2024-11-21 21:01:24
The “carrying capacity” of the Earth is the academic term for how many humans the Earth can support without going awry.
What can make things go awry? The most obvious limits are space, food, water, and energy, but we already saw in the previous article that these factors would not prevent us from reaching 100B people. Yet the Earth could have many more limits: global warming, lack of phosphorus, too much nitrogen, not enough timber, diseases, waste disposal, the destruction of biological diversity… What makes this analysis difficult is that there could be millions of such limiting factors. How can you prove that none of them are really limiting? That’s what we’re going to attempt.
The way to do this is by analyzing the arguments of all the experts who think the Earth has a limited carrying capacity. And there are a lot of these experts!
The first thing you should notice is that, weirdly, most analysts believe the Earth is already at its carrying capacity! Look at the graph above: the mode1 is at 8B people! WHAT A COINCIDENCE, SHERLOCK.
What is the likelihood that we’re just at the limit of the Earth? Very low. My immediate reaction to this is: Most analysts simply lack imagination. They see the current world, notice that there are some problems, and conclude that we’re hitting our limits.
The poor quality of these studies was highlighted 30 years ago in this paper, which found six different approaches to assessing the carrying capacity:
Geographic Regional Division: The academics divided the Earth into regions and assumed maximum population densities for each. The problem with that is that they didn’t detail their assumptions and also used fixed numbers, rather than assuming that technology keeps improving and we keep finding better ways to do things!
Curve Fitting: Analysts who just consider past growth and assume it will continue. Of course, you can’t do that because fertility rates and life expectancy change!
Single Constraint: Focus on one limiting factor—usually food. But as we have seen, food is not a limiting factor! Are there others?
System Models: Academics create complex computer models incorporating multiple interdependent factors using complex equations. But these models have lots of untested assumptions, and they seldom pinpoint what exactly will be the proverbial straw that breaks the camel’s back.
Take as an example The Limits to Growth, a 1972 report that raised the alarm about the Earth’s population growth rate, and how it meant humanity would run out of many resources as it grew. Alarmism works, so the authors sold plenty of books and made a living off of their pessimism. But criticisms of the work were brutal, and reality has caught up with its authors: This was 50 years ago, and so far, humans have not run out of a single resource. Let’s repeat this, because many people don’t internalize it.
So far, humans have not run out of a single resource.
Think about it! Can you name a single one? Go search for it if you don’t believe me!
In fact, we keep finding more and more resources! Whenever a resource runs out, it becomes very expensive, and some clever people focus all their efforts on finding more of it. Case in point: lithium. A few years ago, there was a widespread fear that batteries would consume all the known lithium on Earth. What happened?
Why? Because of news like this:
In this article, one of the authors of The Limits to Growth updates her thinking. It’s an illuminating article to understand how the authors think. Most of it is handwringing about complex models, but when the rubber meets the road, their arguments are pretty weak:
Another limit to food production is water. In many countries, both developing and developed, current water use is often not sustainable. In an increasing number of the world’s watersheds, limits have already been reached. In the U.S. the Midwestern Ogalallah aquifer in Kansas is overdrawn by 12 cubic kilometers each year. Its depletion has so far caused 2.46 million acres of farmland to be taken out of cultivation. In an increasing number of the world’s watersheds, limits have already, indisputably, been exceeded. In some of the poorest and richest economies, per capita water withdrawals are going down because of environmental problems, rising costs, or scarcity.
As we learned in the desalination articles, this thinking is static! It assumes that the problems of today and yesterday can’t be solved, without even looking at the places that have already solved them, like Israel and Saudi Arabia!
Since there are an infinite number of stupid arguments to make against the growth of humanity, I can’t address them all. Instead, we’ll examine the single strongest study on carrying capacity, see if it has any merit.
A team of 28 academics have come up with the Planetary Boundaries, a series of nine processes that threaten to collapse under the weight of humanity’s impact. From what I’ve seen, it’s the most serious attempt to quantify what can go wrong. According to the team’s latest report in 2023, six of the boundaries have already been transgressed.
Let’s look at each of the six transgressed boundaries.
The report mentions CO2 and radiative forcing2 as the main issues.
