The great horse manure crisis of 1894 happened (primarily in London) when horse manure was no longer valuable enough to pick up for a profit. https://en.wikipe

The great horse manure crisis of 1894 happened (primarily in London) when horse manure was no longer valuable enough to pick up for a profit. https://en.wikipedia.org/wiki/Great_horse_manure_crisis_of_1894 https://en.wikipedia.org/wiki/Great_horse_manure_crisis_of_1... It seems highly unlikely to me that this would have been a problem in Ancient Rome.