Friday, August 17, 2018

The global economy, heat engines, and economic collapse

British Petroleum provides some pretty nice tools for visualizing energy consumption like the figure above which drives home effectively the point of just how fast our demand for energy is growing, roughly quadrupling in the past 50 odd years.

In order to understand this growth better, I think it's important to ask why we need energy in the first place. This may seem like a pretty bone-headed question -- of course we need energy. But energy is not an essential ingredient in traditional macro-economic models. In the best case energy is treated as a quantity that can be "substituted" for other ingredients of the global economy as capital and labor.

As a physicist, this seems totally nuts as our individual ability to work rests on the availability of energy. We're not somehow divorced from the laws of the universe. I've never heard of someone being an effective element of the labor force who had completely ceased to eat. And food sure doesn't materialize without work being done.

Instead, I think it's appropriate to treat civilization as a what can be termed a thermodynamic heat engine. The idea of a heat engine was first envisioned by French engineers in the early 1800s. In a car, work is done to propel a car forward by consuming the chemical energy in gasoline at high temperatures and dissipating it as waste heat at low temperatures with the pistons moving up and down in between.

In one way, we're very similar. We consume energy to go through the cyclic motions of going to and from work and the grocery store, sending out internet search requests, and pumping our hearts. All these actions require a temperature gradient where energy is released at high temperatures and dissipate at cold temperatures, whether with our cars, our computers, or the gradient from the inside to exteriors of our bodies. In fact, we can see all of human civilization as a "super-organism" that consumes primary energy to engage in all of its internal circulations, ultimately radiating waste heat to the atmosphere and then to cool of space.

High potential primary energy resources like oil and coal sustain civilization’s circulations against dissipation of waste heat. ‘Useless’ energy ultimately flows to space through the cold planetary blackbody temperature of 255 K. In between lies civilization, including people, their activities, and
all their associated circulations, whether or not they are part of the GDP.

Civilization Growth

A key difference between human civilization and a car is that it can grow. By growing, its thermodynamic engine expands. A larger engine consumes more, dissipates more, and does work ever faster. This positive feedback provides a recipe for exponential growth.

Civilization uses energy consumption mostly to sustain existing circulations. A small fraction is also used to grow civilization through an incorporation of new raw materials (e.g. iron and wood) into its structure. Thermodynamically, this is possible only if civilization consumes a little more energy than it dissipates. A small fraction of the energy that is consumed is available to incorporate raw materials to build civilization.

We’re actually pretty familiar with this. If we eat too much we get fat. I’m told that consuming an extra 3500 calories beyond what we need leads to a pound of weight gain. This is the energy required for the body to turn food into flesh.

A child consumes food today in some proportion to the child’s body mass. The child experiences a production of mass if there is a convergence of energetic flows such that it dissipates less heat than is contained in the food energy eaten. The child’s current size is directly a consequence of an accumulation of prior mass production. Its current rate of food consumption is also a consequence of prior production. As the child grows it eats more. As the child approaches adulthood, the disequilibrium between consumption and dissipation narrows, and (hopefully!) the production of new mass stalls.

So economic production, or the GDP, can be seen as the consequence of this imbalance: production is positive only when primary energy consumption is greater than the rate at which civilization dissipates energy due to all it’s internal circulations. If production is positive, civilization is able to incorporate raw materials into its structure. It grows, and then uses the added population and infrastructure created with the materials to consume even more energy.


I think this is what is happening with the BP statistics. Because the GWP exists, we grow, and then use our growth to access more energy which we can then consume with the higher infrastructure demands. The relevant equation is that every 1000 dollars of year 2005 inflation-adjusted gross world product requires 7.1 additional Watts of power capacity to be added, independent of the year that is considered.

Right now, energy consumption is continuing to grow rapidly, sustaining an ever larger GWP. But it is not the rate of energy consumption that supports the GWP, but the rate of growth of energy consumption that supports the GWP.

This important distinction is flat out frightening. The implication is that if we cease to grow energy and raw material consumption globally, then the global economy must collapse. But if don't cease to grow energy consumption and raw material consumption then we still collapse due to climate change and environmental destruction.  Is there no way out?


  1. Is there a way out? The usual response from eco-friendlies is "Sure! We just convert to renewables and climate will not collapse us!". My response to them is - sounds great... but the numbers just don't pencil out. Nature's laws are not normative, their quantitative. And they are absolutely inviolate. Converting to renewables itself takes energy and when you attempt to factor that in, given the bloated fossil fueled civilization that we are stuck with as our t=0 initial conditions, then it looks pretty darn hard to find a graceful exit. It's possible perhaps, but only if we become different animals than we seem to be. The qualitative difference between what is needed, and what is the usual assumed path, is that what's needed is a big dose of Civilization Pain, and THAT we absolutely won't tolerate voluntarily. So it looks like it'll instead be involuntarily. It is physically possible for all 7 billion of us "get religion" and immediately go on a massively Spartan lifestyle change diet, meanwhile diverting every spare dollar to decarbonizing. But will we? Very hard to imagine it actually happening. Instead, we elect demagogues and "strong men" who will tell us what we would rather hear, rather than the Truth. And meanwhile, the sequestered carbon in soils, vegetation, the ocean, the permafrost... will be re-awakening and re-emerging to make up for the carbon we imagine we'll stop burning. We'll now have to built massive infrastructure and consume new energy (solar? wind?) to air-capture CO2 and push it back down from where it came from, and quickly, to shut off these feedbacks.

