The Sahara’s Carrying Capacity

Keywords: Malthus, Marxism; Adam Smith; ideology; EROEI; wind turbine; net energy; photovoltaic cells; Concentrating Solar Power; sustainability; limits to growth; Jane Jacobs; Daniel Ben-Ami; carrying capacity; Ashley Singer; Club of Rome.

I’m continuing my debate with my Malthusian friend whose lengthy response to my last blog entry you can see in his comment. We both take this dispute seriously, as we should. I can’t remember the quotation, but someone once said that the course of human history was determined by the popularity of particular economic theories. It’s true. What would the world have been like without Marxism? Or without Adam Smith? Or Malthus? Gosh – imagine that! All these dead economists are still influencing the way we live. Nowadays maybe Malthus is even more influential than Marx.

Some other kinds of ideology besides economic notions also shape the course of history. Religion, for example. I think fundamentalism wrecked my mother’s life, just as it is destroying Islamic lives today. People used to climb willingly to the top of pyramids in Yucatan to have their hearts cut out. But not all religious people are so ideological.

It must have been ideology that destroyed the Easter Islanders. Why else would they have cut down all their trees? Any idiot could have seen what was coming, but they continued right until the end. Even animals don’t necessarily do that. Where there is a predatory relationship between wolves and moose, the wolves might be expected to eat all the moose and then starve to death themselves, but they don’t. They start practicing birth control of some sort, and inhibit their reproduction until the moose population recovers. But human ideologues don’t change their ways, no matter what bleak future can be foreseen. I hope our economic discussion can be more rational than that.

I have two issues with my Malthusian friend, one factual and the other theoretical. The factual one has to do with his claim that all renewable sources of energy have lower net energy than fossil fuels. I went hunting some more for evidence and found a few more estimates of EROEI (Energy Return on Energy Invested). Some of them fit the disappointing generalization about renewables, but others do not.

Big Scrub Environment Center wrote in the winter of 2005:

“Both solar parabolic dish and wind turbine return 30 times more energy than was used to manufacture them – about the same return as the cheapest oil discovered in Saudi. Oil, on average now, has an EROEI of 8.4. Oil’s chief advantage is its high energy density as a transport fuel. Coal’s EROEI is about 25 now and dropping. Nuclear power plants with an EROEI ranging from 3.84 to 4.5 take about 10 years to build. PV panels themselves have an EROEI of 4 and if batteries are included the EROEI is 2.”

A journal article about biomass fuels in Nigeria calculated these net energies:
• biogas from livestock manure: 10-11
• ethanol from sorghum 2.6
• ethanol from sugarcane 2.8
• ethanol from cassava 1-2
• ethanol from maize 1

C. J. Cleveland gave these figures:
• Crude Oil in 1930: 100
• Crude Oil in 2000: 20
• Coal in 1950: 100
• Coal in 2000: 80
• Gasoline: 10
• Corn ethanol: negative
• Oil Shale: about 5
• Coal liquefaction: 1.1

Another journal article, “Permanently dispelling a myth of photovoltaics via the adoption of a new net energy indicator,” recommended changing the way of measuring the net energy of photovoltaic cells. The authors propose an indicator called “EYR” which seems comparable to the EROEI. They define it as “‘how many times the energy invested is returned or paid back by the system in its entire life.’ ... Unity is established as the break-even point, and above that the higher the EYR the better.” They give the following estimates:
• EYR for a rooftop PV mounted on grid system:
Australian insolation levels: 11.2 N. Europe insolation: 6.2
• EYR for a solar home system (off-grid)
Australia insolation: 6.0 N. Europe insolation: 3.3

Several times I found references to wind turbines as having EREOI results at 20 or above. A journal article on tidal generators (“underwater windmills”) estimate that they will have an EROEI of 40; they will pay back the cost of their construction within 4 to 6 months and continue operating for 20 years.

The most remarkable sources of electricity are not yet operational on a significant scale, but their net energy will be exceedingly promising. One innovation consists of kites tethered to the ground but flying in the jet streams, where there is no problem of intermittency, and the wind is phenomenally powerful. The developers are comparing these devices to nuclear power plants in terms of the energy they will generate. They will provide electricity at 1.4 cents per kilowatt hour — the cheapest power source in the world.

But that’s not all. Coming up next are “Concentrating Solar Power” generators, which are already mature technologies that can be brought into play very soon. The one shown above has already been functioning at Barstow, California for fifteen years. There’s a “power tower” surrounded by a large field of sun-tracking mirrors that concentrate sunlight onto a receiver at the tower’s top. It creates steam and generates electricity, and the price compares favorably to that of oil, though no specific net energy numbers have been published yet.

That's enough about net energy. My conclusion is that most renewable sources at present do not yield as much power as most non-renewables, but there are a few exceptions already and technology is moving fast. The future looks bright.

Now I want to turn to the theoretical dispute with my Malthusian friend. There are several facets to the debate, all somehow reflecting our differing opinion about whether there are inherent tendencies of living organisms to reproduce up to the limits imposed by the finite material subsistence base. The limit of growth to Malthus was primarily food, but other writers expect limits to be imposed by the depletion of energy and raw materials.

