In this article, Jeanette Fitzsimons considers an issue with very important implications for both the coal industry and the prospects of making major greenhouse gas emissions reductions: whether, and to what extent, we can make steel without using coal. We welcome your comments and feedback – please send your responses to email@example.com.
Can we make steel without coal?
Coal is the most concentrated source of carbon dioxide and the biggest threat to the climate through accelerated global warming. Leading climate scientist James Hansen of NASA and Columbia University says that if we are to stabilise climate at a safe level the world needs to phase out coal burning to zero by 2030.
This is supported by analysis by Carbontracker and others that 80% of the known reserves of coal must be left in the ground forever if we are to limit warming to two degrees.
Coal Action Network Aotearoa (CANA) is committed to opposing all new coal mines in order to meet that target. However, 60% of Solid Energy’s coal production in NZ is for steel making, mainly for export, and the company says that “there is no way of making new steel without coal”.
If this is true, principled climate campaigners must either stop opposing new coking coal mines on climate change grounds, (Happy Valley, Denniston Escarpment, Mt William, Pike River) or propose a world with no new steel. (There are of course strong biodiversity reasons for opposing some of these mines but it is a different argument.)
Fortunately Solid Energy’s claim is not true.
Why is coal used to make iron and steel?
Firstly coal is converted to lump coke in a coking oven. A particular rank of coal, known as “coking coal”, is required to make the preferred quality of coke.
Then raw iron is made by reducing (removing the oxygen from) iron ore (iron oxide) by reacting it at high temperature with coke in a blast furnace. About half of the carbon in the coke combines with the oxygen from the iron ore to make CO2. The rest of the coke is burned in a blast of air in the blast furnace to provide the required high temperature; making more CO2. The resulting pig iron typically contains 2.5-4.5% carbon, making it relatively brittle and unsuitable for most uses.
Steel is made in a subsequent process as an alloy of iron and carbon (along with some other elements). Around 1% of the carbon from the coke remains in the raw iron to provide the source of that carbon. So coal (as coke) is a reducing agent, a source of energy to drive the process and a source of carbon to incorporate in the steel. Alternative processes need to meet all three functions. This is why you have to do more than just substitute a different energy source.
In New Zealand, the coking coal occurs on the west coast of the south island. The bitumen in the coal binds it into lumps in a coke oven. Coking coal is higher in carbon content than cheaper coals and lignite which are used in power stations and industrial boilers.
New Zealand’s Glenbrook Steel plant uses a different process. It is a unique design, developed to use NZ iron sands and sub-bituminous coal from Huntly.
What quantities are we talking about, globally and in NZ?
World steel production is over a billion tonnes per year (tpy) and uses about 1.4 billion tonnes of coal – roughly a quarter of all coal mined, and 12% of all hard coal. The carbon content of mined coking coal is around 77%, so global steel production consumes about one billion tonnes of carbon.
The Glenbrook plant (now owned by Bluescope) makes 600-650,000 tpy steel and uses 750,000 tpy Huntly coal plus 1,000 GWh electricity and some Natural Gas, supplying 90% of NZ’s needs. It also recycles steel.
Can we make steel with less coal?
For a start, we could recycle much more than we do.
Steel can theoretically be recycled indefinitely, with the remelting and alloying process ensuring its quality. That requires energy, but much less than to make new steel, and it needs no new source of carbon so is generally produced in electric arc furnaces. The current global rate of steel recycling is 30%, helping keep carbon emissions from pushing ever higher. Obviously there are limits to what can be collected for reuse but it should be possible to raise it to 80%, and would be if there was a sufficient price on carbon. Failure to price environmental damage leads to massive waste because collecting material for reuse is “just not worth it”.
The Direct Reduced Iron (DRI) process makes raw iron with inputs only of electricity and natural gas. India produces some 68MT/y by this method. If the electricity is renewable and the gas used is biogas from waste, this approach could be made sustainable. However DRI is often alloyed with scrap steel in the steel making step, so to add DRI to recycled steel complicates lifecycle analysis.
There are various processes that reduce the coal needed for a tonne of steel. The University of NSW has developed a polymer injection technology where some of the carbon and energy come from used car tyres, with 1 million car tyres substituting for 15,000 tonnes of coal. (1) This is useful while there are large quantities of used car tyres but is not a long term solution. Alternatively, the Hisarna process uses coal directly rather than making coke, reducing coal input by around 20%. (1)
The steel industry worldwide is putting serious effort into finding ways of reducing carbon emissions from steel making – within the current economic framework. But we are looking for something that could replace coal altogether.
Is it technically possibly to make steel without coal?
The obvious answer is that it must be, as early iron and steel production used wood-derived charcoal instead of coal-derived. However the scale of today’s industry is vastly bigger than two hundred years ago.
