Doc #90 — Scrap Metal as Resource

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RECOMMENDED ACTIONS

NZ’s accumulated scrap metal is not going anywhere — it sits in scrap yards, farm paddocks, and the built environment, and it will still be there in six months. The policy directive to stop exports requires only a written ministerial order notifying existing scrap merchants and auto dismantlers of the new operating conditions — a low-cost, low-logistics first step. But building a national scrap census, alloy identification training programme, and regional sorting infrastructure are institutional efforts that compete for attention with food distribution, medical triage, and power grid management in the first weeks. The scrap programme starts with that initial directive and scales up through Months 2–6.

First month (Phase 1)

1. Issue a national directive: no export, disposal, or uncontrolled scrapping of any metal. Existing scrap merchants, auto dismantlers, and metal recyclers are notified that their operations continue under national resource authority oversight. Their existing inventories become part of the national metal reserve.
2. Secure all scrap processing equipment. Shears, balers, torches, cranes, magnetic separators, and mobile scrap handlers are strategic assets.

Months 2–3 (Phase 1)

3. Inventory scrap merchant stocks. NZ’s scrap metal dealers — Sims Metal (NZ’s largest, multiple locations), Ward Recycling, Metalman Recycling, and regional operators — hold significant tonnages of already sorted, processed scrap. This is the most accessible metal supply. This inventory folds into the general asset census (Doc #8).⁴
4. Classify experienced scrap graders and metallurgists as critical-skills personnel. People who can identify alloys by visual and physical methods are rare and valuable.
5. Begin planning scrap allocation. Sorted scrap flows to: (a) Glenbrook EAFs as supplementary feed (Doc #89); (b) existing NZ foundries for casting (Doc #91); (c) blacksmith forges for direct reworking (Doc #91); (d) machine shop stock (Doc #91).

Months 3–6 (Phase 1)

6. Conduct a national scrap metal census as part of the broader asset census (Doc #8). Categories: (a) already at scrap merchants, sorted and unsorted; (b) auto dismantlers — vehicle bodies and components; (c) shipping container depots; (d) structural steel in condemned or non-essential buildings; (e) rail — disused sidings, surplus track; (f) farm machinery graveyards; (g) industrial scrap at factories and workshops.
7. Establish alloy identification training at regional centres. Teach spark testing, magnet testing, and chemical spot testing to scrap workers and general tradespeople. Course material is described in Section 4 of this document.
8. Designate regional scrap collection and sorting yards — at least one per major region, co-located with or near existing scrap merchant operations where possible.

Months 6–12 (Phase 1)

9. Complete scrap merchant inventory nationally. Establish total tonnage by grade (carbon steel, stainless, cast iron, copper alloy, aluminium).
10. Establish the priority recovery list (Section 6): which categories of scrap offer the highest value relative to recovery effort?
11. Begin systematic recovery of high-priority scrap — starting with shipping containers, which are a concentrated, accessible, low-alloy carbon steel source.
12. Distribute alloy identification field guides to all regional scrap facilities and engineering workshops.
13. Coordinate with Glenbrook (Doc #89) on scrap utilisation. Determine what proportion of Glenbrook’s charge can be scrap (reducing demand on ironsand and coal), and what scrap quality standards the EAFs require.

First year (Phase 2)

14. Establish regular scrap collection rounds in each region — systematic collection from farms, industrial sites, and urban areas.
15. Develop induction furnace scrap melting capability at regional foundries (Doc #93) for applications that do not require Glenbrook’s scale.
16. Begin systematic vehicle fleet cannibalisation (Doc #88) with metals recovery as a secondary output — vehicles designated as donor units are stripped for parts first, then processed for scrap metal.
17. Establish copper and aluminium recovery circuits separate from steel — these metals are too valuable to lose into steel melts.

Ongoing (Phase 2+)

18. Continue systematic recovery as infrastructure ages and equipment reaches end of life. Scrap generation will accelerate as pre-war equipment wears out.
19. Develop scrap-based steel production at smaller, distributed facilities — potentially using induction furnaces — to supplement Glenbrook production and serve regional needs (Doc #89).
20. Monitor tramp element accumulation in recycled steel. As copper-contaminated scrap is recycled through multiple generations, steel quality degrades. Dilution with Glenbrook’s virgin ironsand-based steel is the primary mitigation.

