In your quest to recycle plastic around you, you will come across LDPE sooner or later. LDPE or plastic number 4 stands for Low-Density Polyethylene. It is a clear, low-density plastic most seen in product packaging. It is a cousin to HDPE or High-Density Polyethylene, sturdier and used to make boxes and containers.
LDPE was first produced in 1933 by Imperial Chemical Industries, making it one of the oldest plastics to be still in use. It is relatively transparent, flexible, does not break or tear easily, and withstands several harmful chemicals.
Because of these benefits, LDPE is widely used today in making containers, pallet wraps, packaging, shrink wraps, and clear plastic bags, even though many modern plastics like polypropylene are available now.
In 2019, the US production of LDPE amounted to 3.46 million metric tons. That’s the weight of nearly 6 million humans, and that’s the amount produced every year by the US alone. Now EPA data shows that a mere 5.7% of this is recycled, and the rest usually ends up in a landfill.
The Problem with Throwing Away Plastics
Before Leo Baekeland created the first plastic Bakelite in 1907, if you approached the average 19th century Joe and talked of a rigid material that did not rust, corrode, and lasted more than a lifetime, he would have concluded you were talking about some costly metal.
If you then tried to convince him that it could be produced at the cost of a few cents and could be bought very cheap, you would probably have found yourself in the psychiatric ward of some hospital. But plastics are all that; they have changed the world in the last hundred years.
Many things we take for granted today would have been impossible to make without plastics, and a lot of today’s products would have been much costlier. It would not be wrong to say we live in the age of plastic.
But now, more than a hundred years later, we are slowly waking up to the horrors that come with this material.
All plastics, including LDPE, are non-biodegradable. That means they do not rot and decay as materials as wood do. Thus, any plastic thrown away will, like your most embarrassing memories, stick around for thousands of years and keep polluting the environment. Burning them is also not a solution, as that means releasing lots of toxic gases into the atmosphere.
A lot of the plastic that is thrown away ends up in the ocean, where it pollutes and devastates marine ecosystems. Polluting plastic has even been found in the deepest reaches of the earth’s oceans.
But there is an even more insidious and dangerous way in which plastic is hazardous to life. While plastics like LDPE cannot be decomposed naturally, the elements, especially flowing water, can still be broken down into pieces.
These pieces get smaller and smaller until they are microscopic in size, called microplastics. Microplastics are not only a huge threat to ecosystems; they are also finding their way into humans through food chains and drinking water.
How to Use Recycled LDPE?
Scientists are trying to find a way to degrade somehow or decompose plastics, and while many promising avenues are opening up, we do not have a working method yet. So, for now, the best strategy is to reduce the amount of plastic such as LDPE going to landfills and rivers. We can do this by:
1. Using less LDPE
2. Reusing LDPE
3. Recycling LDPE
LDPE can be recycled to produce a number of things such as:
Furniture from LDPE
Recycled LDPE can be used to make mainly outdoor furniture. Any furniture that is kept outdoors, such as park benches, camping chairs, or even the chairs in your garden, is exposed to erosion and degradation by the elements.
Recycled plastics offer a cheaper alternative to wood and metal for making such furniture. In contrast, the natural resilience of plastics means they can take a beating and remain undamaged for a long time in such conditions.
Plastic Lumber from LDPE
Recycled LDPE can be processed with composites to create plastic lumber, which is a substitute for natural lumber. It is mainly used to make stuff like outdoor decking or outdoor furniture, and this kind of lumber has some definite advantages over natural wood.
First, it is much more durable and requires less maintenance when compared to wood composites. Second, it is created by heating plastics and molding them to desired shapes.
Thus, the lumber can be of any shape and size, which is impossible with the natural variant. Using recycled plastic lumber also means less raw lumber is used, meaning fewer trees are cut down, making it even more environmentally friendly.
Recycled LDPE can again be turned into film plastic for packaging. In this way, it can be recycled and reused for a very long time.
Shipping Envelopes from LDPE
Recycled LDPE can also be used to make the plastic envelopes that your packages from Amazon come in.
Paneling from LDPE
Panels can be made out of recycled LDPE, and they are cheaper than other composites while also being waterproof and resistant to swelling and delamination. They can be cut and drilled just like normal paneling and can be again recycled at the end of their use.
Rubbish bins from LDPE
Recycled LDPE can be turned into rubbish bins. These usually need to be resilient to face street life.
