The average person understands why recycling is important and takes steps each week to put the plastic products they use in the recycling bin. But what happens once that plastic is picked up from your curb and how is it turned into plastic lumber? Here’s a basic step by step breakdown of the entire process.
Plastics Travel From Your Curb To A Material Recovery Facility
Though the below steps vary with different municipalities the below is a typical process.
Everyone has seen a recycling truck pick up plastics and other materials from their personal recycling bin. The truck then takes those plastics to a Material Recovery Facility (MRF).
Once in the MRF, all of the materials are unloaded from the truck and placed onto a conveyor belt. This conveyor belt moves the products onto an inclined screen. Gravity does the work here, allowing paper products to travel up and heavier containers to fall down onto a new conveyor belt.
The heavier containers then run through a line of workers who proceed to pull out any trash or materials that can’t be recycled. Container material and color separation is also addressed here.
Containers that make it through this process are then run through a series of magnets. The magnets pull out steel products, delivering them to the appropriate holding container. An eddy current is then used to pull any aluminum and other non magnetic products off of the conveyor belt and into a holding container.
Glass and plastic containers continue on where another small incline is used to allow the heavier glass to fall through into a container and the lighter plastic to travel on.
Some MRFs hire workers to manually sort the plastic into types and color, however, there is another method called optical sorting which uses puffs of air to perform this same process.
Once the plastic has been sorted it is compressed and baled into large clusters that can weigh anywhere from 1,000 to 1,500 pounds! These bales are then purchased by manufacturers to be used to make new products.
From Plastic Bales To Plastic Pellets
At Plastic Lumber Yard, our lumber in most cases is made from 100% recycled HDPE. How do massive bales of HDPE turn into lumber? First it has to be washed and pelletized. Bags and film need to be densified before the palletization process.
The recycled plastic, such as milk jugs, are first placed into a grinder where the plastic is chopped into 2-3mm pieces.
These flakes are then washed to remove any residue. Thanks to the nature of HDPE, the clean plastic floats to the surface in the washer while dirt and label residue are drained off.
Once dry, the flakes are put into a pellet making machine that uses heat and pressure to mix melt and turn the plastic flakes into a viscous state. This viscous plastic is then pushed through a strand die and cutter where it is cut into pellets that are typically ¼-⅜” in size. At this point the pellets are ready for the next step.
The Final Step: The Extrusion Process
Now the plastic pellets are ready to be blended with the other ingredients such as color, UV and antioxidant protection, foaming agents and other property enhancers and conveyed into another extruder where the blend is heated again to roughly 240 degrees Celsius (464 degree Fahrenheit). This melts the blend into a consistent mix which is further pumped through the plank shaped molds and allowed to cool.
During the extrusion process other additives can be included. For example, our lumber includes UV stabilizers that help to prevent the color in our lumber from fading when exposed to the sun. Embossment is also an option that can be included providing slip resistance and a more natural wood look to the plastic lumber.
Not All Plastic Lumber Is Created Equal
This process might seem simple but in reality, it’s not. Like any product, plastic lumber can be made poorly. At Plastic Lumber Yard, our team has spent decades learning and helping refine this process resulting in specific construction materials that will surpass expectations. You can rest easy knowing that you are working with the finest materials in the industry.