LOW←TECH MAGAZINE English

Thematic Book Series: Too Much Combustion, Too Little Fire

Tue, 04 Nov 2025 00:00:00 +0000

Image: Book cover.

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For most of history, the multifunctional fire was the only source of energy in the household. It served as a cookstove, toaster, heating device, lighting source, hot water boiler, clothes dryer, and refrigerator, among other functions. During the twentieth century, the fire was replaced by a wide range of appliances plugged into central infrastructures.

In this series of articles, LOW←TECH MAGAZINE critically examines the efficiency, sustainability, health, and safety of the fire and its flame- and smoke-free modern alternatives. What are we saying when we argue that electrical appliances are “better” than a traditional fire?

Contents table

Too Much Combustion, Too Little Fire
Thermo-electric Stoves: Ditch the Solar Panels?
How to Make Biomass Energy Sustainable Again
Well-Tended Fires Outperform Modern Cooking Stoves
If We Insulate Our Houses, Why Not Our Cooking Pots?
Wood Gas Vehicles: Firewood in the Fuel Tank
Medieval Smokestacks: Fossil Fuels in Pre-industrial Times

Available in our bookshop

Patrons get free access to ebooks, as well as early access to new print books at a reduced price.

Other books in the series

How to build a low-tech internet?, Kris De Decker, Roel Roscam Abbing, Marie Otsuka, 2023. Ebook edition.
How to downsize a transport network?, Kris De Decker, 2023. Ebook edition.
Heating people not spaces, Kris De Decker, 2024. Ebook edition
How circular is the circular economy?, Kris De Decker, 2025. Ebook edition

The Low-tech Magazine archives are also available as a chronological series consisting of four volumes.

The Compressed Book Edition

Thu, 20 Mar 2025 00:00:00 +0000

Image: The Compressed Book Edition. Image by Marie Verdeil and Hugo Lopez.

The Compressed Edition is available in our bookshop as a paperback and hardcover.

In 2018, Low-tech Magazine launched a low-energy website that runs on solar power. To reduce energy use and make the content accessible for readers with old computers and slow internet connections, we opted for a back-to-basics web design, optimising image and file sizes, as well as using a static site generator instead of a database-driven content management system. In 2019, we also launched a book edition of Low-tech Magazine, which consists of three volumes with articles and one volume with comments.

The Compressed Book Edition

While a book looks and feels more low-tech than a website, it has an environmental footprint as well. Industrial book publishing and distribution involves wood harvesting, pulp and paper production, printing, ink-making, and lots of shipping throughout the supply chain. Even if the wood for paper production is harvested sustainably, which is rarely the case, all these processes require energy and produce carbon emissions.

To address these issues, and to keep practicing what we preach, Low-tech Magazine has now made a “compressed edition” of the chronological book series. Inspired by the image compression on our website, we squeezed the article catalog of three volumes into just one book. Consequently, we reduced the paper consumption and carbon emissions by almost a factor of three. The compressed edition contains 84 articles and over 700 images on slightly more than 600 pages.

We did this by switching to a smaller font size (similar to the one used in the comments book), by downsizing most images, and by opting for a two-column layout. I rewrote some articles, especially older ones, resulting not only in fewer pages but also in better articles. Laia Comellas and Marie Verdeil collaborated on the design of the compressed edition.

Image: The original, "uncompressed" book series. Image by Marie Verdeil and Hugo Lopez.

Books or Website?

Ever since the launch of the book collection, readers have asked what is most sustainable: reading Low-tech Magazine online or on paper? While it’s a relevant question, comparing the carbon emissions of books and websites is complex and somewhat pointless. There are so many variables influencing this calculation that you could tilt the result toward your preferred answer.

Comparing the carbon emissions of books and websites is complex and somewhat pointless.

A crucial factor is the time spent reading. If you only read a few articles, reading online likely has a lower carbon footprint. But, if you read all articles, and maybe even go back to them regularly afterward, the difference between online and offline reading becomes smaller. For the books, all carbon emissions occur before the reading process starts. In contrast, the more time you spend on the website, the higher the carbon emissions. ¹

There’s another difference between online and offline reading: Unlike a website, a book can be read by more than one person without raising its carbon emissions — for example, when it’s available in a library. ² Books usually have very long lifetimes, between 25 and 500 years. ³ Therefore, they can be read by dozens of people. That is especially the case for hardcover books, which take a bit more resources to produce than paperbacks but are more resistant to abuse.

Carbon Emissions & Energy Use

To estimate the carbon emissions of Low-tech Magazine’s books, I used a study of a 320-page hardcover book weighing 0.75 kg. ³ According to the researchers, the complete production process of the book has a carbon footprint of between 2 and 3 kg of CO2-equivalents, depending on what happens when the book is discarded after 25 years (landfill or recycling).

The three “uncompressed” paperback books together weigh 2,531 grams, which corresponds to an estimated carbon footprint of between 6.7 and 10.1 kg CO2-equivalents. For the compressed edition, at 929 grams, the carbon footprint comes down to between 2.48 and 3.70 kg of CO2-equivalents. These numbers are surprisingly high compared to the carbon footprint of Low-tech Magazine’s web server, which we calculated to be 9 kg CO2-equivalents per year. ⁴ Although our web server runs on solar power, these carbon emissions result from producing the solar panel, the battery, the solar charge controller, and the printed circuit boards, measured across their estimated lifetime.

However, the book does not require any infrastructure to be read, while the carbon footprint of our web server is only one part of the total footprint of the website. Readers of the website need a computer to access it, and the resulting energy use and carbon emissions of powering and manufacturing that device should also be included. Assuming 60 hours to read all the articles, a laptop power use of 25-50 watts, and the average power grid carbon intensity in Europe (300g/kWh), the power use of the laptop would add between 0.45 and 0.90 kg of carbon emissions for reading content online.