As we noted in How Bad Is CO2?, it’s true that CO2 levels are higher than they were two centuries ago, and that this is causing global warming. But in the grand scheme of things:
CO2 levels are still lower than they’ve been throughout most of the world’s history.
Plants have been reducing atmospheric CO2 for millions of years, at times to dangerously low levels.
Now that the concentration is higher, plants are thriving, growing faster than ever.
The problem with CO2 is not its level itself, but how fast the level is rising, warming the globe too quickly for species to adapt.
More specifically, the risk is that there are tipping points that global warming can hit, like warming up Greenland too much, which could stop the Atlantic Meridional Overturning Circulation (AMOC), throwing northern Europe into a glacial age.
So yes, it’s true that we have too much CO2 in the atmosphere and that we are adding even more. But we already know how to solve this! In short:
Solar energy and global electrification will dramatically shrink the emitted CO2 in the coming decade. Within a couple of decades, our CO2 emissions will be much lower.
We will still have to sequester the CO2 that is already in the atmosphere, but we know how to do it: With technologies like olivine weathering.
In the meantime, we should reduce global temperatures, which we can do cheaply and with minimal side-effects using sulfate injection.
Which means we should nuance the concept of planetary boundaries. Yes, there are limits to what the Earth can withstand. Yes, sometimes we pass these limits. But that doesn’t mean we can’t subsequently course-correct. In the 19th century, London was impossibly polluted, and now its air is clean. Humans need to suffer from problems before they look for solutions.
We see this in the famous Kuznets’ curve applied to the environment:
We are seeing this play out in the evolution of CO2 emissions per capita:
CO2 emissions have been shrinking since 1980 in developed countries like the US and the EU, although they’re still growing in poor and middle-income countries like China and India—to the point that China now emits more CO2 per capita than the EU, even if the EU is 2.5x richer than China on a per capita basis.
So does the CO2 situation mean we can’t get to 100B humans? Absolutely not. It just means that, on the path to 100B, we will hit some roadblocks that we’ll need to clear. That’s it.
The Planetary Boundary papers tell you that the heating of the Earth comes not just from CO2 emissions, but also methane, and darkening the surface of the Earth3, while aerosols reflect heat. The balance is radiative forcing, and today it’s at 2.91 W/m2 (watts per square meter) but according to the papers, 1 W/m2 would be optimal. Here’s the breakdown:
Carbon Dioxide (CO₂): +1.66 W/m²
Methane (CH₄): +0.48 W/m²
Other gases: +0.5 W/m²
Aerosols: -0.5 to -2.5 W/m2
Additional ozone in the troposphere: +0.35 W/m²
Clearing forests: -0.2 W/m²
We can see that radiative forcing is mostly CO2—which we’ve covered. The other big culprit is methane, which is a potent greenhouse gas, but unlike CO2, it disappears from the atmosphere in about 12 years. And we’re getting much better at spotting it. For example, it used to be impossible to see methane leaks because the gas is transparent, but thanks to SpaceX, we can now send cheap satellites to space that can visualize these leaks. Here are orbital images from the company OSK showing methane leaks:
So as we solve CO2, we’ll also solve methane, and it will be even easier since we just need to stop releasing it, rather than also sequestering it, like for CO2.
In other words, climate change is not an obstacle to get to 100B humans.
We’re clearing our forests. This isn’t good, nor is it sustainable.
To get where we are, the world has cleared too many wild forests and has sacrificed too much biodiversity. This is terrible; we should not have done it.
But here we are. We can’t change the past.
But we can change the future.
So why did we clear so many forests, and can we change that?
We cleared our forests for agriculture—mainly crops (52%) and grazing (37%). Eurasia did this thousands of years ago, when forests in places like Europe, the Middle East, China, or India were cut down to give space to humans and their farms. We don’t realize this because it was before history—there was no writing, so no records. We lost a tremendous amount of biodiversity then, like mammoths or saber-toothed tigers. What we are seeing now in places like the Amazon Rainforest or Indonesia’s forests is just the modern version.
Can we stop that from happening in the future, or would a path to 100B people force us to continue uprooting nature?
One of my favorite sayings is from William Gibson:
The future is already here; it’s just not evenly distributed.
