Trying to recycle a daily ton of wet mixed plastic
I operate a recycling paper mill in Massachusetts, USA. We use Sorted Office Waste as our incoming raw material. As part of our paper recycling pulping process, we separate out the contaminants. One of the biggest contaminants is mixed plastics – anything that might be part of office waste (plastic folders, tape, buttons, etc.) and the pile of mixed plastics is wet and ground up from the pulping process. We generate about a ton each day. We want to turn this waste mixed plastic into something very crude, maybe pallets or lumber or similar at the very least, avoid sending it to the landfill. Can wet plastic be extruded? If we press it, will that get it dry enough for processing. Any ideas?
Picture #1: The raw material – waste from my office waste paper recycling operation
Picture #2: Plastic brick made from compressing waste plastic mixed with Liquid nails
Picture #3: Plastic brick made from compression alone
Wet plastic is very hard to process with a high moisture content.
You could dry it using some of your waste heat of your pulping process & then press or extrude it into moulds.
Here is one company making plastic timber.
How do you separate out the plastic from the paper ?
Keep up the good work.
After solving the moisture content issue, I think the problem you’ll have to deal with a mixture of polymers. It seems you already work at a pretty big scale, so getting inspired by what these guys do (combining mixed polymers of soft and hard plastic in a recycling process) might be of interest to you:
I am wondering if we could bring this process to a smaller scale. Any thought?
Thanks for replying and for sending the video. I know so little about the chemistry of plastics. In the video it looks like they are using only plastic bags. I appreciate that they are using different types of bags (does that mean different polymers?), but I don’t know if that translates into so many different plastics like I have. I’m going to contact the folks in the video to see if they can help.
Thank you for your reply and for sending the video. We are very efficient in the paper mill and have little to no waste heat to use in drying the plastic. If we set up an industrial-sized operation, we’d need to use expensive New England electricity – something that I am trying to avoid at this point. We have a screw press that we are going to set up and that will get us to a certain level of dryness, but we’ll see if it gets dry enough.
The plastic dumps out of our pulper through a screening unit that allows small paper fiber to pass through, but anything larger (plastic, etc.) gets segregated.
My latest attempts involve drying the plastic through a tabletop press, mixing the relatively dry plastic with a variety of glue products and then pressing it again in a brick press. I’m getting plastic “bricks”, but they don’t cure hard / firm enough to be used as lumber – too bendy.
Have you considered a centrifuge similar to the spin cycle of a washing machine.
Thank you for your idea. We do have a screw press that is designed for squeezing the plastic to a certain level of dryness. We haven’t installed it yet, but will soon. We’ve been trying to develop a solution at the “bench” level before we invest too much money in heavy equipment.
I’ve been pressing plastic material in a brick press to dry it, then mixing in some adhesive (Liquid Nails, Loctite, etc.) and then pressing it again. We are getting solid blocks, but they are taking up to two weeks to cure / dry. I think getting to bone dry will help this, but bone dry will require electricity which is expensive in New England.
They mix PP and PE in the process, which represents most of the soft plastics (as you seem to have on your pictures).
I can’t really help on the electricity issue. For sure, to recycle plastic, you’ll need heat and energy.
Maybe you could contact cementries or other industries that could be interested in using your mixed plastic in their process?
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