Image: The Compressed Book Edition (hardcover). Image by Marie Verdeil and Hugo Lopez.

To this should be added the energy that was required to manufacture the laptop and the power grid (of which in both cases only a part can be attributed to reading Low-tech Magazine). Because life cycle analyses show that the energy used for manufacturing a laptop surpasses its operational energy use, we can — conservatively — double this result to between 0.90 kg and 1.8 kg of CO2-equivalents. ⁵ Because our website uses very little energy, almost the complete carbon footprint of Low-tech Magazine is due to the devices of our readers.

The book needs to be read by at least two to three people before its environmental footprint becomes smaller than the one caused by reading all Low-tech Magazine articles online.

Nevertheless, this carbon footprint is still lower than the 3 kg of CO2-equivalents for the compressed book edition. Although this is a very rough estimate, it seems to suggest that this book needs to be read by at least two to three people before its environmental footprint becomes smaller than the one caused by reading all Low-tech Magazine articles online. Of course, we have set the bar very high for ourselves because of our light-weight website. Compared to the old blog, which was much more carbon-intensive than the solar-powered website, the compressed book edition — and perhaps even the uncompressed book edition — would be the more sustainable option even if it is read only by one person.

How Many Trees Have We Cut Down?

The environmental footprint of books does not only show in carbon emissions. Books are made from paper, and paper is — nowadays — almost exclusively made from dead trees. With close to 10,000 Low-tech Magazine books sold, an uncomfortable question pops up: how many trees did I kill? That is not an easy question to answer, because the only reference I could find says that “one tree can produce 25 books” ⁶, without specifying what size of tree or type of book these numbers refer to.

Nevertheless, if this estimation is valid, the Low-tech Magazine books would be responsible for chopping down roughly 400 unspecified trees. Whether or not these trees were replaced by other trees, I have no way of knowing. However, by reducing the page number from 1,700 to a little over 600 pages, at least the Compressed Edition attempts to limit this resource use.

Compressing the content — an editorial and design choice — produces a larger reduction in resource use than printing on recycled paper could ever do.

Low-tech Magazine’s “tree consumption” could be further reduced by printing on recycled paper, and we would probably do so if our book distributor and printer — Lulu — would offer that option. However, printing on recycled paper is not a panacea. Paper can only be recycled a couple of times before it needs to be incinerated or landfilled.

Partly because of this, and partly because of economic growth, there is not enough recycled paper available to print the ever-increasing number of books that are published each year. If Low-tech Magazine prints on recycled paper, it means that someone else won’t. Moreover, printing on recycled paper often increases the carbon emissions of paper production. ³ Compressing the content — an editorial and design choice — produces a larger reduction in resource use than printing on recycled paper could ever do.

How Many Books are Thrown Away?

The carbon footprint and wood consumption of an individual book only tell a part of the story. Most environmental damage in the book industry is done by overproduction. A very large number of printed books are not sold but discarded before anyone can read them. Overproduction occurs in two ways. First, most books that come on the market fail commercially, which is a consequence of the business strategies of book publishers. ⁷ Large publishers invest in a massive number of titles in the hope that one will become a bestseller.

Image: The Compressed Book Edition (paperback). Image by Marie Verdeil and Hugo Lopez.

Second, higher print runs significantly lower the printing costs per copy, and thus encourage overproduction. To give an example, printing 100 copies of a 600-page book costs 7,3 euros per copy, while printing 1,000 copies costs only 4,30 euros per copy. ⁸ As a result, it can be more profitable to print more books and discard the unsold copies. Even books that are in demand can be thrown away. For example, unsold copies at events are usually destroyed rather than sent back to publishers because it’s cheaper. ⁹

A less wasteful approach is printing on demand, in which a copy only gets printed once it is bought. In this case, there is no waste unless a book is printed badly. However, the energy use and carbon emissions per printed copy are probably higher, with the printing equipment taking a larger share in the total resource use. The printing costs are much higher, too (around 15 euros per copy for a 600-page book). ¹⁰ Almost all Low-tech Magazine books are printed on demand, but we can only do this because we have our own direct sales channel (the website). If books are sold through Amazon or in bookstores, print-on-demand results in a very high sales price or a very low profit for the book publisher.

Other Low-tech Magazine Books

The launch of the compressed edition does not mean that the “uncompressed” books will no longer be for sale. They will be redesigned in the next months, reflecting the same changes in articles (shorter and better) but printed with a larger font, larger images, and a one-column layout. Their carbon footprint will decrease compared to the earlier volumes but in a less spectacular way. Nevertheless, while those uncompressed books remain the most comfortable option for reading Low-tech Magazine, we expect a significant part of potential buyers to opt for the more compact edition, as it provides the most bang for the buck.

Obviously, “compressing” the books also addresses printing costs, which have skyrocketed in the last few years. Higher printing costs result in a higher sales price and a lower profit, or both. The compressed edition allows us to roughly halve the sales price for the whole archive while maintaining two-thirds of the profit. For the redesigned uncompressed editions, a more modest reduction in the page number will allow us to keep the current sales price but restore the profit per copy to pre-pandemic levels — important for the survival of the magazine. After all, people buy books for the content they contain, not for their weight on paper.

Ebooks and Thematic Books

The Compressed Edition is part of an ongoing research project into the sustainability of Low-tech Magazine’s publishing operations. Apart from the solar-powered website, we have introduced ebooks (2024), and these are perhaps the most sustainable option to read Low-tech Magazine. We also started the publication of a thematic books series (2023), aimed at people who are only interested in certain topics and themes of Low-tech Magazine. The ebooks and thematic books are made in collaboration with Marie Verdeil.

