Unitec’s innovative research helps reduce plastic entering landfill

Reusable timber covers

A Unitec research project on reducing construction waste has led major building suppliers to develop an innovative timber cover that replaces single-use plastic on building sites. The Covers are heavy duty tarpaulins and can be used many times over, while also protecting the timber from knocks and weather in transit and on site.

The initiative stemmed from a project run by students doing a Bachelor of Engineering Technology (Civil) in the School of Building Construction. Over 2017 and 2018, the students conducted audits of construction waste on building sites to ascertain how much was being discarded and where it was ending up.

Although this study showed that useful materials could be recovered and reused by sorting through waste, one of the problematic areas was the amount of discarded plastic that couldn’t be recycled.

A huge source was from construction timber, typically delivered to building sites in packs up to six meters long and covered in a plastic wrap to protect from the weather while stored on site. The plastic is usually discarded into the general waste bin and taken to landfill because no reuse stream exists. It is thought this Construction and Demolition (C&D) waste contributes at least 10,000 tonnes to the amount of plastic entering landfills in Auckland annually.

The Unitec research group decided to address this problem and applied to Auckland Council’s Waste Minimisation and Innovation Fund, alongside construction firms Naylor Love and Mitre-10 MEGA, to trial an initiative that could transform the way timber is delivered and stored on construction sites throughout the country.

On talking to the suppliers, the Unitec research team discovered that the plastic wrap was mainly to protect the timber against ultraviolet light rather than water damage and could therefore be replaced with more sustainable materials.

This led to Naylor Love and Mitre-10 developing the purpose-made Timber Pack Covers to replace the single-use plastic.

A further initiative of adding an option to the Mitre-10 online portal where customers could choose to have materials wrapped and packaged in plastics showed a high rate of opt-out success. Over 12 months and with 13,091 online trade orders, 97% were supplied unwrapped and just 3% supplied wrapped.

This work is important as C&D waste accounts for a high proportion of the waste that goes into landfill in most countries, says Associate Professor Dr Terri-Ann Berry, Director of Unitec’s Environmental Solutions Research Centre.

The proportion of construction waste (by weight) going into landfills compared to the total amount of waste varies between 13 and 61 percent depending on the country, with an average of around 30 percent.

C&D waste also has environmental implications when disposed into landfill, such as the release of inorganic pollutants and greenhouse gas emissions.

Sorting waste during the audit

During the Unitec audit, the students separated the waste into timber, concrete and masonry, plasterboard, metals, and plastics and packaging. Untreated timber and concrete & masonry waste were collected by the public or reused on-site, while plasterboard was sent to be recycled, metals sold as scrap material, and plastics and packaging returned to the supplier.

Most treated timber was sent to landfill, and some was reused for small projects (such as on animal farms). Photos of waste were posted online on the Free Stuff and TradeMe sharing websites, so the public could arrange to pick up the materials for no charge.

Because materials such as wood, metals and concrete make up most of C&D waste, their recovery has typically received the most attention and has been largely driven by the commodity values of these products. Unfortunately, the relatively low production cost of plastics means there has been little economic incentive to recycle or recover it from C&D waste, which prompted the development of the covers.

Unitec’s Civil Engineering students have been instrumental in driving this waste-reduction research from its inception, says Terri-Ann. “Towards the future, these sustainable waste solutions will be carried forward into their prospective workplaces to support better environmental outcomes.”