To know what would happen in the future, we need to look at current trends and project them into the future.
2024-11-19 21:02:11
Some people fear there are too many humans on Earth.
They’re wrong.
We could 12x our population, from 8B today to 100B if we wanted to, while maintaining quality of life on Earth.
Where would we all fit?
Could we feed everybody?
Wouldn’t pollution explode and ecosystems collapse?
This is what we’ll answer today.
Today’s world population is ~8B, and according to the UN, it will peak close to 10B around 2080:
This is probably an overestimate: It’s not the first time the UN has revised the estimate downwards, and it has incentives to not reflect the true decline in population forecasts.1
So we’re on a trajectory to only reach about 10B people at most, and one of the reasons is that many people aren’t having kids because they fear overpopulation and the destruction of the environment.
I was a college student when I read Mr. Ehrlich’s “The Population Bomb.” I took it to heart and now have no grandchildren, but 50 years later the population has increased to eight billion without dire consequences. I was gullible and stupid.—David Henderson, EconLib
So should we be concerned about reaching 10B people? After looking at the numbers, I believe we shouldn’t, because the Earth can carry at least 10x more people.
The Netherlands is the 6th happiest country on Earth.
It has ~18M people living on ~33,500 km2. That’s a population density of ~545 people per km2.
And the Netherlands is nice!
If the Earth had the population density of the Netherlands, it could hold 70 billion people!2
And the Netherlands doesn’t pack people with particular intensity:
Dutch scientist Antoni van Leeuwenhoek (1632-1723) estimated that if the population of Holland in his day (one million people) were extrapolated across the estimated area of inhabitable land around the globe, it would equal 13 billion people. Now, that same extrapolation yields 70 billion. Increase population density in the Netherlands a bit and extrapolate it to the rest of the world, and you get 100B.
If there were that many people, most would live in dense urban areas. The city of Hong Kong, for example, has 40k people per square km.3
If Algeria had the population density of Hong Kong, we would get to 100B people. The rest of the world—98%—would be left to nature.
Of course, neither of these extremes will happen. What we will get is hundreds of megalopolises like Hong Kong, huge swaths of built up areas with densities like in the Netherlands, and plenty of open land leftover. The point is we can fit if we want to. There’s physical room for us while still retaining nice natural areas.
This assumes we would keep the population density of Hong Kong, but in fact we can already build much taller buildings if we want to. As technology gets better, we will be able to pack even more people per km2, leaving even more areas free of humans, if that’s what we want.
We could also expand the land we live in by making the uninhabitable habitable. A perfect example is the Sahara desert, a huge sea of nothingness.4 The only things we need to make it livable are water and cooling. I explained in Can Solar Costs Keep Shrinking? that very cheap electricity is coming, and in the desalination articles how the vast majority of deserts could be habitable today with desalinated water.
Speaking of water: Do we have enough?
With 100B humans, we would need much more water. And you might be concerned about the fact that we’ve already been using our aquifers to water our crops and hydrate ourselves.
But the only reason this is a problem is because we’ve been using the water that is conveniently below our feet, the way the English of the 18th century first used the coal that was lying on the beach before venturing deeper into mines. Similarly, as water from aquifers becomes scarcer, we will look to the sea for more. Consider this:5
70% of the Earth’s surface is water.
The Earth’s total water supply is basically constant.
Water changes form, from liquid in the sea to gas in the clouds to rain or snow.
It also changes location, from sea to mountains to rivers to aquifers to fields.
Only 2.5% of our water is freshwater.
We can participate more actively in this cycle, transforming saltwater into freshwater, the way the Earth does naturally today.
The cost of desalination today is $0.40/ton—93% less than what San Franciscans pay for their tap water.6
Most crops could be profitably grown with desalinated water today if the water cycle was controlled (ie, no spillage or filtering in the soil).
You can read more in the desalination articles.
OK, so we have plenty of water, we just need to convert it from saltwater to freshwater. But what about food?
In How Can Vertical Farms Become Viable?, I highlighted how the Netherlands’ agricultural productivity is 100x that of Nigeria for crops like tomatoes:
And this is why the Netherlands is the second largest global food exporter!