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ECONOMIC JUSTIFICATION

The alternative to scrap recovery

Without systematic scrap recovery, NZ depends entirely on Glenbrook’s primary production from ironsand. Glenbrook’s annual output under recovery conditions is estimated at 150,000–300,000 tonnes per year (Doc #89), constrained by graphite electrode and refractory depletion. Scrap recycling supplements this in several ways:

Scrap in Glenbrook’s EAFs: Adding scrap to the Glenbrook charge reduces the proportion of direct-reduced ironsand, which reduces energy consumption per tonne (scrap is already metallic iron; it needs only melting, not reduction). This also reduces coal consumption (less ironsand to reduce in the kilns) and extends graphite electrode life (scrap melts faster than DRI, reducing arc-on time per heat). Adding 20–30% scrap to the Glenbrook charge — a common practice at EAF steelworks globally⁵ — could increase effective output by 20–30% while reducing per-tonne consumable consumption.

Distributed scrap melting: Regional foundries with induction furnaces or cupola furnaces (Doc #93) can melt scrap steel and cast iron locally, producing castings and rough stock without any demand on Glenbrook’s constrained consumables. A regional foundry melting 500 kg heats of scrap iron in an induction furnace requires electricity, a refractory crucible (which itself wears and must be relined — see Doc #93 for refractory dependency), and functioning power electronics (copper coils, capacitors, cooling water) — but no graphite electrodes, no coal, and no ironsand pipeline.

Direct reworking: Some scrap — particularly leaf springs, rail sections, structural sections, and heavy forgings — can be cut, forged, or machined directly into new products without melting. A blacksmith (Doc #92) heating and forging a vehicle leaf spring into a tool blade skips the entire melting and casting chain. This is the most energy-efficient form of scrap recovery. The performance gap is real but manageable: a blade forged from a leaf spring (medium-carbon chromium-vanadium steel) holds an edge adequately but is not equivalent to purpose-made tool steel (W1, O1, or similar) in hardness, wear resistance, or consistency. For most agricultural and general-purpose tools, scrap-forged products are serviceable.

Person-years and payback

Establishing the national scrap sorting and distribution system: Approximately 10–20 person-years of effort in the first year — inventory, training, facility setup, initial collection. Much of this labour comes from redirecting existing scrap industry workers, who already have the skills and physical infrastructure.

Ongoing scrap recovery: The existing scrap industry in NZ employs several hundred people.⁶ Under recovery conditions, scrap collection and processing becomes a larger operation as the scope expands from commercial scrap to systematic recovery from the entire built environment. An ongoing workforce of 300–500 people nationally is a reasonable estimate for mature-phase scrap recovery.

Value of output: Every tonne of sorted, processed scrap steel delivered to a foundry or to Glenbrook displaces a tonne of primary production that would have consumed coal, electricity, ironsand, and — critically — irreplaceable graphite electrodes. At Glenbrook’s estimated electrode consumption of 1.5–3.0 kg per tonne of steel from ironsand (Doc #89), each tonne of scrap substituted for ironsand saves approximately 1–2 kg of graphite electrode. Across 50,000–150,000 tonnes of scrap per year (depending on collection capacity and sorting throughput), that is 75–450 tonnes of electrode saved — potentially months of additional Glenbrook operating life.

Breakeven: Immediate. The scrap industry infrastructure already exists. The metal already exists. The incremental cost of redirecting existing operations from export to domestic recovery is minimal compared to the value of the metal produced.