Book Launch Event

We hold a book launch event in Barcelona on March 28.

Image: Book launch event in Barcelona. Poster by Hugo Lopez.

That is mainly because of the energy use of the end-use devices that people use to access the website. Surprisingly, the number of website visitors has no influence on the power use of our web server. That is likely due to the fact that it is a very lightweight, static website. For “normal”, dynamic websites, the energy use is closely related to the number of visitors. ↩︎
Low-tech Magazine’s books are available in several libraries. See: https://search.worldcat.org. If it is not available in your local library, you can file an acquisition request there. ↩︎
Wells, Jean‐Robert, et al. “Carbon footprint assessment of a paperback book: Can planned integration of deinked market pulp be detrimental to climate?.” Journal of Industrial Ecology 16.2 (2012): 212-222. ↩︎ ↩︎ ↩︎
See: “How sustainable is a solar powered website?”: https://qelnixcor.cloud/2020/01/how-sustainable-is-a-solar-powered-website/ ↩︎
There’s also the power use of the router. However, while the grid-powered router uses 240 Wh of electricity per day, it is shared by all website visitors (and by the author). Even on a calm day (around 2,000 unique visitors), extra energy use due to the router is only 0.12 watt-hour per visitor. That is much lower than the energy use of the laptop, even during a relatively short visit. ↩︎
https://publishyourpurpose.com/blog/environmental-impact-book-publishing/ ↩︎
Biel, Joe. People’s Guide to Publishing: Building a Successful, Sustainable, Meaningful Book Business From the Ground Up. Microcosm Publishing, 2018. ↩︎
Based on the prices of expresta.eu ↩︎
Bookstores need to prove that they destroyed the books by ripping off the covers and sending them to the publisher. Source: personal communication with book sellers at events. ↩︎
Book cost calculator, Lulu. https://www.lulu.com/pricing ↩︎

How to Escape From the Iron Age?

Mon, 18 Mar 2024 00:00:00 +0000

Image: Steel rebar construction for the concrete foundation of a wind turbine in Gilliam County, US. Image by Goose Chap, Wikimedia Commons (CC BY-SA 4.0)

Trapped in the Iron Age

In 1836, Danish antiquarian and curator Christian Jürgensen Thomsen distinguished three prehistorical eras based on the dominant materials used for weapons and cutting implements: the Stone Age, the Bronze Age, and the Iron Age.¹ Thomsen’s classification refers to the past, but according to his criteria, we have never evolved beyond the Iron Age. Even in the 21st century, iron remains the dominant material, not just for weapons and cutting implements but for about every modern technology.

We now use most iron in the form of steel. However, according to Thomsen’s criteria, we cannot speak of a “Steel Age.” First, steel is merely an alloy of iron (>98%) and carbon (<2%). Second, humans have been producing steel since the beginning of the Iron Age. That is a little-known fact in the Western world, where steel production only took off in the nineteenth century with fossil fuels. However, Asian and African metallurgists developed high-quality steels much earlier, and this knowledge eventually allowed Europeans to do the same – on a much larger scale.²

By 2021, the global iron and steel output reached 1,950 million tonnes (Mt). That is 22 times larger than the combined aluminum and copper output (88 Mt). The global iron and steel output corresponds to five times the global plastics output (391 Mt) and dwarfs the worldwide production of silicon (8.5 Mt) and lithium (0.1 Mt).³⁴ Steel is the fundamental material of industrial societies. Without plastics, lithium, or silicon, we would still be in an industrial society. Without iron and steel, we would be thrown back 3,000 years into the Bronze Age.

Where is all that steel?

The massive presence of steel in industrial society is not so obvious.⁵ At home, we find several steel appliances such as the refrigerator, washing machine, water boiler, bathtub, and cooking, heating, and cooling appliances. However, only 2-3% of total steel production ends up in domestic appliances.⁶⁷⁸ Outdoors, there’s a lot of steel in the form of vehicles. These are especially passenger cars that use around 10% of all steel globally (20% in rich countries). Busses, trucks, trains, and ships add another 4-5%. Altogether that is still less than 20% of the global steel output.

Most steel is embedded in other materials, located underground, or far away from residential areas.

Most steel is embedded in other materials, located underground, or far away from residential areas. More than half of global steel production goes into construction, which includes buildings (residential, commercial, industrial) and infrastructures (bridges, tunnels, harbors, canals, runways, oil rigs, refineries, pipelines, power plants, transmission lines, railways, subways, and so on). Much of that steel is embedded in concrete. Reinforced concrete is the world’s primary building material, and concrete is the only material that can match the output of steel (1,819 Mt in 2021).

Roughly 15% of global steel production serves to make machinery, including machine tools, industrial equipment, electrical hardware, and construction, mining, and farming machines. Even products made of other materials – such as other metals, plastics, and wood – are shaped by steel tools.⁵ The final 15% of steel production ends up in a variety of objects, from screws over food packaging to furniture and shipping containers.⁶⁷⁸

Image: Reinforced concrete is the world’s primary building material. Hole on Interstate 84, US. Image by Tony George, Oregon Department of Transportation, Wikimedia Commons (CC BY 2.0).

