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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. ↩︎
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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. ↩︎
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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/ ↩︎
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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. ↩︎
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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. ↩︎

Thematic Book Series: How to Downsize a Transport Network?

Sat, 07 Oct 2023 00:00:00 +0000

Image: Book cover. [How to downsize a transport network?](https://www.lulu.com/shop/kris-de-decker/how-to-downsize-a-transport-network/paperback/product-42n4p7.html?q=&page=1&pageSize=4), Kris De Decker, 166 pages, Low-tech Magazine, 2023.

Fast and cheap transportation props up industrial societies, both for the moving of people and cargo. However, our transport networks are very wasteful of energy and utterly dependent on fossil fuels. In this series of articles, Low-tech Magazine critically examines the call for electrified vehicles, which depend on unsustainable batteries and infrastructures.

Much more important than the chosen power source is vehicle design: size, weight, speed, acceleration, and comfort level. Furthermore, public transport is more resource efficient, and we could electrify it without batteries.

The book’s second part deals with long-distance transportation: planes, trains, sailing ships, and ocean liners. By placing transportation technology in a historical context, Low-tech Magazine challenges our high-tech approach to sustainability and highlights the possibilities of alternative solutions.

Contents table:

How to Downsize a Transport Network: the Chinese Wheelbarrow
The Citroën 2CV: Cleantech from the 1940s
The Status Quo of Electric Cars: Better Batteries, Same Range
Electric Velomobiles: as Fast and Comfortable as Automobiles, but 80 times more Efficient
Get Wired again: Trolleybuses and Trolleytrucks
High Speed Trains are Killing the European Railway Network
Life Without Airplanes: from London to New York in 3 Days and 12 Hours
How to Design a Sailing Ship for the 21st Century?

How to downsize a transport network?, Kris De Decker, 166 pages, Low-tech Magazine, 2023. Ebook edition.

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

Other thematic books in the series:

How to build a low-tech internet?, Kris De Decker, 162 pages, Low-tech Magazine, 2023. Ebook edition.

Heating people, not spaces, Kris De Decker, 142 pages, Low-tech Magazine, 2023. Ebook edition.

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

How to Design a Sailing Ship for the 21st Century?

Tue, 11 May 2021 00:00:00 +0000

On board the ship *Garthsnaid* at sea. A view from high up in the rigging. Image by Allan C. Green, circa 1920.

The sailing ship is a textbook example of sustainability. For at least 4,000 years, sailing ships have transported passengers and cargo across the world’s seas and oceans without using a single drop of fossil fuels. If we want to keep travelling and trading globally in a low carbon society, sailing ships are the obvious alternative to container ships, bulk carriers, and airplanes.

However, by definition, the sailing ship is not a carbon neutral technology. For most of history, sailing ships were built from wood, but back then whole forests were felled for ships, and those trees often did not grow back. In the late nineteenth and early twentieth century, sailing ships were increasingly made from steel, which also has a significant carbon footprint.

The carbon neutrality of sailing in the 21st century is even more elusive. That’s because we have changed profoundly since the Age of Sail. Compared to our forebears, we have higher demands in terms of safety, comfort, convenience, and cleanliness. These higher standards are difficult to achieve unless the ship also has a diesel engine and generator on-board.

The revival of the sailing ship

The sailing ship has seen a modest revival in the last decade, especially for the transportation of cargo. In 2009, Dutch company Fairtransport started shipping freight between Europe and the Americas with the Tres Hombres, a sailing ship built in 1943. The company remains active today and has a second ship in service since 2015, the Nordlys (built in 1873).

Since then, others have joined the sail cargo business. In 2016, the German company Timbercoast started shipping cargo with the Avontuur, a ship built in 1920. ¹ In 2017, the French Blue Schooner Company started transporting cargo between Europe and the Americas with the Gallant, a sailing ship that was built in 1916. ² All these sailing ships were constructed in the twentieth or nineteenth century, and were restored at a later date. However, a revival of sail cannot rely on historical ships alone, because there’s not enough of them. ³

The Noach, built in 1857.

At the moment, there are at least two sailing ships in development that are being built from scratch: the Ceiba and the EcoClipper500. The first ship is being constructed in Costa Rica by a company named Sailcargo. She is built from wood and inspired by a Finnish ship from the twentieth century. The second ship is designed by a company called EcoClipper, which is led by one of the founders of the Dutch FairTransport, Jorne Langelaan. Their EcoClipper500 is a steel replica of a Dutch clipper ship from 1857: the Noach.