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1. NZ’S SCRAP METAL INVENTORY

1.1 Vehicles

NZ’s approximately 4.4 million registered vehicles⁷ represent the single largest concentrated stock of steel, aluminium, and copper in the country. A typical passenger vehicle contains approximately 800–1,200 kg of steel and iron, 80–150 kg of aluminium (engine block, cylinder head, transmission case, wheels), 15–25 kg of copper (wiring harness, alternator, starter motor, radiator), plus smaller quantities of zinc, lead (battery), and other metals.⁸

Estimated vehicle fleet metal content:

Metal	Per vehicle (approx.)	Fleet total (approx.)
Steel and iron	900 kg	3.5–4.5 million tonnes
Aluminium	100 kg	350,000–450,000 tonnes
Copper	20 kg	70,000–90,000 tonnes
Lead (batteries)	10 kg	35,000–45,000 tonnes
Zinc (coatings, die castings)	10 kg	35,000–45,000 tonnes

These are rough estimates based on typical vehicle composition data applied to NZ’s fleet. The actual figures depend on the fleet mix (older vehicles tend to be heavier and contain more steel; newer vehicles have more aluminium and electronics). The census (Doc #8) would establish better numbers.

Recovery timeline: Most vehicles will be cannibalised for spare parts first (Doc #88), with metal recovery as a secondary step after all useful components have been stripped. Vehicles designated as Category 4 (donor pool) in the spare parts triage are the primary source for early scrap metal recovery from the fleet.

1.2 Shipping containers

NZ has a large stock of shipping containers — at ports, depots, on farms (used for storage), and at commercial premises. The exact number in-country at any time is uncertain, but estimates suggest 150,000–300,000 containers of various sizes.⁹ A standard 20-foot container weighs approximately 2,200 kg empty; a 40-foot container approximately 3,700 kg.¹⁰

Estimated container steel stock: 400,000–800,000 tonnes.

Shipping containers are an excellent scrap source:

• Known alloy: Container steel is predominantly Corten steel (weathering steel, typically ASTM A588 or the Australian/NZ-adopted equivalent AS/NZS 3678 Grade 350L0 with weathering chemistry) — a low-alloy carbon steel with small additions of copper (0.25–0.55%), chromium, nickel, and phosphorus that provide atmospheric corrosion resistance.¹¹ This is a known, consistent composition.
• Accessible: Containers are concentrated at depots and ports, not dispersed across the landscape.
• Processable with available equipment: Container walls (typically 1.6–2.0 mm steel sheet) can be cut with oxy-acetylene torches, angle grinders, or mechanical shears. The flat panels produce clean, stackable scrap. This requires functioning cutting equipment, adequate gas supply or electrical power, and attention to zinc oxide fume if painted surfaces are present — it is not a trivial operation, but it is within the capability of any scrap yard with basic equipment.
• Caveat: The copper content of Corten steel (while low) contributes to the tramp element problem when the steel is recycled. For applications where copper sensitivity is a concern, container steel should be diluted with low-copper scrap or Glenbrook primary steel.

1.3 Structural steel in buildings

NZ’s commercial and industrial buildings contain significant structural steel — in frames, roof trusses, mezzanine floors, portal frames, purlins, and girts. Residential buildings use less structural steel (NZ is predominantly timber-framed), but do contain steel roofing (COLORSTEEL — zinc-aluminium coated steel, Doc #97), steel fixings, and reinforcing bar (rebar) in concrete foundations and floors.

Estimate: NZ’s total steel-in-buildings stock is difficult to quantify without a building-by-building survey. A rough estimate based on NZ’s building stock and typical steel intensity suggests several million tonnes nationally, though the vast majority is in active use and should not be recovered until the building reaches end of life or is designated for demolition.

Recovery approach: Building steel recovery is a long-term activity. In the near term, only buildings that are condemned, damaged, or designated for demolition should be stripped for steel. Systematic demolition for steel recovery is a later-phase activity when scrap demand exceeds easier sources (containers, vehicles, stockpiled scrap).

Alloy note: Structural steel in NZ is predominantly mild carbon steel (Grade 300 or 350 to AS/NZS 3679)¹² — a well-characterised, low-alloy composition that sorts cleanly from stainless and non-ferrous metals by magnet test and is compatible with standard EAF processing. Note that recycling still requires the full sorting, sizing, and de-contamination steps described in Section 5; “known composition” means fewer sorting errors, not fewer processing steps. Rebar is similarly basic carbon steel. Stainless steel appears in handrails, kitchen equipment, and some architectural applications — it must be sorted separately.

