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Vinyl sheet piles have gained popularity in various construction projects due to their durability, versatility, and environmental benefits. However, as these products reach the end of their lifecycle, the question of recycling arises. In this article we take a closer look at the Pietrucha Vinyl Sheet piles to explore the possibilities and limitations of recycling such PVC profiles, shedding light on the environmental impact, technical challenges, and potential innovations in the recycling process.

In line with the intensifying public debate over the impact of human activity on the accelerating climate changes, the construction industry has witnessed a significant shift towards sustainable practices, prompting a reevaluation of the materials used in various projects. Vinyl sheet piles, known for their corrosion resistance, long lifespan, and low maintenance requirements, have become a popular choice. As the construction sector increasingly adopts eco-friendly practices, the need to understand the recycling possibilities of vinyl sheet piles has become an important consideration.

This article aims to look into the possibilities and limitations associated with recycling vinyl sheet piles, as seen from the Pietrucha perspective as a European manufacturer. Understanding the environmental impact, technical challenges, and potential innovations in recycling these materials is essential for promoting a circular economy within the construction industry.

Manufacturing technology

To gain a clearer understanding of the potential for recycling vinyl sheet piles and the challenges associated with it, it is crucial to understand the production process of these materials. Such knowledge can provide valuable information on what measures can be taken to enhance their recyclability.

Vinyl sheet piles are typically made from polyvinyl chloride (PVC) or similar synthetic polymers, which, compared to steel, often have a more environmentally friendly production process [1]. PVC is derived from natural gas or petroleum through a chemical process. Additionally, various additives such as plasticizers, stabilizers, and impact modifiers may be included to enhance specific properties like flexibility, durability, and resistance to environmental factors. Main steps of the production process of such a profile are:

• compounding - the selected PVC and additives are combined to ensure uniform distribution of additives throughout the PVC resin, creating a consistent and well-defined material composition,
• extrusion - the compounded PVC is then subjected to extrusion, where it is melted and shaped into a continuous profile with desired shape and size,
• cooling and cutting - the vinyl sheets are cooled to solidify the material. Subsequently, they are cut to the required lengths. The cooling process is crucial to maintaining the structural integrity of the vinyl sheet piles,
• quality control - different measures are implemented throughout the production process to ensure that the vinyl sheet piles meet the required specifications. This may involve testing for dimensions, mechanical properties, and other performance criteria.

As a result, a profiled sheet of the required configuration is obtained, with a designed cross-section and constant characteristics. The shape of the plastic sheet piles affects how much energy and water is used during manufacturing [2]. Periodically, remnants from the production of profiles emerge, particularly during the initial stages of extruding a new profile. In such circumstances, these residuals are systematically reintegrated into the production workflow, a strategic measure employed to mitigate waste accumulation.. The process of production of such a profile is executed in a workshop, as the one  presented in Figure 1.

Figure 1: Extrusion of vinyl sheet piles by Pietrucha

Some vinyl pile manufacturers produce them in the co-extrusion process, meaning the outer layer of the piles is coated with higher quality PVC and the center is filled with much lower quality PVC that is not resistant to UV rays and oxidizes easily. This can cause the emission of microplastics during use and significantly diminishes the recyclability of such co-extruded profiles.

 

Figure 2: Extruded vs Coextruded Vinyl Sheet Piles

The production process of the vinyl sheet piles may pose challenges to recyclability of such materials as the presence of additives and stabilizers in the produced profiles may hinder the efficient separation and processing of PVC during recycling. Despite such challenges, efforts have been made to improve the recyclability of PVC, and advancements in recycling technologies are being explored [3]. Some initiatives focus on developing more environmentally friendly additives or alternative formulations that facilitate the recycling process and reduce the environmental impact.

It's important to note that recycling infrastructure and capabilities vary by region, and the recyclability of vinyl sheet piles may depend on local facilities and regulations. In areas where robust recycling programs exist, there may be opportunities to recycle PVC materials more effectively.

Durability and Longevity

The durability and strength of vinyl sheet piles reduces the frequency of replacements, potentially minimizing overall environmental impact ensuring performance for over 50 years [4]. Vinyl's corrosion resistance eliminates the need for coatings or any additional protective measures. When used in construction, vinyl sheet piles withstand the test of time, providing long-lasting structural support for applications like retaining walls and flood barriers. Extended product lifespan directly translates to reduced demand for raw materials and lower energy consumption associated with production. This not only conserves natural resources, but also diminishes the carbon footprint linked to manufacturing processes.