“Old designs are not necessarily the best", says Jorne Langelaan, “but whenever proven design is used, one can be sure of its performance. A new design is more of a gamble. Furthermore, in the 20th and 21st century, sailing technology developed for fast sailing yachts, which is an entirely different story compared to ships which need to be able to carry cargo.”

More economical sailing ships

These two ships – one under construction and one in the design phase – have the potential to make sail cargo a lot more economical than it is today. That’s because they have a much larger cargo capacity than the sailing ships currently in operation. As a ship becomes longer, her cargo capacity increases more than proportionally.

The EcoClipper500 is a full-scale replica of the Noach.

The 46 metre long Ceiba is powered by 580 m2 of sails and carries 250 tonnes of cargo. The 60 metre long EcoClipper500 is powered by almost 1,000 m2 of sails and takes 500 tonnes of cargo. For comparison, the Tres Hombres is not that much shorter at 32 metres, but she takes only 40 tonnes of cargo – twelve times less than the EcoClipper500. A larger ship is also faster and saves labour. The Tres Hombres requires a crew of seven, while the EcoClipper500 only has a slightly larger crew of twelve.

Life cycle analysis of a sailing ship

Although the EcoClipper500 is still in the design phase, she will be the focus of this article. This is because the company conducted a life cycle analysis of the ship prior to building it. ⁴ As far as I know, this is the first life cycle analysis of a sailing ship ever made. The study reveals that it takes around 1,200 tonnes of carbon to build the ship.

Half of those emissions are generated during steel production, and roughly one third is generated by steel working processes and other shipyard activities. Solvent-based paints as well as electric and electronic systems each account for roughly 5% of emissions. The emissions produced during the manufacturing of the sails are not included because there are no scientific data available, but a quick back-of-the-envelope calculation (for sails based on aramid fibres) signals that their contribution to the total carbon footprint is very small. ⁵

The EcoClipper500 has a carbon footprint of 2 grammes of CO2 per tonne-kilometre, which is five times less than the carbon footprint of a container ship.

If these 1,200 tonnes of emissions are spread out over an estimated lifetime of 50 years, then the EcoClipper500 would have a carbon footprint of about 2 grammes of CO2 per tonne-kilometre of cargo, concludes researcher Andrew Simons, who made the life cycle analysis for the ship. This is roughly five times less than the carbon footprint of a container ship (10 grammes CO2/tonne-km) and three times less than the carbon footprint of a bulk-carrier (6 grammes CO2/tonne-km). ⁶

Looking aft from aloft on the 'Parma' while at anchor. Alan Villiers, 1932-33. Villiers's work vividly records the period of early 20th century maritime history when merchant sailing vessels or ‘tall ships’ were in rapid decline.

Transporting one ton of cargo over a distance of 8,000 km (roughly the distance between the Caribbean and the Netherlands) would thus produce 16 kg of carbon with the EcoClipper500, compared to 80 kg on a container ship and 48 kg on a bulk carrier. The proportions are similar for other environmental factors, such as ozone depletion, ecotoxicity, air pollution, and so on.

Although the sailing ship boasts a convincing advantage, it may not be as big as you might have expected. First, as Simons explains, there’s scale. A container ship or bulk carrier enjoys the same benefits over the EcoClipper500 as the EcoClipper500 enjoys over the Tres Hombres. It can take a lot more cargo – on average 50,000 tonnes instead of 500 tonnes – and it needs only a slightly larger crew of 20-25 people. ⁷

Second, fossil fuel powered ships are faster than sailing ships, meaning that fewer ships are needed to transport a given amount of cargo over a given period of time. The original ship on which the EcoClipper500 is based, sailed between the Netherlands and Indonesia in 65 to 78 days, while a container ship does it in about half the time (taking the short cut through the Suez canal).

Building a fleet of sailing ships

There’s two ways to further lower the carbon emissions of sailing ships in comparison to container ships and bulk carriers. One is to build ships from wood instead of steel, such as the Ceiba. If the harvested trees are allowed to grow back (which the makers of the Ceiba have promised), such a ship may even be considered a carbon sink.

