Recyclability & Recycling Of Metal Cladding

New Zealand Metal Roofing Manufacturers (NZMRM), as does every industry that wants to survive, is looking at the sustainability of their products and member companies.  We have been operating a Sustainability Sub committee for the last two years, and this was a topic at the Adelaide conference.  We are now planning to publish in Scope a series of articles about various aspects of sustainability to inform our members and customers and to help designers make appropriate choices in a society that is placing increasing value in being “Green”.   A sustainable building industry consists of sustainable products and sustainable industry making them.

While some aspects of the sustainability of metal cladding products are still under consideration by the industry and the NZMRM, you will soon become aware of the sustainable manufacturing process used by New Zealand Steel at the front end of the life of steel cladding, and this is a story worth telling and one to be proud of.

What is not in dispute but also not well known is the other end of the life of steel and indeed all metal cladding – its ability to be recycled and its actual level of recycling.  In fact the metal used in cladding (and elsewhere of course) is both able to be recycled with no loss of quality, and actually is recycled to a very high degree.
In this article, we have collated information from world sources and specifically New Zealand sources to discuss the generic recyclability and recycling of metal, in particular steel, and about the unique system and cycle operating in New Zealand, which works well for all parties.   What follows has been taken from a number of sources and all data, volumes, numbers etc. are derived from published information so are only as accurate as the sources.  The comment and conclusions are the author’s.   We deal primarily with steel, which is by far the main material used for metal building cladding, but many of the comments also apply to aluminium, certainly at world level.

Recyclability vs recycling

It is important to separate these two similar sounding operations.  Steel is the ultimately recyclable material. It is unaffected by recycling and recycled steel is as good as new, but has much less embodied energy.  All steel products have the ability to be recycled, but the degree to which they are recycled does depend on how much they are mixed with other materials and the difficulty of recovery.  Reuse of material similarly depends on its quality at the end of the life of whatever contains it.  Structural steel is very reusable and quite easily recycled.  Steel cladding can be reused depending on its condition (and may end up on a lower quality building) but is very easily recycled (and is easier to melt than structural steel). Steel used as reinforcing in concrete is easy to recycle but difficult to recover.  Steel used in motor car bodies is highly contaminated with other materials.  In spite of this variability steel for recycling is a valuable resource and 85-90% of steel used in construction is recycled globally.   Over 60% of all steel used globally is subsequently recycled.

The ability to be recycled

A number of common materials can be recycled in the sense of being removed from a form which is no longer needed and then converted into something else.  A number of products themselves are able to be reused once the item into which they are incorporated is no longer required.
Metals in various forms, glass, plastics, paper, timber, fabrics and others are able to be reused in some way, and we are all familiar with the recycling programmes of local councils – unheard of 10 years ago but now common – in which various materials are left outside to be “recycled”.  We have the idea that they are reused in some way without being very aware of what this might be.
In fact, to varying degrees nearly all these – apart from metals – are either not actually reused in a recognisable way or are degraded during reprocessing from the original form or quality (often referred to as “down cycling”).  Nearly all non-metals even if reused as part of a new or similar product are in a product of lower quality or value with reduced physical or aesthetic properties. 

Metal and specifically steel cladding (which after all is what we make and sell) can both be reused in its same form and more importantly it can be recycled into product indistinguishable from the original, totally undegraded and capable of being recycled indefinitely.   Steel cladding which is generally unmixed with anything other than metal coating and paint and has thin sections is easy to recycle, compared with e.g. reinforcing steel buried in concrete. 

Throughout its history steel has always been recycled and all steel contains a proportion of recycled material from 10 – 100%, so that any steel currently in use actually has some content that may have been used many times and be 100’s of years old. 

Recycling levels

Because of the factors discussed above and below – (no loss of quality, scrap required for efficient function of steel mills, much lower energy content), steel has a very high level of recycling – typically up to 90% of all steel embodied in buildings and in artefacts which have ended their useful life ends up being recycled into fresh steel ready to start as good as new, into a long new useful life.
In the case of building cladding, quite a lot does actually get reused (rather than recycled as material) although generally in a lower value role – e.g. steel roofing from an office might end up as a fence or a farm shed.  The actual percentage of steel which is recycled obviously depends on the application, so that steel which can be reused when a building is taken down is different to steel in a crushed motorcar body or an old fridge, but overall it is very high.  Some global figures are appended. 
Steel manufacture and recycling
Today, steel is nearly all made by one of two processes world-wide.  The Basic Oxygen Furnace (BOF) is the main method for converting iron metal made from iron ore into steel.  It needs to use some recycled steel for efficient running and will use from 10-25% of recycled material.  This may be in-plant scrap (“pre-consumer recycle”) or bought-in scrap metal that is derived from steel items past their usefulness (“post-consumer recycle”).  Typically a BOF unit will use all its own in-house scrap and some bought-in material.
The Electric Arc Furnace (EAF) can also convert iron into steel but is the main way of consuming scrap steel materials (post-consumer), and the process requires a minimum level of at least 30% scrap to function.  EAF units run from 30 to 100% scrap. A number of mills with EAF only use scrap steel as a raw material.

Because steel is a durable material and is used mainly in quite long-life products (unlike packaging materials) and is also in increasing demand, the amount of scrap available (even at very high recycling rates) is not sufficient to feed the demand and so virgin steel continues to be made from iron ore.  Many global steel companies have both types of furnace and are able to take in and reuse large amounts of scrap steel – typically as much as they can get, because reprocessing scrap steel requires less energy than making new steel.