So if you shape the world into the image of today’s Netherlands, not only do you fit 70B people, but you also end up with a huge food surplus.
And this is without vertical farming! In The Promise of Vertical Farming, I highlight how we could grow food more efficiently in vertical farms with solar panels than in open land. The only issues are energy costs and labor, but energy costs are about to shrink by 10x, and labor costs are a matter of automation. So the Netherlands’ productivity could increase 10-15x with vertical farming, feeding many more than 100B people. (More info on vertical farms here and here).
And since it would take us centuries to reach 100B people, we would have time for technology to keep improving, shrinking energy and labor costs, making food plentiful. Imagine AI managing our vertical farms with nuclear energy in underground facilities. How much food could we produce? As much as we want!
You might say: Yeah but that’s for crops. What about meat? Of course, we couldn’t feed 100B with free-range, grass-fed beef. But we could grow that same beef in a facility. Lab meat is already a reality, and by the time there are 100B of us, the technology will be good enough.
Fun fact: After chicken, the second biggest source of protein for humans is not beef, it’s not pork, it’s farmed fish! And it’s growing fast.
You can farm fish anywhere on land, just build bigger pools. Build them underground if you want to save surface space.
And that’s just using land! There are huge swaths of ocean devoid of life, but we could fertilize them to increase sealife and harvest the booming fish population. Fish is an extremely efficient source of protein,7 so we could use it to feed a world population of 100B many times over.
So the only food limit is our imagination.
100B humans is 12x the current population. Once we get there, our energy consumption will be more efficient, but we will also require much more of it. So let’s assume we will also need 10x more energy per person than we do today. That’s a total of 120x the amount of energy we produce today! Where are we going to get it from?
Today, we consume 180,000 TWh of energy per year.8
If we grew our energy demand by 120x, we would need about 21 million TWh. How much of that could come from solar electricity?
You can see from this map that the Sahara has plenty of surface area that receives over 2,200 kWh of solar energy per year.
Once we have 100B people, our solar panel efficiency will be at the very least 30%, so we can generate 660 kWh of electricity per m2 of Sahara every year. So how much surface do we need to cover to gather 21 million TWh of electricity? About 33M km2, which is a bit more than two Russias.
I can guarantee you this won’t happen. So solar electricity won’t be enough. It could work if we captured solar energy in space panels and beamed it to the Earth, but I don’t want to assume science-fiction for this article. For that same reason, I don’t want to assume we will figure out fusion. Luckily, we have another, already proven tech.
As I explained in Why Nuclear Is the Best Energy, we have enough uranium and thorium on Earth to power humanity until the Sun explodes and engulfs the Earth. If our population and energy consumption keep growing, at some point our demand will outstrip the supply of solar energy, and nuclear energy will become the only viable solution. Thankfully, nuclear is the cleanest source of energy, so we’re covered.
Paradoxically, the drawback is not the use of nuclear energy, but the simple fact that if we use 120x more raw energy than we do today, this energy will dissipate in the atmosphere and warm it up. Anders Sandberg estimates9 that this would add about 1ºC to the atmosphere. Will this be a problem?
It depends on how long it would take for us to get to 100B humans? Right now, humans are not having enough babies. So we would first need fertility to turn around. Let’s imagine a crazy scenario where we get to 2.5 children per woman. That would mean every generation (let’s say 30 years), our population grows by 25%. It would take us 300 more years to get to that point. Meanwhile, CO2 is a 21st century problem that is very likely to be solved by the end of the century, as I’ll cover in the premium article this week.
So 1ºC of additional heat sounds manageable, and if we don’t want to tolerate even that, we can inject sulfur in the stratosphere or put mirrors in space.10
In other words: We already have the technology to power a world with 100B humans, and by the time we get there, we will be able to mitigate the only big downside—a warming of the atmosphere from all this new heat.
To host 100B humans, the Earth will have enough:
Space
Food
Water
Energy
What about the other factors. What about pollution? Are we going to destroy the Earth in the process? What’s this thing about CO2 that you’re talking about: Will it really be solved within a century? Are we going to exhaust the Earth’s resources?