The environmental footprint of the steel industry

Steel is often presented as one of the most sustainable materials. Unlike plastics, steel can be recycled without any loss in quality. The steel industry has made great advances in energy efficiency, more so than many other industries. Making one ton of crude steel now requires roughly 20 gigajoules (GJ) of primary energy on average – three times less than in 1950.⁹ This compares very favorably to other materials such as aluminum (175 GJ/t), plastics (80-120 GJ/t), or copper (45 GJ/t).⁷ Unlike plastics, steel is a biodegradable material.¹⁰ Finally, iron ore is not in short supply. It makes up 5 percent of the Earth’s crust and is fourth in abundance among the elements.¹¹ For comparison, copper only makes up 0.01%.⁵

However, despite all these advantages, the global iron and steel industry consumes more energy and produces more carbon emissions than any other industry. The total primary energy use of crude steel production was 39 exajoules (EJ) in 2021, which corresponds to 7% of all energy used worldwide in that year (595 EJ). The greenhouse gas emissions are even higher because around 75% of energy use comes from coal – the fuel with the highest carbon emissions. In 2021, the iron and steel industry produced 3.3 Gt of carbon emissions, roughly 9% of global emissions (36.3 Gt).¹² The concrete industry follows closely with 8%.

The iron and steel industry consumes more energy and produces more carbon emissions than any other industry.

The estimates above come from the World Steel Association and the International Energy Agency. These data are available for all metals and have been documented over a long period, allowing for historical comparisons. However, they only refer to the smelting of the metal. They do not include the energy use and carbon emissions for mining and transporting iron ore, coal, limestone, scrap, and steel products. Nor do they include the energy and emissions for coke production and ore preparation – all essential to the steel production process.⁷

Scientific studies that have set wider boundaries for the iron and steel industry conclude that the energy cost of steel production increases by 50% to 100%.¹³ One report concludes that the methane emissions from metallurgical coal mining alone could increase emissions by 27%. Another study estimates that seaborne transport of iron ore and steel adds 10-15% extra emissions.¹⁴¹⁵ Iron and steel production also create other environmental problems, such as high water use, solid waste production, and significant air and water pollution.

The carbon footprint of the iron and steel industry is incompatible with current ambitions to eliminate net carbon emissions by 2050, even less so because steel production is very likely to expand further. Steel production grew tenfold since 1950 and doubled between 2000 and 2020, growing faster than many researchers had predicted.¹⁶ Furthermore, efficiency gains have decreased, and there is a scientific consensus that current technologies have reached their thermodynamic limits.⁷⁹¹⁷ During the last two decades, the average energy use for the production of 1 ton of steel has remained around 20 GJ/t.⁹¹⁸

How to make steel without fossil fuels?

There are two ways to make steel, and one is much more sustainable than the other.¹⁹ On the one hand, there is the blast furnace or basic oxygen furnace, in which steel is made from iron ore and coal. This technology is – in its essential form – 2000 years old. On the other hand, there is the electric arc furnace, in which steel is made from steel scrap and electricity. The electric arc furnace, which is a relatively new technology, consumes much less energy than the blast furnace, makes use of a recycled resource (no need to mine iron ore), and works without the direct use of coal or other fossil fuels (the electricity can be supplied by solar, wind, or atomic power).

The most energy-efficient electric arc furnaces now consume less than 300 kilowatt-hours of electricity per ton of steel produced.⁹²⁰ Hypothetically, if we had produced all steel in 2021 (1,950 Mt) in such furnaces, the total power consumption of the global iron and steel industry would have been only 585 terawatt-hours (Twh). That corresponds to just one-third of all electricity generated by wind turbines worldwide in the same year (1,848 Twh). Unfortunately, more than 70% of global steel output was made in blast furnaces fed by coal and iron ore.⁹²⁰ A blast furnace consumes twenty times more energy and cannot be operated by electricity because coal is both the fuel source and the chemical reductant. The combustion of coal produces carbon monoxide that reduces the iron from its ore.⁷

Not enough scrap available

The solution seems obvious: let’s produce all that steel in electric arc furnaces. However, this is impossible. There’s not enough scrap available: the continuous growth of the global steel output makes a circular flow of resources impossible.²¹ It takes decades before most steel becomes available for recycling. For example, there is 543 Mt of steel stocked in ships.²² The scrap available for recycling in 2021 corresponds to the production level of 1965 when global steel production was less than one-quarter of what it is today (450 Mt).⁹¹⁰¹⁵²³ Consequently, the other three quarters need to be produced in blast furnaces using coal and freshly mined iron ore.

Image: Cars for scrapping at the Port of Cardiff. Gareth James via Wikimedia Commons (CC BY-SA 2.0).

Nowadays, China produces roughly half of the steel in the world and does that almost exclusively (+90%) in blast furnaces using coal and iron ore. Many other steelmaking nations have a higher share of electric arc furnaces. However, it makes little sense to point the finger at China. First, the US and Europe have outsourced many of their industries to China since the 2000s, a trend that corresponds neatly with the growing steel output in that country. Furthermore, twenty to forty years ago, China hardly used any steel. Consequently, there is almost no scrap available. China has no other choice than to use blast furnaces.²⁴

Ever higher grades of steel

A second obstacle is the continuous development of higher grades of steel. There are now over 2,500 different types of steel with a variety of properties, such as increased strength, tolerance to high temperatures, or corrosion resistance.⁷⁹²³²⁵ Although these higher quality steels can be produced in electric arc furnaces, they are not made from scrap, and they have much higher energy use.

Steel available for recycling forms a mix of steel grades. That mix is suitable for making plain carbon steel but not highly alloyed steels, which require scrap with similar qualities. However, that scrap is not available. For example, stainless steel, the most produced special steel grade, has a recycling rate of only 15%. Almost 60 Mt of stainless steel was produced in 2021, compared to only 4 Mt in 1980.²⁶ The traditional use of stainless steel was in cutlery, surgical tools, and medical and food processing equipment. However, it is now also used in the construction of tunnels and outdoor furniture, wastewater treatment, seawater desalination, nuclear engineering, and the production of biofuels.⁷

The low recycling rate and the need for the extraction of additional elements such as chrome and nickel make higher grades of steel more energy-intensive to produce. For example, stainless steel production requires almost 80 GJ per ton, four times more than the production of plain carbon steel.⁷²³ The continuous development of higher-grade steels is stimulated by environmental legislation (such as the use of lighter steel in cars) and by competition from other materials, mainly aluminum and plastic composites.⁷⁹²³²⁵ Ironically, the competition with these materials, which consume even more energy, makes steel less and less sustainable.