I agree that some societies have become extinct as a result of this problem, but I don’t think it’s inevitable. The truth is, human intelligence can usually invent solutions that make for greater efficiency and allow for economic growth to continue. That’s why Malthus’s predictions, as well as those of Paul Ehrlich in 1969, failed to come true. The ecological economists such as my Malthusian friend like to discount the importance of improving efficiency. For example, they claim that whenever efficiency is introduced, people will just consume more in a “rebound,” so that the total use of energy remains as high as before. That’s not correct. There have been studies (I’m not giving footnotes in this blog but I could) showing that there is a small rebound, but it doesn’t amount to a major part of the incremental efficiency. Industrial and post-industrial society have become vastly more efficient, and we enjoy the benefits.

That brings me to another point: the question of sustainability.” The assumption underlying this concept supposes that whenever we develop or grow economically, it is by “using up” resources that we should be saving for future generations. For example, in 1972 the “Limits to Growth” report predicted that the world’s supply of gold would run out in nine years, mercury in 13 years, natural gas in 22 years, oil in 20, silver in 13, and zinc in 18 years.

Not only were these predictions totally wrong, but the whole theory of sustainability behind the predictions forgets that future generations may actually be helped if we develop our economy and our technology today. Yet it is true: Entrepreneurial inventiveness and creativity today are the most useful contributions we can give to future generations.

For example, Jane Jacobs once wrote a book challenging a similar faulty assumption. When I was an undergraduate, I was taught that throughout most human history there had been no surplus food and therefore no cities. Only after surpluses occurred (owing to the excellence of environments such as Mesopotamia) did cities emerge. What Jacobs argued instead is that cities paid their own way. Cities are always the centers of creativity. Where cities emerged, smart elites lived there, inventing new ideas that enabled agriculture to produce the very surpluses that supported themselves.

The same idea applies today. Half of the human population now lives in cities. These urban environments are challenging, but they are also the locus of human creativity. They pay their own way. Technological inventions require cities and will continue developing if populations become urbanized. The greatest contribution we can make to the future is not to reduce our standard of living (though if you want to do that, okay) but rather to figure out how to make our economies more efficient and effective.

Fortunately, we are in a position to do so. We live in “post-industrial society,” and instead of producing tangible objects, we do such intellectual activities as I’m doing now — writing a blog — or as I will be doing tomorrow: writing an article about climate change for a book. This is the application of “human capital,” the source of our economic efficiency. To run a financial institution, say, requires only a small fraction of the BTUs required by manufacturing or construction companies.

The economist Robert Solow pointed out in the 1980s that technology is the real driver of economic development, but he expected there to be diminishing returns to capital investment in machines, so that each country would eventually reach a steady state instead of continuing to grow. More recently, however, mainstream economists have emphasized the crucial importance of human capital, which in fact has increasing rates of return. Therefore, investment in human abilities does not bring the economy to a steady state, but (joy, joy!) will make it continue to grow.

However, during the past year or so William Easterly has in turn pointed out the error of that theory too. Education does not necessarily pay off as hoped. Instead, it leads to growth only when it leads to lucrative employment. If there are no good jobs, education does not help. And when there are good, high-tech jobs, the knowledge tends to “leak,” for, unlike material things, information is not conserved. People learn technology from others, then apply it in their own work, making their economies more efficient and making themselves more prosperous, healthy, and able to defend against natural disasters. Economic growth requires technology, which does not arise automatically. Technological know-how emerges only in response to actual financial incentives.

My friend says that I am mistaken in claiming that the earth’s carrying capacity is increasing. (Sigh.) Very well, let me question the concept of carrying capacity. A dictionary of biology defines the term as “the maximum population of a particular species that can be supported indefinitely by a given habitat or area without damage to the environment.” But as Daniel Ben-Ami notes,

“ the carrying capacity of the earth in relation to humans is its productive capacity divided by one person’s basic needs. But the productive capacity of the earth has grown enormously as the world has become more efficient economically. So ‘carrying capacity’ is not a fixed quantity but at most a statement of a particular ratio at a particular time....For instance, bauxite or uranium have no value in a primitive society where they cannot be utilized, but in an economy that produces aluminum or harnesses atomic power they become valuable resources.”

There is nothing fixed about the carrying capacity of a piece of land. Take the Sahara Desert, for example. Its carrying capacity for human beings is almost zero. Hardly anyone lives there. But now think of the Concentrating Solar Power installation that is going to be constructed there. As Ashley Singer writes in The Guardian of November 2006,

“The researchers say a relatively small amount of the world’s hot deserts — only about half a percent — would need to be covered in solar collectors to provide the entire world’s electrical needs.”

My point: What yesterday was hot, dry, miserable land with no carrying capacity whatever may become tomorrow a perpetual source of power for the whole of humankind. Given that reality, the concept of “carrying capacity” loses significance. Ironically, the main organization promoting this solar power generator in the Sahara is the Club of Rome— the group that used to promote the “limits of growth” theory. And in creating this new source of energy, they are increasing the world’s carrying capacity, bless them.