The campaigners collected enough stubs to fill 40 plastic buckets, then emptied them into a mound to raise awareness about the often-overlooked form of pollution.
Climate activists in Portugal collected some 650,000 cigarette butts and piled them up in the heart of Portugal's capital Lisbon in an effort to raise awareness about this often-overlooked form of pollution.
"The main problem with cigarette butts is that they are not biodegradable - they contain a form of plastic and, even worse, a lot of toxins, heavy metals and chemicals," explains Andreas Noe, the German activist behind the initiative.
According to the World Health Organization, 4.5 trillion cigarette ends are thrown away each year worldwide.
Noe has stockpiled the cigarette butts at Lisbon's famous Praça do Comércio. He explains that the 650,000 butts are just one week of collection.
"The main problem with the butts, it's not biodegradable. So basically it contains a form of plastic and even worse, a lot of toxins and heavy metals and chemicals. With any rain all those toxins are getting flushed out the cigarette butts and getting straight on the street, from the sinks, into for example here right, we are next to the Tagus river and it goes all straight into the ocean."
"The city [Lisbon] is not capable of treating the water from the street so everything goes straight into the ocean," Noe concluded.