It is worthy of note that the embodied energy aspect of Life Cycle Assessment of steel requires that both new manufacture and reuse are considered, so that all steel has a multi-level energy cost reflecting the fact that any new steel made will almost certainly be recycled many times way into the future and so the energy required to make it progressively decreases as it is successively recycled.

The New Zealand scene

Globally then, steel mills making all sorts of steel products use both recycled (pre- and post-consumer scrap) and virgin iron made from iron ore.  The proportion varies from mill to mill; some only use scrap and others use smaller amounts of it in their mix.  Overall a very high level of recycling is achieved.

New Zealand (of course) is different.  We only have two steel mills and they have effectively split functions.  Pacific Steel Group (part of Fletcher Building) started operation at Otahuhu in the late 50s to process New Zealand’s scrap metal, and now uses an EAF to do only this.  Scrap metal including steel is collected around the country by collection agencies (coordinated by Sims Metal) and as much steel as Pacific Steel can handle is used here and the rest exported to other mills overseas for recycling.  Pacific Steel converts this scrap into high quality reinforcing steel for use in reinforced concrete and into wire, and uses 100% post-consumer scrap in their EAF.

New Zealand Steel (now part of Bluescope Steel, an Australian manufacturer also operating throughout Asia) started manufacturing steel at Glenbrook in 1963.  After many decades of research, a process had been developed to process the local ironsand in a unique-to-NZ process, which has a small ‘ecological footprint’, and the Glenbrook plant was built to use this process. 
After various changes in technology (and ownership) New Zealand Steel now uses a BOF and makes all new steel from iron with only about 12% in-plant waste (pre-consumer scrap) added.

New Zealand Steel manufactures coil and sheet for use in building cladding and other industries.  The coil may be metal-coated with zinc (galvanised steel) or aluminium/zinc (Zincalume ®), and may be painted on a coil-coating line or unpainted.  The steel cladding materials NZMRM members use and supply primarily come from NZ Steel, with a small amount imported from Asian mills.

For New Zealand this is a very neat system and ensures that steel used in buildings, both for reinforcing and cladding, is made with maximum efficiency and minimum transportation.   Both plants have a high level of “sustainability” which they strive to improve as an ongoing process.

Thus in purchasing steel made in New Zealand you can be sure it has been made with maximum recycled content for reinforcing steel and maximum recyclability for cladding.  New Zealand has a high level of recovery of steel products either for reuse or recycling at Pacific Steel.

All good, you might think, but there is one problem with this very neat system.

Energy rating systems

For a number of years there has been an increasing global demand for energy efficient buildings.  Typically this starts with office buildings and then extends to institutions like schools, and finally to domestic dwellings.  The methods of rating buildings is (of course) different in different countries but generally the system looks at the derivations of the raw materials used, the transportation of materials and of people to the building, the energy used during construction and during life, the water used and processed, and finally the ability to be reused or recycled at the end of the building’s life.
This is only a summary, and you can find more details easily on the internet.  There are some well-known rating systems including BREEAM (early 1990’s) in the UK, Casbee in Japan, and LEED (2000) in the United States. These are of varying ages and levels of development and New Zealand is a rather late starter in this area.
Australia developed a system called the Green Star Rating (so far for new office buildings only, but rating systems for other buildings exist, and the intention is that all new buildings will eventually be covered by this system - sooner rather than later).  New Zealand has chosen to follow suit with a very similar Green Star NZ rating system.  Unfortunately both of these are somewhat different to either BREEAM or LEED in their regard for the recycled content of steel.
Without going into the somewhat complicated details – BREEAM gives points for “responsibly sourced” products (which you have to prove); LEED gives points for two levels of recycled content (not recyclability), one low and one modest, and also gives points for fairly short distances from manufacture to use (500 miles/800 kms – which is not that short!)
To achieve points with either Green Star system requires the steel used in a building to have a high recycled content - “Up to two points are awarded where it can be demonstrated that the percentage of all steel used in the design has a post-consumer recycled content greater than x % as follows - 1 point = 60% by mass and 2 points = 90% by mass”.  Exactly what this means (read it again) is not clear to me, but it is clear that steel manufactured by New Zealand Steel will contribute no points to the total.  Neither is there any recognition of distance travelled, either way (i.e. no penalty for long distance and no benefit for short distance).
What this means for NZ is that reinforcing steel and wire receive 2 points while cladding made in NZ receives none.  Imported cladding from 10,000 kms away, painted with paint of unknown quality, and sourced from a plant or country with no known sustainability credentials, can get two points if it is made in an EAF.

It is recognised elsewhere that both systems complement each other and should not be regarded differently.  If there was no BOF process there would be no new steel to be recycled.

The NZ Green Building Council which operates the NZ Green Star rating system invited submissions to be incorporated into the new version and the NZMRM (and New Zealand Steel) did make a submission pointing out this issue, but the latest version (June 2008) is unchanged.


Regardless of the Green Star rating system issue, steel is the most highly recycled building material in the world.  You can use it or design for its use in buildings knowing that this in some way contributes to the sustainability of New Zealand as a whole.

Appendix – useful snippets of data

In 2005 globally approximate ratio of BOF to EAF was 2:1.

280,000 tonnes recycled pa in NZ.  Produced 620,000 tonnes.  Recycled content thus 45% of new.  In Australia 65%.

Recycle rate of steel from buildings 85%

In the USA 29% of steel made by BOF is recycled content.  For EAF it is 83%.

Recycle rates of structural steel 98%.  Reinforcing steel 65% (more difficult to recover from concrete).

Steel made from recycle may use only 25% of the energy used to make new steel.