World Energy Use and Ecological Productivity — an Order of Magnitude Perspective

Latest edit: Feb 19, 2013 – added disclaimer about uncertainty in remaining coal reserves; minor grammatical improvements

The world’s economy uses 31 billion barrels of oil per year, and there is roughly a trillion left to be extracted. Similar numbers apply for coal and natural gas, except gas is usually expressed in trillion or quadrillion cubic feet. If you’re like me when first introduced to these numbers you probably react with, “OK whatever, that’s just big numbers”. After a million they all sound like gazillions.

An easier way to visualize energy use is to express it on a scale that everyone can relate to. It turns out that yearly global oil consumption, 31 billion barrels, is close to one cubic mile of oil (1.18). When you add in all the other “technical” energy we use like coal, natural gas, nuclear, etc., it comes to a grand total of 3.1 cubic miles oil equivalent (in terms of energy). It’s not that much, is it? That’s the volume of an average mountain. If you looked at the whole world on Google Earth you wouldn’t even see it.

Since the world will run out of fossil fuels in the not-too-distant future (a Hubbert linearization estimates that 90% of all oil, gas and coal that will ultimately be extracted will have been by 2070 — note: there is still quite a bit of uncertainty about how much recoverable coal remains), then either some other energy source will rise to the occasion to take the place of fossil fuels, or we will just use less energy. The future will follow one of those two paths, or maybe a combination of both.

The most obvious candidate for that new source of energy is solar, since it is abundant and everyone can have access to it. Another likely source going forward will be biofuels, since biomass burns when dry. Wind will play a lesser role, as it is secondary to solar energy, as are biofuels. And there’s nuclear but I won’t address that as it has many technical hurdles to overcome, and others do a much better job than I could.

In this post I want to address the biofuel situation, which of course encompasses food. What I’ll do is provide some calculations which you may or may not find interesting. But the purpose of this post is to put energy into an order of magnitude perspective, so at the end I will summarize everything in bold type and a chart so that it’s crystal clear.

From my favourite ecological energetics webpage, we see that the planet has a total annual photosynthetic Net Primary Production (NPP) of 224 petagrams, or billion tonnes (Gt), of organic matter. This is the total amount of net biomass produced by every plant on the planet for a whole year. “Net” accounts for the plants’ own biomass that they burn in order to live, just as we do – it’s just that plants can produce their own biomass when it’s sunny – they are autotrophs, whereas we have to eat others to get ours – we are heterotrophs. Global production is divided roughly evenly between the oceans and the land. However, we harvest more of the land’s productivity than the oceans’, for obvious reasons.

For confirmation of this number, another source says that 105 Gt of carbon is produced by the planet, and if we assume this material to be equivalent to cellulose, then with a molecular mass ratio of 44% carbon to cellulose, this works out to 238 Gt of organic matter. So the estimates are pretty close to each other (224 vs. 238). Expressing this in barrels of oil equivalent, we multiply 224 Gt by the ratio of 17 MJ/kg for carbohydrate energy content over 46 MJ/kg for oil. We get 83 Gt oil equivalent, which is 579 billion barrels.

If you’re the kind of person that likes to calculate things from scratch by yourself, then you can confirm the above 224 Gt biomass number by going back to the above ecological energetics webpage, in which you will find a chart in Figure 4 showing yearly productivity of various ecosystems, in Calories per m2 per year. The conversion factor to bring to kg is that the most productive ecosystems with  a productivity of 9,000 Cal/m2/yr corresponds with 2 kg/m2/yr of biomass. Using this number, and scale it for all the other ecosystems in that chart, go to Google Earth and make an estimate for the area extent of each ecosystem type. Multiply it out and you should get around 200 Gt of biomass per year.

This 579 billion barrels is equivalent to 22 cubic miles of oil, which is 19 times greater than yearly oil consumption and 7 times greater than the total technical energy used by our economies. This is how much net energy (after respiration) the planet sequesters from sunlight per year through photosynthesis and stores in the form of plant tissue.

