren, they will live beyond the end of the century. What does this mean for them?

The most recent IPCC report gives a very detailed risk assessment of the consequences of rising temperature. We have already experienced the effects of climate change creating severe wind, fires and flooding. But the biggest risk is about food. The IPCC expresses this as the risk of global food insecurity, which means the risk of significant starvation in some areas. The Paris Agreement was based on a target of 1.5 degrees, because at that level, the risk of food insecurity is less than “very high.” However, earlier this year, the World Meteorological Office predicted that there is a chance of 66% that annual surface temperature rise will reach 1.5 degrees within the next four years. In other words, we made a pledge seven years ago in Paris that we would hold the average temperature rise below 1.5 degrees and global temperatures are likely to exceed this limit within the next four or five years.

Although the media hasn't yet recognised this, acting on climate change is about avoiding a global war over food shortage. The IPCC report explores this in more detail, showing how the countries near the equator will become hotter and have less rain, so their food productivity will go down. Generally, those are poorer countries, so they will struggle to buy food in a constrained global market with rising prices. And although there is a possibility of increased productivity in Russia, the history of politics does not give us a lot of hope that excess food would be supplied cheaply to people in poorer countries who are unable to pay.

When we talk about climate change, we're not talking about just one thing we could add to the basket of all other concerns. We're talking about the survival of the human race. And the problem, the world-war over food, is likely to occur in the lives of my children and my students. It's that urgent and that's why I want to be absolutely serious about the scale of action that we take. We cannot just make token gestures about the environment, such as putting the newspaper in the recycling bin before flying off for a weekend’s holiday. We must act now and act with proportionate scale.

I thought everything I have shown you so far was already bad enough, until in the past two months I saw two graphs that really scare me. The first one shows the extent of ice at the South Pole in mid-winter and this year, it is substantially lower than all recent years. The second graph shows the global average sea surface temperature. In every previous year the peak temperature was in March, but this year, the hottest ever sea surface temperature was recorded, not in March, but in August. These are the first indicators of what climate scientists call a tipping point, when the rate of global warming accelerates radically. The graphs reinforce the message that we have to act, and we have to act now.

We can respond to climate change in roughly four ways.

We can do what the economists have been telling us to do for 30 years and price carbon emissions in order to motivate a technological change. However, that will not be pain free. The pricing has to be high enough to eliminate, for example, all flying or all use of gas boilers or gas cooking or the use of all combustion engines in travel. That requires a very high price and people won't like it.

We could regulate. And the European legislation that bans combustion engine in cars is the most important climate legislation yet passed. We need much more of it, and to my understanding, that is how we should deal with the issue. Climate change is an issue of health and safety. It's not primarily an issue of economics.

We could act by voluntary restraint or by finding products that the market finds so attractive that they give up emitting products by preference, but so far that hasn't been very effective.

Or we can continue to do what we're doing and ignore climate change while talking about it. We could continue saying, “Oh but we must keep flying because we have to talk to each other”. This will lead to a World War over food, and that will be painful too.

So whichever mode we take, our response to climate change is not going to be comfortable or politically attractive for anybody.

But I want to convince you that the restraints that are required to deliver a safe climate also create a vast range of opportunities for us.

There are first-mover advantages to be captured by investors. The Danish wind company, Vesta, were until the last couple of years the world's largest because they saw the opportunity early. Tesla has done very well as the pioneer of exciting electric cars and that creates a model for other innovative companies to follow.

There are also rich research opportunities once you see the scale of action and the scale of challenges that we have to address.

I want to add one slide which is very personal to our community. My talk is about the role of metal forming in zero-emissions. But we must also think about the role of metal forming researchers in a world of zero-emissions. The graph shows current data on the emissions per person in different countries. I tried to cover most of the countries with many representatives at this conference and the world average is about 6.9 tonnes of CO2 equivalent (i.e. including the effects of methane and other radiative forcing) per person per year.