However, there’s a good reason why the EcoClipper500 will be made from steel: the company’s aim is to build not just one ship, but a fleet of them. Jorne Langelaan: “There are few shipyards who can deliver wooden ships nowadays. Steel makes it easier to build a fleet in a shorter period.”

A possible compromise would be a composite construction, in which a steel skeleton is clad with timber keel, planks, and deck. Andrew Simons: “This would reduce the carbon footprint of construction by half. It could also be feasible to make superstructures and some of the mast sections and spars from timber instead of steel.”

Driving sprays over the main deck of the 'Parma'. Alan Villiers, 1932-33.

Towards the future, another possibility to further decrease a sailings ship’s emissions per tonne-km is to build it even larger. While the EcoClipper500 has much more cargo capacity than the cargo sailing ships now in operation, she is far from the largest sailing ship ever built.

Historical ships such as the Great Republic (5,000 tonnes), the Parma (5,300 tonnes), the France II (7,300 tonnes), and the Preussen (7,800 tonnes), were more than 100 metres long and could take more than ten times the freight capacity of the EcoClipper500. Langelaan already dreams of a EcoClipper3000.

Passengers

Most cargo sailing ships travelling across the oceans today can also take some passengers. Fully loaded with cargo, the EcoClipper500 takes 12 crew members, 12 passengers, and 8 trainees (passengers who learn how to sail). If the upper hold deck is not used for cargo, another 28 trainees can join, so that the ship can take up to 60 people on board (with a smaller cargo volume: 480 m3 instead of 880 m3).

The carbon footprint for passengers amounts to 10 g per passenger-km, compared to roughly 100 g per passenger-km on an airplane.

Consequently, and since ocean liners have disappeared, the EcoClipper500 also becomes an alternative to the airplane. According to the results of the life cycle analysis, the carbon footprint for passengers on the EcoClipper500 amounts to 10 grammes per passenger-kilometre, compared to roughly 100 grammes per passenger-kilometre on an airplane. Transporting one passenger thus produces as much carbon emissions as transporting 1 tonne of freight.

Engine or not?

Importantly, the life cycle analysis of the EcoClipper500 assumes that there is no diesel engine on-board. On a sailing ship, a diesel engine can serve two purposes, which can be combined. First, it allows to propel the ship when there is no wind or when sails cannot be used, for example when leaving or entering a harbour. Second, combined with a generator, a diesel engine can produce electricity for daily life on board of the ship.

For most of history, energy use on-board of a sailing ship was not too problematic. There was firewood for cooking and heating, and there were candles and oil lamps for lighting. There were no refrigerators for food storage, no showers or laundry machines for washing and cleaning, no electronic instruments for navigation and communication, no electric pumps in case of leaks or fire.

However, we now have higher standards in terms of safety, health, hygiene, thermal comfort, and convenience. The problem is that these higher standards are difficult to achieve when the ship does not have an engine that runs on fossil fuels. Modern heating systems, cooking devices, hot water boilers, refrigerators, freezers, lighting, safety equipment, and electronic instruments all need energy to work.

Crewman of the 'Parma' with a model of his ship. Alan Villiers, 1932-33.

Modern sailing ships often use a diesel engine to provide that energy (and to propel the ship if necessary). An example is the Avontuur from Timbercoast, who has an engine of 300 HP, a 20 kW generator, and a fuel tank of 2,330 litres. Large sail training vessels and cruising ships have several engines and generators on-board. For example, the 48m long Brig Morningster has a 450 HP engine and three generators with a total capacity of 100 kW, while the 56m long Bark Europa has two 365 HP engines with three generators – and burns hundreds of litres of oil per day.

Depending on the lifestyle of the people on board, the emissions per passenger-km may rise to, or surpass, the levels of those of an airplane.

Obviously, the emissions and other pollutants of these engines need to be taken into account when the environmental footprint of a sail trip is calculated. Depending on the lifestyle of the people on board, the emissions per passenger-km may rise to, or surpass, the levels of those of an airplane. To a lesser extent, electricity use on-board also increases the emissions of cargo transportation.

Energy use on board a sailing ship

The EcoClipper500 has no diesel engine on board, which is a second reason to focus on this ship. Obviously, a sailing ship without an engine cannot proceed her voyage when there’s no wind. This is easily solved in the old-fashioned way: the EcoClipper500 stays where she is until the wind returns. A ship without an engine also needs tug boats – which usually burn fossil fuels – to get in and out of ports. For the EcoClipper500, these tug services account for 0.3 g/tkm of the total carbon footprint of 2 g/tkm.