Steel and renewable energy

The steel industry is heavily dependent on the energy supply, but the energy supply is also heavily dependent on the steel industry. Almost 10% of the global steel output goes into building and maintaining energy supply infrastructure. That amount corresponds to the entire steel output in 1950. A great share of that steel goes to gas and oil infrastructure.²⁷. Oil and gas mining, production, and transportation require steel for offshore drilling platforms, pipelines, refineries, tankers, and storage tanks. Coal mining depends on steel for cutters, loaders, conveyors, excavators, and trucks.⁷

Unfortunately, the planned switch to low-carbon energy sources and the electrification of heating and transport technologies will not decrease our dependency on the steel industry – on the contrary. A low-carbon power grid requires much more steel (and other materials) than an infrastructure based on fossil fuels. Wind and solar power are very diffuse power sources compared to fossil fuels. Therefore, it takes much more materials (and land) to produce the same energy. In jargon, wind and solar have low “power density” or high “material intensity.”²⁸²⁹³⁰³¹³²

A low-carbon power grid requires much more steel than an infrastructure based on fossil fuels.

The “steel intensity” of thermal gas and coal power plants is between 50 and 60 tonnes of steel per megawatt of installed power.³³ Hydroelectric power plants have a lower steel intensity, with 20-30 tonnes of steel per MW.⁷³³ Atomic power’s steel intensity is also lower at between 20 and 40 tonnes of steel per installed MW.³³³⁴ On the other hand, solar PV requires between 40 and 170 tonnes of steel per installed MW.³³³⁵ Although there is little or no steel in the solar panels themselves, it’s the material of choice for the structures that support them.

Steel and wind power

The most steel-intensive power source – by far – is the modern wind turbine. The steel intensity of a wind turbine depends on its size. A single, large wind turbine requires significantly more steel per megawatt of installed power than two smaller wind turbines.³⁶ For example, a 3.6 MW wind turbine with a 100-meter tall tower requires 335 tons of steel (83 tons/MW), while a 5 MW wind turbine with a 150-meter tall tower needs 875 tons of steel (175 tons/MW).³⁷ The trend is towards taller wind turbines and a higher steel intensity.

Image: Steel towers for wind turbines in the port of Rotterdam. Image: Melle Smets.

Steel consumption further increases for offshore wind turbines. Onshore wind power plants rely on reinforced concrete for their foundations, but offshore wind turbines need massive steel structures such as monopiles and jackets.³⁸ The steel intensity for offshore wind turbines is calculated to be around 450 tonnes per MW for a 5 MW turbine – eight times higher than the steel intensity of a thermal power plant.³⁶. As these wind turbines get taller and move into deeper waters, their steel use further increases.

The most popular offshore wind turbine nowadays has a capacity of 7 MW, while the largest ones have a capacity of 14 MW.³⁶ If we make a conservative estimate based on the data above (the steel intensity doubles for every doubling of the power capacity), a 14 MW offshore wind turbine would require 1,300 tons of steel per MW or 18,200 tonnes in total. Such a wind turbine thus consumes 24 times more steel than a coal or gas power plant of the same power capacity.

Shorter life expectancy

The difference between renewable power sources and fossil fuels becomes even larger if the steel intensity is calculated per unit of energy rather than power (MWh instead of MW). In contrast to coal and gas power plants, the output of wind and solar power plants depends on the weather, and they do not always produce their maximum power capacity. Therefore, replacing 1 MW of fossil electricity generation capacity requires the installation of (on average) 4 MW of solar power or 2 MW of wind power.³⁹ A 14 MW offshore wind turbine thus has a steel intensity that is almost 50 times higher than a fossil fuel power plant for every kilowatt-hour of electricity produced.⁴⁰

A 14 MW offshore wind turbine has a steel intensity that is almost 50 times higher than a fossil fuel power plant for every kilowatt-hour of electricity produced.

Solar and wind power plants also have shorter lifetimes (20-30 years) compared to thermal power plants (30-60 years).³¹ While this does not affect the steel intensity per MW of power installed, it again increases the steel intensity per unit of energy produced over time. That does not always lead to a doubling of steel use because foundations for offshore wind turbines and structures for solar panels may have longer lifetimes than the power sources they support and could thus be reused.⁴¹

Power transmission infrastructure

The data above only include the steel used in the power plants themselves. For fossil fuel power plants, they do not include the steel used in the pipelines, oil rigs, coal excavators, and the like. However, the same goes for the low-carbon power sources. Because they need much more resources than thermal power plants (steel but also other metals and materials), they depend on a global mining and transport infrastructure that is just as steel-intensive as the supply chain for fossil fuels.

