"First we thought of pigeons, which would have been great because there are so many of them in cities," Ruben van der Vleuten, co-founder of Crowded Cities, told The Next Web. Unfortunately, there's not much research into pigeons' intelligence, making training them difficult.
Crowded Cities estimates that worldwide 4.5 trillion cigarette butts become litter annually. According to the American Nonsmokers' Rights Foundation, that means an estimated 1.69 billion pounds of cigarette butts wind up as toxic trash every year, and the butts aren't biodegradable.
The waste poses a danger to children from potential toxic exposure, and toxins in the butts can leach into water to kill or injure wildlife.