What to do about your plastic construction waste: Closing the loop on pipes

Exploring ways to minimize construction and building waste is a passion for Dr. Terri-Ann Berry, Co-Director of the newly formed Environmental Innovation Centre (EIC). Terri-Ann has partnered with experienced Master Builder Nigel Benton to develop practical environmental solutions for the construction industry. The team at the Environmental Innovation Centre (EIC) are writing a monthly column in Building Today on practical advice for managing construction waste and other environmental issues builders might come across.

Closing the Loop on Pipes!

Have you ever noticed just how much room pipe off-cuts take up in your skip? It’s a big problem and can represent around 20% by weight of total construction plastics coming from a construction site.

Pipes are predominantly made of one of two plastics, HDPE (high-density polyethylene) and PVC (polyvinyl chloride). Both plastics offer versatility, affordability and chemical resistance, while also being durable, strong, and flexible so ideal for use in drainage, irrigation and plumbing. However, they are both derived from fossil fuel, energy intensive to produce and can contribute to environmental pollution, if disposed of incorrectly.

When managed properly, plastic can undergo multiple recycling cycles. However, historically, PVC recycling has been challenging to recycle in NZ due to sorting and separation requirements and concerns about additives used during PVC production. By contrast, HDPE is comparatively easier to recycle but still needs on-site sorting and separation. So, most pipe off-cuts have historically been destined for landfills due to the lack of recycling facilities capable of handling construction waste at scale. The encouraging news is that both PVC and HDPE plastics can be recycled in New Zealand.

This situation started to change in 2022 when one of New Zealand's main pipe suppliers, global company Aliaxis (Marley NZ), announced an $11.5 million investment initiative aimed at reducing plastic construction and demolition waste in the country. Collaborating with Waste Management New Zealand (WMNZ), Unitec Institute of Technology and our team at EIC, Aliaxis secured a Plastic Innovation Fund grant for $4.464m from the Ministry for the Environment to build HDPE and PVC pipe recycling capacity in New Zealand. This project underscores the importance of collaboration in the sustainability sector, connecting industry, government, scientists, and communities. Since its inception in September 2022, the project has already produced significant results across three key areas:

1. Investing in new plastic recycling facilities across New Zealand to sort, wash, and shred PVC and HDPE plastic from construction, demolition, commercial, and industrial sources. Aliaxis and WMNZ formed Plastics Recycling NZ, which acquired recycling expert Compounding Specialists Ltd (Comspec) in Christchurch, handling over 4000 tonnes of plastic resins annually.

2. Establishing a network of metropolitan and regional PVC and HDPE collection services in partnership with Waste Management New Zealand. Currently, there are 30 recycling drop-off locations nationwide (see Marley website: https://www.marley.co.nz/find-a-recycling-drop-off/), allowing for free disposal of pipe waste, with the requirement that pipes must be free of rings, tapes, and stickers. In 2022, Aliaxis successfully recycled an impressive 702,000 kgs of plastic, avoiding an estimated 800 tonnes of CO2e emissions. WMNZ can also provide skip bins for sorting pipes on construction sites, and transport sorted pipes to Marley and their sister company RX Plastics.

3. Conducting research by EIC (formerly ESRC at Unitec) and BRANZ into practical solutions to minimize plastic construction waste and raise awareness of plastic recycling. A significant aspect of this project is providing scientific research into on-site waste management, with the EIC subcontracted to produce a variety of tools for use in the construction sector. EIC is developing a website to host a range of educational resources to make managing plastic waste more accessible and manageable for the construction industry. This will include signage, instructional videos, and information on recyclers.

So, what happens with the collected pipes material? It will be utilized at Marley and RXP sites to manufacture the next generation of PVC and HDPE piping systems for building, infrastructure, and agriculture projects across NZ, completing the loop and reducing overall plastic resin importation.

Participating is simple: separate your pipes into HDPE and PVC, ensure they are free of duct tape, concrete and rings, then drop them off at one of Marley's designated locations — all at no cost to you. If working on larger projects you can also separate on site and have the pipe collected by WMNZ and other collectors. By doing this, you are reducing the waste you send to landfill (saving money) and contribute to the larger goal of closing the loop on pipes to make a tangible difference for our environment and for future generations.

Some common pitfalls to look out for are polybutylene pipes and PEX pipes, which cannot currently be recycled by Marley. These should go into general waste for now.

If you have any questions for the team that you would like answered in this column, please contact us.

Learn more about the Marley take back scheme here: https://www.marley.co.nz/sustainability/recycling/