Furthermore, because they are more diffuse power sources with intermittent and unpredictable power production, often located far away from energy consumption centers, renewable power plants drive the expansion of transmission infrastructure. That infrastructure is also based on steel – from switchyard equipment over towers to conduction cables.²⁸²⁹³⁰³¹³²⁴²

Finally, low-carbon power sources also have a high need for special grades of steel, which are more energy-intensive to produce. Steel for off-shore wind turbines should resist corrosion, and stainless steel is increasingly used for solar panel support structures.⁴³ Electrical lamination steel (iron-silicon) is indispensable for transformers in the power network.⁷ Nuclear power plants may have a relatively low steel intensity but are completely built up of energy-intensive specialty steels. For example, cladding the fuel elements containing fissionable uranium requires zirconium steel, while all structural elements contain austenitic stainless steel.⁷⁴⁴

Low carbon grid cannot be made from recycled steel

The high steel intensity of low carbon power sources confronts us with a so-called “catch-22”, a situation in which there seems to be no escape from a problem no matter what we do. We need much more steel if we replace thermal power plants with renewable ones. Because there is not enough steel scrap available, we can only produce that extra steel from iron ore in blast furnaces burning fossil fuels. To address climate change, we need to build low-carbon sources quickly and in great numbers. However, to achieve circular material flows and build low-carbon power sources from scrap and renewable electricity, we would have to do the opposite: slow down the development of a low-carbon power grid.

Image: Steel foundations for off-shore wind turbines. Image by Glen Wallace, Wikimedia Commons (CC BY 2.0).

A well-cited study from 2013 concluded that if wind and solar power would supply 25,000 Twh of electricity – which corresponds to total global electricity demand in 2021 – we need about 3,200 Mt of steel to build the power plants alone.³³⁴⁵ Global electricity demand is projected to grow to between 52,000 and 71,000 terawatt-hours in 2050, which would increase the extra steel demand to between 6,400 and 8,960 Mt.⁴⁶ Spread out over the lifetime of solar panels and wind turbines (25 years), we would have to produce 256 to 358 Mt extra steel per year to make wind turbines and solar panel structures – comparable to the steel demand for passenger cars (195 Mt) and other transportation modes (98 Mt) combined.

That is still a very optimistic estimation. Electricity demand only makes up around 20% of total energy demand. If the total energy demand (177,000 Twh in 2021) would be supplied by wind and solar, we would need 22,400 Mt of steel. That’s an extra 896 Mt steel per year – as much as the global production in the early 2000s. You could argue that electricity can be used more efficiently than fossil fuels, for example, in cars and heating systems. However, at the same time, total energy demand is expected to rise further, countering the gains made by increased energy efficiency.

The high-tech solutions

The steel industry counts on technological solutions to make steel production carbon neutral. One option is to replace coal by gas, an approach that is already common in the Middle East and North America. Gas-based steelmaking results in somewhat lower carbon emissions, but they are still much higher than in the case of the electric arc furnace. Therefore, most attention goes to hydrogen, which can replace purified coal (coke) as a reducing agent in a direct reduction shaft furnace.⁴⁷ However, hydrogen-based steelmaking does not offer an escape from the catch-22 because it further increases the need for a steel-intensive infrastructure.

The production of hydrogen is energy-intensive. It takes 50-55 kilowatt-hour to make 1 kg of hydrogen and 60 kg of hydrogen to make 1 ton of steel.⁴⁷ The production of 1 ton of steel from hydrogen thus consumes 3,000 kWh of electricity, which is ten times higher than the electricity use of an electric arc furnace making steel from scrap. Consequently, hydrogen-based steelmaking requires roughly ten times more wind turbines and solar panels than scrap-based steel production – and thus ten times more steel. On top of this comes the steel for building the pipelines and storage tanks that are part of the hydrogen infrastructure.

Image: Worker in a blast furnace. Bundesarchiv, B 145 Bild-F079044-0020 / CC-BY-SA 3.0.

Carbon capture and storage, in which the carbon emissions of steelmaking plants are captured and then stored underground, faces the same problems. It requires a steel infrastructure and extra energy, thus indirectly raising the use of fossil fuels. Reverting to older, preindustrial steelmaking processes is not the answer either. Today’s blast furnace is essentially still the blast furnace from earlier centuries, only much more energy efficient.⁷

The low-tech solutions

The picture painted above seems to offer little hope for carbon-neutral steelmaking and power production. However, there is a low-tech solution that could achieve it. We could adjust steel production to the available scrap supply both in quantity and quality. That would allow us to produce all steel from scrap in electric arc furnaces, dramatically reducing energy consumption and eliminating almost all carbon emissions. Of course, the intent should not be to replace steel with plastic composites and aluminum because they are even more energy-intensive to produce. The only solution is to reduce material use overall.

We could adjust steel production to the available scrap supply both in quantity and quality.

Reducing the steel output and using more common steel grades would not bring us back to the Bronze Age. As noted, global end-of-life ferrous scrap availability was approximately 450 Mt in 2021, which would allow us to produce roughly one-quarter of the current steel output. Furthermore, the scrap supply will continue to rise for the next 40 years, enabling us to produce more and more low-emission steel each year. By 2050, scrap availability is expected to rise to about 900 Mt, almost half of today’s global steel production.⁴⁸ All that extra steel could be invested in expanding the low-carbon power grid without raising emissions first.

There is a lot of room to reduce the steel intensity of modern society. All our basic needs – and more – could be supplied with much less steel involved. For example, we could make cars lighter by making them smaller. That would bring energy savings without the need for energy-intensive high-grade steel. We could replace cars with bicycles and public transportation so that more people share less steel. Such changes would also reduce the need for steel in the road network, the energy infrastructure, and the manufacturing industry. We would need fewer machine tools, shipping containers, and reinforced concrete buildings. Whenever steel intensity is reduced, the advantages cascade throughout the whole system. Preventing corrosion and producing steel more locally from local resources would also reduce energy use and emissions.¹⁰¹⁴

The continuous growth of the steel output – the increasing steel intensity of human society – makes sustainable steel production impossible. No technology can change that because it’s not a technological problem. Like forestry can only be sustainable if the wood demand does not exceed the wood supply, steel is sustainable or not depending on the balance between (scrap) supply and (steel) demand. We may not be able to escape the Iron Age, but we have an option to escape the catch-22 that inextricably links steel production with fossil fuels.⁴⁹