I looked into this, and the answer is no for a simple reason: Every person afraid that we’re going to run out of something or pollute the Earth too much never accounts for a changing world. Look at what I just described in terms of food, water, and energy: Our technology is already close to what we need to get to 100B. If you just assume that technology will keep improving the way it has, we will have the technology we need. These details are what we’re going to explore in this week’s premium article.
Fertility rates globally are shrinking faster than anticipated, yet many countries’ finances are based on high projections of population growth. If the UN were to highlight how population projections are too optimistic, it would expose the fragile state of these finances, so it has a strong incentive to slowly revise the number downwards rather than making a dramatic adjustment all at once.
The Earth has 107M km2 of habitable land, and another 20M km2 of barren land (mostly desert). In a future world, we could use both the barren and the habitable land to accommodate people. This does not include glaciers, but if we included them, we could have a total population of 77B.
Hong Kong has many parks and green spaces. The city itself has about 3M people in ~75 km2.
I can already hear some people: “No but the Sahara is full of life and has plenty of endemic species!” No it does not. It has 2-3 orders of magnitude less organic matter per square meter than places like jungles. It does have some special endemic species, but you can easily conserve them, corralling them in reserves, while using the rest of the land for human habitation.
This is not apples to apples, because tap water also pays for canals, storage, water treatment… But it gives you a sense of orders of magnitude.
Fish converts two thirds of its protein intake into its own protein. This compares to 10% for beef.
1 TWh is 1 million megawatt-hours.
I saw it in one of his tweets but couldn’t find it again, so I asked him about it in person when I met him in a conference in 2024 and he confirmed the number.
Space mirrors are probably doable today, but since we’re not doing it yet, this approaches science-fiction.
2024-11-14 21:03:01
Earlier this week, I made the case that desalination will be able to fulfill most of our freshwater needs. But is this realistic? Has it been done before? Won’t it cause pollution? Can the economics be as good—or even better—than I described? This is what we’re going to explore today. And we’ll start with the country that’s the most advanced in this field.
Israel has 9.5 million people and five big seawater desalination plants in operation.
They produce enough freshwater to provide over half the country’s supply, including nearly all its tap water!
When I quoted a cost of $0.40/ton of water in my previous article, the figure comes from a new desalination plant in Israel that is about to open, Soreq 2.
Today, Israeli households pay ~$30/month for their water. This is about half of what Angelenos pay.
More than half of Israel’s water—including that for industrial and even agricultural uses—comes from desalinated water! This is a country that is poorer than the US but in the same wealth ballpark as countries like France, South Korea, or Japan. If Israel can do it, so can they.
But the extent of Israel’s desalination plans are even more monumental.
This is the Dead Sea between Israel, the West Bank, and Jordan:
The sea is actually much smaller than the seabed, and about half of the remaining seabed is dedicated to salts extraction. The rest of the sea has been shrinking, as you can see in this video:
If you don’t feel like clicking on it, here’s a before and after of the last 40 years:
It’s been drying up for decades.
This is happening because the main source of water for the Dead Sea is the Jordan River, and Israel has been using that water for irrigation.
So much so that the Sea of Galilee started drying up. This was a national emergency, as it provided 25% of the country’s freshwater at the time. Now saltwater is heavier than freshwater, so the bottom of the sea is much saltier than the top, and if the freshwater at the top disappears, the lake’s surface water can become very salty very fast, in an irreversibly damaging process.
That’s why the Israelis decided to reverse the flow of freshwater: In times of drought, when the Sea of Galilee runs low on freshwater, Israel desalinates water from the Mediterranean and sends it to the Sea of Galilee to refill it!
This started only recently, and most of the time Israel doesn’t need to do it because rainwater is sufficient to refill the lake—especially now that the population consumes so much desalinated water. But during droughts, Israel refills the lake.
Refilling a lake with desalinated water!
And the surplus of water is so high that Israel is becoming a freshwater exporter!
Israel, therefore, exports the equivalent of about a third of its freshwater production.
So yes, desalination can water a country.
It’s going to be hard.
2024-11-12 21:01:47
Desalination is finally cheap, and it’s only getting cheaper. Will this usher in a world where humans won’t thirst for water anymore? Where water shortages will be a thing of the past? Where we will be able to live in areas that once were barren deserts?