1.4 Rail

NZ’s rail network includes approximately 3,700 km of operational track, plus additional sidings, branch lines (some disused), and industrial rail.¹³ Rail steel is high-quality carbon steel with controlled manganese content — typically 0.6–0.8% carbon, 0.7–1.2% manganese — making it an excellent material for forging into tools and components directly, without melting.¹⁴ Blacksmiths prize rail steel.

Recovery approach: Operational rail must not be touched — the rail network is a critical transport asset (Doc #61). Disused sidings, mothballed branch lines, and rail from industrial sites are the appropriate recovery targets. NZ has hundreds of kilometres of disused rail that could be recovered.¹⁵ Each metre of standard rail weighs approximately 40–50 kg, so 100 km of disused rail represents 4,000–5,000 tonnes of high-quality steel.

1.5 Farm machinery and equipment

NZ’s approximately 52,000 farms¹⁶ hold large quantities of steel in tractors, implements, water systems, fencing, sheds, and accumulated scrap. Farms are the single largest category of “machinery graveyards” in NZ — many farms have decades of accumulated defunct equipment sitting in paddocks and sheds.

Characteristic: Farm scrap is highly variable in alloy composition and heavily weathered. It includes mild steel (shed framing, tanks, fencing), cast iron (engine blocks, pump housings, plough parts), high-carbon steel (plough shares, cultivation discs, springs), and small quantities of non-ferrous metals. Sorting requires on-site identification.

1.6 Industrial and commercial scrap

Factories, workshops, ports, and commercial premises hold steel in equipment, racking, shelving, tanks, pipework, and accumulated offcuts. This is a diffuse source — many sites with modest quantities — but it includes some of the highest-quality scrap (known-grade offcuts from fabrication shops, clean machine shop turnings).

1.7 Non-ferrous metals

Beyond steel and iron, NZ’s accumulated stock of non-ferrous metals is critical:

• Copper: In wiring (buildings and vehicles), electric motors, transformers, heat exchangers, plumbing pipe (older buildings), and copper roofing/flashing. Total NZ copper stock is likely 200,000–400,000 tonnes, though most is in active use (building wiring, power distribution).¹⁷ Copper is irreplaceable for electrical applications and NZ has no significant domestic production. Every kilogram of copper recovered from scrap is precious.
• Aluminium: In vehicle components, window frames, cladding, cookware, and industrial equipment. NZ’s accumulated aluminium stock is likely 500,000–1,000,000 tonnes.¹⁸ Note: the Tiwai Point aluminium smelter (Bluff, Southland) remains operational as of this document, though its long-term future is uncertain — a planned 2021 closure was averted by a renegotiated power contract, and operations continue subject to ongoing commercial negotiations.¹⁹ If the smelter is operating at the time of the event and has alumina stocks, it can produce primary aluminium for some period (see Doc #109 for the full smelter decision framework). All other domestic aluminium is recycled or imported stock. Aluminium is easily remelted (melting point approximately 660°C, well within foundry capability) with minimal oxidation loss, and is the most accessible casting metal for foundry start-up (Doc #35) — though remelting mixed alloys produces uncertain compositions, making scrap sorting by alloy type important.
• Lead: Primarily in vehicle batteries. NZ’s approximately 4.4 million vehicles hold an estimated 35,000–45,000 tonnes of lead in batteries.²⁰ Lead is essential for battery production and has few substitutes.
• Bronze and brass: In valves, fittings, propellers, musical instruments, decorative items, and bearings. Total stock unknown but modest. Essential for bearing production (Doc #35) and marine hardware.
• Zinc: On galvanised steel (roofing, fencing, structural steel), in die-cast components, and as plating. Cannot be economically recovered from galvanised steel coatings but contributes to the composition of recycled galvanised scrap.

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2. ALLOY IDENTIFICATION: WHY IT MATTERS

2.1 The tramp element problem

When different alloys are melted together indiscriminately, the resulting metal contains all the alloying elements from all the inputs — and most of these cannot be removed by standard steelmaking processes. The most damaging contaminant is copper:

• Copper cannot be oxidised out of steel during refining (unlike carbon, silicon, and manganese, which can be removed with oxygen blowing).²¹
• Copper concentrations above approximately 0.2–0.3% cause hot shortness — the steel cracks during hot rolling or forging because copper forms a low-melting-point phase at grain boundaries.²²
• Each recycling pass through the scrap-melt-use-scrap cycle increases the copper concentration if copper-bearing scrap is included.

