Difficult plastic wastes in construction — what are they and can we avoid them?
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.
At EIC, we often get asked what is the “worst” type of waste we find in the skip? When the team characterises waste streams at a workspace or on a construction site, finding huge volumes of wasted soft plastics in the skip is never good but at least it gives us an opportunity to investigate avoid, reuse or recycle options (Figure 1).
Figure 1: Waste management pyramid
Looking at our simplified waste hierarchy, the best thing to do is to avoid producing waste in the first place. It is great if you can find the time to talk with your suppliers about reducing unnecessary waste reaching your site, like some packaging. But if unavoidable, it is preferable to use plastics which can be easily reused or recycled and remember that not all our regions in NZ are equally blessed with reuse and/or recycling capabilities. When you are choosing a recycler, location is especially important and, in some locations, you may not have much choice but where you do have a choice, also consider what is going to happen to your waste once it leaves you.
Recycling – Single Stream vs Multiple Stream
If you're going to recycle something, it's ideal to recycle plastics into similar high-quality products instead of downcycling them to less valuable products. For example, recycling old building materials back into other building materials, instead of combining different materials into one product. This means recycling one type of plastic (a single waste stream) instead of many types mixed (multiple waste streams). Recycling a single type of plastic keeps it purer, maintains its value and makes it easier to recycle again at the end of its life.
Figure 2: (Left) Shrink wrap is recycled back into builders’ polythene film (DPM). (Right) Polystyrene back into polystyrene.
But back to worst wastes - there are some items which are guaranteed to make us sigh when we find them in your skip. There are some items which cannot be recycled due to material structure, material type or lack of local recycling capability. We would like to introduce you to our top three “usual suspects” in order of the best of the worst to the very worst of the worst! We hope that you may be able to use this guide to avoid these waste streams coming to your site and the landfill disposal costs that they could incur.
Problem plastics - Composites
Plastic materials made of various plastics or other materials (i.e. “composites”) make it much harder to recycle. These are not single-stream, therefore must either be disassembled for recycling or go to a multi-stream recycler. The extra time required for disassembly means these items are less likely to be recycled. For example, any products with paper incorporated into them, or cable reels made of multiple plastic types or materials (Figure 3).
Figure 3: (Left) Cable reel made of plastic, cardboard and metal fasteners. (Centre) Cable reel made of #5 PP and a #3 PVC core. (Right) Material cover made of plastic and paper
2. Problem plastics – Backing tapes
The backing tape of some adhesive products such as building paper is often made with silicon, which currently cannot be recycled in New Zealand. This produces a large amount of waste as the backing tape has an equal surface area to the product itself. It is important not to mistake this for low-density PE (or LDPE) and/or shrink wrap, which can both be recycled.
Figure 4: (Left) Building paper. (Right) Backing product of building paper (silicon-based)
Some backing tapes are made of a combination of paper and plastic, which cannot be recycled by either paper or plastic recyclers. These are paper-based with a plastic coating and tear easily.
3. Problem plastics – Woven plastics
Some plastics are difficult for recyclers to process due to their physical structure; for example, any plastic with a weave usually cannot be recycled as they are too difficult to shred and granulate into smaller pieces. Figure 5 shows woven polypropylene (PP) timber covers (1), woven PE sheets (2) and clear woven PE sheets (3).
Strapping is usually tangled, may have metal buckles on them, and is often woven. Sample 4 in Figure 5 is made of PP. Polyethylene terephthalate (PET) strapping usually cannot be recycled (sample 5), as most PET recyclers in NZ only accept PET from food and drink containers (e.g. meat trays, drink bottles).
Figure 5: (1) Woven PP timber covers. (2) Woven LDPE sheets. (3) Woven LDPE Clear sheets (4) PP strapping - woven, tangled and with metal buckles. (5) PET strapping
What can we do?
We estimate that these non-recyclable plastics account for about 30% of all plastic waste coming from a construction site in Auckland. This percentage depends on the location of the site and whether recyclers are available in the region. The good news is that as New Zealand's recycling industry continues to expand, opportunities for recycling various products are likely to increase. For instance, the future introduction of adequate shredders for non-food PET could enable the recycling of PET strapping, which is currently challenging to process. EIC is also investigating ways to improve the movement of waste from site to recycler and improve the recyclability of construction waste in the future.
For products that still cannot be recycled, it might be wise to avoid them or switch to recyclable alternatives that create less waste (for example, avoiding woven timber covers). This is not always possible, as a better alternative may not yet be available. In some cases, contacting suppliers to request minimal or no packaging may be a good solution.
Ideally, suppliers would replace non-recyclable products with recyclable ones – something that EIC has been trying to encourage. By taking these steps, we can reduce the amount of plastic waste that NZ construction sites send to landfills.
Please let us know if you have found any other “worst” wastes that we can investigate!
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: www.marley.co.nz/sustainability/recycling.