Our Love Of Sewers: A Lesson in Path Dependence

Originally posted by dave praeger on 06/18/07

This was originally posted on the Poop Culture blog and then on DailyKos. Nonpartisan requested that I post it again here.

For the first humans who gave up the nomadic life and settled into towns and villages, the problems quickly piled up. Quite literally, I mean: stinking, fly-covered piles of you-know-what. Sedentary humans rapidly learned that civilization and sanitation are inseparable — without laws and taboos regulating the disposal of human waste, stench and disease overwhelm civility and decorum.

Today we rely on toilets, sewers, and sewage treatment plants to keep us safe from our waste. But despite millions of lives saved, this sanitary model is not the paragon of human achievement. Rather, it’s a jury-rigged series of fixes applied to salvage an infrastructure designed in accordance with flawed science. It’s far from the ideal sanitary model. But in the short term, we’re stuck with it.

Which means that while civilization’s last great sanitary leaps came from London and Washington, the next is more likely to come from Lagos.

The economic concept of path dependence explains how the set of decisions one faces for any given circumstance is limited by the decisions one has made in the past, even though past circumstances may no longer be relevant. Sewers, for instance, rely on a certain amount of water being flushed down toilets to push the waste through the network of pipes. Though the technology exists to drastically lower the 1.6 gallons per flush our toilets currently use, we’re locked into using that ridiculous amount of water for fear that our sewers might grind to a stagnant halt without it.

Path dependence also explains why it wasn’t until 1972 when Washington finally decided it was time for America’s sewers to end their then century-long practice of channeling raw poop straight into America’s waterways.

Until the late 19th Century, most Westerners deposited their poop into backyard cesspools. This sanitary model was completely overwhelmed by growing population densities during the Industrial Revolution, subjecting civilization to seven great cholera pandemics and millions of deaths as a result. In the mid-1850s, a London doctor named John Snow discovered that cholera was spread by fecal contamination of water. Cities across the world slowly turned to sewers as the best means to remove waste from the population that creates it, led by London in 1859.

But to the scientists and engineers of the time, it was enough to simply direct a city’s sewers to outflow directly into running water. This seems stupid today, but it was in perfect accordance with the science of the time, which held that “the solution to pollution is dilution.” By the time Germ Theory rolled around and science realized that raw waste, diluted or not, was a vector for pathogens, we were way too invested in sewers to give up on them.

So America turned then to purification plants to sanitize municipal drinking water, enabling upstream cities to continue dumping sewage while helping downstream cities avoid that pesky dysentery. Not only was this system unable to scale to every single point of inflow, it did nothing to alleviate the environmental havoc being wreaked on the waterways. But the country was unwilling to give up on sewers, which meant the only choice was to jury-rig a treatment system: sticking multimillion dollar scrubbing plants at sewage outflow points to sequester organic matter from the 32 billion gallons of water we flush every day. There are over 16,000 such plants today; and since 1972, the government has invested a further $250 billion dollars in this sanitary model.

When the weather is nice, this model seems to work. (A steady rain in cities with combined wastewater/stormwater sewers overwhelms treatment plants, forcing them to discharge their untreated flow straight into the water.) Still, in spite of its general adequacy, this sanitary model is hugely expensive, wasteful, and energy intensive. It’s far from ideal. Rather, given our situation, it’s the best we can hope for. 

“The best we can hope for.” Such a phrase is the hallmark of path dependence.

Do I have something better in mind? In my book, I speculate on the future of what, to me, is the most promising alternative: fuel cells that turn poop into power.  Though it’s admittedly decades away, this is my vision of utopia: your poop is collected in your basement and harnessed to power your household.

And if you went “ewwww!” at the thought of collecting poop as a resource, then you’re suffering ideological path dependence. The flush toilet has locked you into an ideology in which poop should only flush down a black hole and disappear forever. That’s not to say I envision a future in which you shovel poop into your fuel cell like coal into a furnace, of course; but, as I wrote in the New York Times, civilization needs to learn to view poop not as waste but as a resource.

This is the one sanitary advantage held by a city like Lagos. Lagos is, in places, a failed city with a failed sanitary infrastructure. While this means Lagos suffers from terrifying sanitary conditions and periodic cholera outbreaks, it also gives them an opportunity. Just like many developing countries have leapfrogged expensive land-based telephone infrastructures straight to the efficiency and cost-effectiveness of mobile phones, so too can cities like Lagos benefit from *not* being locked into sewers and sewage treatment plants.

Because, unlike us, change won’t have to be justified against abandoning the billions already invested and the ideology already assimilated. Instead, when their turn finally comes, they’ll be able to learn from our century-plus of trial, error, capital outlay, resource drain, and energy consumption, and leapfrog that path altogether.


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