Phosphorus-free diet? Column in KompyuterrOnline #42

In my previous column I did not justify the claim that humanity will soon have to change its relationship with the environment. Frankly, this idea seems to me a kind of “common ground.” Yet even the discussion on the site showed that many thoughts need to be examined with full rigor.
Here I will discuss one simple statement. Many intelligent people involved in technological progress consider talks about the depletion of non‑renewable resources to be short‑sighted. History shows that as humanity develops, the relative importance of resources changes. Perhaps we should worry not about conserving current resources, but about accelerating the transition to a phase in which they will no longer be needed?
There is some partial truth to this approach, but to avoid the trap of misunderstanding, it is important to discuss the details carefully. Let us proceed unhurriedly.
The specificity of our species lies in the fact that, for its modern condition, non‑renewable resources are critically important.
Solar energy flows to Earth; on the planet’s surface this flow is repeatedly transformed and ultimately leaves it as low‑energy thermal radiation. This flow is converted by living matter, the atmosphere, and the hydrosphere, driving biogeochemical cycles across the globe. Unfortunately, the material cycle cannot be closed completely: some fraction of substances is always lost. Where does the “lost” material end up, for example, in a forest near Moscow? Rain and rivers carry it to the sea, where it is buried in sedimentary rocks.
Therefore, besides the solar energy flux, life on our planet depends on another flux that we have called **khtonic**. This is the dissipation of the Earth’s primordial, mother energy. This energy drives continental drift, uplifts mountains, and triggers volcanic eruptions. Khtonic forces raise sedimentary rocks from the ocean floor, expose them to the destructive action of organisms, water, and air, and thereby replenish the essential elements for life on the Earth’s surface.
Clear so far? All species except ours are embedded in some “cell” of this cycle. The activity of processes in each cell is limited by the energy and material fluxes entering it.
We (the fan‑fares!) have moved beyond the limits that constrain any other species. We use not only the solar energy currently pouring onto Earth, but also the energy that entered the planet in geological deep time. We now live primarily thanks to the energy of fossil fuels. And we must admit that this situation cannot be conserved for long.
In 1956 American geophysicist King Hubbard described the dynamics of oil production. Initially oil was used very little. Then it became the “blood” of the economy, and its extraction grew. New reserves were discovered, production expanded in known fields. Over time, discovered reserves will begin to decline. Rising oil prices will drive the development of increasingly complex fields, but sooner or later oil production will cease.
Since any process that grows at the beginning of its history and declines at the end must have a maximum somewhere in the middle, Hubbard (arbitrarily) suggested that the oil‑production curve should follow a Gaussian shape. For the United States the Hubbard peak was reached in 1971, and for the world as a whole, apparently, in 2006. Uncertainty about the timing of the peak is linked both to the influence of crises and to the fact that the real oil‑production curve has a considerably more complex form than a Gaussian.
Does the “end of oil” mean economic collapse? Probably not. Of course, rising oil prices can cause many economic perturbations, but one can hope they will not destroy civilization.
On the other hand, consider that a few centuries ago oil was not regarded as a strategic raw material. We know that technological development accelerates. Should we assume that in a century oil will be as important for us as it is today?
An analogy: Russia has become the main gas supplier to Europe, for which a gas valve is a more serious weapon than tanks and missiles. Yet one of the threats to its gas‑monopoly role is the technology for extracting shale gas. The largest deposits of this resource are in Ukraine and Poland. The harsher Russia squeezes the pipe, the stronger the incentives for its southwestern neighbors to develop shale energy.
Now imagine that the latest reports about a successful (and energetically profitable) implementation of cold nuclear fusion finally turn out to be true! How would this affect oil energy? How important is it to cling so tightly to the resources we use today?
Which resources are indispensable? For example, technological metals (according to the views of John Lifton). To build an aircraft you need titanium and rhenium. For batteries – lithium and lanthanum. For computers – germanium, gallium, indium, europium, and many others. For a hydrogen‑fuel‑cell vehicle – platinum and palladium. Why do these metals become more expensive? Because the amount of them accessible to humanity is extremely limited. Of course, there is a lot of them in Earth’s core, but extracting them would require more energy, technology, and surface reserves than are available.
Perhaps when humanity exhausts the supplies of platinum and palladium, it will develop catalysts, say, from silicon? Twenty minutes after writing the previous sentence I found an almost perfect confirmation of this idea. So let us hope that today’s critical needs for technological metals will weaken over time. Yet, likely, new critical materials will replace them.
