Tag Archives: EROEI

Energy Return on Energy Invested

Shedding our Fossil Fuel Suit

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iron man-esque graphic

From Pixabay (Ramdlon)

Fossil fuels have leveraged human power and ingenuity to a remarkable degree. Their discovery and accelerating utilization utterly transformed lifestyles, achievements, and even how we perceive ourselves as a species.

Yet, one thing we know for certain about fossil fuels is that they are a finite resource on this planet—slowly developed in select locations over hundreds of millions of years and being used about a million times faster than the rate of production. We know that we have already consumed a sizable fraction of the initial inheritance: perhaps now halfway through the irreplaceable allotment of oil. So we know that this phase of the human adventure is a temporary one.

The quintessential graphic for conveying this idea is one I have used many times, because I believe it is the most important plot modern humans could possibly absorb. Human energy use has shot up in the last 150 years, and in the context of fossil fuels will plummet on a similar timescale, leaving—what, exactly?

fossil fuel usage is recent, fast, and will be over soon

The fossil fuel energy explosion that powers our current fireworks show is a momentary phenomenon that will be over in a historically short time.

Over timescales relevant to civilization (which began 10,000 years ago with agriculture and cities), plots of almost anything relating to human activity look like hockey sticks: population, agricultural output, industrial output, mined materials, deforestation, species extinctions, and so on [see this later post]. Many of these certainly correlate to population growth, but the per capita impacts also have shot up, compounding the human footprint to a frightening degree. At this point, humans and their livestock account for 96% of mammal mass on the planet, leaving a mere 4% for all wild animals (half of this from massive whales and other marine mammals). It’s not just a footprint any more: it’s a boot on the throat of the planet, leaving non-human life gasping and silently begging for even a little mercy. Is anybody getting video of this?

Almost all of this explosive impact can be traced to fossil fuels, which I have started visualizing as a suit donned by humans that has given us literal superpowers. What would we be without our fancy suit?

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Space-Based Solar Power

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A solar panel reaps only a small portion of its potential due to night, weather, and seasons, simultaneously introducing intermittency so that massive storage is required to make solar power work at a large scale. A perennial proposition for surmounting these impediments is that we launch solar collectors into space—where the sun always shines, clouds are impossible, and the tilt of the Earth’s axis is irrelevant. On Earth, a flat panel inclined toward the south averages about 5 full-sun-equivalent hours per day for typical locations, which is about a factor of five worse than what could be expected in space. More importantly, the constancy of solar flux in space reduces the need for storage—especially over seasonal timescales. I love solar power. And I am connected to the space enterprise. Surely putting the two together really floats my boat, no? No.

I’ll take a break from writing about behavioral adaptations and get back to Do the Math roots with an evaluation of solar power from space and the giant hurdles such a scheme would face. On balance, I don’t expect to see this technology escape the realm of fantasy and find a place in our world. The expense and difficulty are incommensurate with the gains.

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The Biofuel Grind

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[An updated treatment of some of this material appears in Chapter 14 of the Energy and Human Ambitions on a Finite Planet (free) textbook.]

When we enter the decline phase of conventional oil—likely before 2020—we will scramble to fill the gap with alternative liquid fuels. The Hirsch Report of 2005, commissioned by the U.S. Department of Energy, took a hard look at alternatives that could respond to the scale of the problem in time to have an impact. Not one of the approaches deemed to be currently viable in the report departs from fossil fuels. But what about biofuels? To what extent can they solve our problem? We’ll dip our toes into the math and see where a first-cut analysis leaves us.

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The Energy Trap

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[This topic also appears in Chapter 18 of the Energy and Human Ambitions on a Finite Planet (free) textbook.]

Many Do the Math posts have touched on the inevitable cessation of growth and on the challenge we will face in developing a replacement energy infrastructure once our fossil fuel inheritance is spent. The focus has been on long-term physical constraints, and not on the messy details of our response in the short-term. But our reaction to a diminishing flow of fossil fuel energy in the short-term will determine whether we transition to a sustainable but technological existence or allow ourselves to collapse. One stumbling block in particular has me worried. I call it The Energy Trap.

In brief, the idea is that once we enter a decline phase in fossil fuel availability—first in petroleum—our growth-based economic system will struggle to cope with a contraction of its very lifeblood. Fuel prices will skyrocket, some individuals and exporting nations will react by hoarding, and energy scarcity will quickly become the new norm. The invisible hand of the market will slap us silly demanding a new energy infrastructure based on non-fossil solutions. But here’s the rub. The construction of that shiny new infrastructure requires not just money, but…energy. And that’s the very commodity in short supply. Will we really be willing to sacrifice additional energy in the short term—effectively steepening the decline—for a long-term energy plan? It’s a trap!

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Can Economic Growth Last?

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[An updated treatment of this material appears in Chapter 2 of the Energy and Human Ambitions on a Finite Planet (free) textbook, and also forms the basis for a 2022 article in Nature Physics.]

As we saw in the previous post, the U.S. has expanded its use of energy at a typical rate of 2.9% per year since 1650. We learned that continuation of this energy growth rate in any form of technology leads to a thermal reckoning in just a few hundred years (not the tepid global warming, but boiling skin!). What does this say about the long-term prospects for economic growth, if anything?

Gross World Product

World economic growth for the previous century, expressed in constant 1990 dollars. For the first half of the century, the economy tracked the 2.9% energy growth rate very well, but has since increased to a 5% growth rate, outstripping the energy growth rate.

The figure at left shows the rate of global economic growth over the last century, as reconstructed by J. Bradford DeLong. Initially, the economy grew at a rate consistent with that of energy growth. Since 1950, the economy has outpaced energy, growing at a 5% annual rate. This might be taken as great news: we do not necessarily require physical growth to maintain growth in the economy. But we need to understand the sources of the additional growth before we can be confident that this condition will survive the long haul. After all, fifty years does not imply everlasting permanence.

The difference between economic and energy growth can be split into efficiency gains—we extract more activity per unit of energy—and “everything else.” The latter category includes sectors of economic activity not directly tied to energy use. Loosely, this could be thought of as non-manufacturing activity: finance, real estate, innovation, and other aspects of the “service” economy. My focus, as a physicist, is to understand whether the impossibility of indefinite physical growth (i.e., in energy, food, manufacturing) means that economic growth in general is also fated to end or reverse. We’ll start with a close look at efficiency, then move on to talk about more spritely economic factors. Continue reading →

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