For comparison, how much of this NPP gets deposited in the ground? Proxy measurements indicate that atmospheric carbon dioxide concentrations were around 4000 ppm by volume 450 million years ago. Since then that carbon has been deposited in the ground, dissolved in ocean seawater, and trapped at the bottom of the ocean as methane clathrates, except for the 400 ppm still in the atmosphere.

On page 10 of this paper you will find estimates for the deposition rates of fossil fuels over this period hundreds of millions of years ago. I will sum them up as follows: 2000 m3/yr heavy oil, 800 m3/yr oil, 500,000 m3/yr gas, and 50,000 t/yr coal. When you do all the conversions that comes to a  grand total of 208,000 barrels of oil equivalent per year, or about 3 million times less than global NPP. 208,000 barrels might sound like a lot but do you know how much that is? Here is a nice order of magnitude perspective that anyone can appreciate — it’s ten olympic sized swimming pools — a year! This is equal to 0.0003% of fossil fuel extraction rates today, or 0.00004% of NPP. It’s a pittance! In other words, the amount of global NPP that was deposited in the ground, over a whole year, was equivalent to ten seconds’ worth of global NPP!

It is estimated that a total of 969 Gt of oil equivalent fossil fuels will be ultimately extracted, corresponding to 35 million years’ worth of fossil fuel deposition. Assuming that most of those fossil fuels will be burned in a period spanning about 200 years of human history, we are burning through them at a rate 175,000 times greater than deposition rates!

How Much of Global NPP Do We Take Today?

To further develop this order of magnitude energy analysis and better elucidate the predicament we face, let’s calculate how much food energy we harvest. I presented this data in my previous post. The human population consumes 18,700,000,000,000 Calories of food per day. To get an estimate of how much total food is harvested we need to include animal feed. So in my spreadsheet, for each country I factored in what percentage of the diet consists of animals, and then increased this portion by the trophic efficiency factor, which I will assume to be 10% on average. This gives a total of 47,300,000,000,000 Calories. This is based on 6.7 billion people so I’ll scale it up for 7 billion and we get 49,500,000,000,000. A number I typically encounter is that about half of our harvested food is wasted before going down our gullets, so double this to 100,000,000,000,000 Calories per day. Convert to megajoules and we get 151,000,000,000,000 MJ of food harvested from the planet per year.

But we also need a factor to account for unused stems, leaves and roots left over after harvest. Although we don’t directly consume this material, called “stover”, it is necessarily produced along with the food that we do eat, since you can’t grow corn or rice without stems, leaves and roots. This source uses a stover ratio of 50% for corn crops (also see here for further discussion of how much of this material can be removed from the site for biofuels before impacting food productivity). I will assume it’s similar for other crops as well so I’ll increase our food harvested total by this factor of 2. This gives a total of 300,000,000,000,000 MJ of biomass produced by the planet each year for the purposes of providing food for humanity. Assuming food has an energy content of 25 MJ/kg (somewhere between carbohydrates / proteins at 17 MJ/kg and fats at 37 MJ/kg), we get 12 billion tonnes. We can also express it as crude oil equivalent, assuming 5,882 MJ/barrel, which is 51 billion barrels, or 2.0 cubic miles of oil.

We also need to include the amount of biofuels and wood products we harvest. 3.5 billion m3 of wood are used each year for lumber, paper, and firewood which, assuming an energy content for wood of 17 MJ/kg, works out to 4 billion barrels oil equivalent. Let’s add that to 51 to get 55. Add in 28 billion gallons of liquid biofuels a year, which is equal to a minor 0.43 billion barrels, and now the total comes to 55.5 billion barrels (oil equivalent) of biomass produced by the planet for the purposes of food, fuel, lumber and paper. This amounts to 9.6% of global NPP of 22 cubic miles.

For comparison, in the results section of this paper you will find a 12% figure for total harvest. That is slightly larger than my 10% estimate but I think I may have overestimated the trophic efficiency of meat production on a global scale, especially fish as they feed several rungs up the food web. Either way, it’s pretty darn close so let’s call it a day and confirm that, yes, about 12% of the planet’s biological productivity is appropriated by humanity.