Without a diesel engine, the ship also needs to generate all energy for use on board from local energy sources, and this is the hard part. Renewable energy is intermittent and has low power density compared to fossil fuels, meaning that more space is needed to generate a given amount of power – which is more problematic at sea than it is on land.

Renewing caulking on the poop of the 'Parma'. Alan Villiers, 1932-33.

To make the EcoClipper500 self-sufficient in terms of energy use, a first design decision was to shift energy use away from electricity whenever possible. This is especially important for high temperature heat, which cannot be supplied by electric heat pumps. The ship will have a pellet-stove on board to provide space heating, as well as a biodigester – never before used on a ship – to convert human and kitchen waste into gas for cooking. Thermal insulation of the ship is another priority.

Nevertheless, even with pellet-stove and biodigester (which themselves require electricity to operate), and with thermal insulation, energy demand on the ship can be as high as 50 kilowatt-hours of electricity per day (2 kW average power use). This concerns a “worst-case normal operation” scenario, when the ship is sailing in cold weather with 60 people on board. Power use will be lower in warmer weather and/or when less people are taken. During an emergency, the power requirements can amount to 8 kW, while more than 24 kWh of energy can be needed in just three hours.

Hydrogenerators

How to produce this power? Solar panels and wind turbines are only a small part of the solution. Producing 50 kWh of energy per day would require at least 100 square metres of solar panels, for which there is little space on a 60 m long sailing ship. Vulnerability and shading by the sails make for further problems. Wind turbines can be attached in the rigging, but their power output is also limited. The low potential of solar and wind power are demonstrated by the earlier mentioned sailing ship Avontuur. She has a 20 kW generator, powered by the diesel engine, but only 2.1 kW of solar panels and 0.8 kW of wind turbines.

The hydrogenerator is the only renewable power source that can provide a large sailing ship with enough energy for the use of modern technology on board.

The hydrogenerator is the only renewable power source that can provide a large sailing ship with enough energy for the use of modern technology on board. Hydrogenerators are attached underneath the hull and work in the opposite way as a ship’s propeller. Instead of the propeller powering the ship, the ship powers the propeller, which turns a generator that produces electricity. In spite of its name and appearance, the hydrogenerator is actually a form of wind energy: the sails power the propellers. Obviously, this only works when the ship is sailing fast enough.

Furling sail on the main yard of the Parma. Alan Villiers, 1932-33.

The EcoClipper500 will be equipped with two large hydrogenerators, for which Simons calculated the power output at different speeds, taking into account the fact that the extra drag they produce slows down the ship somewhat. He concludes that the EcoClipper500 needs to sail at a speed of at least 7.5 knots to generate enough electricity. At that speed, the hydrogenerators produce an estimated 2,000 watts of power, which converts to roughly 50 kWh of electricity per day (24 hours of sailing).

At a lower speed of 4.75 knots, the generators produce 350 watts, which comes down to 8.4 kWh of energy over a period of 24 hours – only 1/6th of the maximum required energy. On the other hand, at higher speeds, the hydrogenerators produce more energy than necessary. At a speed of almost 10 knots they provide 120 kWh/day, at a speed of 12 knots this becomes 182 kWh/day – 3.5 times more than needed.

Saltwater batteries

According to her hull speed, the EcoClipper500 will be able to sail a little over 16 knots at absolute top speed – this is double the minimum speed required to generate enough power. Achieving this speed will be rare, because it needs calm seas and strong winds from the right direction. Nevertheless, in good wind conditions, the ship easily sails fast enough to produce all electricity for use on board.

Good wind conditions can last for days, especially on the oceans, where winds are more powerful and predictable than on land. However, they are not guaranteed, and the ship will also sail at lower speeds, or find herself in becalmed conditions – when hydrogenerators are as useless as solar panels in the middle of the night.

Because she has no engine, the EcoClipper500 faces a double problem when there’s no wind: she cannot continue her voyage, and she has no energy to maintain life on board.

Because she has no engine, the EcoClipper500 faces a double problem when there’s no wind: she cannot continue her voyage, and she has no energy to maintain life on board. The first problem is easily solved but the second is not. Life on board goes on, and so there is a continued need for power. To provide this, the ship needs energy storage.