Other tramp elements include tin (from tin-plated steel cans and solder), chromium and nickel (from stainless steel mixed into carbon steel scrap), and molybdenum (from tool steel). Each degrades the properties of the resulting steel in different ways.

2.2 The practical consequence

If NZ’s scrap metal is melted without sorting, the resulting steel will progressively degrade in quality with each recycling generation. Within a few cycles, the copper content may render the steel unsuitable for hot working — it can be cast but not rolled or forged.²³ This would be a severe loss of capability, eliminating the ability to produce rolled sections, drawn wire, and forged tools from recycled steel.

The solution is sorting: identifying alloys before melting and keeping different grades separate. Clean, low-copper carbon steel scrap can be recycled indefinitely. Copper-bearing scrap (Corten containers, electric motor scrap mixed with copper windings) must be kept separate or diluted with sufficient low-copper stock or virgin Glenbrook steel to keep the final copper content below the hot shortness threshold.

2.3 Dilution with virgin steel

Glenbrook’s ironsand-based steel has essentially zero copper — it is primary metal from ore.²⁴ Blending Glenbrook steel with scrap provides the dilution needed to manage copper accumulation. This is one of the critical reasons Glenbrook’s continued operation matters even as scrap recycling expands: Glenbrook produces the “clean” steel needed to dilute the inevitable copper buildup in recycled material.

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3. THE NZ STEEL CYCLE

3.1 Primary production plus recycling

The optimal NZ steel system is not “Glenbrook OR scrap” — it is both, working together:

• Glenbrook produces primary, low-impurity steel from ironsand. This serves applications requiring controlled chemistry (wire rod for drawing, sheet for forming, plate for pressure vessels) and provides dilution stock for managing tramp elements in recycled material.
• Scrap recycling (at Glenbrook and at regional foundries) supplements primary production, serving construction, general fabrication, and casting applications where some variation in composition is tolerable.

In the global steel industry, approximately 30% of steel production comes from scrap-based electric arc furnaces.²⁵ Under NZ recovery conditions, the scrap proportion of total steel supply should be as high as possible — every tonne of scrap used at Glenbrook is a tonne that did not require coal-based reduction, did not consume ironsand pipeline capacity, and did not consume additional graphite electrode.

3.2 Scrap at Glenbrook

Glenbrook’s EAFs can accept scrap as part of their charge. In normal practice, EAFs that process direct-reduced iron (like Glenbrook) typically blend 20–40% scrap with the DRI charge.²⁶ This practice:

• Reduces energy consumption (scrap requires only melting; DRI requires both melting and final reduction of residual oxides)
• Increases melt rate (scrap melts faster than DRI)
• Reduces electrode consumption per tonne of steel produced
• Adds steel production capacity without increasing kiln throughput

Requirement: Scrap fed to Glenbrook must be sized (cut to fit the furnace), cleaned (free of excessive rust, oil, or non-metallic contamination), and sorted (low-copper carbon steel, not mixed stainless or copper-bearing alloys). NZ’s scrap industry has historically operated under ISRI (US Institute of Scrap Recycling Industries) grading codes adapted for the Australian and NZ trade context, with the Australian Scrap Metal Specification (published by the Australasian Institute of Scrap Metal Recyclers) providing NZ-relevant grading definitions.²⁷ NZ Steel’s own acceptance specifications, developed through its existing commercial scrap purchasing operations, are the definitive reference for Glenbrook’s requirements and should be consulted directly with NZ Steel metallurgists.

3.3 Scrap at regional foundries

NZ foundries (Doc #93) melt scrap in induction furnaces and cupola furnaces. For iron castings, the charge is scrap cast iron (engine blocks, pipe fittings, machine bases) melted in a cupola with charcoal and limestone. For steel castings, scrap steel is melted in an induction furnace. For non-ferrous castings, scrap bronze, brass, and aluminium are melted in crucible furnaces.

