re these suppliers of mulch sourcing their ingredients from...

re these suppliers of mulch sourcing their ingredients from natural sources or the rubbish tip?

Do you have roadside collection of green bins where you live?
Where I am there is weekly green bin collection.
The green bin is for garden and food organics.
Things like vegetation, vegetable, meat scraps along with pet poo and cardboard, etc.

One of my neighbours is terrible at sorting their waste. They put the wrong things in the bins all the time.

The green bin contents are eventually placed in big piles and composted.
The end product can be a mixture of composted organics mixed with waste from cutting pine logs at the sawmills which is sold as mulch.
So it's important that the processors screening equipment can keep unwanted ingredients to a minimum.
I sometimes find little bits of plastic or fabric in bulk mulch of that type.

Additionally it can be expensive to dispose of asbestos legally so some people hide small amounts in their general rubbish while others dump larger loads where they hope they won't be noticed illegally dumping. They do similar with rubber products like inner tubes and tyres.