Last year I did an analysis to try to understand whether it’s possible to feed the world sustainably. Today I’d like to try to understand what happens to countries as they must rely upon the sun for energy (and, indirectly, wealth).

An old proposition in the sustainability community is that the material wealth we enjoy today in industrialized nations is based in large part on our energy consumption. Take that away, and our vaunted industrial, intellectual, and entrepreneurial prowess will do little to sustain our material wealth. I think there’s quite a bit of truth in this claim, and the data at least supports the notion that there is a correlation — Gapminder enables charting of fairly-recent energy and economic data; this chart shows energy use per capita vs. GDP per capita. (One thing you can see, if you move the year slider at the bottom of the chart, is that while individual countries have moved up or down over the years, the correlation has remained remarkably constant.) In any case, for the purpose of this post, I’m going to set the validity of the claim aside and assume that it’s true. I’m also going to set aside the problem with using GDP to measure wealth, as it doesn’t really matter for the analysis below.

So, supposing that wealth (per capita) as we currently conceive of it is based in the flow of energy (per capita), where does that leave us in a world with few or no fossil fuels? Well, we could look to alternative energy sources, but I’m going to take Odum’s assertion as a given: “The natural conversion of sunlight to electric charge that occurs in all green-plant photosynthesis after 1 billion years of natural selection may already be the highest net emergy possible.” This means that we can assume in pure net emergy terms that growing plants to fuel society directly and indirectly is more efficient than most alternative energy schemes. (I’ll come back to the case of Iceland later.)

That brings us back to what the land can yield. In my calculations last year, I estimated that arable land yields about 1-2 W/m^2 of harvestable energy. Given that, we can then estimate the potential energy (really power, since it’s in terms of Watts) yield per country by looking at the arable land available per capita. This dataset from the World Bank provides hectares per person for the countries of the world.

At the top of the list is Australia, which, if climate change doesn’t hit its arable land hard, will have a huge 2.13 hectares per person to work with. Multiplying the land energy yield of 1-2 W/m^2 and we get 21.3 kW to 42.6 kW per person — a huge potential value. The United States, at 0.51 hectares per person, would be at 5.1 kW to 10.2 kW per person; today the U.S. uses about 10 kW per person, so this isn’t far off. China is at 0.13 hectares per person, which would be 1.3 kW to 2.6 kW per person — also not far off from today. The countries that are most obviously in trouble, by this calculation, are those that have extraordinarily high energy use today but little arable land — many nations in the Middle East and small, wealthy nations like Luxembourg and Singapore fall into this category. Earlier I said Iceland is a special case; it has high energy use but may be able to sustain it because of its unique geothermal resources.

Granted, this calculation assumes intensive cultivation and doesn’t account for the need to feed the people (and animals) that do the work, and there’s a diminishing return on hectares per person (that is, it’s unlikely that a single person will be able to double their personal energy yield going from 1 hectare to 2 hectares, since it’s just too large for one person to intensively cultivate at that point). I think it’d be fair to halve the values, at a minimum, to account for this. And due to the need for a large fraction of the population to be involved in growing plants at least part time, there’d necessarily be less time for other work, and that would likely shrink the range of specialized occupations from what we have today. Despite all this, the calculation still indicates that a country like Australia could be in good shape — not far from where it is today — if it were to really transform itself economically so as to base its wealth on sustainable horticultural practice. That is, it might be able to achieve a fairly high equilibrium state of both energy use per capita and wealth per capita. And even the United States wouldn’t be that far off — perhaps 50-60% lower than today.

What does this mean for the future? I’m not sure, but I think it indicates that when the fossil fuel trapdoor opens there’s potentially a floor not far beneath our feet, one that’s available to us if we’re willing to do the hard work to base society’s wealth on what the sun provides to us through plants.

Photo credit: Wikipedia/CGoodwin/CC BY-SA 3.0