## Introduction

Here we go again. Any time there is some kind of breakthrough in nuclear power generation, there are crowd cheers about our energy production problems being solved, or closed to being solved. And with every time this happens, I'm forced to remind people that no improvement in energy production will “solve” our energy issues, unless we tackle the growth in consumption. And since those improvements will more often than not lead to an increase in the growth rate of energy consumption, these breakthroughs —however locally promising they may be— will end up being deleterious on longer —but not even that much longer— time spans.

## Context

The news of the day is a breakthrough in nuclear fusion, with the National Ignition Facility at the Lawrence Livermore National Laboratory announcing fusion ignition, i.e. the ability to trigger a self-sustaining fusion process that produces more energy than it consumes.

This is wonderful news. It's a scientific and technological advancement that humans have been dreaming about for more than a century, and one that paves to way to a potentially cleaner and safer energy production mechanism than anything we've seen so far.

It's also still far from being anywhere close to actually be productive in that sense, as detailed by Michael Schirber in this article on APS (if not else because the amount of energy used to start the reaction is still orders of magnitude higher than the one released by the reaction).

Still it's an important result, and one that gives much better hope that the energy production based on nuclear fusion may actually be finally within reach, and that this may revolutionize energy production dramatically reducing its environmental impact, as well as its cost.

Unfortunately.

## The dangers within

I've said it before, but I will say it again, because apparently this is a point where repetita iuvant: no form of power generation bound by the 90PJ/kg limit will suffice unless we curb the rate at which energy consumption grows. It doesn't matter if it's fission or fusion. It doesn't matter how efficient the energy production is. The only thing that matters is that exponential growth is faster than our perception. And as I mentioned in the first post of this series, the cheaper and the cleaner the energy production is, the higher the risk is that its adoption will lead to a faster growth rate in energy consumption.

In scarcity, people are frugal; in abundance, wasteful.

You don't need to teach someone who can barely make ends meet how to conserve food, water, heat or money. Yet a billionaire will not care about fuel costing 3 times as much as before when choosing to fly somewhere on their private jet.

There's a reason why energy conservation and efficiency have become such a hot topic in the last 50 years: the 1970s energy crisis (which also gave a strong push to the investment in nuclear (fission) energy production, until the Chernobyl disaster in 1986 cooled off much of the enthusiasm). Why does this matter? Because the discourse in the last years has largely shifted from efficiency and lower consumption (or at least lower growth in consumption) to a wider-reaching ecological discourse (“green” energy, low emissions, you name it).

There are different reasons for this change in topic, ranging from a genuine interest into the increasing threat of global warming and anthropic influence on climate change to the easier manipulation of the discourse into a business opportunity (“greenwashing” and friends). But the shift in attention is deleterious: not because reducing pollution is bad, but because pollution and the energy crisis are deeply interconnected by … energy consumption growth.

Let's pretend for a moment that tomorrow nuclear fusion became commercially viable, providing us with the cheapest, lowest-environmental-impact energy source we could have dream of. Let's pretend that with a single flip of a switch all energy consumption could be switched over to this cheap, low-impact source. This would absorb instantly a sizable fraction —I'd even go as far as say: the majority if not all— of the clamor about the environment, the carbon footprint, and all the “hot takes” that have replaced in the public discourse the only thing that really matters: energy consumption growth.

In such a scenario, it doesn't matter if a billionaire's private jet or yacht consumes in a year as much as half the population of the country they live in: there's so much cheap energy, and the higher consumption has so little impact that … who cares? Very few care now that it has an enormous impact on the environment and it risks depriving more important resources from having access to cheaper energy; how much would people care when it wouldn't?

In such a scenario, there's simply no interest in tackling the fundamental problem. In fact, quite the opposite, we can expect a radical upturning of the perspective from the general population: if energy is so easy to obtain and it has so little environmental impact, why would it even matter to keep its consumption in check, or to request that it be kept in check from government bodies? The most likely outcome of such a scenario is a sudden jump in energy consumption growth, as the limiting factors of cost and pollution prevention regulation are removed: from the rest of the world catching up to the “Western” standards of living more quickly to the “West” coming up with even higher-maintenance standards to compensate for the environmental damage of the last centuries (air conditioning everywhere, massive desalinization plants for fresh water, pervasive augmented reality, you name it, it'll be there).

And the net effect of this will be catastrophic, because no energy source can sustain exponential consumption growth for long, and by the time people realize that even the nuclear fusion fuel can run out it will be too late —again— and the collapse will be so much harder.

## “The most abundant element in the universe”

Much of the enthusiasm behind nuclear fusion comes from fallacies similar to the ones we've already discussed in our previous chapter of this series: material abundance and constant consumption rates. And we've seen already that at the current growth rate the mass of our entire solar system won't last 30 centuries, regardless of energy production system (and assuming optimistically 100% efficient mass-to-energy conversion). And we've seen some interesting computations on the EET for fission fuel. So this time we'll play around with the numbers for fusion.

