Be it high strength steels and knitted metal, or more futuristic aerogels, metal foam and amorphous metal, new materials are turned into products with better properties and reduced weight. This cuts transport emissions. Meanwhile, improved process efficiency is reducing the footprint of bulk production.
A lot of our energy use comes from moving things around, often things made out of steel. Steel is one of our most abundant materials, 1.5 billion tonnes being produced annually. There are good reasons for this: steel is low-cost, pliable, strong and durable. It also is recyclable, with well developed retrieval processes. The high recycling rate notwithstanding, mining will still be required for the foreseeable future; the industrialization and development taking place in countries like China and India is driving a rapidly growing demand.
Inevitable process emissions
When considering climatic influence, steel making not only has to take energy use into account – the chemistry of the process itself also creates additional emissions. Iron ore (Fe3O4 or Fe2O3) has to be reduced to iron by heating it with carbon. The carbon is then oxidised, reacting with the oxygen to create carbon dioxide. Additional oxygen is added when the iron is turned into steel – a process called decarburization. This lowers carbon content, but releases even more carbon dioxide.
Because of these reactions – and the substantial amount of energy needed to keep them going – steel making is responsible for a tenth of all greenhouse gas emissions.
Not all steels are created equal
Steel is actually a common label for many different materials. Swedish steel companies alone produce thousands of varieties, all differing in their properties, and new kinds are continously being developed. For instance, a research team in South Korea recently claimed groundbreaking progress in creating cost-effective lightweight steel by using aluminum in the alloy.
With modern steel varieties, equal or better strength can be provided by less material, thus reducing weight. This sets of a snowball effect, saving energy and emissions wherever the steel is subsequently used or transported.
The Swedish steel industry has filled the niche of engineering steels adapted to certain applications, and is leading the way in materials development. SSAB’s high strength steel is one example, the Ovako developed Isotropic Quality, unique in its purity and low level of inclusions, is another. The latter is used in diesel engines, where the ability to withstand heavy loads is crucial. (See also ”High-tensile steel provides better environmental performance”). The widespread collaboration in research and development between steelworks in the nordic countries has proven to be a hotbed of innovation.
Looking for future solutions
Swedish mining company LKAB has teamed up with other parties across Europe in a project called ULCOS. The aim is to find plausible ways towards a future low-emission steel industry. In one of the methods currently being researched, top gas recycling, the off gases from the furnace are captured and separated. Carbon monoxide is then recycled as a reducing agent to save coke, while the isolation of carbon dioxide could provide a facilitating step towards CCS technology (carbon capture and storage, see ”Emission-free coal-fired power generation?”).
Three other process concepts are also under way. HIsarna brings several process steps together in the same reactor, improving efficiency. In ULCORED, ore is direct-reduced (without melting) by natural gas instead of coke. The ULCOWIN concept, finally, would use electrolysis to separate the ore into iron and oxygen.
Electrolysis is a method necessarily used to obtain other metals, such as aluminum. Since aluminum is a more reactive element than carbon, bauxite, the chief ore of aluminum, is immune to being reduced in the iron ore fashion. The major drawback is that electrolysis requires much more energy – but if the future brings clean and abundant energy from renewable sources, this would ultimately be a way to solve the issue of process emissions.
Scan Arc Plasma Technologies is a Swedish company developing a process similar to HIsarna. In their electric furnace, the heat for the smelt reduction is transferred by a gas heated to plasma (see also ”Plasma processes can halve carbon emissions”).
Other materials competing
Processes are being improved to obtain better versions of familiar materials with less emissions – but brand new materials classes are also seeing the light of day. Many are trying to replace steels with composites (see articles ”Composite materials help make fuel efficient cars” and ”Lightweight materials permit smarter transport”), and the mind-boggling properties of graphene is sparking a lot of ideas (see ”Super material with environmental potential”).
The Swedish school of textiles has collaborated with steel and car industries to create a new sheet material for cars. The idea is to sandwich a knitted metal fabric between two thin sheets, into a strong three-layer laminate. This reduces overall weight by 40 percent.
The knitted metal sheets are close to production, but porous materials as a weight-reducing replacement for solid ones is a concept likely to gain even more traction in the future. Ultralight materials, such as aerogels and metal foams, are examples of the same principle taken one step further.
Metal foams are still mostly found in research laboratories. They are pure metal, still extremely light and very elastic because of their structure. They can be created by setting up a lattice of nanosized tubes, as a kind of mould to be covered with metal. The lattice is then removed, and what is left is a porous, sponge-like foam.
Aerogels: isolating, absorbing, filtering
Some have claimed that aerogels will grow to have an impact on society on a par with plastics by 2050. Being yet another class of nano-porous materials, aerogels contain some of the lightest materials known. They are constructed by the mixing of silica, polymers, carbon or metal with a solvent. The solvent is then allowed to evaporate through a special process, leaving an end product where only a few percent of the volume is occupied by solid matter. An aerogel often appears semi-transparent, like a block of smoke. Nevertheless, it can support heavy loads.
As a consequence of the high porousity, a small volume will convolute a large surface area. This is a property making aerogels ideal for filtering tasks – to clean water, or, perhaps, to filter out green house gasses. Besides having very low density, they are also remarkably good thermal insulators.
Aerogels are likely to become a material of choice in the thermal insulation of buildings, pipelines and more. Within the EU alone, insulation of buildings could potentially save six times the amount of Sweden’s total carbon emissions annually, so the climatic impact could be substantial. The huge absorbing capacity of aerogels could also provide an opportunity to mop up oil spills in an efficient manner, perhaps even allowing the oil to be salvaged for use.
Swedish Aerogel, a growing start-up company, has patented their own method to create such materials.
Amorphous metals differ from ordinary metals in how the atoms align themselves within the material. Metals in general are crystalline, their atoms ordered in structure. In amorphous metals – or glassy metals as they also are called – they are not. Instead, like in glass, the atoms are uncoordinated, following no repeating pattern throughout the material. This makes amorphous metals stronger, but still not brittle like glass. Obtaining them is difficult, but one way is to cool molten metal very rapidly, before crystals are allowed to form. One special characteristic is their soft transition between solid and liquid state; this could make injection moulding a possible way of shaping them into objects – just like with plastics. Lacking the structural defects crystalline materials always exhibit, amorphous metals are also corrosion resistant by nature.
Amorphous alloys are already finding a niche in energy efficient grid converters, and Swedish Exmet AB is attempting 3D printing with amorphous metal. In the future – provided the methods of creation are developed further – amorphous kinds of steel might turn out stronger than anything we have seen before.
Steel is common and often seen, and a layman might therefore think of it as a static product of old technology. The truth is, furnaces are steaming with creative new ideas, both for new materials and better processes. The small but continous steps of improvement in large-scale production and the technological leaps of new materials being introduced are adding up to environmental advantage.
The article was published in March 2015