From this it may seem like we have quite a bit of room to maneuver going forward because the total amount of technical energy we use is equivalent to only 1/7th of the total NPP of the planet. And we already harvest 1/8th of NPP for food, biomass, etc. No problem — when we run out of fossil fuels we’ll just add another 1/7th of the planet’s NPP to our plate to take a total of 1/4 of global NPP and it should be solved. We can fit that in, right?

Well, it’s not that simple because not only do we appropriate productivity by harvesting biomass, but we also degrade habitat and expropriate land from otherwise productive uses. When all this is factored in, as the above study suggests, the total amount of global NPP appropriated by us — harvest plus degradation — is twice that at about 24% of total potential global NPP. If extrapolated linearly, to double that appropriation in order to replace fossil fuels with biofuels, we’d need 48% of NPP. That is half the planet’s total productivity! Now we’re getting tight…

Will We Be Able to Increase Our Share of NPP Going Forward?

Would we be able to achieve an appropriation of 50% of the planet’s productivity necessary to replace fossil fuels with biofuels? We’re already halfway to 50%, so why not? Again, it’s not that simple, because the 22 cubic miles of global NPP incorporates the total amount of vegetation grown everywhere on the planet. It accounts for every single leaf on every tree, every blade of grass, every root, and every microscopic plankter in the far reaches of the ocean. In order to be able to realize all the energy from that 22 cubic miles (oil equivalent) of global NPP, we’d have to completely harvest for our own uses every single piece of vegetation, algae, and plankton that grows on Planet Earth, every year! There would be no trees left anywhere as they would not be allowed to grow beyond year one (or if they were allowed to grow, then all of their dead leaves would have to be harvested and their entire root systems dug up afterwards so as to harvest that biomass). Every square inch of the planet would have to start from scratch from a sterile moonscape, every year. There would be no animals other than a few species we use for food — 99% of the world’s species would go extinct. Not only would this be impossible from a practical standpoint — how would we be able to harvest every single root, plankton and other piece of organic matter before they have a chance to decompose? — but additionally, from an ecological point of view it would imply that nutrient cycling in ecosystems would stop. With no decomposition there would be no more replenishment of soil nutrients as we harvest and remove plant material. Those nutrients would all have to be replaced by us. Where would we get them from? How would we apply them to every square inch of the productive planet? Would we distribute our sewage back over every square inch of land? How would we do that? It’s totally unfeasible, so the real capacity of the planet to provide biofuels and food for us is vastly below this 22 cubic miles oil equivalent of NPP.

I think the best analogy to explain the problem with wringing more and more NPP out of the planet is to imagine a wet sponge. Initially, it’s super easy to squeeze water out of a saturated sponge — you just have to pick it up and water drips out by itself. This corresponds with the easy NPP — things like the Newfoundland cod stocks when the white man first came over, and many other historical fish stocks around the world before being depleted. All we had to do was throw some nets over the side and that productivity was easy to harvest. Another example would be shooting 70 million bison from trains when the American West was being conquered.

After these kinds of easy NPP were harvested and the sponge stopped dripping, we then had to move on to squeezing the sponge a bit. This involved converting the Great Plains into farms — it required a bit of work. Another example would be chasing after increasingly difficult fish stocks with gigantic ocean-going factory fishing freighters whose catch in the lawless open oceans is limited only by the sheer inaccessibility and dispersion of the remaining fish stocks.

These sources of NPP we’ve also now mostly depleted. Beyond these, we now have to squeeze the sponge harder and harder to get NPP out. But there comes a point where no matter how hard you squeeze, you just can’t get any more water out of the sponge. This is the difficult NPP that we will never be able to harvest — how are we going to be able to harvest oceanic plankton photosynthesis? That’s a significant chunk of global NPP. And there will always be weeds and such growing in the corners of the continents, even if we strip all ecosystems bare. We’d need a certain amount of residual vegetation growing on the land in order to maintain society before we collapse, so this amount of NPP will be inaccessible to us.