Each of these applications requires scrap of known or controlled composition. The foundry operator needs to know what alloy is in the charge — a bronze casting contaminated with zinc from included brass has different properties than the intended gunmetal (zinc additions shift the alloy toward red brass or yellow brass composition, altering fluidity, strength, and corrosion resistance).²⁸ An iron casting made from scrap that included steel gives a different microstructure (lower carbon equivalent, reduced graphitisation) than one made from all-iron charge. Sorting is foundry input quality control.

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4. ALLOY IDENTIFICATION METHODS

This section describes practical alloy identification methods that work without laboratory equipment — methods that can be taught to scrap workers and tradespeople in hours to days, not years.

4.1 Visual and physical identification

Before any testing, a trained eye sorts much of the scrap:

• Colour: Copper and copper alloys are visually distinctive (red-brown for copper, yellow for brass, brownish for bronze). Aluminium is light-coloured and lightweight. Stainless steel is often identifiable by its bright, non-rusted surface in conditions where carbon steel has corroded.
• Weight (density): Aluminium is about one-third the density of steel. Copper is denser than steel. Lead is very dense. Experienced scrap handlers develop an intuitive sense for alloy type based on the heft of a piece relative to its size.
• Corrosion pattern: Carbon steel rusts red-brown. Stainless steel does not rust (or develops only light surface staining). Aluminium develops a white oxide. Copper develops green patina. Cast iron rusts more uniformly than wrought steel.
• Form and application: The product itself indicates the alloy. Vehicle leaf springs are medium-carbon steel (0.5–0.6% C). Stainless kitchen sinks are 304 or 316 stainless. Copper plumbing is copper. Structural I-beams are mild carbon steel. Knowing what an object was used for gives a strong indication of its composition.²⁹

4.2 Magnet testing

A permanent magnet (a strong neodymium magnet is ideal, but any magnet works) is the simplest sorting tool:

• Strongly magnetic: Carbon steel, cast iron, most tool steels. These are the bulk of NZ’s scrap and the primary recycling target.
• Weakly magnetic or non-magnetic: Austenitic stainless steel (304, 316 — the most common stainless grades), some high-manganese steels. Non-magnetic steel almost certainly means stainless, which must be sorted separately from carbon steel.
• Non-magnetic: Aluminium, copper, brass, bronze, lead, zinc. All non-ferrous metals are non-magnetic.³⁰

Limitations: Ferritic and martensitic stainless steels (400-series) are magnetic and will be sorted into the carbon steel stream by magnet testing alone. These grades contain chromium (11–27%) which contaminates carbon steel. However, 400-series stainless is less common in NZ than 300-series; the most likely source is cutlery, some automotive trim, and some industrial applications. The spark test (Section 4.3) can further distinguish these.

4.3 Spark testing

Spark testing is the cornerstone skill of scrap metal identification. When a piece of metal is held against a grinding wheel, the sparks produced have characteristic patterns that indicate the carbon content, alloy type, and approximate grade. An experienced spark tester can distinguish dozens of alloys.³¹

The method: Touch the metal lightly to a bench grinder or angle grinder running at normal speed. Observe the spark stream in subdued light (shade, not direct sunlight) against a dark background:

• Low-carbon steel (mild steel, 0.05–0.2% C): Long, smooth spark lines with few forks. Light straw to orange colour. Relatively few bursts.
• Medium-carbon steel (0.3–0.6% C): More forks and secondary bursts (small explosions at the spark tips as carbon burns). Brighter orange.
• High-carbon steel (0.7–1.2% C): Abundant secondary and tertiary bursts — the spark stream looks like a miniature fireworks display. Bright white bursts. Tool steel produces the most complex burst patterns.
• Cast iron: Short, dull red sparks with few forks. Carbon content is very high (2.5–4%) but the carbon is present as graphite flakes that burn differently from dissolved carbon in steel.
• Stainless steel (austenitic, 304/316): Short, sparse sparks. Orange-red, relatively straight with few forks. Distinctly less voluminous than carbon steel. The high chromium content suppresses the spark stream.
• Manganese steel (Hadfield steel, ~12% Mn): Moderate, orange sparks — can resemble medium-carbon steel to beginners, but the stream is typically shorter and less voluminous.
• Wrought iron: Very few sparks, long smooth lines, nearly fork-free. Unlikely to be encountered in NZ scrap but useful to know.