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Forthcoming article, Kris De Decker, Low-tech Magazine. Subscribe to Low-tech Magazine’s newsletter. ↩︎
Idoine, N. E., et al. “World mineral production 2017-21.” (2023). https://nora.nerc.ac.uk/id/eprint/534316/1/WMP_2017_2021_FINAL.pdf ↩︎
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Colás, Rafael, and George E. Totten, eds. Encyclopedia of iron, steel, and their alloys (Online version). CRC Press, 2016. ↩︎ ↩︎ ↩︎
https://www.steelonthenet.com/consumption.html. Meanwhile the data on this page have been updated for 2023. ↩︎ ↩︎
Smil, Vaclav. Still the iron age: iron and steel in the modern world. Butterworth-Heinemann, 2016. ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
“Steel in buildings and infrastructure”, World steel association. https://worldsteel.org/steel-topics/steel-markets/buildings-and-infrastructure/ ↩︎ ↩︎
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Between 25 and 33% of the annual steel production is destroyed once in service by corrosion. See: Iannuzzi, M., and G. S. Frankel. “The carbon footprint of steel corrosion.” npj Materials Degradation 6.1 (2022): 101. https://www.nature.com/articles/s41529-022-00318-1.pdf ↩︎ ↩︎ ↩︎
“Iron”, Encyclopedia Britannica ↩︎
The potential of hydrogen for decarbonising steel production. European Parliament: https://www.europarl.europa.eu/RegData/etudes/BRIE/2020/641552/EPRS_BRI(2020)641552_EN.pdf ↩︎
Lenzen, Manfred, and Christopher Dey. “Truncation error in embodied energy analyses of basic iron and steel products.” Energy 25.6 (2000): 577-585. & Oda, Junichiro, et al. “International comparisons of energy efficiency in power, steel, and cement industries.” Energy Policy 44 (2012): 118-129. Both found in: Smil, Vaclav. Still the iron age: iron and steel in the modern world. Butterworth-Heinemann, 2016. ↩︎
“Pedal to the metal”, Caitlin Swalec, Global Energy Monitor, June 2022. https://globalenergymonitor.org/wp-content/uploads/2022/06/GEM_SteelPlants2022.pdf ↩︎ ↩︎
Yellishetty, Mohan, P. G. Ranjith, and A. Tharumarajah. “Iron ore and steel production trends and material flows in the world: Is this really sustainable?.” Resources, conservation and recycling 54.12 (2010): 1084-1094. ↩︎ ↩︎
See, for example: Hatayama, Hiroki, et al. “Outlook of the world steel cycle based on the stock and flow dynamics.” Environmental science & technology 44.16 (2010): 6457-6463. This paper predicted steel demand to reach 1.8 billion tonnes only by around 2025. ↩︎
De Beer, Jeroen. Potential for industrial energy-efficiency improvement in the long term. Vol. 5. Springer Science & Business Media, 2013. ↩︎
Wang, R. Q., et al. “Energy saving technologies and mass-thermal network optimization for decarbonized iron and steel industry: A review.” Journal of Cleaner Production 274 (2020): 122997. ↩︎
About 5% of global steel is produced by a third method: gas-based direct iron reduction. These furnaces use gas instead of coal and have therefore lower carbon emissions. However, emissions are still much higher than in the case of the electric arc furnace. Gas-based steelmaking mainly happens in the Middle East and North America. ↩︎
He, Kun, and Li Wang. “A review of energy use and energy-efficient technologies for the iron and steel industry.” Renewable and Sustainable Energy Reviews 70 (2017): 1022-1039. This source gives a value of 1-1.5 GJ/ton of crude steel. ↩︎ ↩︎
This also holds true for many other materials. See: “How circular is the circular economy?”, Kris De Decker, Low-tech Magazine, November 2018. https://qelnixcor.cloud/2018/11/how-circular-is-the-circular-economy/ ↩︎
Kong, Xianghui, et al. “Steel stocks and flows of global merchant fleets as material base of international trade from 1980 to 2050.” Global Environmental Change 73 (2022): 102493. ↩︎
ODPADKA, PROIZVODNJA JEKLA IZ JEKLENEGA. “Scrap-based steel production and recycling of steel.” Materiali in tehnologije 34.6 (2000): 387. ↩︎ ↩︎ ↩︎ ↩︎
In the West, the expansion of steel use happened over a period of 150 years, in tandem with technological evolution. In contrast, China compressed this technological evolution in just a few decades: shipping and railways, electrification, steel buildings, the car and the airplane, the internet, and renewable power technologies. There are still large parts of the world where the steel intensity of society is very low, such as India and Africa. There is thus still a lot of room for the growth of the steel output. Source: Smil, Vaclav. Still the iron age: iron and steel in the modern world. Butterworth-Heinemann, 2016. ↩︎
AHHS Application Guidelines, WorldAutoSteel. ahssinsights.org/news/intro ↩︎ ↩︎
Sverdrup, Harald Ulrik, and Anna Hulda Olafsdottir. “Assessing the long-term global sustainability of the production and supply for stainless steel.” BioPhysical Economics and Resource Quality 4 (2019): 1-29. ↩︎
Conseil, Laplace. “Impacts of energy market developments on the steel industry.” 74th Session of the OECD Steel Committee, Paris, France (2013). Found in: Smil, Vaclav. Still the iron age: iron and steel in the modern world. Butterworth-Heinemann, 2016. ↩︎
Deetman, Sebastiaan, et al. “Projected material requirements for the global electricity infrastructure–generation, transmission and storage.” Resources, Conservation and Recycling 164 (2021): 105200. ↩︎ ↩︎