Electrolysis has been shown to be capable of coal-free steel production but the technology is said to require another 20 years of development before full commercialisation. (1) However, this is roughly the time it will take under Hansen’s scenario to phase out coal directly, making it a possible option for the future.
Charcoal made from wood or other biomass can provide the reducing function, a source of energy and the minor carbon component in steel; with further heat obtained from electricity or natural gas (or biogas). However, even the small quantities of iron and steel made a couple of centuries ago, along with the heavy demands of ship building, had a serious impact on Europe’s forests. The scale of steel demand is now many times greater, so the real question is about scale and sustainability. Climate change cannot be considered in isolation from land use, food production, and forestry policy.
Is there enough wood or other biomass, and where would it come from?
Wood could be grown in plantations for use in the steel industry, just as it is now grown for timber. But land is a limited resource and is also needed for food and buildings and for the protection of wild nature and other species. There have been various attempts to calculate how much land you would have to devote permanently to rotational wood harvest for each tonne of steel to be made annually. The estimates vary between two and seven hectares per annual tonne, depending on species, climate, soil and process efficiency. Clearly the world is not going to devote 2-7 billion hectares (13%-50% of the global land area) – or even a small fraction of that – to steel making, and nor should it.
However, all existing forestry operations have residues of woody material of low commercial value. As well as prunings and thinnings, harvesting residues like branches, bark and damaged logs average at least half the tree. Woody waste from crops – such as coconut shells and husks, corn stover, grain stalks – can be added to this.
Figures from the Food and Agriculture Organization of the UN (2) estimate annual waste from commonly cultivated crops is in the region 25-176 exajoules (Ej – 1018 joules). Parikka (3) estimates annual waste biomass from all sources is around 64 Ej and compares this with total global energy use from all sources for all purposes of 440 Ej. For comparison, global coal use for steel making is around 22 Ej. (5)
Carbonscape, a NZ firm which has developed new very efficient technologies using microwaves to process wood waste into charcoal, calculate that with their process it would take 1.6BT biomass globally to replace all the coal currently used in iron and steel making. That is around 3% of the 50 B tpy of world annual biomass productivity. Carbonscape is not yet in commercial production but has produced test batches of charcoal to secure an order for 9,000 tonnes from NZ Steel.
While these numbers are far from precise they do indicate that far more waste biomass than needed is available. Of course, not all waste can be easily recovered; some of it will be too far from steel mills to justify the transport energy and cost; some of it already has alternative uses; and the green leaf and twig waste (a small proportion of the forestry total and probably more of the crop waste total) should remain on site to return nutrients to the soil.
However, the most important question is whether the forestry and other biomass operations on which steel making might piggy-back, should all continue.
Are the forestry operations that produce the residues themselves sustainable?
Brazil produces some 23-36 million m3 of biological charcoal each year to make iron and steel. Some of it is from planted woodlots on a 7 year rotation but most is from old growth forests. There is a major international campaign to stop this logging of old growth forests to supply the steel industry.
Much logging in tropical countries is actually illegal as well as unsustainable and the world’s old forests are diminishing fast, along with the wildlife and indigenous communities they sustain. We cannot both campaign against cutting forests unsustainably, and rely on residues from this practice to fuel our steel mills.
If a plantation forest is managed well, using its residues for energy and carbon is a big environmental plus. But how is the steel maker (supposing they even care) to tell the difference between charcoal from sustainably managed forests, and that from illegal and unsustainable cuts? It seems impossible.
Yet there is already a world wide system in place to do just that for timber, paper and packaging.
The Forest Stewardship Council (FSC) certification system operates in 80 countries and five continents. It certifies that a product comes from a forest that is legally harvested and well managed with regard to environmental protection, wildlife conservation, and safe and fair working conditions. It also outlaws genetically engineered trees, citing risks of increased flammability, invasiveness and contamination of native forests with engineered traits.
Forests may be planted or well managed natural forests where high wildlife densities and populations of animals like great apes and tigers, are retained.
Globally 165 million ha of forest are certified, and this number is growing fast. The system includes chain of custody certificates in 105 countries so a product can be tracked through the value chain. NZ has 1.4 million ha under certification. Currently the system is not applied to residues but there is no reason why it should not be and there is some reference in the literature to extending it to residues for biofuels.
A similar area of forest is certified under the parallel certification system, PEFC. The two systems are gradually converging.
Is the wood residue in the right place?
Handling, drying and transport are major costs to recovering wood residues for use. However, if it is planned right the forestry industry already has much of the equipment needed on the site, and removing waste can be a bonus for an industry which otherwise has to work around it or burn it.
There are many different logging practices, some of which make it much easier to recover the residues. Practices such as taking the whole logs to a skid site, cutting and stacking at the time of logging, and the use of mobile chippers can reduce costs. Carbonscape says their micro-wave charcoal technology lends itself to small scale units for decentralised processing in the forest. A NZ wood fuel supplier says the energy required to haul a truckload of dry chip regionally is equal to only about 4% of the payload.
