Removing plastic from woodchips/compost

Hi Permies,

2 questions is it better to process plastic out of compost before or after making it?

What are the latest techniques or machinery available for this process?

Looking at process about 6000m³ initially and then hopefully minimum plastic content 3000m³ annually.

Will be using the ASP composting method.

Fanks!

What is the source material for the compost, what sort of plastics are mixed into it, and how did the plastics get mixed in?

Since you be using the ASP composting method I am assuming this will be done on a large scale.

It is best to keep plastics out of compost so to me the issue is how hard will it be to remove the plastic and what method would be the easiest and cheapest way to remove the plastic?

I personally feel that removing it after it has been composted might be the easiest and cheapest due to volume.

I don't have any science. I can't give you a chemical analysis. All I have is a general impression of the way things work. ~Everything decomposes. Everything eventually breaks down. That is why it is such a poor idea to use used railroad ties or treated lumber when building raised beds. What has been added to the wood to keep it from deteriorating, will eventually leach out of the wood and befoul your soil. The artificials that have been added to the wood to kill the bacteria before they can act on the wood will get into your food. And in this case, what kills bacteria form of life cannot be good for animal form of life.

I should think the same thing would happen with your compost problem. To some degree or other that plastic in your future compost will break down into parts too small to find and remove. At the least the plastic will decompose enough to leave behind at least some minor amount of the chemicals it is made of. None of this is good or healthy. It is my guess that if you really want to honest about what you are producing or using, you would not produce a product that has hidden problems in it. As a very first step, I'd get the plastic out, and properly dispose or recycle it. Just like you want to properly make great compost. It may be more work, but we all really need to think long term. It would be nice if each and every one of us thought about the coming generations, and what we may be doing to affect them.

The municipal compost program that my city participates in is a customer of Engineered Compost Systems https://compostsystems.com/category/blog/
They linked to an article addressing contaminants from food service waste stream entering the composting pool: The Art and Science of Contaminant Management
They talk about using screening and windsifting which is what I would imagine to be the most effective tool in a compost system on a large scale.
They also have a number of posts and resources for municipal scale compost systems on their blog. I dont know if this is the scale you are talking about but it seemed like the closest that I personally know of.