Author Aaron Burman, Senior Engineer

Author Aaron Burman, Senior Engineer

Last night my 8 year old son got to talking about climate change as he was getting ready to fall asleep. He was asking where everything came from, and we talked about how paper comes from trees, plastics from oil, leather from cows and many others. He made the observation that everything comes from natural resources. This is very true, but how can we get the most out of them? Like how the Native Americans used every part of the buffalo, right? Of course this got me thinking about building the circular economy, and in the recycling value chain, the MRF is positioned at the center of it. So how is the world of the MRF changing to keep the circular economy spinning?

As I’m sure everyone can see in their own lives, the mix of materials that is entering the facilities is changing. The quantity of newspaper, the once dominant material, is plummeting, the mix of plastics is broadening, and the pressure to continue adding new materials is increasing. Companies that manufacture products and packaging would love for each of their materials to be accepted at MRFs nationwide and sent back out into the recycled marketplace.

If at any point you feel like the recycling economy isn’t doing enough, divide your take out meal into all of the materials that a MRF would need to sort it into: paper bag, separate from the plastic clamshell (cleaned out, of course), separate from the polycoated paper cup (accepted in some MRFs ranging from Seattle to Northern Michigan), separate from the cup lid, separate from the cup sleeve, and all of that separate from the napkins, straw and cutlery (not accepted). Not an easy task when trying to process 1,500 lbs every minute.

Each MRF is unique in its design and the end markets that it targets. Almost all single stream facilities, which accept all recyclable materials commingled in a single cart or bin, use “disk screens” to separate the paper from bottles and cans. The disk screens use mostly round, elliptical or triangular disks that cause the flat items such as paper and cardboard to be pushed to the top and also get the round items like bottles and cans to roll to the bottom. As more MRFs accept thermoform plastics such as clamshells, and other plastic containers like yogurt cups, the efficiency of the screens in separating these materials can be vastly different from how they handle soup cans and soda bottles. As can be imagined, the flow of square or flat materials on these screens may end up being different no matter if they are made of paper, plastic or metal. Getting through this initial sort and onto the paper line or the container line correctly is critical, for materials to be further sorted to the right grade, as the facility is set up to sort each material on only one of these lines.

As MRFs have increased throughput, they need strong end markets that can accept a range of materials to justify sorting to each of the grades. No matter how good a MRF is, or its optical sorters, the bales of sorted materials will never be perfectly pure. To compensate, end markets have increased their own ability to do additional sorts on material coming out of MRFs so that they can accept a broader range of materials, increasing the volume of material they can process. A good example of this is the increase in sophistication of PET processing. PET is the plastic with a #1 resin code and is used in your soda bottle, as well as many boxes for strawberries, spring greens and the like. It seems odd to the layman, but PET bottles that were going into single stream recycling were not, until recently, able to be turned into new bottles. All of the recycled PET (rPET) that was used in bottles was coming from states with 5¢ and 10¢ deposits, which allowed for a very clean stream. Currently, there is a growing contingent of facilities that can turn a wide variety of post-single stream PET containers into new bottles. And, they can separate out and market the other resins that end up in the PET bale including the bottle caps and other plastics. Truly closing the loop.

There are continuous efforts to add new materials – currently including polycoated fiber, flexible plastics, textiles and some durable goods – to the single stream mix to be sorted at MRFs. Packaging and other industries, along with communities, will need to actively engage with MRFs and their end markets to understand material acceptance and sorting, thereby ensuring that processing costs and material revenue can continue to be balanced, and more materials can truly enter the circular economy. That way my son can rest easy at night knowing we are not wasting any part of our resources.