To cover the needs for three days drifting in cold weather, an energy storage of 150 kWh would be required, not taking into account charge and discharge losses. Five or seven days of energy use on-board would require 250 to 350 kWh of storage. For emergency use, another 25 kWh of energy storage is needed.

Scraping the deck onboard the 'Parma'. Alan Villiers, 1932-33.

Not having an engine, generator and fuel tank saves space on board, but this advantage can be quickly lost again when one starts to add batteries for the hydrogenerators. Lithium-ion batteries are very compact, but they cannot be considered sustainable and bring safety risks. That’s why Jorne Langelaan and Andrew Simons see more potential in – very aptly – saltwater batteries, which are non-flammable, non-toxic, easy to recycle, have wide temperature-tolerance, and can last for more than 15 years. Like the biodigester, they have never been used on a sailing ship before.

Unlike lithium-ion batteries, saltwater batteries are large and heavy. At 60 kg per kWh of storage capacity, a 150 kWh battery storage would add a weight of 9 tonnes, while a 350 kWh storage capacity would add 21 tonnes. Still, this compares favourably to the total cargo capacity (500 tonnes), and the batteries can serve as ballast if they are placed in the lower part of the ship’s hull. The space requirements are not too problematic, either. Even a 350 kWh energy storage only requires 14 to 29m3 of space, which is small compared to the 880m3 of cargo volume.

The emissions that are produced by the manufacturing of the hydrogenerators, biodigester, and batteries are not included in the life cycle analysis of the ship, because there are no data available. However, these emissions must be relatively small. Hydrogenerators have much higher power density than wind turbines, and thus a relatively low embodied energy. A quick back-of-the-envelope calculation learns that the carbon footprint of 350 kWh saltwater batteries is around 70 tonnes of CO2. ⁸

Human Power

There’s another renewable power source and energy storage on board of the EcoClipper, and that’s the humans themselves. Like the pellet stove and the biodigester, the use of human power could reduce the need for electricity. Nowadays, cargo ships and most large sailing ships have electric or hydraulic winches, pumps, and steering gear, saving manual labour at the expense of higher energy use. In contrast, EcoClipper sticks to manual handling of the ship as much as possible.

Crew at the capstan of the Parma, weighing anchor. Alan Villiers, 1932-33.

Simons and Langelaan are also considering the addition of a few rowing machines, coupled to generators, to produce emergency power. Two rowing machines could provide roughly 400 watts of power. If they are operated around the clock in shifts, they could supply the ship with an extra 9.6 kWh of energy per day (ignoring energy losses) – one fifth of the total maximum electricity use.

In fact, as I tell Simons and Langelaan ten rowing machines operated continually in shifts would provide as much power as the hydrogenerators at a speed of 7.5 knots. If there are 60 people on board, and everybody would generate power for less than one hour per day, no hydrogenerators and batteries would be needed at all. “A very interesting thought”, answers Simons, “but what impression would we be painted with?”

Hot Showers?

Even with a biodigester, hydrogenerators, batteries, and rowing machines, the passengers and crew on board the EcoClipper500 would be far short of luxurious, and perhaps too short of comfortable for some. For example, if 60 people on board the ship would take a daily hot shower – which requires on average 2.1 kilowatt-hours of energy and 76.5 litres of water on land – total electricity use per day would be 126 kWh, more than double the energy the ship produces at a speed of 7.5 knots.

The ship could supply this energy at a higher sailing speed, but there would also be a need for 4,590 liters of water per day, a quantity that could only be produced from seawater – a process that requires a lot of energy. Even a crew of 12 taking a daily hot shower would require 25.2 kWh of energy per day, half of what the hydrogenerators produce at a sailing speed of 7.5 knots. The Bark Europa is the only sailing ship mentioned in this article that has hot showers in every (shared) cabin, but it is also the ship with the biggest generators and the highest fuel use.

On the forecastle head of the Parma in fine weather. Image by Alan Villiers, 1932.

Andrew Simons: “On the EcoClipper500 there needs to be a manageable compromise between energy use and comfort. Energy use on board will have to be actively managed. Resources are finite, just like for the planet. In many ways the ship is a microcosm of challenges that the wider world has to face and find solutions to.”

Jorne Langelaan: “At sea you are in a different world. It doesn’t matter anymore if you can take a daily shower or not. What matters are the people, the movements of the ship, and the vast wilderness of ocean around you”.