The emissions caused by our profession are completely dominated by flying. If you fly for just over 30 hours per year in economy, you cause the same harm as adding one average person to the world population. If you travel to two international conferences per year as a student in economy, you are already having more effect than adding one person to the world population. If you are a rich professor and you're travelling to those two conferences in business class, the effect is double. I think many of us fly long-distance much more than twice per year.

This graph is a fact. To me, it's like saying that Hooke’s law is true. We use the Youngs modulus because it's a scientific fact and we act on it. This graph is a fact. Please check it. Print out the slide and put it up in in your institute and think about it as you make your choices.

Production of steel and aluminium

Returning to our main theme, industrial emissions are completely dominated by the production of the bulk materials. What options do we have for making steel and aluminium with zero emissions?

For 30 years, the steel industry has talked about adding carbon capture and storage to steel production, but only one plant exists in the world. It's in Abu Dhabi, it's small and the carbon is captured and used to help extract more oil from the ground, which is uncomfortably ironic. There is no independent verification of the data from this site and no other plants for steelmaking with carbon capture and storage are currently under construction. In ten years of looking, I have not yet found a paper written about carbon capture and storage, except by people who want it to happen, so I think there may be an optimistic bias in the reports. But regardless of the performance data, so far carbon storage has only been deployed at a very small scale.

As a result, over the last three years the steel lobby has moved towards hydrogen. You can make steel using hydrogen direct reduction followed by an electric arc furnace. A demonstrator plant for this is being built in Sweden. However, if you want to make steel with hydrogen, you need a lot of emissions-free electricity. It takes seven times more electricity to make steel with hydrogen than to make it by recycling. That would be fine if we had a world surplus of emissions free electricity generation. But we don't. Only one third of global electricity generation is currently emissions-free. As a result, hydrogen steel production is a really interesting and important research and development project for the future, but it is not going to scale over the time we have left to act on global warming, because we won't have the electricity to power it.

The ULCOS project in Europe has looked at a whole range of other initiatives, but none of them have had a significant impact.

However, recycling is going to grow. In our book, we noticed that human beings are happy when they own ten tonnes of steel, which is approximately the equilibrium stock of steel in use in developed economies. We can use that knowledge to predict world demand for steel, assuming everybody tries to develop along the same economic path. This leads to the prediction that, if we ignore climate change, global demand for steel will rise to between 2,500 and 3,000 million tonnes per year by 2050. But on average, steel goods last for about 40 to 50 years and steel has always been collected efficiently for recycling. As a result, we know that the world's production of steel by recycling is going to at least double and possibly treble over the next 30 years, whereas the total world capacity for blast furnaces has already peaked, even if we ignore climate change. If we act on it, the blast furnaces must all shut, and recycling will become our dominant supply.

I know less about aluminium production but have found emissions data for average primary production from the International Aluminium Institute which I believe is authoritative. Nearly all emissions today are related to electricity generation because aluminium production is so electricity intensive. If that electricity came from renewables or nuclear power, we would very nearly have an emissions free supply of aluminium. The largest remaining contribution to emissions is from the consumption of the carbon anodes, and that's proved very difficult to address. Even 40 years ago, the industry was trying to develop inert anodes yet they're still not ready. It maybe that some of the people at this conference could contribute to research in that area.

This survey shows that there are some options for making steel and aluminium without emissions, but all such options depend on access either to emissions-free electricity or access to carbon capture and storage. However, the metals producers are not the only sector that want those resources. If you look at the decarbonisation plans of the aviation industry, they hope to use emissions-free electricity or carbon storage or biomass. So does the car industry. So do national plans for heating and cooling houses.

So, we can only work out what is the likely supply of emissions-free electricity for the steel and aluminium industry if we see them in the context of the whole picture.

