The Danish city of Aarhus has stopped requiring its inhabitants to sort garbage into biological and non-biological garbage. The non-biological garbage was incinerated, and the biological used to generate biogas.
A study by Professor Thomas Christensen of Denmark’s Technical University and two Ph.D. students showed that there was no environmental benefit, and an additional cost of about $3 million per year.
A major problem in this case was the color coded plastic garbage bags. To avoid that the bags broke while being handled and the garbage got mixed up, they had to be extra strong. The environmental costs of the heavy duty plastic bags were greater than the benefits from the scheme.