Here I want to discuss in detail one extremely important technology.
This technology is undeniably critical. Its required elements must be supplied at any cost; their substitution is impossible. Consumption of these elements cannot be reduced below a certain level. Do you see what I am talking about? The very life itself, more precisely – the biological processes that underlie our existence.
Each cell’s metabolism requires a specific set of biogenic elements. The list is long, but they clearly differ in criticality. The most critical is phosphorus.
Phosphorus is absolutely essential for every cell. For instance, the backbone of DNA consists of a chain of monosaccharide residues linked by phosphoric‑acid groups.
Compare the phosphorus cycle in a natural forest and in a field. In a forest there is a certain phosphorus stock. Organisms eat each other, transferring phosphorus atoms. When they die, phosphorus returns to the soil, from where it quickly re‑enters living matter. Water running off the forest in heavy rain carries away some phosphorus, but the loss is small and is compensated by phosphorus released from weathering rocks.
In a field the situation is completely different. The harvest, which contains a substantial amount of phosphorus, is removed and taken elsewhere. If phosphorus loss is not compensated, field fertility will catastrophically decline. What to do? Apply fertilizers. Phosphorus is applied in quantities far exceeding the removal because excess phosphorus stimulates plant growth. Where does the fertilizer phosphorus come from? It is extracted from phosphorus‑bearing rocks. With the first rain, a significant portion of the applied phosphorus is washed off the field, carried into rivers (causing algal blooms), and ultimately ends up in the ocean. Thus, virtually all processes in the biosphere affect the phosphorus cycle.
As a curiosity, not long ago a gamma‑proteobacterium of the family Halomonadaceae was found in Mono Lake, California, which uses arsenic (including in its DNA) instead of phosphorus! The lake is poisoned with huge amounts of arsenic, yet life can adapt to such an environment. However, for us (and for the organisms we eat) arsenic is a potent toxin. We need phosphorus.
Humanity has repeatedly accelerated the transfer of phosphorus into sedimentary rocks. So far this process is balanced by excessive extraction from phosphorus‑bearing deposits. But will those deposits last long enough?
Valuable data on this are presented in the article by Alexey Gilyarov, which in turn recounts an editorial piece from *Nature*.
We have already passed the peak of phosphate‑fertilizer production. Their output is decreasing, and low‑grade, inconvenient, contaminated phosphorus sources are being developed. They will suffice for a few decades. And then?
No one really knows what will happen afterward. The phosphorus we have scattered throughout the biosphere and that has settled on the ocean floor has become inaccessible to us. To lift and concentrate it would require colossal energy expenditures – which are currently unavailable and, in general, not foreseeable.
How to measure phosphorus availability on planetary scales?
Planetary phosphorus availability = (Number of phosphorus atoms circulating in ecosystems + number of concentrated phosphorus atoms in exploitable rocks) / (number of dispersed phosphorus atoms in oceanic sediments). Clearly, with each passing year (or day, or hour!) phosphorus availability declines. Only a few processes counteract our activity of developing phosphate deposits and dispersing this element. Among them is the transport of phosphorus onto land via the guano of piscivorous birds. The largest stores of this decomposed guano accumulated in South America. This product is called guano (you can easily find a Russian term with a similar sound and meaning). Thus, South American guano reserves have been depleted – humans used them far faster than they could be replenished.
The main process that could increase planetary phosphorus availability is the uplift of bottom sedimentary rocks to the surface with subsequent erosion and exploitation. This process involves colossal khtonic energies. Nevertheless, it is orders of magnitude weaker than human activity! Over a year we disperse phosphorus that khtonic forces have concentrated over vast time spans.
The measures we can contemplate do not increase phosphorus availability; they only slow its decline. For example, we can use phosphate fertilizers more efficiently. In fact, even a significant rise in their price will have a beneficial effect. Prices have already started to increase, and it is clear that phosphate fertilizers will continue to become more expensive. Not yet to the point of selling gold to buy superphosphate, but already enough to make serious savings worthwhile.
Perhaps someday runoff from agricultural areas will be filtered through massive stands of algae, maybe even genetically modified ones. Algal biomass would bind phosphorus and other biogens, after which it would be harvested and used as fertilizer. Yet even this measure would only slow the decline of planetary phosphorus availability, not reverse it.
How to ensure a non‑depleting development of humanity against the backdrop of continuously decreasing phosphorus availability? I do not know, and I suspect no one does.
But we must think about it now.