How (Not) to Run a Modern Society on Solar and Wind Power Alone, Kris De Decker, Low-tech Magazine, September 2017. https://qelnixcor.cloud/2017/09/how-not-to-run-a-modern-society-on-solar-and-wind-power-alone/ ↩︎ ↩︎
Kleijn, René, et al. “Metal requirements of low-carbon power generation.” Energy 36.9 (2011): 5640-5648. ↩︎ ↩︎
Weißbach, Daniel, et al. “Energy intensities, EROIs (energy returned on invested), and energy payback times of electricity generating power plants.” Energy 52 (2013): 210-221. ↩︎ ↩︎ ↩︎
Chen, Zhenyang, Rene Kleijn, and Hai Xiang Lin. “Metal requirements for building electrical grid systems of global wind power and utility-scale solar photovoltaic until 2050.” Environmental Science & Technology 57.2 (2022): 1080-1091. ↩︎ ↩︎
Vidal, Olivier, Bruno Goffé, and Nicholas Arndt. “Metals for a low-carbon society.” Nature Geoscience 6.11 (2013): 894-896. The data are in the supplementary info: https://www.nature.com/articles/ngeo1993#Sec5 ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
“Energy”, American Iron and Steel Institute. https://www.steel.org/steel-markets/energy/ ↩︎
“Steel is the power behind renewable energy”, Arcelor Mittal. https://constructalia.arcelormittal.com/en/news_center/articles/steel-is-the-power-behind-renewable-energy#:~:text=Steel%3A%20a%20key%20material%20in%20a%20less%20carbon%2Dintensive%20world&text=Without%20steel%2C%20none%20of%20the,Schrijver%2C%20CEO%20of%20ArcelorMittal%20Projects. ↩︎
Topham, Eva, et al. “Recycling offshore wind farms at decommissioning stage.” Energy policy 129 (2019): 698-709. ↩︎ ↩︎ ↩︎
Gervásio, Helena, et al. “Comparative life cycle assessment of tubular wind towers and foundations–Part 2: Life cycle analysis.” Engineering structures 74 (2014): 292-299. & Rebelo, Carlos, et al. “Comparative life cycle assessment of tubular wind towers and foundations–Part 1: Structural design.” Engineering structures 74 (2014): 283-291. ↩︎
Assessing the significance of steel to the global wind industry, S&P Global, Commodity Insights. December 2021. https://www.spglobal.com/commodityinsights/en/ci/research-analysis/assessing-the-significance-of-steel-to-the-global-wind-industry.html ↩︎
Bolson, Natanael, Pedro Prieto, and Tadeusz Patzek. “Capacity factors for electrical power generation from renewable and nonrenewable sources.” Proceedings of the National Academy of Sciences 119.52 (2022): e2205429119. https://www.pnas.org/doi/10.1073/pnas.2205429119 ↩︎
This result corresponds well with Vidal, Olivier, Bruno Goffé, and Nicholas Arndt. “Metals for a low-carbon society.” Nature Geoscience 6.11 (2013): 894-896. The data are in the supplementary info: https://www.nature.com/articles/ngeo1993#Sec5 ↩︎
For off-shore wind turbines, the lifetime of the foundations is estimated to be 100 years, so in principle they could serve for replacement wind turbines of the same size. On the other hand, it is not self-evident that these steel foundations will eventually be recycled. First, only around 10% of decommissioning costs can be recovered by recycling the metal, meaning that it is not economically and perhaps even energetically interesting to do it. Second, in some cass marine life has flourished around the foundations. The four offshore wind farms that had been decomissioned in 2019 lasted for 15, 18, 20 and 26 years. Source: Topham, Eva, et al. “Recycling offshore wind farms at decommissioning stage.” Energy policy 129 (2019): 698-709. ↩︎
See https://www.fedsteel.com/insights/steels-role-in-the-us-power-infrastructure/ ↩︎
See https://industry.arcelormittal.com/products-solutions/Products_in_the_spotlight/magnelis ↩︎
Maziasz, Philip J., and Jeremy T. Busby. Properties of austenitic stainless steels for nuclear reactor applications. Oak Ridge National Lab.(ORNL), Oak Ridge, TN (United States), 2012. ↩︎
Part of this has already been built. The researchers start from the solar and wind power production in 2013, which was 400 Twh, while both power sources produced 2,894 Twh in 2021. ↩︎
Electricity consumption worldwide from 2000 to 2022, with a forecast for 2030 and 2050, by scenario. Statista. https://www.statista.com/statistics/1426308/electricity-consumption-worldwide-forecast-by-scenario/#:~:text=According%20to%20a%20recent%20forecast,on%20the%20energy%20transition%20scenario ↩︎
Bhaskar, Abhinav, et al. “Decarbonizing primary steel production: Techno-economic assessment of a hydrogen based green steel production plant in Norway.” Journal of Cleaner Production 350 (2022): 131339. ↩︎ ↩︎
Scrap use in the steel industry, World Steel Association. May 2021. https://worldsteel.org/wp-content/uploads/Fact-sheet-on-scrap_2021.pdf ↩︎
Another motivation for reducing the steel intensity of modern society is to limit the consequences of geopolitical conflicts. The more steel we produce for peaceful purposes, the more steel becomes available for war and destruction. Remarkably, the production of military equipment is absent from modern steel statistics, and if mentioned, its share is very low. However, in times of war, steelmaking facilities switch to producing steel for military purposes. The steel industry can thus be converted into a weapons industry at any moment, and there is now a lot more steel production capacity available than there has ever been in history. ↩︎