I only published 2 articles over the last 2 weeks instead of 4. So consider my 2nd week of holidays of the year taken. I will likely take the last 2 in December.
1.1B some have access to freshwater year round. What if we could eliminate their plight forever? That's what we could achieve with cheap water.
But we could do much more than that.
Few people live in the most parched parts of the world.
These areas account for ~14% of all land:
If we could make these areas inhabitable, we could increase our habitable land by about 18%. We could convert places like those on the left into ones like those on the right:
This is already happening. There are about 21,000 desalination plants around the world, supplying water to over 300 million people—about 4% of the world’s population.
Yet the potential is much higher, since nearly 3B people suffer from water scarcity, and if water was more plentiful and cheaper, everybody would consume even more of it.
That’s why the number of desalination plants keeps growing:
The most standard approach to desalination is reverse osmosis: You take some saltwater, push hard on it,1 and pass it through a membrane that retains all the salts and lets freshwater through. It’s like squeezing freshwater out of saltwater.
This is what a membrane looks like close-up:
Reverse osmosis is so much better than every other method of desalination2 that we’re just going to focus on it from now on.
Until very recently, reverse osmosis was extremely expensive, so it was reserved for uses where water is the most valuable, like drinking water in places like Israel, Saudi Arabia, or Dubai. But the cost of reverse osmosis has been shrinking dramatically, and since this trend will continue, it will soon be cheap enough to use in ways we couldn’t imagine before.
For desalination, we measure water in terms of cubic meters (m3): a cube of one meter per side, which conveniently3 weighs 1 metric ton (T), so I’ll use tons of water from now on—even if in the literature, people tend to use m3.
Today, desalinating water can cost as little as $0.40/ton.4 This number changes based on factors like local energy or construction costs, the source of water, and the size of the plant, but aiming for $0.40/ton for new plants is in the right ballpark.
And what goes into that cost? Approximately this:
Which means that desalinating a ton of water costs approximately:
$0.15 in electricity
$0.18 in construction costs and financing
$0.08 in operating costs and maintenance
Let’s look at the two main costs.
The electricity cost depends on how much electricity is consumed and the price of that electricity.
The calculation of $0.15 per ton of water is based on the consumption of new, big industrial plants that are best-in-class today, which can use as little as 2 kWh of electricity per ton of water.5 Some research desalination plants achieve 1.8 kWh/ton, but this is getting close to the physical limit of 0.79-1 kWh/ton6, so I don’t think this can shrink much more. Let’s assume we can adopt that 1.8kWh/ton in the industry, for a 10% reduction over current industrial best practices.7
What about the price? Until now, the cheapest source of energy for desalination tended to be fossil fuels: Countries burned oil and gas to convert seawater into freshwater. Although solar photovoltaics are now the cheapest source of electricity, desalination plants still can’t take advantage of them because they are too expensive to build, and the plants must run 24/7, which requires batteries. When you add batteries to solar costs, they are still not competitive with oil and gas—especially in the oil rich gulf states.
But the prices of both solar photovoltaics and batteries have been dropping at about 12% per year for decades! That’s why solar plus batteries can now cost $0.12 per kWh,8 and that number will keep falling at ~12%/year. Within a decade, even if subsidies disappear, the cost of electricity will go down by 50-65%.
A 10% reduction in electricity consumption and a 50% reduction in electricity prices will mean a total reduction of 55% in electricity costs, from $0.15/ton to $0.07/ton, with fewer constraints to scaling up.9
CAPEX for desalination plants includes things like land, construction, buildings, canals for water to come in and out, pretreatment systems for the water, pumps, energy recovery devices, utilities connections (power, water), engineering, design, permits…
These costs are hard to reduce, but each time a new plant is built, companies find ways to make them cheaper. All in all, they’ve been able to reduce costs by 15% every time the installed capacity doubles.
Capacity has increased by ~6% per year in the last few years.10 If this speed continues, within 10 years we will have installed 75% more desalination capacity. That translates to a reduction of CAPEX costs of ~11%, from ~$0.18 to ~$0.16/ton.