Measuring the right things

This article has compared the EcoClipper500 sailing ship with the average container ship, bulk carrier, and airplane in terms of emissions per tonne- or passenger-kilometer. However, these values are abstractions that obscure much more important information: the total emissions that are produced by all passengers and all cargo, over all kilometres.

The international ocean freight trade increased from 4 billion tonnes of cargo in 1990 to 11.2 billion tonnes in 2019, resulting in more than 1 billion tonnes of emissions. International air passenger numbers grew from 1 billion in 1990 to 4.5 billion in 2019, resulting in 915 million tonnes of emissions. Consequently, lowering the emissions per tonne- and passenger-kilometre is neither a necessity nor a guarantee for a reduction in emissions.

If we cut international cargo traffic more than fivefold, and passenger traffic more than tenfold, then the emissions of all container ships and airplanes would be lower than the emissions of all sailing ships carrying 11.2 billion tonnes of cargo and 4.5 billion of passengers. Vice versa, if we switch to sailing ships, but keep on transporting more and more cargo and passengers across the planet, we will eventually produce just as much in emissions as we do today with fossil fuel powered transportation.

The mizzen of the 'Grace Harwar'; view aft from the main crosstrees. Alan Villiers, 1932-33.

Of course, none of this would ever happen. The amount of cargo that was traded across the oceans in 2019 equals the freight capacity of 22.4 million EcoClippers. Assuming the EcoClipper500 can make 2-3 trips per year, we would need to build and operate at least 7.5 million ships, with a total crew of at least 90 million people. Those ships could only take 0.5 billion passengers (12 passengers and 8 trainees per ship), so we would need millions of ships and crew members more to replace international air traffic.

We should not be fooled by abstract relative measurements, which only serve to keep the focus on growth and efficiency.

All of this is technically possible, and as we have seen, it would produce less in emissions than the present alternatives. However, it’s more likely that a switch to sailing ships is accompanied by a decrease in cargo and passenger traffic, and this has everything to do with scale and speed. A lot of freight and passengers would not be travelling if it were not for the high speeds and low costs of today’s airplanes and container ships.

It would make little sense to transport iPhones parts, Amazon wares, sweatshop clothes, or citytrippers with sailing ships. A sailing ship is more than a technical means of transportation: it implies another view on consumption, production, time, space, leisure, and travel. For example, a lot of freight now travels in different directions for each next processing stage before it is delivered as a final product. In contrast, all sail cargo companies mentioned in this article only take cargo that cannot be produced locally, and which is one trip from producer to consumer. ⁹

This also means that even if sailing ships have diesel engines on board, they would still bring a significant decrease in the total emissions for freight and passenger traffic, simply because they would reduce the absolute number of passengers, cargo, and kilometers. We should not be fooled by abstract relative measurements, which only serve to keep the focus on growth and efficiency.

More about the EcoClipper500. Most images: Alan Villiers collection.

Between 1978 and 2004, the Avontuur was operated as sail cargo vessel under Captain Paul Wahlen. The Apollonia, originally built in 1946, is another cargo sailing ship in operation since 2014. It is 19.5 metres long and carries 10 tonnes of cargo. ↩︎
Very recently, Grain de Sail was built and launched for Trans-Atlantic shipping of wine and cocoa. She is a modern sailing ship without an engine, built from aluminium, and can take 35 tonnes of cargo. ↩︎
Andrew Simons: “There are plenty historical sailing ships, but either very costly to get into service as a regulatory compliant cargo vessel, because they are still used for other purposes, or not suitable.” ↩︎
The study can be downloaded when you subscribe to EcoClipper’s newsletter. The research is based on a typical life cycle analysis, but note that this is not a peer reviewed study. ↩︎
Unfortunately the envelope got lost. ↩︎
In the case of the EcoClipper, most of the emissions are produced during the construction of the ship, while in the case of bulk carriers and container ships, they are mainly produced during operation and fuel production. ↩︎
The largest container ships now take 190,000 tonnes of cargo. ↩︎
There is not much data available on saltwater batteries, but they are less energy-intensive to build than many other types of batteries. The calculation is based on an estimate of 66 kg CO2/kWh of storage capacity and three generations of batteries over a period of 50 years. ↩︎
Almost one third of all cargo transported are fossil fuels themselves. ↩︎