As an illustration of the durability and longevity of such a solution, we can look at the comparison between using steel sheet piles and vinyl sheet piles for shore protection against erosion mentioned in An Assessment of Vinyl Sheet Piles For Long Term Applications, Piyush K. Dutta; Uday K. Vaidya [4]. The publication includes visuals of both steel and PVC sheet piles installed approximately six years ago. Figure 3 illustrates that the PVC sheet pile remains free from any observable signs of degradation.

Figure 3. Clear superiority of PVC over steel for durability. Both were installed six years ago at 228 Esquinance Street , Mandeville, LA. The steel sheet piles on the right show advanced corrosion.
Source: [4].

By choosing materials with extended lifespans, construction projects contribute to a reduction in the frequency of replacements and the associated waste production. Therefore, it is worth to explore new technologies and make sure which ones are better suited for the specific project than others.

One noteworthy aspect of vinyl sheet piles is their potential for reuse. After serving their primary function, these plastic sheet piles can be extracted from construction sites. With proper cleaning and maintenance, the material can be reintegrated into new projects, repurposed for the same application (further extending its life cycle), or just recycled to be used in production again.

Innovations in Vinyl Sheet Pile Recycling

One of the primary methods for recycling vinyl sheet piles involves material recovery and reuse. The sheets can be collected after their intended use, cleaned, and processed to create new vinyl sheet piles.
This approach not only reduces the demand for virgin materials but also minimizes the environmental impact associated with manufacturing new products. Implementation of advanced sorting technologies, such as near-infrared spectroscopy, to enhance the separation of PVC from other materials are being developed, which can help to increase the quality of the recycled product.

Mechanical recycling involves breaking down the vinyl sheet piles into smaller pieces, which are then melted and reformed into new products. This process helps retain the material's properties and reduces the overall environmental footprint. The majority of unmixed PVC waste is reintegrated directly into production. The PVC industry has implemented several well-established initiatives for the retrieval of post-consumer waste, which are widely recognized in the market [5].

Another developing method is chemical recycling which is an emerging technology that utilizes chemical processes to break down the vinyl molecules into their original components. This method offers the potential to recover high-quality raw materials for manufacturing new vinyl products. As research and development in chemical recycling progresses, this method could become a key player in the sustainable management of vinyl sheet piles enabling the production of high-quality recycled material.

Last but not least, a focus on eco-design strongly contributes to optimizing the operational efficiency of the recycling supply chain. Manufacturers focused on eco-design are incorporating recycling considerations into the design of PVC products, with a focus on enhancing recyclability at the conclusion of their life cycle. [6]

Conclusion:

The recycling of vinyl sheet piles presents possibilities and limitations that demand careful consideration. While the environmental benefits are evident, technical challenges, such as contamination and quality concerns, need to be addressed.

Innovations in sorting technologies and chemical recycling processes hold promise for overcoming these challenges and making vinyl sheet pile recycling a more viable and sustainable option. As the construction industry continues its commitment to sustainability, stakeholders must collaborate to develop and implement effective recycling strategies.

By addressing the challenges and leveraging innovative solutions, the recycling of vinyl sheet piles can contribute significantly to a circular economy, minimizing environmental impact and promoting a greener future for construction projects.

It is essential for investors to make informed decisions when selecting vinyl sheet piles. By paying attention to the manufacturing technology and the quality of the material used, they can ensure the desired results and a long-term product life. Careful research should be conducted before investing in vinyl sheet piles to ensure the product is of high quality and resistant to oxidation. By doing so, they can be confident that they are investing in a product that not only will last for years to come.

 

Literature:

1. The comparison of the environmental impact of steel and vinyl sheet piling: life cycle assessment study. A. Marcinkowski1, J. Gralewski.
2. SUSTAINABILITY ASSESSMENT OF PLASTIC SHEET PILING, A. Al-Ashaab, B. Varro, D. Coley, M. I. Luna, J.Madrigal, S. Prokhorov, J. Roszak, P. Tola.
3. Mechanical Recycling of PVC Wastes. Study for DG XI of the European Commission in co-operation with: Plastic Consult (Italy), COWI (Denmark).
4. An Assessment of Vinyl Sheet Piles For Long Term Applications, Piyush K. Dutta; Uday K. Vaidya.
5. PVC recycling technologies, VinylPlus.
6. https://www.linkedin.com/pulse/challenges-innovations-pvc-recycling-charlie-chen-dkggf/ - accessed on 24.01.2024.