22nd January, 2019

Recycling Plastic Building Materials: PVC vs. HDPE

Conserving and protecting the environment is very important. As the leading manufacturer of structural recycled plastic lumber, one way we help preserve Mother Nature is by manufacturing environmentally-friendly building materials. Another is by educating companies on how they can dispose of these materials at the end of the product life-cycle that doesn’t cause further damage to the environment and human health. Let’s look at the difference between PVC vs. HDPE.

The issue is that most plastic isn’t recycled, and the composition of the plastic material can make this even more of a challenge. As more companies participate in green initiatives, like recycling, millions of pounds of plastic can be kept out of landfills and oceans that otherwise harm the earth and marine life. However, not all plastics are treated the same, and some plastics are more harmful to the environment than others.

There are six common types of plastic used in America today. HDPE (High Density Polyethylene) and PVC (Polyvinyl Chloride) are two of the most common plastic composite building materials used in the construction industry. Focusing on these two materials, PVC vs. HDPE, let’s dig deeper into the composition of these plastics and how to dispose of them at the end of the product life-cycle.

PVC – Polyvinyl Chloride, More Harmful Than You Might Think

PVC is one of the most common types of plastic produced in America and is most commonly used as a building material. In fact, about 75% of all vinyl produced is used for long-lasting building and construction applications like siding, pipes, wiring coverings and fencing. As a building material, PVC is rigid and strong, doesn’t corrode and is resistant to moisture. While there are benefits of using PVC as a building material, there are numerous environmental and health disadvantages, especially in the disposal of this product.

Manufacturing Process

When burning or manufacturing Polyvinyl Chloride, dioxins are released into the air, which is a highly toxic compound that is harmful to humans and the environment. Another harmful outcome of the burning or manufacturing PVC is the production of Vinyl Chloride. This colorless gas is exposed through inhalation and has been linked to certain cancers including liver, brain and lung.   

Recycling PVC

Not only is this material harmful when it is manufactured, but disposal also has negative effects. One way to dispose of this material is to dump it into a landfill, which may be the most harmful disposal method because PVC isn’t biodegradable. Meaning, it keeps its original composition for hundreds of years and never breaks down, and oftentimes landfills will not accept PVC.

Another way to dispose of PVC is to recycle the material. However, due to the complex chemical composition of PVC, recycling this material is not as easy as it sounds. Depending on the application, other additives can be manufactured with the PVC, making it even more difficult for the material to be recycled. There are two main processes for recycling PVC; mechanical recycling and feedstock recycling. Many corporate recycling centers will not accept PVC material to be recycled.

  • Mechanical Recycling: This process includes grinding the PVC into smaller pieces. These smaller pieces are then melted down and re-molded into different products. In this process, there is no chemical reaction. The pieces are simply melted down and re-purposed into different shapes and PVC products. The recycling process is meant to remove additives and contaminants to repurpose the material into a raw version that can then be manufactured into new PVC products. However, during the manufacturing process, a wide range of chemical additives are combined with PVC to enhance performance characteristics. When it’s time to recycle the product, it’s difficult to determine what additives were included at the time of manufacture, and many of these additives are not recyclable. This makes it difficult to determine the end-product composition, which can affect the performance characteristics of the recycled material.
  • Feedstock Recycling: This process breaks down the PVC into components using chemical methods, which are then used to produce new PVC as feed for manufacturing processes or fuel for energy recovery. Feedstock recycling treats the mixed or unsorted PVC waste and recovers the valuable material, which is then used for new PVC products. This process is often rather expensive and oftentimes the amount of valuable recovered product is very low, that it doesn’t justify the initial cost of the recycling method.

Goodbye, PVC

Since disposing of this material in a safe and efficient way is difficult, and due to the harmful effects on the environment and human health, many cities have created policies to reduce the use of PVC as a building material:

  1. New York City, Boston, Seattle, San Francisco and Buffalo, NY have passed legislation that reduces the City’s purchase of PVC as a building material
  2. Many countries have banned the use PVC. Germany banned the disposal of PVC in landfills in 2005, and Sweden started using PVC restrictions in 1995 to discontinue all PVC use
  3. Many fortune 500 companies including Wal-Mart, Microsoft, Honda, Apple, Nike and Sony have committed to phasing out PVC and switching to safer products.

As many companies, states and countries say goodbye to PVC, what is an alternative? Enter High-Density Polyethylene. This building material is another type of plastic that holds many benefits like that of PVC but is much more environmentally-friendly from process to finished product.

HDPE – High-Density Polyethylene, The Environmentally-Friendly Building Material

Recycled High-Density Polyethylene is commonly used to make playground equipment, fencing, boardwalks and marine industry applications like fendering systems and substructure components. It is known for its strength, durability and weather and chemical resistance. As a great alternative to traditional building materials like wood, metal and concrete, HDPE plastic is an environmentally-friendly building material that is built to last. This material is seen in many commercial industries like marine, industrial, outdoor, agriculture and fencing, and can replace wood in many construction applications.

Manufacturing Process

HDPE plastic lumber can be manufactured using three different processes; Continuous Extrusion, Molding and Multiple Extrusion Technology. Each process is environmentally-friendly in that harmful gases are not produced and emitted through the air that can injure human health or the environment. Tangent utilizes all three processes to manufacture durable and strong building materials for a diverse portfolio of building and construction applications.

Recycling HDPE

HDPE plastic lumber is not only manufactured using recycled material, but it is also recyclable. Unlike PVC, the performance and technical properties of HDPE are consistent with the original material; meaning that there is less chemical variation from additives during the manufacturing process. This makes the range of raw material narrower, and therefore easier to remove contaminants during the recycling process. Recycling HDPE using the mechanical recycling method is quite efficient and cost-effective.

During this recycling process, the material is sent through streams of water, which separate contaminants from the original material. Since HDPE material floats in water, and contaminants like glass, metal and paper do not float, it is easier to remove contaminants than PVC. It is also easier to recycle HDPE than PVC because it generally has fewer non-recyclable additives included during the manufacturing process, which is more difficult to remove and separate in the recycling process.

Recycling PVC vs. HDPE

No matter the building material, once it has reached the end of its life-cycle, it’s important to recycle the product. Instead of sending it to a landfill, where PVC will not degrade and isn’t biodegradable, using a product that is easily recyclable and is safe for the environment is a great way to help conserve the environment and protect Mother Nature. When looking at PVC vs. HDPE, it’s obvious what plastic wins out.

While PVC can be recycled, finding a recycling center that accepts PVC can be challenging, and it may end up costing more in time and resources than can be recovered. Instead, choose a building material that is better for the environment, and can easily be repurposed.