Some residues will of course be on steep inaccessible slopes, in areas too remote from steel mills. It is beyond the scope of this paper to estimate how much of the globally available wood residue might be harvested for making charcoal.
Other advantages of wood over coal
A wood-based process is much cleaner, with no sulphur or mercury emissions, low oxides of nitrogen, no toxic coal mine tailings, less ash which is not a toxic waste, less slag to dispose of, and less lime needed because charcoal is basic rather than acidic. It is claimed there are fewer industrial accidents than with underground coal mining.
Because of these side benefits, the Norwegian ferro-silicon industry is willing to pay twice as much for wood charcoal as for coal (per unit fixed carbon) for smelting.
What are the big obstacles?
Leaving aside the biggest issue, which is total lack of political will or interest in climate change as a problem, there are two issues which need to be addressed.
The first is scale, as it is for all sustainability questions. The capacity of the atmosphere to absorb carbon is not the only limited resource. Constantly growing steel production within an infinitely expanding economy will very soon run up against limits of land and water to produce biomass. These limits are not an argument to continue using coal – itself a limited resource – as to do so will change the climate and destroy many other resources. Steel making can continue in a sustainable society without coal, but on a limited scale.
The second is price. As long as coal pays nothing for its contribution to climate change, sustainable alternatives will be more expensive. (Under NZ’s ETS, coal mining for export pays nothing for its carbon emissions, either here or in China, India, or Japan, our main markets.)
A serious price on carbon without loopholes, preferably internationally co-ordinated, is necessary and urgent if steel making is to move away from coal. Necessary – but not sufficient. If a price on carbon is all that occurs the world’s forests will be raped to supply the steel industry. So controls on forestry are needed too. A requirement that all steel fuel come from FSC certified forests or sustainable agriculture would do it.
How much steel do we really need?
In a sustainable society steel use, like everything else, will be moderated. The first and easiest step is to cut out waste. When the rate of building new infrastructure stabilises and we are not constantly building more bridges and high rise short-lived buildings, demand for steel will drop. Design for durability and repair will play a part. There are also materials that can substitute.
Steel framework in up to 6 storied buildings can be replaced with pre-stressed laminated timber, a process developed at Canterbury University. They then become a store of carbon rather than a source of emissions. (However, a small amount of steel is used in a strengthening rod and end caps).
What do we need, to create a sustainable steel future?
First, a substantial price on carbon. That will help drive the wood based technologies and recycling. A recent Otago University thesis estimates that even $50/tonne would be enough to drive all technically feasible boiler fuel substitutions of wood for coal. (4)
Second, we need good resource studies and mapping of the wood residue resource, along with improved harvesting techniques and equipment. Scion is doing some of the former.
Third, we need to expand the FSC and make certified residues mandatory in this country. There are moves towards that overseas.
Once these are done we need a national strategy on the priority use of wood residues. Transport fuels, boiler fuel and smelting fuel are all likely to compete for the available wood and allowing the market to sort out what we use here and for what, and what we export, risks very perverse outcomes. (For example exporting charcoal might be more profitable but if it leaves us without transport fuel at home could cripple our economy.) It is inexcusable that no government has embarked on this work, or even plans to.
Most of all though, we need a change of mindset, where climate change is recognised as serious enough to change our way of doing things, and to learn to prosper within the limits of the biosphere.
This brief survey has not attempted to quantify the amount of steel needed to run a stable society, nor the quantity that could be made sustainably without coal, nor the quantity of wood residues that are available, easily harvestable and close enough to steel production sites, though some ballpark indications have been given. Work on refining this is urgent.
However we can conclude that it is quite feasible to make steel without coal and in some places it is already being done.
If wood or other biomass residues are used instead of coal, the main limiting factor is the quantity of residue from sustainably managed forests or cropping. Ultimately the limiting factor is land and land use competition. The FSC certification process could be used to ensure that wood residues are sustainable. Although the quantity is limited, it is large.
The current world production of steel, let alone its constant expansion, is not sustainable, but in a stable state economy a mix of substitution, much greater recycling and the use of biomass residues instead of coal can enable steel production to continue.
A sufficient price on carbon is essential, along with further quantification of the availability of wood residues and the development of more efficient technologies to enable this.
Most of all we need a change of political will to prioritise action on climate change and end the mad rush for growth at all costs so that these options are pursued.
What is clear however, is that there is no case for soft-pedalling our demand that no new coal mines be opened.
1. Croezen, H and Korteland, M, A long term view of CO2 efficient manufacturing in the European region CE Delft 2010
4. Deller, Nic, Replacing NZ’s Coal Consumption with Energy from Wood Residues: a feasibility study B App Sci dissertation, EMAN 490 Otago University 2012
5. World Coal Association Coal and Steel Statistics 2012