A penal treadmill in Burma, showing how coerced human-power is combined with technology to produce surplus value.

Penal treadmill in Burma, between 1890 and 1899. Credit: Wellcome Collection via Wikimedia

The Return of the Penal Treadmill

Business Obscura Aug 23, 2022

One barrel of oil has the same energy output as 5 years of human work.

150 years into humanity's big experiment with oil, we've lost track of this critical fact. We're energy blind, thinking of energy in terms of dollars instead of the energy return on investment, or EROI, leading us to spend valuable resources it took the earth millions of years to create on frivolous nonsense like mowing our lawns.


When the photo above was taken in Rangoon in the 1890s, the EROI of a barrel of oil was more than 100 to 1. That means that to produce 100 barrels of oil, you'll burn just one.

Now we spend one barrel, and get just 1o or 11 back. Some estimates put it even lower. The writing is on the wall. The cost of energy - in both dollars and energy - is rising sharply and will only continue to climb.

In nature, the hard EROI equation is 3 to 1. An eagle won't spend the energy to chase a rabbit unless it's going to gain 3x the calories it spent in the hunt. Anything less is a losing strategy.

And for us humans, it's estimated that complex societies require an EROI of 11 to 1. When we fall below this line, we're headed for societal collapse.

Thankfully, we're not at that point. While the EROI of oil has risen dramatically, other energy sources have held their return on investment. Coal for example, has remained remarkably steady at roughly 35 to 1, which is why I'm certain that we'll eventually burn every ounce of it we can get our hands on.

But let's consider one of the darker implications of this rapid decrease in our ability to generate cheap, abundant energy.

The Penal Treadmill

Lake any good British engineer, the inventor of the penal treadmill was ever on the lookout for maximum leverage.

Imagine a paddle boat wheel, that people climb endlessly, turning a crank and generate energy. It can be used to spin a fan, pump water, or most commonly, to grind grain. They called it 'grinding the wind'.

In 1818, Sir William Cubitt introduced the penal treadmill as a "means of usefully occupying convicts" in the prisons at Bury St. Edmunds and Brixton, rationalizing that ffenders should be taught "habits of industry".  Of course this is double speak for 'if you ain't making me profit, I got no use for ya."

This more profitable form of prison labor gave 19th century wardens and magistrates a reason to grow their flock of prisoners. No surprise that the Victorian age was the most significant period of prison construction in Britain's history.