  2. I'm only half joking when I say I expect to see an abrupt shift towards fascism as a means for enforcing the austerity required for collective survival. Surely there are historians who have explored whether and how political systems reflect resource availability and environmental conditions.

    1. yeah, except the fascists will enforce austerity not for OUR collective survival but to support THEIR kleptocracy. If your point is that they may commandeer this argument as a means to justify instituting fascism, at this point nothing would surprise me.

  3. i'd like you to explain why your theory uses watts (energy as flow) vs joules, (Energy as quantity), W = J/sec of course.

    For why TG's theory has gotten so little traction in 10 years, see Ugo Bardi on the Peer Review process and his own description of the travesty he endured when he first submitted his papery. Bardi at

    1. From a thermodynamics perspective, civilization is an open system that survives by converting high potential energy (or low entropy) density fuels into low potential (or high entropy) density waste heat. It is the continual conversion of one to another that sustains all that we do, including our thoughts, thereby defining our wealth - our collective capacity to think and do.

  4. From a thermodynamics perspective, isn't civilization just like Mr. Creosote? He is a monstrously obese restaurant patron who is served a vast amount of food in a Monty Python film. After being persuaded to eat an after-dinner mint, he explodes. Did Mr. Creosote have any other way out?

  5. As far as I understand thermodynamics, though, there is no "pushing CO2 back where it came from" without expending even more energy than that which was obtained from its release.

    I'd be interested to learn differently.

    1. Roughly. Your argument is strictly true if the goal were to return CO2 to its original form as a fossil fuel. If it is converted to another solid or liquid form, then the chemistry can allow for this being done using less energy than was obtained during the initial release. Either way, the amount of energy is significant enough as to likely be prohibitive economically.

  6. It seems that returns to capital are being fabricated by financial institutions to give the impression of growth. Even though things may be slowly collapsing even now in certain areas, central banks blowing asset bubbles and media propaganda can give the impression of "all is well". Of course, most people on the ground will experience some dissonance between their real lives and the message. You may find some discussion at interesting, but it's not peer reviewed and if it had to be, it wouldn't exist.

    1. Nate Hagens makes the valid point that all "growth" these days is really paid for by debt. However, in the civilization thermodynamics sense, that doesn't matter. It's still spending in service of taking things to a lower entropy form that must then be forever supported against decay. So yeah. Not only do we get stuck with the energy bill for this, but gotta repay the principal and interest since we're borrowing it from future generations. Maybe the "good" news is that they may not survive to hound us for collection! What a world we live in.

  7. "So, even if sunlight and wind is seemingly infinite, our planet Earth is not. Any short-term material gain of ours is a loss for the world around us. Renewables only accelerate this process."
    More excellent, honest work from Tim Garrett who Professor Guy McPherson often quotes.
    I've added this to the comments section my blog post on the same subject;

  8. "every 1000 dollars of year 2005 inflation-adjusted gross world product requires 7.1 additional Watts of power capacity to be added"

    I'm not clear on this wording. The paper you point to seems to say something slightly different, "7.1 ± 0.1 Watts of primary energy consumption is required to sustain each $1000 of civilization value"

    Can you explain this a little more? What is the 7.1 watts "added" to? Perhaps a simple example of, say, a GWP of $2000 in one year (call it year 1 of a civilization) and $2006 the next, might help, or would that be too simple?

  9. The first statement is the first derivative of the second with respect to time.

    The equations in the paper pointed to are most precise. But simply, the GDP is production, and production adds. Even if there is no GDP growth, as long as there is the existence of the GDP there is fabrication of new materials and societal connections that represent an addition to total civilization wealth. Wealth does not exist in and of itself but only insofar as it can sustain all the back-and-forth of civilization's activities. These circulations require energy.

    So every dollar of GDP adds to wealth and requires and additional 7.1 additional Watts of power capacity.

    Every dollar of wealth - accumulated through past production - requires 7.1 Watts of power capacity

    Key to the calculations is inflation adjustment which accounts thermodynamically for decay

    1. Thanks. I think I'm closer to an understanding now. It was the "added" that was throwing me. So, in my example, ignoring the energy needed to create the first $2000 of GDP, to sustain that first year's $2000, the second year's power capacity need to be 14.2 watts. In the third year, another 14.6 watts would need to added to the previous year's capacity, making 28.6 watts (plus whatever is needed to create new GDP). Is that right?

      Sorry if this seems silly, just trying (and previously failing) to understand what your work shows.

    2. Definitely not silly. It seems so counterintuitive I think because we have become so accustomed to living in a capitalist society that we can't imagine a world without economic production that isn't tallied with currency.

      But yes, even if the GDP is constant from year to year, the power capacity would still grow. The P in GDP really does stand for something. And whatever is produced has no value without continuous energy consumption to maintain the circulation that connect it to everything else.