Other operation and maintenance costs are likely to drop a bit, because otherwise they would make a bigger share of costs as CAPEX and electricity costs shrink, and that would put pressure on them to shrink too. Let’s assume they go down by 25%, to $0.06. All in all, it looks like within a decade, the cheapest desalination will go from ~$0.40-0.50 today to ~$0.29-30.
What does that mean? Is this cheap enough for us to drink this water? Manufacture things with this water? Grow produce at these prices? Can we create new cities in the desert with these water costs?
This is how $0.30 compares to the price of tap water in different world capitals:
In other words, in the vast majority of the world, desalinating seawater is cheaper than the current price of tap water! And it’s only going to get cheaper!
Here’s one way to make this intuitive: A standard US household uses about 380 tons of water per year. Such a household in San Francisco would pay $2,000 in water per year. The desalination of this amount of water would only cost $114, or less than $10/month. It would consume less electricity than the fridge!
At this cost, virtually all tap water in the developed world could be replaced by desalinated freshwater. This means that we can now build cities in deserts!
Or at least, in deserts close to the sea. Can we do the same inland?
This paper said back in 2005 that lifting one ton of water 100 meters costs approximately the same as 100 km of horizontal transport, or about $0.05/ton. Let’s assume that is still the cost.11
This means that, if we are willing to pay $1 per ton of water, we would need $0.40 for desalination, and would have $0.60 left for transportation. That’s enough to send water inland by 1,200 km or elevating it 1,200 meters—or a combination of the two.
If I’m not wrong, this means that virtually all the land that is green or red here in Australia could be reached at $1/ton or below.
What about the Sahara?
The vast majority of the Sahara could receive desalinated water at $1/ton or less. All but the tallest mountains could receive water at $2/ton or less.
I am doing back-of-the-envelope numbers here. Maybe water transportation in the Sahara is a bit more expensive, or some other assumption doesn’t hold perfectly. The point is not to claim that all the Sahara could receive cheap desalinated water, but rather that technology is already at a point where we could start building cities in the Sahara if we wanted to.
And if it’s true for the Sahara, it’s also true for Arabia, southern Argentina, Somalia, the Thar Desert in India, the flatlands of Pakistan, and some parts of Central Asia—all of which are close to the sea and at low altitude.12
That said, most water is not directly consumed by humans.
Most water goes either to industry or to agriculture. If these desert places were to be economically viable, they shouldn’t just have drinking water—they should also have water primarily dedicated to these other purposes.
In emerging countries, water is used mostly in agriculture, and in rich countries, it’s a mix of agriculture and industry. So what are water prices like in agriculture and industry around the world?
This is the wholesale cost of water in different California counties, which is characteristic of what industries pay for water:
The price of desalinated water is in the right ballpark! It looks like:
In Germany, the cost of processing water is similar to that of desalinating it, around $0.50/ton.
In Spain, industrial water costs $2/ton.
In Japan, the production of water costs $1.2/ton.
In Australia, industries pay $0.31/ton.
Frequently, industrial water requires treatment, and that is one of the main drivers of costs. From what I can tell, these costs tend to be similar or higher to those of desalination. Desalination costs would be on top of treatment, so water would be more expensive, but it wouldn’t be tragically more expensive.
What does this all mean?
For countries where water is plentiful and industries where water is a huge fraction of costs, desalination is probably not viable for industry.
But for countries where water is already scarce, or for industries that don’t depend mainly on water, bringing desalinated water is completely plausible!
This gives you a clue on the viability of desalinated water for agriculture.
According to this paper, water prices for agriculture in Europe range from $0.05 to $1.65 per ton. This means that, today, desalinated water would already be a viable alternative in many places!
But outside of Europe, most water for irrigation comes directly from rivers, is not treated, and is very cheap. In California, its price ranges between less than $0.01/ton to $0.40. In the Imperial Valley, one of the biggest sources of produce on Earth, a ton of water costs about 1-2 cents. These prices are common across the US.
According to this paper, agricultural water costs just a few cents per ton in countries like Canada, Morocco, Australia, the UK, Turkey, Spain, or Jordan. Desalinated water would be competitive in others, like Israel, the Netherlands, Tanzania, or Chile.
When water is the main component of a crop’s costs, producing that crop in most countries won’t be viable. But water cost does not factor heavily into every agricultural product!