This is the problem with increasing our take of NPP, in that it gets harder and harder to get an additional unit out once we start taking significant proportions — and we’ve basically maxed it out already. And my sponge analogy is not as accurate as it could be, since you can probably squeeze about 90% of the water out of a sponge, leaving 10% behind. With our harvest of global NPP, it’s probably the reverse of that — we can maybe sustainably harvest about 10% of global NPP, which is where we are today. A better analogy than a sponge would be trying to squeeze water out of a wet running shoe. Try it and you’ll see what I mean.

Considering the impossibility of harvesting anything remotely close to 100% of NPP, it really is astounding that we’ve even reached 24% (well, 12% if you only consider the harvest). You seriously need to take a moment to contemplate the amazing feat humanity has achieved in that accomplishment. I’ll say it again: we harvest for ourselves / degrade one quarter of every piece of plant matter that the planet produces (or was able to historically produce before we degraded it). This is so far beyond anything that any animal species has come close to achieving in the history of the world, it’s not even funny. Any other species would have collapsed from overpopulation eons ago. How is it that we have managed to hold on so long? We use technology and advances made in the Green Revolution, that’s how.

But we’ll just find ways of further increasing the planet’s total NPP to meet our energy and food needs. There may be limits, but our ingenuity will keep pushing them Back to the Future”, is what we’re being told by the cornucopians. We’ll just keep piling on more Green Revolution.

Really? According to the above referenced paper, global NPP has actually gone down 10%, despite the Industrial and Green Revolutions! What?!?!? All that’s happened is that humanity has transformed the kind of NPP growing on the planet from hard unpalatable trees, thorn bushes and other such unpleasantries into plant matter which is more compatible with our own delicate palettes and harvesting equipment.

But if I drive around I can see lots of forests. And there’s tons of forest up north. There’s no way we harvest 12% of all the vegetation on the planet“, one might wonder. But this masks what’s really going on. If you look at pages 10 onwards of this study you will see that per-hectare agricultural yields have increased 2 to 6 fold as a result of the Green Revolution (and yearly % increases are now dropping). What’s happened is that the ecological productivity that we have degraded in many ecosystems has been offset by increases in the productivity of land under intensive agricultural management (especially irrigated arid areas). The net impact of this has been a reduction in global NPP of 10% (so does that mean I should decrease my global NPP estimate from 22 cubic miles to 20?)

Beyond this, northern forests aren’t highly productive — they may have a large standing biomass which gives a visual impression of abundance, but the yearly production rates aren’t overly high compared with lower-latitude agriculture. We put our agriculture in the most productive areas, leaving the remainder for wilderness. Here are some numbers to provide perspective for this: the most productive ecosystems are estuaries, swamps, tropical rainforests and warm temperate forests which can produce about 2 kg of biomass per square meter per year. Northern forests produce about 1.5, savanna 0.8, and temperate grassland about 0.5 kg/m2/yr. In comparison, a typical Iowa corn field today produces about 1 kg/m2/yr, which is about double what that land would have produced historically as natural grassland with bison.

But the critical point to this comparison of ecological productivities is that the NPP produced by natural ecosystems is for the most part retained in that ecosystem. That vegetation is harvested by animals and the fertilizer nutrients of N, P, K etc. are returned to the soil to be recycled into future growth. In contrast, with modern agriculture, we are continually taking that biomass production off the land, and those nutrients eventually end up in our sewers and flow out rivers to the ocean. So it’s not really comparing apples to apples to say that an Iowa corn field produces roughly the same biomass as a productive savannah, because the only reason that Iowa corn field is able to produce so much biomass is because we replace, using fertilizers, the nutrients that were removed by the corn harvest.

