Metals are often said to be “non-renewable.” It’s suggested there’s no other way to deal with it. But we can renew them—though what’s usually meant is reuse or recycling: renewed use of something that already exists. And that, in turn, is called circular. But that’s not quite correct: it’s prolonged use, or rather, linear slowdown. That’s still good, but it’s not circular. So, the terms “renewable” or “non-renewable” are not quite right in this context, and they create confusion.
These terms can carry multiple meanings and suggest that metals and organic materials are equivalent in this regard. As a result, “renewable” is also a misleading term when applied to organic substances that do truly renew themselves—referring not to their application but to their stock. Take wood, for example: “renewable” could be interpreted as meaning you can dismantle a wooden house and reuse it. That’s technically true, but not the intended meaning of the word. Organic materials are regrowable: literally, they grow out of the ground; and figuratively, their stocks increase.
And metals? Well, interest groups would have you believe we can only deplete them, that we can merely reuse them. But that’s not an accurate picture: even metal stocks can grow again!
“All things flow,” someone once said—and this “flow” deposits new ore concentrations on the Earth’s surface from time to time. So, they too can “regrow,” meaning the reserves can increase again. Granted, over very long periods—but still. The idea of a so called ‘technological’ cycle limited to extended use is nonsense. Technology is universal; it also applies to the bio-cycle. What’s really at play here is a geo-cycle, driven by tectonic and volcanic processes.
The Question then is: How Much? How much metal is added each year? That would represent our sustainable “budget,” allowing us to live without depleting the reserve. Others have looked into this, such as Odum, who tried to calculate the entire formation process fifty years ago [1], or more recently, Bardi [2]: “In tens or hundreds of millions of years, a large fraction of what we have dug from the Earth will have been transported by the oceanic conveyor belt to the edges of the continents and recycled in the mantle. Part of it will have returned to the surface in the form of ores and deposits…”
Bardi suggests we measure this in terms of the energy required to not wait for that natural deposition, but to extract metals directly from seawater (where most metal ions end up). From there, you can estimate the solar energy needed, and also the space-time context (output per year per field). I initially did this too, but it’s a bit cumbersome.
There’s a simpler, more direct way: calculate the actual flow rate of metal [paper see 3]. The example is described in the new book as well: The Space-Time economy – (embodied) Land as the capital for post fossil living.[4]
I take a simplified route via shallow iron deposits along water streams—so-called “bog iron” deposits. You’ve likely seen them: reddish banks of small streams. In earlier times, they were a key source of iron. Which is why data on these “oer” banks exist, such as this: it can take just a few decades for a bog iron bank to form.*
A Wageningen University report on bog iron in the Netherlands says: “Translated to the amount of bog iron processed between 1700 and 1900 in the Achterhoek region, we arrive at approximately 450,000 tons.” Combining this and other data gives the following estimate:
Suppose this processed “bog iron,” originating from eastern Netherlands, is attributed to the area of Groningen, Friesland, Overijssel, Drenthe, and Gelderland. Assume (conservatively) that half of it grew over “decades,” and the rest was older stock. Then about 225,000 tons would have regrown over an area of 16,500 km². That’s 136 kg per hectare, and over 200 years, about 0.7 kg per hectare per year.
That’s the flow rate, or the space-time concentration rate of iron! (Excluding the energy from oak trees needed for smelting—see the book. [4])
This is a maximum, and likely an optimistic estimate: there are limited known sites, and such large reserves probably built up over longer periods. And geological iron ore deposits formed by tectonic and volcanic activity are even slower. But this “bog iron” estimate gives us a first reference value, at least a ceiling. Staying below that rate would be a huge step toward balanced resource use.
Practical Implications? If the flow rate of iron is 0.7 kg/ha/year—the rate at which reserves regrow—then producing a basic bicycle of about 10 kg would require 14 years of iron yield from one hectare. Now consider that each person in the Netherlands has about 0.2 ha of available space/land. So per person, it would take 5 times as long—about 70 years—for the iron needed for one bike.
In other words: just one bike per lifetime. And no car, no BBQ—nothing else made of iron. So the bike we already have, which can last a lifetime, is incredibly valuable (though not yet valued like gold…).
This may not be entirely realistic—limiting ourselves to one bike per life—but it does highlight the need for extreme thrift. (It also supports my long-held argument: convert existing cars to electric instead of building new ones. That would save a lot of space-time.)
Similar estimates can be made for other metals (next week: copper), and minerals can also be evaluated as constant streams. In this way, all resources can be classified by their “flow speed.” Some cycles are fast—like fiber materials—while others, like metals, are extremely slow.**
As Heraclitus said: Panta Rhei. A truth—and perhaps also advice, as Lao Tse added: Let things flow (Wu Wei). So the speed of life is indirectly determined by the flow rate—e.g., one bike per person. From 5 km/h walking to 15 km/h cycling—in thousands of years of evolution. But that’s about as far as it goes.
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* These bog iron deposits are essentially iron leached through groundwater, intercepted and deposited before reaching the ocean.
** Optimistically, the “bog iron” route yields about 35 million tons of iron globally. Current global consumption? 2,160 million tons—a factor of 60 more.
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Side Notes:
- Metals can regrow! Stocks can increase. So “renewable” can actually mean “regrowable”! Unlike energy: it doesn’t deplete, nor can it be renewed—only the capacity for transformation is lost. Materials, on the other hand, can be reused, though this requires energy input. There is a constant flow of usable energy—from the sun. “Renewable energy” refers usually to this ongoing external stream: if not used, it’s lost, but it keeps flowing. Raw materials do not have such an infinite stream—only a cyclical one, whose concentrated stocks must continually be replenished, and that’s space-time dependent.
- Think one step further: energy isn’t lost, but its ability to do work is. The same applies to matter—it loses structural integrity when it degrades. Unless, of course, we put in massive energy to turn for example dust back into bricks. The reverse is also true in energy: cooled air can be reheated with energy input. So in essence, there is no fundamental difference between energy and matter. But within a closed system, both degrade in quality—that’s thermodynamics. Only the constant solar influx from outside the system keeps Earth and the cycles going. And unless used or captured in materials, most of that energy flow is lost. Hence, all internal-system solutions that don’t use solar input (directly or indirectly) are inherently degrading the system.
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References
[1] Odum, Howard, Environmental Accounting: Emergy and Environmental Decision Making, 1995 ISBN: 978-0-471-11442-0
[2] Before the Collapse, A Guide to the Other Side of Growth , Ugo Bardi, 2019, ISBN978-3-030-29037-5
[3] paper: https://iopscience.iop.org/article/10.1088/1755-1315/1078/1/012125
[4] book: The Space Time economy – (English e-book) https://www.ribuilt.eu/product/the-space-time-economy/ Dutch: Post Fossiel Leven: https://www.ribuilt.eu/product/post-fossiel-leven/