Aggregation and deployment rates for zero-emissions technologies

The plans discussed at the COP 26 meeting in Glasgow two years ago were based on broad agreement about the most politically attractive approach to solving the climate problem. We would manage transport by using either electric batteries, hydrogen or biofuel. We would generate electricity either from renewables, nuclear or using carbon capture and storage with fossil fuels. We would use hydrogen, carbon capture and storage for industry. We would solve waste and deforestation by legislation, and we would have to use direct air capture to counter other Agricultural emissions.

That is the prevailing techno optimistic policy programme, which I argued against in my letter to Nature in 2016. It's absolutely pervasive and it's totally implausible. So, after the COP 26 meeting, I did a rough cut analysis which we’re now developing as an online calculator, to show how these technology plans drive demand for the three key-resources of emissions-free electricity, carbon storage and biomass.

The analysis shows that, relative to where we are today, the policy space discussed by the United Nations meetings requires eight times more emissions-free electricity and 600 times more carbon storage than we have today. Can we grow our supply of these resources by this much in the next thirty years?

Well, we can make a good guess at the answer, because we know in history how fast energy systems have grown. Over my lifetime, global generation of emissions-free electricity has increased at a linear rate. The rate changed slightly with the expansion of wind generation starting in about 2010, but there is no hint of exponential growth.

Despite all the marketing dollars of the oil and gas industry, total global capacity for carbon capture and storage is currently 0.04% of annual global emissions and is growing at a steady rate of 0.008% per year. In other words, it is so small that we should discount it completely when planning to deal with the critical challenge of human survival.

The use of biomass by humans has, in the past 70 years, grown in line with the population, but every conservationist everywhere says that we must not use any more.

So, I can predict that over the next 30 years, emissions-free electricity supply will grow at recent rates or, if I'm ambitious, the rate might double, but it is very unlikely to be higher than this. Let me say the same for carbon capture and storage and accept that we can't expand our use of biomass.

As a result, there is no way that the policies being discussed by governments and by the incumbent emitting industries can be delivered in the time we have left to act. In reality, all climate policy will be constrained by the available supply of carbon storage, and emissions-free electricity.

We noticed these constraints about four or five years ago and did an analysis of what the UK would look like if we were realistic about how much electricity, carbon capture and storage and biomass we would have. Out of our analysis, we wrote the report “Absolute Zero”, to explore how we could deal with climate change in the UK if we were realistic about resource availability. I thought this report was a rather conservative reference case, but it has been seen as a radical challenge and has now become the most accessed resource ever released by the University of Cambridge.

if I now translate our analysis, at global scale, to predict the available supply of zero-emissions metal, we could produce either about 200 megatons per year of hydrogen steel, or around 1500 megatons per year of recycled steel. Balancing the two suggests that we will add around 600 or 700 megatonnes of production to today’s steel recycling capacity, and as a result will have about half the supply of steel that we would like if economic development continued without climate change.

That sets a very clear agenda for us. Our priorities in the world of metal forming are to halve the demand for new metal.

Opportunities in restraint

The price of steel and aluminium will go up and therefore there will be pressure from everybody from the construction industry, the car industry and all other collaborators in our research to make better use of less metal. And that's where the opportunity is for us.

But it matters that we work on things that are big. I've tried to read the title of every paper at this conference to look for papers on construction and I don’t think there are any. Construction uses half of all the world steel’s and is by far the most important user of metal forming by volume. Yet at the moment this community is not working on it.

The strategies we can support are those of Resource Efficiency, and the pyramid of Resource Efficiency strategies is quite familiar in policy circles. So, I want to try to articulate some of the opportunities for us in each of these four areas.

Steel has always been recycled right back to 5000 BC. It takes so much energy to make steel that we have never thrown it away. But the two main problems we have in recycling with high quality are contamination by copper and tin. They cause hot shortening in the steel after it has been cast. Therefore, we need to find a way of getting them out.

Contamination with tin seems to be quite well controlled because it's mainly associated with food packaging and there are four de-tinning plants in the world that work quite effectively.