So although you can indeed drive around and see lots of productive forests, and therefore be lulled into a false sense of security about how much we are taxing the planet’s ecosystems, consider what would happen to the productivity of that forest land which currently produces 1.5 kg/m2/yr if we were to start harvesting 1.0 kg/m2/yr of that and removing it from the site! We wouldn’t have many forests around for long, would we?

Also consider that much of the agricultural production we currently enjoy resulting from the Green Revolution has a heavy reliance on industrial automation, machinery, and especially fossil fuel and irrigation inputs. In fact, the above study points out that, “Increased use of fertilizer has been a major factor explaining perhaps one third to one half of yield growth in developing countries since the Green Revolution” (page 9) — and nitrogen fertilizers are made from natural gas. Irrigation accounts for 20% of the yield gains in the last 20 years (page 8). The inescapable vicious circle plaguing biofuel production should now be evident, in that the techniques and chemicals used to boost NPP (i.e. fossil fuels) are the very substances that will purportedly be replaced by … biofuels! But it’s biofuel production that would need those inputs! Doh! That’s why US corn ethanol production barely has a positive net energy return, and why it’s only viable because of subsidies and relatively cheap fossil fuels. Brazilian sugar cane is substantially higher but I wonder how much of that is dependent on fertilizer inputs? How sustainable is it? Would you believe that even with all of Brazil’s bio-ethanol and oil extraction activities, it’s still a net oil importer?

So one inevitably has to wonder: how much will global NPP decrease when fossil fuels (and irrigation water) run out? And don’t forget about Peak Phosphorus. To just maintain current food production after we run out of fossil fuels, we’d need to increase by some factor the percentage of global NPP devoted to us (and total global NPP will be dropping…) So pick a number; your guess is as good as anyone’s. I’ll say agricultural productivity drops an average 3 fold from the current artificially boosted, unsustainable levels. This means that in order to maintain current food harvest rates, the proportion of global NPP devoted to human food production would jump from 8% to 24%. Plus we’d also have to apply this factor to biofuel production, because that would no longer be benefiting from fertilizers / irrigation either. It’s a double whammy hit. Add in our additional degradation of 12% which decreases global NPP even further, plus another factor increasing that, as now we’d need 3 times the area to produce the same amount of food, so that brings us up to something like 50% of NPP, using conservative figures. And I haven’t even considered increased food spoilage resulting from a breakdown in the food transport and storage systems, or future population increases, or increased soil salination which will not be easily addressed because we’ll be running out of fresh water with which to flush that salty arid agricultural land with.

And don’t forget that in order to turn biofuels into something useful (like fuel for an engine), a large portion of the original energy is wasted, whereas with fossil fuels most of the energy is conserved (80% for oil sands, all the way up to near 95% for some of the better gas and oil sources remaining). So to merely convert all of our current fossil fuel consumption over to biofuels would require increasing biomass harvest rates for this purpose by another factor of 2 or 3 beyond what we’ve already added. Now we’re probably up to 200% of NPP, realistically. Biofuels are totally unfeasible.

Now, I’ve only considered factors that would tend to make our food / NPP situation worse going forward. I sure sound like a party pooper. What about all that glass-half-full stuff, how we’re supposed to maintain a positive outlook on things regardless of what a rational analysis might suggest, to maintain faith in the magic of Treknology and iPads through thick and thin? What about factors that would tend to make our food situation better, that provide some balance to my doom and gloom, some hope for the future?

Which are what, pray tell? As stated above, global NPP has gone down 10% even factoring in the Green Revolution. Many seem to believe that the genetic advances made in the Green Revolution have engineered plants that can produce biomass more efficiently than traditional varieties can. We have improved on nature, so the story goes. But alas, this is not so… All’s those genetic advances have achieved is produce plant strains that can better utilize the external inputs that we throw on the land (i.e. irrigation, fertilizers, and pesticides). Take away those external inputs, and all the genetic modifications we put so much faith in today are for naught! The traditional crop varieties we are losing will do a much better job of producing food when we no longer enjoy these external boosts to productivity. It’s like comparing a 4 cylinder econobox car to a Hummer. The Hummer is much better at producing large amounts of power … assuming it can be fed with large amounts of gasoline. But when we run short of gasoline, which car would be better at moving you from point A to point B? If there was a way to increase long term sustainable NPP yields, we can be sure that Mother Nature would have already figured it out and implemented it long ago (the one exception to this would be using otherwise wasted solar energy to desalinate sea water and irrigate deserts — plants haven’t figured out how to do that yet).

