Introduction

As practising “green building” professionals, we are all constantly searching for the best materials for our projects. The selection of building materials that are well-engineered, cost-effective and ecologically-sound is a process that defines our effectiveness and ultimately the success of our projects. We all know how challenging it is to stay ahead of the “technology curve”, and that our understanding of the latest innovations in materials is critical to the realization of results that meet or exceed industry standards and the needs of society in general.

Technological advances in the design and production of recycled plastic “green” building materials provide us with opportunities to “push the envelope” with respect to the three important criteria mentioned above. Up-to-date and accurate information is the key to being positioned to take advantage of advances in green building materials. The following article first steps back slightly to examine the primary concepts behind the role of recycled plastics in green infrastructure projects, then looking at more-specific applications and the future of plastics, so that we all may be completely informed in our choices going forward.

What are Thermoplastics?

Also known as “engineering plastics”, thermoplastics comprise a group of materials that exhibit superior mechanical and thermal properties in a wide range of conditions over and above more commonly used commodity plastics and other materials. The term usually refers to thermoplastic (softer) materials as opposed to “thermoset” (harder) plastics. Engineered thermoplastics are typically used for parts rather than containers and packaging. A thermoplastic is made from polymer resins that can be reheated and reshaped repeatedly. These important characteristics allow the manufacturing process to be reversible, therefore making most thermoplastics recyclable.

Why Recycled Thermoplastics?

  • Recycled plastic provides a sustainable source of raw materials to the green manufacturing and building industry.
  • Reduction of environmental impacts, such as greenhouse gas emissions, associated with the production of new plastic-rich products.
  • Greatly reduces the amount of plastic entering the primary waste stream, thus sparing our already overcrowded landfills.
  • Reduction in consumption of the world’s limited natural resources, i.e.: oil.
  • Recycled plastic production represents far less “embodied energy” than the production of new, virgin polymer products.
  • Recycling in general promotes sustainable lifestyle choices.
  • Recycled plastic parts lower the cost of product manufacturing and transportation (shipping).
  • Thermoplastic products can be recycled again and again, whereby effectively closing the “lifecycle loop” of the resource.

What is Green Infrastructure anyway?

Depending on which particular interest group is defining it, green infrastructure has been used to refer to everything from innovative green roofs, to more ecologically-sensitive stormwater management systems, to large integrated networks of natural areas. What these different interpretations have in common is the essential recognition that our built environment and our ecological environment are irreversibly connected and closely interrelated.

When the term is used at a smaller scale, such as an urban park or streetscape, our working definition can be an interconnected system of man-made landscapes, natural areas and open space that preserves and enhances the sustainability of the ecosystems promotes clean air and water, and significantly benefits people and wildlife. It should be pointed out that green infrastructure at the smaller; “implementation-level” involves the design, manufacture and installation of the best possible components of the physical systems, such as tree grates, structural soil cells, permeable pavement, drainage systems, etc.

Some other informative definitions of green infrastructure are:

“Green infrastructure can be considered a conceptual framework for understanding the “valuable services nature provides the human
environment.” At the national or regional level, interconnected networks of park systems and wildlife corridors preserve ecological function, manage water, provide wildlife habitat, and create a balance between built and natural environments. At the urban level, parks and urban forestry are central to reducing energy usage costs and creating clean, temperate air. Lastly, green roofs, walls, and other techniques within or on buildings (and building sites) bring a range of benefits, including reduced energy consumption and dramatically decreased stormwater runoff. Regardless of scale, green infrastructure provides real ecological, economic, and social benefits.”

American Society of Landscape Architects 

“As communities develop and climate patterns shift, stormwater management needs can only be expected to grow. While single-purpose grey stormwater infrastructure is largely designed to move urban stormwater away from the built environment, green infrastructure reduces and treats stormwater at its source while delivering many other environmental, social, and economic benefits. These benefits not only promote urban livability but also add to the bottom line.”

US Environmental Protection Agency

The Benefits of Green Infrastructure

Green infrastructure systems protect and restore naturally-functioning ecosystems and provide a framework for future development. These systems provide a wide range of ecological, social, and economic functions and benefits, such as cleaner air and water, restoration and conservation of natural resource processes, enriched habitat and enhanced biodiversity, increased recreational and transportation opportunities, improved human health, and better connections to nature. Well-designed and implemented man-made and natural green spaces have proven to increase property values and significantly decrease the costs of public infrastructure and public services.

The Benefits of Recycled Thermoplastic Materials

  • Durability-recycled plastic building products have proven to be extremely resistant to harsh environmental conditions. Plastic does not have to be painted, resists corrosion, and can be engineered to be incredibly strong.
  • Non-toxic-recycled plastic materials/parts will not leach undesirable chemicals into the environment.
  • Lower production costs-recycled and repurposed plastics are far more cost-effective than using expensive virgin polymer resins.
  • Lower shipping costs-plastic materials typically weigh less than other materials (wood and steel for example) thus transportation costs are lower.
  • Reduced environmental impacts (reduced embodied energy)-it simply requires less overall energy to produce, transport and installs recycled plastic products.

Some specific Applications of Recycled Plastic in Green Infrastructure

  • Streetscapes
  • Green Roofs
  • Structural Soil Cells
  • Porous Pavement Systems
  • Stormwater Drainage Structures
  • Green Walls
  • Tree Pit Systems

LEED Credits for Recycled Plastic Materials

LEED (Leadership in Energy and Environmental Design) offers credits for the use of recycled products, including recycled plastics, in buildings, site development and landscaping in their highly regarded green building rating system.

Specifically, products like Citygreen Stratacell and Stratavault Systems may qualify your project for generous contributions toward LEED certifications, with recycled content being a high contributor. Contact info@citygreen.com for more information regarding their products and LEED credits.

Visit usgbc.org for more information and proposed changes to LEED rating systems.

The Future of Plastics and Green Infrastructure

The future “Greening of Plastic” doesn’t stop with the efficient recycling of a petroleum-based resource. Advances in science are forthcoming that will further revolutionize the way we manufacture and use plastic. The development of “organic plastics” or Polypropylene Carbonates (PPCs) is moving forward, and in the near future, plastics will be made from the combination of carbon dioxide and propylene oxide. This new product will perhaps eliminate the need for petroleum-based plastics altogether while utilizing a largely unwanted and ecologically-harmful element. Whether transparent, flexible, or rigid, PPC is poised to become the revolutionary product of the plastic world, and in a few short years, can be mass-produced by the chemical giant BASF.

Plastic, no matter the source, will continue to be a major factor in improving the durability and energy efficiency of future green infrastructure. The continued use of recycled thermoplastic materials will undoubtedly result in significant reductions in the overall carbon footprint of infrastructure development around the world.