One of the biggest and most dishonest talking points of fusion fans is that since the fuel is hydrogen, «the most abundant element in the universe», it's virtually impossible to run out: for all intents and purposes, it will last “forever*”.
(*conditions may apply)

We already know that no matter how large the amount of fuel is, as long as it's finite and the consumption keeps growing exponentially (i.e. at a constant rate) it'll run out —and much earlier than predicted (how does 50 centuries sound for the entire mass of the galaxy converted to energy at 100% efficiency, again?), but where the talking point fails miserably is that while it's true that hydrogen is the most abundant element in the universe (estimated around 75% of matter is hydrogen), or even the solar system, it is not the most abundant element on this planet. (Why? Because most of the hydrogen in the universe is in the stars where it's already being used to run a nuclear fusion process!)

And the statistics are even worse if we look at “free hydrogen”, rather than hydrogen in other molecules (such as water or hydrocarbons). If we look at the abundance of hydrogen on Earth, it barely makes the top-10 in abundance for the crust, hidden in that 1.2% of “other trace elements”. In the atmosphere, it's even more rare: at ground level it's 0.6 parts per million (PDF warning), and we have to climb to the exosphere (starting approximately 700 km above sea level) to find it in more consistent concentrations … in a medium so rarefied it doesn't even behave like a gas anymore.

I'm sure you can see where this is going, and it shouldn't be a surprise, when we've already seen in the previous chapters how quickly we'd run out of fuel on Earth regardless of energy generation method. But wait, there's more!

Nuclear fusion doesn't use “classic” hydrogen (aka protium), actually: the most important elements for the fusion process are deuterium (around 2 in 10,000 hydrogen atoms) and tritium, the hydrogen isotopes with extra neutrons (1 and 2 respectively), and if the “successful” (for appropriate definitions thereof) experiment that renewed the enthusiasm in the fusion process recently is any indication, tritium is of particular importance (although in theory we could do without). And tritium is also the rarest of the isotopes: due to its 12-year half-life, it's barely found in nature (we're talking 1 in ${10}^{18}$ hydrogen atoms, at scale), and is more typically produced as a byproduct of other processes —such as nuclear fission, or other fusion processes.

I'll leave it as an exercise to the reader this time to estimate the mass of the available “free” molecular hydrogen and the corresponding EET for fusion power generation at current (or higher!) growth rates. After three chapters, and with the help of the form in the second chapter of the series, there shouldn't be any need for hand-guiding you through the process.

## The not-so-clean energy source

Of course once we run out of molecular hydrogen —in contrast to other fuels for power generation— there are several orders of magnitude of fuel still available. The problem is that accessing this destroys the second myth peddled by nuclear fusion supporters: that fusion is the cleanest form of energy generation, even more so than fission, and without the risks deriving from radioactive waste typically associated with fission.

Leaving aside that any talk about the cleanliness and riskiness of the process (e.g. per unit of energy produced or per unit of power generation) is pure speculation, and will remain so until the first commercially viable fusion power generation plants are finally deployed and have proven themselves for a few decades at least, even from a purely theoretical standpoint the myth is on shaky ground. Indeed, the myth is tightly bound to the one about the abundance of hydrogen: assuming you have plenty of molecular hydrogen available, the fusion process is indeed one of the least impactful forms of energy generation. The question is: how do you get that hydrogen in the first place?

Fusion would be really clean if we could just have a passive collector of molecular hydrogen from the atmosphere, and extremely efficient ways to prepare it for the fusion process (e.g. deuterium extraction, tritium generation), but we have neither. And even if we did, where would we get the hydrogen from when we run out of the free molecular hydrogen in the air, something that is bound to happen sooner rather than later if we get seriously invested on fusion?

And this is where things become interesting: while there's definitely room to invest in the capturing of the hydrogen released e.g. by volcanic activity, the more readily accessible “stores” of hydrogen are water, carbohydrates and hydrocarbons. And the processes to extract hydrogen from these have two important downsides in the context of our discussion: they are either very energy intensive (which brings us back to the increased energy consumption, or in a restricted view to a lower power generation efficiency), or quite environmentally unfriendly (e.g. combustion, water depletion), when not both.

I can already see the objections about how these would still be less of an environmental problem than, say, the drilling and mining required for fossil and fission fuel, and while that may be the case now, I'd like to revisit this when the requirements for hydrogen extraction/production raise to the needs of our present and future power generation requirements.

## Nuclear will not save us

I'll refrain from going on a tirade that would just repeat the conclusion of my previous chapter, but a recap is appropriate still.

The fuel employed, the process used to produce the energy don't matter. The single most important factor is how quickly energy consumption grows. And the cheaper the energy generation is, the more quickly its consumption will grow. If anything, a more efficient and cleaner energy production method is more likely to boost energy consumption, that will result in an even harder fall when the ceiling is hit.

Still, I'm glad for the progress in the research on nuclear fusion, and while I believe that the press release is laced with excess optimism, I'm looking forward to the time, a few more decades from now, when the technology will have progressed enough to turn fusion into a viable power source. Any option we have at our disposal to minimize the environmental impact of energy generation and optimize energy production with the means we have our disposal is more than welcome.

Of course, in those few decades our global power consumption will have doubled again (at least), unless the global economy suffers another major collapse. (It's fascinating, really: take any year-over-year global power consumption change and you can identify recessions simply by looking at when it energy consumption change dropped close to zero —or worse, went into the negatives.)

And if we don't fix that, nuclear will not save us.