In 1915, William Carlos Williams published a poem about dog waste. When industrial fertilizer replaced dung heaps, its spoils helped fund the spread of plastics. “Pastoral” shuns rural landscape in favor of a city scene, with an old man walking in the gutter. In Williams’s assessment, the man “gathering dog lime”—a euphemistic name for dog dung—does work “more majestic than / That of the episcopal minister.”

A 21st-century reader would likely find the man’s action unremarkable. Today, dog feces are understood to have dangerous levels of E. coli and salmonella, not to mention untold parasites. Therefore, they must be tucked away in plastic bags and deposited at the nearest poop station. Williams’s old man is significant for his dignity but not his occupation.

But it wasn’t always this way. Animal waste once provided a necessary ingredient for agriculture, especially at a local scale. When industrial methods of fertilization combined with germ theory, dung heaps became outmoded. Then the same chemical industries that synthesized fertilizer developed plastics, the materials now used in bags to clean up dog poop instead of recycling it.

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Before Western societies built conduits to flush excrement into the waterways, it was piled into dung heaps for reuse. Even in the Middle Ages, the stuff was a source of valuable materials, even if a noxious one. For alchemists, dung heaps were a source of saltpeter and, for some, including the 12th-century master Morienus, they provided the first materials for fabricating the philosopher’s stone. In an era before the Bunsen burner, dung heaps provided chemical researchers with a source of constant, elevated temperatures. The complex preparations were placed in flasks and buried in piles of manure where they underwent “digestion”—a process of slow heating over many weeks, and one of the fundamental transformations in the alchemical tradition.

In the 19th century, physicians and public-health officials began to understand disease-transmission vectors with more precision, even though germ theory did not triumph until near the end of the century. Particularly in Western Europe, health reforms inspired large urban public works to deal with waste. Government officials inventoried communities, especially where there were concentrations of urban poor. Not surprisingly, they found huge piles of garbage, including human and animal waste, in the streets.

Edwin Chadwick’s 1842 “Report on the Sanitary Condition of the Laboring Population and on the Means of its Improvement” describes the era’s conflicting excremental economies with shock and disdain:

There were no privies or drains there, and the dung heaps received all filth which the swarm of wretched inhabitants could give; and we learned that a considerable part of the rent of the houses was paid by the produce of the dung heaps. Thus, worse off than wild animals, many of which withdraw to a distance and conceal their ordure, the dwellers in these courts had converted their shame into a kind of money by which their lodging was to be paid.

Chadwick’s laboring population was primarily urban, but 19th-century America retained much of its Jeffersonian, agrarian nature. As a result, excrement had a different value in the New World. In 1853, D.J. Browne published The Field Book of Manures (also called The American Muck Book). He devotes a chapter to dog feces, noting that “this manure, wherever it could be obtained in sufficient abundance, has been found to be, it is stated, the ‘most fertile dressing of all quadruped sorts.’” Browne goes on to describe an 18th-century English farmer from Bedfordshire with an abundance of setters and spaniels. Their dung reportedly enabled his gravelly fields to outperform those of his neighbors. He also describes the valuable “corrosive” power of white dog dung, which he attributes to a carnivorous, bone-heavy diet.

Such white dung is the probable source of the appellation “dog lime.” It is likely Williams’s old man with the majestic tread was not cleaning up after his pet like the modern dog walker, but gathering dog lime for his garden. As a result, it probably had a yield superior to his neighbors who did not stoop to such indignity.

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During the 20th century, Western attitudes toward dog ordure shifted. The world is still full of dogs, but owners now fear the diseases this once-useful commodity represents. The triumphs of Joseph Lister, Louis Pasteur, and their fellow germ theorists explain part of the aversion, but not all of it. Industry had a greater role to play in the retirement of animal waste.

For alchemists, dung heaps provided chemicals and constant temperature. But modern chemists made the dung heap obsolete by producing synthetic alternatives. The change began with Friedrich Wöhler’s synthesis of urea in 1828, the first organic compound produced from inorganic compounds. Wöhler’s work paved to way for the Haber process, an industrial-scale ammonia-production method, and the birth of the modern fertilizer industry. (Fritz Haber is also known for managing the laboratory that developed Zyklon B, initially for use as an insecticide, later deployed by the Nazis in their death camps.)

Using Haber’s method in the 1920s, IG Farben, the German chemical cartel, scaled the production of urea from ammonium carbamate, providing the vast amounts of nitrogen required for modern fertilizer production. In a stroke, a nearly odorless powder that comes in a paper bag replaced the noxious, oozing dung heaps of old. Who needs to shovel American muck when you can sprinkle a sack of 10-10-10?

The enormous success of the commercial fertilizer and pesticide industries had far-reaching effects. IG Farben took another substance first discovered in the 19th century, polystyrene, and began large-scale production of plastic. Today, ordinary people encounter this material in the form of packing peanuts or disposable drink coolers. The related material polyurethane followed in 1939; it is fundamental for wood finishes, among many other industrial uses. In the years leading up to World War II, Wallace Carothers tried to industrialize the production of nylon at DuPont, and in the United Kingdom another chemical giant, the English Imperial Chemical Industries, was working to scale production of polyethylene, the most common plastic. Production of polyethylene began in 1935; by the 1950s a series of related discoveries enabled the industrial production of HDPE polyethylene, used for plastic bags, PVC pipes, and other goods.

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In the plastic bag now used to collect and dispose of it, dog lime comes full circle. Low-density polyethylene is found in grocery bags, sandwiches wrappers, and the bags in those boxes set outside city parks—the modern way to gather dog lime. The dung is considered useless and dangerous, and the plastic used to wrap and dispose of it righteous and safe. And yet plastic, the opposite of an oozing, dangerous dung heap, is now a greater threat to human survival, choking sea life, degrading the food chain, polluting the air during manufacture, and overwhelming landfills after disposal. In poop-bag form, polyethylene serves as a sanitary barrier, though its ability to conduct heat still gives contemporary gatherers momentary pause—that jolt of recognition that one is handling, albeit indirectly, an active, vibrant substance.

As Williams’s dog-lime gatherer shows, a long-standing human practice—the cycling of organic materials for the promotion of new life—became converted into a sanitary society disconnected from the ecological practice cleaning up dog poo supposedly also represents. Dog waste is now timeless, wrapped in an eternal casing and buried in a landfill, anaerobic environments where even biodegradable bags stay intact.

So much for the poop scooper’s moral triumph over the church minister. Even so, the conclusion of Williams’s poem still rings true: “These things / Astonish beyond words.”

This post appears courtesy of Object Lessons.