Rubbish bin liners from LDPE
Bin liners, which hold the trash inside the trash bins, don’t need to be the highest-grade plastic.
One thing to remember here is that LDPE is most widely used in packaging goods in industrial settings, so the biggest users of LDPE are commercial enterprises. However, if you look around, you will find a lot of LDPE plastic in your home, too, in the form of wraps, packaging, and carry bags.
Geeky Plasticky Stuff
Before we go into recycling LDPE, let us take a closer look at LDPE itself. Low-Density Polyethylene is a polymer of ethylene, and a polymer is a long chain molecule formed by joining together shorter molecules called monomers. Many polymers are found in nature: silk, wool, and DNA, to name a few, but most modern plastics are made through synthetic processes from chemicals like petroleum.
The secret to the astonishing qualities of LDPE and other plastics can be found in these long molecules. As a general rule, the forces inside a molecule are much stronger than those between molecules.
Thus, a long molecule is much stronger and resilient compared to three smaller molecules of the same total length. And the polymeric molecules of plastic have thousands of monomeric units, sometimes even more, which allows them to have so much strength while remaining so light.
However, this polymeric structure of plastics makes them non-biodegradable and such a threat to the environment.
Challenges in LDPE Recycling
The main challenge in LDPE recycling is contamination. As said before, LDPE is mainly used for packaging other materials. Due to this, and over the process of use and reuse, LDPE can become quite contaminated with whatever it was used to pack.
With rigid materials, it is comparatively easy to clean them. But flexible materials like LDPE are quite difficult to clean: they require thorough washing before they can be recycled. If a piece of plastic is deemed too dirty, it is usually rejected.
LDPE also needs to be separated from other types of recyclable plastics. Being so thin and flexible, they need separate machines for processing. If LDPE ends up in the wrong recycler, it can jam equipment, causing accidents and endangering the plant workers.
LDPE Recycling Process
Collection of LDPE:
For LDPE to be recycled, it needs to be collected first. While commercial enterprises can drop off their waste at a commercial recycler, you can drop your LDPE waste off at the local recycling facilities like curbside recyclers or bottle banks.
Also, check your local grocery, and they often accept LDPE for recycling. You may even pay your nearby recycling plant a visit.
To identify recyclable LDPE, look for three arrows around themselves and the number 4 on your plastic waste. Also, put your LDPE waste in the bin marked for clear plastics- else, you might contaminate a whole batch of recyclable materials and endanger the safety of the recycling workers, as the thin plastics in the wrong recycler can become tangled in the machinery.
Many different kinds of plastic find their way to these recycling plants and must be sorted and separated before recycling. Sorting allows plastics to be separated by use, composition, and color.
This allows the right kind of a plastic waste to go to the right machines and makes the recycling process efficient. LDPE needs to be separated from other types of plastic else, and it can become a hazard for the recyclers.
This is a significant step in recycling plastics in general and LDPE in particular. Since it is so often contaminated, most commonly by product labels, dirt, adhesives, or food residue, LDPE must be thoroughly washed at this stage to remove these impurities. LDPE that is contaminated too much is also discarded at this stage.
The next step is shredding which involves breaking down the LDPE into very small pieces. These tiny pieces can either go into the next recycling step or find applications themselves, for example, as additives in asphalt.
Another round of purification is done at this stage, as the small pieces allow the removal of many impurities that were not possible earlier. This mainly includes metal particles, which can be easily removed from LDPE at this point using a magnet.
This involves heating the shredded pieces to melt them and forming tiny granules or pellets on cooling down. These granules will be used to create recycled plastic products, and the granules are shipped off to different plants to make other recycled products.
Why Recycle LDPE?
Or, more appropriately, why not recycle LDPE? LDPE and other plastics have one great thing going for them. They are nearly indestructible, and they can be used over and over and over again virtually forever. Why are we not recycling all our plastic and making sure we use fewer resources? That is the question.
While the answers might have to do with corporate greed and profitability in recycling, that does not mean that you cannot do your bit in keeping the world free from plastic waste.
Low-Density Polyethylene or LDPE is everywhere and is used mainly as a packaging material. But throwing it away is a terrible idea, as it is dangerous for both the environment and us humans.
However, the good news is that LDPE can be recycled into many things, and almost indefinitely at that. Look for recyclers that accept the number 4 plastic, and you are good to go.