Steel is a hero of the circular economy: Study estimates 85% of Aotearoa’s building and construction steel waste is recycled

By Dr Troy Coyle, HERA CEO

In June 2021, HERA published its Steel Recycling Report that indicated an impressive 74% of scrap steel in New Zealand was recycled. The recycling of steel not only provides significant environmental benefits but also helps to secure the future of the steel industry. Recycled steel is cheaper and easier to produce (recycling steel saves almost 74% of the overall energy used in production), saves natural resources, and prevents excess greenhouse gas usage.

Sector recycles 85% steel waste

We believed the building and construction sector recycled more steel than the New Zealand average. To estimate the sector-specific recycling rate, HERA commissioned thinkstepANZ to investigate. The new report confirms our prediction.

The sector produces 332 tonnes of steel scrap annually, mostly in the form of reinforcing bars, structural sections, and sheet products. This amounts to 50% of the scrap steel produced in New Zealand. Of this, only 50 kilotonnes are lost to landfill. The remaining 85% is recycled.

The study considered the Global Warming Potential (GWP) as the most important environmental indicator. It allows comparisons to be made of the global warming impact of different gases. It is a measure of how much energy the emission of one tonne of CO2 will absorb over a given period of time. In New Zealand, steel accounts for 2.2% of the country’s carbon emissions.

This recovery rate leads to savings in GWP, per tonne of steel scrap generated of 1,249kg CO2-equivalent. The challenge for the industry is to achieve 100% recovery, which would lead to even greater potential savings of 1,473kg CO2-equivalent.

Module D – end of waste state

The report also provides a value for Module D estimates for use in comparative carbon calculation. This should be considered when assessing the relative carbon performance of materials over their life, or in the case of steel, over its infinite potential lives.

This is of particular importance to the infrastructure sector. A holistic view of GWP should account for all components relating to a project during all life stages. Many carbon calculations ignore end-of-life and simply focus on embodied carbon. This is a mistake. Steel can be infinitely recyclable, unlike other materials, like timber, that are more likely to go to landfill sites to release their carbon back into the atmosphere.

Moving to 100% circularity

Moving to 100% circularity is not farfetched. Many countries have recycling rates of over 90% (e.g. UK 95%). The solution is twofold. Firstly, more steel scrap needs to be recovered, and secondly, there is a need to reduce the GWP impact of transport.

The report recommends:

  1. encouraging products to be designed to make disassembly and separation easier at the end of its life; and
  2. improving waste management and recycling infrastructure.

The report demonstrates the role that steel plays in Aotearoa’s circular economy, supporting a whole industry in steel recycling and contributing significantly to global carbon emissions reduction.

Dr Troy Coyle brings more than 20 years’ experience in innovation management across a range of industries including materials science, medical radiation physics, biotechnology, sustainable building products, renewable energy and steel. She is a scientist with a PhD (University of NSW) with training in journalism and communications.

The information and opinions within this column are not necessarily the views or opinions of Xpress Engineer NZ, NZ Engineering News or the parent company, Hayley Media.