Our new report looks at how the New Zealand construction industry can reduce waste, carbon emissions and costs.
The circular economy is often seen as a potential solution to reduce waste and reducing a carbon footprint. However, systems that keep materials in circulation can have a higher carbon footprint than conventional linear systems. The challenge for policymakers is to achieve both outcomes, i.e., a low carbon circular economy. Minimising construction waste is an activity that ticks both boxes.
Measuring embodied carbon in New Zealand's construction industry
Construction and demolition waste is responsible for up to half of all waste generated in Aotearoa New Zealand. The greenhouse gas (GHG) emissions from all waste contribute approximately 4% of the country's total GHG emissions. Minimising waste is one of the New Zealand government’s top priorities.
Buildings are another large source, contributing up to 15% of New Zealand’s total GHG emissions. Approximately half of these emissions are generated through manufacturing and disposing of building products (collectively known as ‘embodied carbon’).
This report uses a ‘bottom-up’ approach to calculate material flows and GHG emissions based on a small set of archetypal buildings. We then scaled this data to the national level using building consents for 2021. We focused on the upfront carbon emissions generated from producing materials through to the building’s practical completion.
What we found
On average, 4.2% of all materials used to build buildings are wasted
These wasted materials contribute 120,000 t CO2e of GHG emissions
Concrete, steel, plasterboard and timber are leading contributors
Reducing construction waste is a win-win-win scenario
- It contributes to a circular economy
- It reduces the carbon footprint at the building level, by avoiding the GHG emissions associated with manufacturing and disposing of wasted materials
- It can reduce the cost of construction by avoiding the need to pay for excess materials that are wasted and disposal fees for those wasted materials