Smiley face stickers on food waste bins have been credited with driving up food recycling rates in Bristol.
Bristol Waste's campaign began in August and in its first month there was a 16% rise in food waste collected.
Gwen Frost, from the firm, said: "I am incredibly proud that we are helping take Bristol one step closer to becoming a zero waste city."
Critics say the company should not have made the stickers out of plastic as they are not environmentally friendly.
Others have criticised the "slim my waste" stickers placed on black bins.
Ceri Davis, from Shirehampton in Bristol, said: "I appreciate they want to improve the food waste recycling rates and one of things I want to do us reduce the amount of plastic we use.
"To see that the bins were wrapped in silly smiley faces - there must have been other ways to drive up recycling rates?"
#SlimMyWaste— Lisa Rosewell (@RosieFoxRox) June 21, 2018
The irony of Bristol Council encouraging recycling by using PLASTIC TAPE around all the bins in the street and posting leaflets through the door with plastic stickers... more stuff to throw away. CAN THESE BE RECYCLED? PR didn't thinknthat through.
Aren't we lucky that the #slimmywaste stickers are STILL all over the bins all over #bristol! Yet another reminder that people don't take #eatingdisorders seriously.https://t.co/yVoXNFQd7z @BristolWaste @bristol247 @BristolPostEnts pic.twitter.com/BmjV4VymcY— Mel Ciavucco (@MCiavucco) August 31, 2018
Ms Frost said the company's leaflets were recyclable, "but we need the stickers to be durable".
"It's been really hard as we're very conscious about the plastic and the recyclability of things.
"We needed them to last the British weather, we needed them to stay on the bins, we didn't want them to fall off and become litter."
The 290 tonnes of food waste collected since August has been sent to a bio-digester in Avonmouth to produce electricity and gas instead of being sent to landfill.
Ms Frost added: "We do expect the food waste tonnages to start dropping but that's natural because what happens is that people see how much food they waste."
The firm, which is owned by Bristol City Council, said it wanted to take action after finding the average black wheelie bin in the city contained 25% of food waste.
It is now introducing brown food waste bins for residents in high-rise flats.