Answer: Horse Manure

While mighty steam engines moved people and product across countries and continents in the mid-to-late 19th century, horses were the transportation method of choice for everything else. Whether you were riding a lone horse to get to your destination or riding in a wagon drawn by horses, you were likely taken to your destination by a horse (and all the goods you purchased were delivered by horse-drawn wagons when you got there).

In the countryside, this didn’t pose much of a problem, but the high density of people and industries in cities meant a high density of horses. In turn, a high density of horses meant a high density of manure. A single horse creates anywhere from 15-35 pounds of manure a day, and big cities like New York City and London had thousands upon thousands of horses. London alone, by 1900, had over 11,000 horse-drawn cabs and several thousand horse-drawn buses that required huge 12 horse teams to pull them. All told, there were over 50,000 horses used just for transporting people. Factoring in the horses used for industries, and the city of London was wrestling with a transportation network that generated in excess of a million pounds of waste a day. Things didn’t look any better in New York, either, where an even greater number of horses and people doubled the amount of waste.

There, and in other major cities around the world, the streets were piled high with manure, manure dust coated everything, and the piles attracted hordes of flies that spread disease. Not only was it an unpleasant and unsanitary situation all around, but people started realizing that if the cities continued to grow, the amount of manure piling up would pile up even higher (after all, the only way to get the stuff out of the city in the first place was more horses). A giant panic ensued and journalists pointed out that based on even simple calculations, the amount of manure that London would be dealing with in 50 years time would be so great it would be slowly burying it.

Fortunately, for those of us that want to enjoy a jaunt down 5th Ave. without walking through piles of horse manure, we know how the story of the urban horse ends: with the advent of the automobile. For all the hiccups we have had over the years ironing out issues with automotive exhaust and pollution, it all pales in comparison to the problem of a major city disposing of several million pounds of manure a day.