Separation at source key to construction waste minimisation

Construction and demolition waste make up half of New Zealand’s total waste going to landfill. In growth areas such as Auckland, the amount of building and construction waste going to landfill is expected to surpass 600,000 tonnes a year – about 85 percent of Auckland’s total waste sent to landfill. That’s four-to-five tonnes of building waste per new home.

No wonder both councils and government are pushing waste minimisation initiatives.  Changing the economics of waste management is at the top of their list, with an expected increase to the country’s waste levy likely to swing the balance in favour of recovery and reuse. However, levy increases only do so much, and industry players must look closer at their own practices to make a real difference.  

Where to look

Designing waste out of a system should be covered in the project plan rather than as an add-on. And the best place to start is where there’s most waste. An Auckland study shows construction waste by weight is made up of timber (20%), plasterboard (13%), packaging (5%), metal (5%) and other (45%). The same research estimates that simply by sorting waste, at least half of it could be diverted from landfill and clean-fill.

The Canterbury earthquakes raised interest in finding recycling options for treated construction timber. Traditionally, industry has shied away from using treated timber as a fuel source, fearful of releasing harmful substances into the environment. However, advances in incineration are opening the furnace door wider to bigger volumes of wood waste. For example, Golden Bay Cement has substituted nearly a third of the coal it burned for wood sourced from demolition and construction waste, in the process cutting CO2 emissions by 58,000 tonnes a year and shaving $3 million a year from energy costs.

Native timber is perhaps more attractive as reusable building material, with several small businesses around the country connecting buyers to sellers and making a buck in the process, with one – Palmerston North-based Reclaimed Timber Traders – making the claim that recycling a house can be cheaper than demolishing it. In fact, if the house was made of native timber, then deconstructing it could cost just about nothing, after the recovered materials were sold, they say. In one case, a classic 1950s 120-square-metre weatherboard home was deconstructed in Auckland, with 87 percent of materials saved from the dump. In comparison, the average house demolished in Auckland created 22 tonnes of waste.

How about plasterboard? Almost 100 percent of waste plasterboard is recyclable, with gypsum – a sulphate – used as a fertiliser, in compost, and as a constituent in many forms of plaster.

And then there’s specialised recovery and reuse, such as Auckland-based Asona, which is developing a cost-effective system to refurbish soiled and damaged ceiling panels. The project is likely to dampen the demand for the one million-plus square meters of ceilings currently shipped to New Zealand each year.

The problem with high building costs

The current building boom has sharpened the focus on minimising waste related to new green-field housing and commercial developments, where the high cost of building makes it cheaper to over-specify materials rather than wait for them to be delivered. Recent research from AUT suggests ‘over ordering’, wastes approximately $30,000 worth of material for every house built. What’s more, in cities such as Auckland, where a construction boom continues and a skills shortage forces up prices, changing procurement practices is likely to meet resistance.

Small is good

But herein lies the opportunity for on-site materials management plans to avoid waste. And this is where EnviroWaste has a role to play. Historically, developers have pushed back on recovery and reuse for practical reasons – there’s no room on site to accommodate the number of bins required to capture different families of waste.

Times and bin sizes are changing. EnviroWaste has developed a smaller bin designed for cramped building sites. Smaller bins, which measure 2.47m long by 1.22m wide and 1.8m high, allow more bins on site for separation. Compared to the standard 9m bin, EnviroWaste’s bins are 280mm narrower and 1.2m shorter. With more bins on site, construction projects are able to take advantage of recycling, separating timber, plastic, metal, and clean-fill, which are picked up and transported to various recycling facilities.   

By Richard Doubtfire, Auckland Regional Manager - Collections