Will photosynthesis be boosted by increased CO2 in the atmosphere? This effect seems to only be evident in C3 plants, not C4, and then only in controlled lab settings. In plant science, there is an analogy to improving yields that is based on a “leaky barrel“. Plants require many conditions and nutrients to be satisfied in order to produce biomass. But their production is ultimately limited by the most limiting input (the lowest leak in the barrel). Plugging up higher leaks, i.e. increasing inputs that are not limiting, will not increase production. This is why, despite CO2 having risen over 25% recently, we have not seen explosive increases in plant productivity outside of that which receives inputs via the Green Revolution. Because CO2 isn’t limiting.

Another impact potentially offsetting agricultural productivity declines will be increased productivity in higher latitudes due to a warming climate. This may happen, but will likely be offset to some extent by ecological collapses occurring elsewhere as climate shifts (for example, shellfish-based oceanic food chains may collapse due to acidification from carbonic acid buildup). It takes a long time for ecosystems to reassert themselves, and with humanity harvesting everything in sight I don’t think it will be quite as straightforward as many would suggest. But, some countries may benefit from this, like Canada. Let’s cross our fingers.

And of course, as we run out of fossil fuels we’ll definitely use energy more efficiently so it’s not like if we have 1/2 the energy we’ll be doing 1/2 the things; we’ll just do them better, maybe do 3/4 the things. And we’ll allocate energy to where it’s needed the most until the bitter end — food production. But this won’t increase agricultural productivity; it will merely delay the decline. Eventually we will run out of fossil fuels for all practical purposes, including food.

Finally, I guess one could argue that we will just eat less meat in the future. Yeah … I guess you could call that a “solution”… when everyone’s forced to eat less meat because there isn’t any around… That sounds more like the verge of an ecological collapse to me. So I place the above factors that might tend to somewhat offset declining agricultural productivity in the dubious box. They will likely have minimal, if any, positive overall impact. I wouldn’t hold my breath expecting any miraculous surprises. The only thing that would have a significant impact would be replacing fossil fuels with another energy source so that we can continue irrigating land, manufacturing fertilizers, and transporting food efficiently.

In my previous post on this topic I calculated how much additional food the planet would have to produce to bring everyone up to a western-equivalent diet – around 3 times as much as today. The next question that followed from this was: “Will the world be able to provide this?” Based on the above analysis, do we really need to spend time breaking out in-depth analyses of yield curves for various crops and investigate which ones show the greatest promise for future improvements? It doesn’t seem like a very useful exercise because we just got our answer, in that tripling current food production would add another 16% to NPP, taking us to at least 40%. Add in another certain percentage to account for additional NPP degradation, plus more for the amount of NPP appropriated for additional biofuel production going forward, plus factor in further reductions to global productivity when fossil fuels and irrigation run out, yadda yadda yadda, well you can see that this easily takes us to 100% of NPP and beyond. Clearly the answer is an emphatic, “NO”. So why is this goal even being seriously discussed?

So to sum up, not only will biofuels not be anywhere near capable of replacing fossil fuels on anything but niche scales, but it will be very unlikely that we would be able to maintain current food production capacity going forward as fossil fuels become scarce. Relying on photosynthetic NPP for energy beyond what we need for food is not the answer; it is a very dangerous path that leads straight into a Malthusian Collapse. Yet without a replacement for fossil fuels that is indeed what we will be doing.

The planet sequesters through photosynthetic Net Primary Production (NPP) 22 cubic miles of oil equivalent energy per year.