Our real problem is copper, which gets into recycled steel when old products are shredded with motors and wiring inside them. We looked at this by asking how you would recycle old cars into new cars and revealed six opportunities. We could look at alternative approaches to shredding. I don't think anybody is working on that here, but shredding is a plastic deformation process in which old cars are hammered in order to cause fracture and to break them into small pieces. We could use better sorting, which is not really our area. We could develop new approaches to melt control. We could develop new processes to deliver copper-tolerant casting. Or we could reduce the copper content in new cars. We have a project in our group at the moment with a UK company making electric motors with aluminium rather than copper windings in order to remove the copper from the recycling stream of the car.

Katie Daehn has done a fantastic job surveying all the existing technologies that could be used to take copper out of the steel melt, and found a whole range of opportunities for process development. Lots of techniques have been tried in lab scale and rejected at the time because they were unprofitable. But we know the economic conditions are going to change.

The second strategy on the Resource Efficiency pyramid is re-use. The most obvious application would be to re-use beams in construction. It feels like it should be a good and profitable idea, and if you compare new steel beams with reused steel beams, the cost of the steel is very much lower. However, unfortunately the cost of reconditioning is roughly equal to this saving and in addition you need a supply chain that currently doesn't exist to create a buffer between the supply of steel from old buildings and the demand for steel in new buildings. There are opportunities for us to try to change the cost structure in that operation.

I ran a project two years ago about the idea of a truly circular car. The phrase circular economy is often used more for marketing than production, but if we wanted a truly circular car, then every atom from the old car should be used to make the new car with no new atoms added. Nobody had ever looked at that, so I asked my student to work out what would be the energy cost and the labour effort required in making a truly circular car. He found that if you separate the car entirely into different material clusters and recycle them by melting, you get a significant energy saving but your labour costs have roughly doubled. It would save even more energy, nearly all of it, if you used all of the old components and repaired them, for example using additive techniques. If you did so, of course, the labour costs would shoot up. This is quite stimulating because it says that thinking about really making a car circular, in effect is about giving it an infinite life. What is our role in supporting truly long life components and renewing them to avoid energy intensive recycling by melting? And how do we get those labour cost down?

I want to talk only briefly about the strategy of avoiding production. When we looked at the longevity of all steel products, we found that only infrastructure is used for so long that it wears out. All other products are discarded because of either changes in fashion or changing user-needs. There are opportunities for us to get involved in this strategy, but to do so we have to be involved with end-users. For example, we know that we could use things more intensively. The average car in the UK is has five seats and is used for four hours per week with an average of 1.6 people in it. We could be involved in re-inventing the way we design and use cars. We could also look for material substitutions, although there aren't any very easy options that scale well.

Or we could be involved in product substitution. I think if I was starting my career now, the most exciting area is wind powered freight shipping. That has to happen, there are two companies in France that have started developing it, and there's a whole raft of innovations to work on. In the 1930s, the wind powered ships from Australia made it to London in only double the time of today's diesel-powered ships, so we know that wind-powered freight can be achieved.

The final strategy for delivering Resource Efficiency is to reduce our demand for metal, and I think that's a big opportunity. We're working on it in the CIRP at the moment and preparing a keynote paper for 2025 to articulate it in detail. We've defined three forms of scrap: manufacturing scrap – for example in producing bearing rings, a third of the metal that was initially cast is cut off before the rings are completed; property scrap – for example, only a very small fraction of a bearing-ring is loaded in use to near the metal’s yield stress, so we can redesign components to exploit metal’s properties more efficiently; specification scrap – for example, we know that most commercial buildings are greatly over-specified, and despite years of rhetoric on “light-weighting” the cars on European roads are now around twice as heavy as they were 30-40 years ago. On average, European cars now weigh twelve times more than the people inside them.

Examples of innovations that reduce metal demand

I want to end this talk with three examples that show how innovations in metal forming can make a significant difference to global metal demand.