A cubic meter of water is 1,000 liters. So for example, a kg of cheese needs over 5 cubic meters of water. If it came from desalinated water, that’s $2 per kg right there. Not viable.
But the cost of desalinated water for citrus, wine, or bananas would be just $0.03/kg. So let’s translate this graph into costs of desalinated water per kg of produce:
Here in lbs, for you Americans:
You know what this means?
It means that deserts couldn’t produce every agricultural product in the world. But they could produce a bunch!
And of course, we saw in The Promise of Vertical Farming that using greenhouses can reduce water consumption by up to 95%. This would divide the cost of water per kg of produce by 20x. For something like cheese, water would now cost $0.10 per kg rather than $20/kg, making the use of desalinated water viable. If it’s true for cheese, it would be true for many other products, including most crops.
Desalinated water now costs as little as $0.40 per ton.13
This is likely to drop to $0.30 in the next decade.
This is already cheaper than residential water in most cities in the world.
It’s also in the ballpark of prices of industrial water. We could use desalinated water in industries that are not too thirsty or in countries with water scarcity.
Many agricultural products could be economically viable in new areas if they were irrigated with desalinated water today.
Even products that require a lot of water could be viable, as long as they are produced in greenhouses and their water is not lost to the ground.
In other words: We could reinvent the world with desalinated water.
More precisely, you increase the pressure on the saltwater side to > 27 atmospheres.
This is because most other common desalination mechanisms require evaporating water, which takes a lot of energy, which is expensive. A world with very cheap energy (even just thermal power, like geothermal) might see other desalination mechanisms win over reverse osmosis, but we’re not there yet.
It’s convenient that one m3 of water weighs one ton, but it’s not a coincidence. Originally, the kilogram was defined as the mass of one liter (or one cubic decimeter) of pure water at its maximum density, which occurs at about 4°C. This means that one cubic meter (1,000 liters) of water would weigh approximately 1,000 kilograms, or one metric ton.
In the US, the Department of Energy tells operators they should aim for $0.50/m3. The new plant of Sorek 2 in Israel has a contract to sell water at $0.40/m3. This is the price, not the cost; the cost is likely lower!
1.8 Kilowatt-hours per cubic meter of water. A kWh for industrial use costs about $0.08 in the US, so 1.8 kWh cost ~$0.14, or about the $0.15 mentioned above.
From Energy Issues in Desalination Processes, Raphael Semiat, 2008
20% corresponds to a drop from 2.5 kWh/ton to 2 kWh/ton, or from 2 to 1.6 kWh
I believe this includes subsidies, but since I haven’t looked into batteries in detail yet, I can’t confirm.
And the energy being used will be clean
It looks like 90% of a pipeline’s costs are CAPEX, and that is unlikely to go down. Electricity is a big part of the remainder, but even if its costs shrink by a lot, it won’t make a big dent into overall pumping costs of water. Maybe there are ways to reduce the CAPEX, but these are not obvious to me from the literature, and I haven’t dealt with pipeline pumping personally so I wouldn’t know. I checked how expensive it is to transport oil through pipelines, and it looks like it costs low single digit dollars ($1-$5) per m3 per 100 km, which would make it about 100x more expensive than moving water. Of course, moving oil will be more expensive than water, but that number being so much higher than $0.05 reinforces that costs much lower than $0.05/m3 to move water 100km are unlikely.
The Chilean Altiplano, the Rockies in the US, and the Namib in southern Africa are too elevated for this, while Asian deserts like the Gobi are too far inland.
Casey Handmer had a look at this article (thank you!) and wondered if cloud seeding would be a cheaper way to get freshwater inland. It looks like cloud seeding costs from a few cents per m3 to $0.20/m3, but since it’s less controlled and some of that water would have fallen somewhere else, it doesn’t look like it’s a viable replacement for now.
2024-11-05 21:02:47
I’ve been asked about wind before. I do love wind; it has many advantages. First, it’s cheaper than solar today.
In fact, it’s the cheapest source of electricity in the world today!
Wind also currently produces about 30% more electricity than solar.
But there are two big concerns about it:
It’s not growing as fast as solar. Why?
It’s intermittent, like …