Humanity harvests 2.6 cubic miles (oil equivalent) of biomass yearly for the purposes of food, fuel, and wood products. A total of 24% of the planet’s total NPP biomass is appropriated by us. This has been enabled by the Green Revolution with its heavy reliance on fossil fuel and irrigation inputs. Even accounting for the stimulated (but localized) production due to the Green Revolution, total global NPP has actually gone down by 10% as a result of humanity’s activities.

Humanity uses about 3.1 cubic miles of “technical” energy per year (oil equivalent) from all sources, mostly fossil fuels. This is equivalent to 1/7th of global NPP. 1.2 cubic miles of this comes from oil.

To replace all of our technical energy with biofuels would quickly bring us impossibly close to 100% of the planet’s total NPP. We can’t expect to achieve anything close to this, from either a practical or ecological standpoint. Even a relatively small increase in biofuel production would push human appropriation of global NPP to dangerous levels (well, we’re already at dangerous levels…)

Not only will it be impossible to bring everyone in the world up to a western-style diet (even assuming fossil fuels do not deplete) but it will be extremely unlikely that even current food production could be maintained once fossil fuels run out, assuming that alternative energy systems do not step up to the plate to help maintain fertilizer, transportation and irrigation inputs.

The red bars show summed values from previous categories. Note that of the 5.6 cubic miles (oil equivalent) of total energy used by humanity, 5.4 comes from ecosystems, in the forms of food, biofuels, or fossil fuels. Anyone who thinks that modern technology has somehow severed our dependence on ecosystems needs to look at the numbers.

It’s pretty clear from this analysis that, without a replacement for fossil fuel energy going forward, WE ARE GOING TO DIE. That sounds like an extreme statement, but the math proves it. Of course, it might be theoretically possible for humanity to manage to scrape by in a wretched state as we totally strip all ecosystems bare looking for desperately needed energy, and somehow manage to keep 9 billion people alive. But this situation will not likely be stable — wars will inevitably be fought over resources and the population will in one way or another be reduced to what is sustainable long term, given the amount of energy that’s available to us — just like every other species in the history of the world has had to contend with. This is the more likely scenario of how a human collapse would unfold.

Coming from this perspective, when I hear some people argue that the economics of today don’t support the development of alternative energy sources, so it’s just not going to happen, I simply don’t accept this. If the energy is potentially there to be able to at least partially replace fossil fuels with solar energy to support electric transportation, desalination and basic human needs, then if the economics don’t currently work, we must make them work, because we simply have no alternative.

If you’ve been to the Himalayas you may have noticed that the forests there look different than elsewhere. The lower branches are all cut off and the forest floor has been swept clean. This is because the locals depend on them for biofuels — they actually collect and burn the pine needles for heat and cooking! This seriously impacts the land’s productivity as nutrient cycling is disrupted. If we do not develop alternative energy strategies to offset fossil fuels then we will be doing this on a global scale. We do not want to go there! Thankfully, due to the tremendous opportunity that solar energy presents, we don’t necessarily have to.

This is why I take issue with the argument that rather than trying to replace fossil fuels, we should just accept defeat, admit that it’s not going to happen, and learn to use less energy in the future — we should just hunker down and make the best of what we’ve got. I reject this. While of course we need to use energy more efficiently, what this argument fails to account for is the tremendous increase in biofuel demand put on the biosphere due to this hunkering down. People will want energy, and they will take it through whatever means are available. But, as I hope I’ve explained, the planet just can’t handle that kind of pressure. “Hunkering down and using the limited available energy more efficiently” is basically codespeak for, “hunkering down and preparing for a Malthusian Collapse, because we refuse to take the actions necessary to divert our demand for energy away from the overly-stressed biosphere”. Using less energy, by itself, is not a solution! We’re acting like deer caught in the headlights, frozen, unwilling or unable to step out of the way to avoid certain death. We need to be pushing hard for effective alternative energy strategies, along with economic changes that put a halt to global economic growth.