The first one is a process from Taiwan for making washers. When you make washers from flat sheets, you blank them by cutting out both the inner hole and the outer circle of the bearing and you generate a lot of scrap. Instead, the company in Taiwan uses a process to make washers from round bars with no scrap at all. Firstly, the bar is extruded to create a flat round head. Then a counterpunch penetrates the head with a punch having the same diameter as the bar. As the counterpunch moves upwards, a washer is released with no scrap at all, which I find fantastic. It's stimulating to realise that we could do things very differently and use material in a much more efficient way if we rethink how we're forming it.

The second example is one that we presented at ICTP in 2011 for rolling I-beams (known as double T-beams in Germany) with a varying section to track the bending moment diagram. We invented a process to do this, and one of our sponsors also explored a different approach. They used a controlled flat rolling process to make variable thickness plates from which they could cut out elements to weld into an efficient beam.

The third example arose from our analysis of the world's use of steel. We spotted that the biggest user of sheet steel is the car-industry, and they throw away nearly half of all the sheet they buy. The problem is in deep drawing. In order to grip the blank round the edges to avoid wrinkling, significantly more metal is required than in the final component, and this is cut off after forming.

To respond to this, I spent a week in 2015 with Dr Omer Music, who is here at the conference, working in my garden shed and trying out different approaches. We made a simple wooden template of a deep-drawn shape and played with sheets of wire mesh as a model material. We tried out lots of forms of origami, pulling and pushing our wire mesh to see how to shape it to our template as efficiently as possible. Eventually we found that if we folded two adjacent edges over the straight lines of the template, we created a conical shape at the corner, which we now call a beak. Because this has curvature, then like a partially formed product in metal-spinning, it has stiffness. We could therefore push against it and create a state of nearly pure shear in the metal. We could see this in the diamonds of the deformed mesh indicating that they retained roughly a constant area.

That was very exciting, so we went to the lab and started to develop the process of folding shearing as a replacement for deep drawing. Soon we had some demonstration parts and this afternoon at the conference, Rishab Arora from our group will present our first paper demonstrating that we can complete the whole process in a single stroke – in effect our process can be implemented as a drop-in replacement for existing deep-drawing tools. The tools firstly fold the sheet in pure bending, a form of origami, and then as they continue their descent, they hold the corners between upper and lower conical dies, and work them outwards in a state of nearly pure shear. The resulting product requires very little trimming and has reduced thinning.

This is very exciting, so of course we filed the patent for the process, and we're building a very flexible machine in our lab to try it out in lots of different configurations. Now, Chris Cleaver, who was involved in the last three ICTP conferences, has left our research group to become chief executive of our spin out company DeepForm Ltd.  We’ve just secured our first customer order to make a full set of tooling and we're in contact with many of the world's car companies about taking the process forward.


Before I conclude I want to mention an opportunity related to this talk. On 5th-6th February 2024, with Professor Dirk Raabe, I'm running a discussion meeting at the Royal Society to look at the metallurgical aspects of everything I've said in this talk. It is of course a hybrid meeting, so please don't fly to come to it. But you can register and join online, or if you're in Europe, come by train and join us in London for two days, exploring more of the science opportunities linked to this talk.

In summary, what I've tried to say today is that current climate policy cannot deliver on its promises because we will not have enough emissions-free electricity, carbon storage or biomass to deliver it. That's not a marginal problem, we cannot get anywhere near the required supply. That means that the future global supply of zero-emissions metal will be much lower than the demand for it that would occur if climate change didn't exist. That shortfall defines our role in metal-forming in supporting the transition to zero emissions.  There are many research and commercial opportunities, but we can only find them by starting from the big picture of metal supply and use, to make sure that the intervention we're working on can make a big difference that can scale globally and rapidly.

This talk has drawn on a lot of data, and you may find some of my conclusions contentious or difficult. If you find the talk helpful, please share this link with others, and if you’d like to learn a bit more about climate mitigation, we’ve created an open short course of six ten-minute videos at

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