When recycling paper or cardboard, what level of contamination with (food) oils is ok?

Question

It's widespread knowledge that paper or cardboard contaminated with oil can cause problems in the recycling process, and an often stated rule is that contaminated material should not be recycled.

However, it would make sense that low levels of contamination are ok.

Are there any widely accepted tolerance levels for contamination by oil, or does it differ depending on the recycler (or worse, do they not even define it)? What are the acceptable levels, if there are any?

If information is available on acceptable levels of contamination with other substances, that would also be of interest.

Somewhat related questions:

• Are pizza cardboards stained with oil still recyclable?
• Is it better to recycle or compost brown paper bags?

Answer 1

As of January 2018 the standards for paper recycling have been tightened and even a small amount of contamination will now render paper loads inacceptable.

The main driving force here is that China has clamped down on contaminated imports of paper and other products in an initiative called National Sword. The new contamination limit is 0.5%, which is remarkably more difficult to achieve than the older limit of 1.5%. However, it's not exactly clear to me what this percentage is specifying. Does it mean that up to 0.5% of the bale mass can be contaminants, or does it mean that up to 0.5% of the cardboard surface may have contaminants on it? This answer is hard to find.

Many countries send paper recycling to China, or at least they were doing so up until this year. That means that this change is likely to affect many cities in developed nations.

At this point, my recommendation to end-users is that cardboard and paper is only acceptable if there is no observable contamination with food particles or oils. Any brown cardboard that has been visibly darkened by oils should be composted or trashed instead of being mixed into recycling.

Answer 2

As I know so far, no oil on paper... when you separate the materials, I've learned to put the paper napkins, paper bags with sauce, and other dirty oily paper in the organic waste.