The increase of e-commerce has drastically changed recycling. Cardboard (OCC) now makes up the largest fraction of the residential recycling stream in volume and in value, and will continue for the foreseeable future. OCC is currently 30% to 40% of the material flow.
In ways this is beneficial as OCC is a high-value commodity that doesn't engage traditional MRF bottlenecks. However, the shift in flow volumes within a MRF creates new challenges and bottlenecks. This change in flow, along with the varying mechanical properties of OCC, requires an adjustment to operational mentality and capital requirements.
The material burden and flow has pushed forward toward the pre-sort, OCC screen, and OCC QC. Some of this is a matter of density. OCC is much less dense than newspaper, so inbound density has dropped by up to 70% in recent years as newspaper decreased and OCC and plastic has increased. To process the same tonnage, one has to push twice the volume across the pre-sort. Compounding this problem, a greater percentage of OCC puts pressure on the presort, OCC screen, and OCC QC.
Material lightening and burden moving forward in the flow causes a number of potential challenges:
Moving downstream, experience shows browns will go with both the 2D and 3D fraction. Approximately 12% will go in large paper, 6% in small paper, and 12% on the container line. It is challenging to gather from multiple points which creates a variety of challenges to solve.
Many of these issues are intertwined. If the system is pushed too hard, contamination goes up, etc. Unfortunately, if the system is bottlenecked at the front, especially at the presort, there's not much to do besides add more people. There isn't any equipment in front of these stations to modify to reduce flow. Most MRFs are having trouble hiring so adding people often isn't viable.
If the presort can handle the material and the OCC screen is big enough, theoretically running the screen faster can enable more material push.
Many boxes are too small to be captured by an OCC screen. Making the OCC screen opening smaller to capture them can push too many prohibitives into the OCC stream to effectively sort. Without making capital changes, these have to be positively sorted somewhere by people or machines. Some operators pull them immediately after the OCC screen to prevent proliferation. Otherwise, they are pulled off the paper and container lines which is challenging without automation.
In order to reduce browns in the OCC screen unders the OCC screen can be sped up. This will also push more non-OCC into the OCC QC.
There are several possible small retrofits with minimal downtime to increase OCC recovery or quality:
Three main mid-sized retrofits can improve OCC recovery.
The first is adding a primary screen prior to the presort, acting as an additional deck of an OCC screen plus reducing burden on the presort. Presorts are struggling because the very existence of that station gets industrial automation backwards. Machines are supposed to help people work, not the other way around.
Adding an auger screen in front of the presort is a fairly simple retrofit. They reduce volume on the presort by approximately 60%, increasing sorter effectiveness and OCC screen efficiency. This results in cleaner OCC at a higher throughput with increased sorting efficiencies downstream.
The second is the OCC screen itself – either adding one or replacing a small one with a larger screen suited to modern material.
The third machine you can add is an optical sorter(s) to increase small OCC recovery and upgrade your large paper fraction material or clean-up the container line.
The MRF of the future eliminates the presort relieving a primary bottleneck and labor center. Then fractionates the stream by size to create more homogenized streams. These streams can then be more efficiently sorted by optical sorters.
Both auger screens and optical sorters are reliable, low maintenance machines. Generating correct sized fractions and then optical sorting allows to future proof a MRF against material changes. Neither of these machines are dedicated to a specific commodity.
Screening and sorting gets you 90% to 95% done. The last part is either manual QC or robots. OCC is the bulk of the material and revenue in most modern MRFs. Once the OCC is solved the rest of the MRF design gets simpler.
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Topics covered: recycling, landfills, collections, organics diversion, waste-to-energy, and much more.
Get the free daily newsletter read by industry experts
Topics covered: recycling, landfills, collections, organics diversion, waste-to-energy, and much more.
A canned wine bottle bill and mattress recycling EPR passed in Oregon, along with a chemical recycling bill in West Virginia. Meanwhile, the fate of New York's packaging EPR proposal is pending in the state budget process.
Fiber markets soared in 2021, thanks in large part to the pandemic's e-commerce boom. Now, billions of dollars in infrastructure investments are coming online and demand is expected to remain strong.
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Topics covered: recycling, landfills, collections, organics diversion, waste-to-energy, and much more.