Since the efficiency of photosynthesis in converting sunlight to chemical energy is about 0.1 to 1% in good times (and only on productive land), whereas solar panels are 10-20% efficient at turning it into electricity, solar provides tremendous opportunities. About 3,850,000 exajoules of sunshine energy is absorbed by the planet every year, which is equivalent to 25,000 cubic miles of oil, or 8,000 times the total technical energy we use. Clearly we aren’t going to be able to pave the whole planet with solar panels, but clearly we wouldn’t have to, unlike relying on biofuels going forward. Indeed, the energy is there. So what’s holding us back? We haven’t yet burned even half the total fossil fuels expected to be burned, so we probably have enough energy available. The energy trap? I don’t think we are quite there yet, with such cheap natural gas flooding the markets. It seems we’re being held back by inefficient economics, politics, and excuses — not by energy.

It takes energy to make solar panels, solar thermal, and the associated electrical infrastructure to go along with this, so in a future post I will tackle the issue of to what extent, both technically and economically, it would be possible to use our remaining fossil fuel reserves to develop some semblance of a renewable solar energy infrastructure going forward post-Peak Oil, so that we could maybe, possibly, hopefully, avoid a planetary die-off.

7 responses

  1. Cold Camel

    Gregor, you are off in your calculations of the energy content of food. There is no way we consume as much energy in food as in fossil energy.

    June 5, 2012 at 3:27 am

    • Hey Cold Camel, thanks for pointing that out. You are right that I made a mistake, but it’s not what either of us thought. I carelessly brought over daily food consumption from my other page but assumed it was yearly. But then I screwed up on the Calories to MJ conversion by a factor of a thousand, so the end result seemed reasonable and didn’t lead me to question it, but it seems that I overestimated food consumption by a factor of almost 3. I’ll fix this tomorrow. Thanks for the comment, it’s good to try to nail down these numbers.

      June 5, 2012 at 7:58 am

  2. Cold Camel

    I calculate that we produce 0.3 cu mi of food a year. Unfortunately biomass still won’t work. If farmers focus on efficiency, productivity must plummet. If a ‘new’ agriculture that was both productive and efficient existed, then modern agriculture wouldn’t.

    The problem is real. Modern agriculture is real. Starvation is real. Solar may be a solution, but solar is a dream. I pay attention to what is real. Go find some kids and play. That is real.

    I have purposely not given you my calculations, because my numbers are fuzzy, and I am not an authority. Nicely written, by the way.

    June 5, 2012 at 4:29 am

    • If I underestimated food production by a factor of 3 then this makes the biofuel situation 3 times worse. That would give me 1.0 cubic miles (oil equivalent). Hey I’m not an authority either but it seems there are few authorities that have a wide perspective of a variety of subjects, so people who have less indepth knowledge about specific things, but cover a wider breadth, may be just as valuable. I will fix the numbers soon.

      June 5, 2012 at 8:04 am

    • So I have looked into my food calculations a bit more and I come up with about 2 cubic miles. This compares with your 0.3 cu mi. I think we are actually not is disagreement really, it just comes down to how one defines food. In terms of how many Calories go down people’s throats, you are probably accurate. But I include more than that:
      1) Food wastage
      2) Trophic efficiency of meat production
      3) All the roots, leaves and stems that go along with food production. You can’t grow corn without all that stuff.

      All these things are necessary contributions that are part of producing the final apple or piece of steak that enters our mouths. I don’t think it’s reasonable to exclude them. Of course there is some overlap with biofuels there, as the unused stems from corn plants could be used for ethanol for example, but then again this would tend to reduce the land’s productivity further and require more fertilizer inputs.

      June 11, 2012 at 2:35 am

  3. Aw, this was an exceptionally nice post. Finding the time and actual effort to create a superb article… but what can I say… I hesitate a lot and don’t seem to get nearly anything done.

    May 18, 2013 at 2:02 pm

    • Thanks Tom, yeah it’s hard to put in the time to do this, working 40 hours a week. There’s lots more ideas I have to write about but I have to restrict myself to one at a time. Hopefully I’ll have another one out soon.

      May 19, 2013 at 3:00 am

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