Training requirement: Spark testing is a learned skill. Beginners should practice with known samples — labelled pieces of mild steel, medium-carbon steel, high-carbon steel, cast iron, and stainless — until they can reliably distinguish these five categories. Competence in basic spark testing can be achieved in 2–4 hours of supervised practice. Expert-level identification (distinguishing between specific grades and alloys) takes months of experience.³²

Equipment needed: A bench grinder or angle grinder. Nothing else. This makes spark testing the most practical field identification method for NZ’s scrap program.

4.4 Chemical spot testing

Chemical spot tests use small quantities of reagent applied to the metal surface to produce a colour reaction indicating the presence of specific alloying elements. The most useful tests for NZ scrap sorting:

• Nickel test: A drop of dimethylglyoxime solution on a surface cleaned with dilute acid produces a pink-red stain if nickel is present (>1%). Positive result indicates stainless steel (300-series) or nickel alloy. Dimethylglyoxime is available from NZ chemical suppliers and has a long shelf life.³³
• Chromium test: A drop of diphenylcarbazide solution on a surface reacted with dilute acid produces a violet colour if chromium is present. Indicates stainless steel or chrome alloy steel.³⁴
• Molybdenum test: Useful for distinguishing 316 stainless (contains Mo) from 304 (does not). Reagents are more specialised.
• Copper test: Useful for confirming copper presence in steels — a surface cleaned with acid and treated with potassium ferricyanide produces a brown stain if copper is present above ~0.1%.

Practical application: Chemical spot testing is more precise than spark testing for distinguishing stainless grades but requires reagent supplies that are finite. It should be used to confirm borderline identifications, not as a first-line sorting tool. Spark testing and magnet testing handle 90% of sorting decisions.

4.5 Portable XRF (if available)

Portable X-ray fluorescence (XRF) analysers provide rapid, accurate alloy identification — the instrument is pointed at the metal surface and provides a chemical composition reading in seconds. NZ has portable XRF instruments in scrap yards, metal testing firms, and some engineering operations. These instruments run on rechargeable batteries, have radioactive or X-ray tube sources with long service life, and are the gold standard for scrap sorting.³⁵

Limitation: Portable XRF instruments are imported, cannot be manufactured in NZ, and have components that will eventually fail (detectors, X-ray tubes, circuit boards). Existing instruments should be treated as strategic assets, allocated to the highest-volume sorting operations, and protected from damage. When they fail, NZ falls back to spark testing, magnet testing, and chemical spot tests — which is why those skills must be taught broadly.

4.6 Summary of identification methods

Method	Equipment needed	Training time	What it identifies	Best for
Visual/physical	None	Days of practice	Broad alloy family	First-pass sorting; non-ferrous separation
Magnet test	Permanent magnet	Minutes	Ferrous vs. non-ferrous; austenitic stainless	Fast bulk sorting
Spark test	Bench/angle grinder	2–4 hours basic; months for expertise	Carbon content; alloy family	Primary alloy sorting of ferrous metals
Chemical spot test	Reagent kit	1–2 hours	Specific elements (Ni, Cr, Mo, Cu)	Confirming stainless grades; copper detection
Portable XRF	XRF analyser	30 minutes	Full composition	High-volume precision sorting; strategic use

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5. SORTING AND PROCESSING LOGISTICS

5.1 The sorting framework

Scrap metal should be sorted into the following categories before reaching any melting operation:

Ferrous (magnetic):

• Clean low-carbon steel: Structural sections, sheet, plate, pipe that is not galvanised or painted with lead-based paint. Free of copper contamination. This is the premium scrap grade — suitable for Glenbrook charge, rolling into new products, and demanding applications.
• Galvanised steel: Zinc-coated steel from roofing, fencing, and structural applications. The zinc coating vaporises during melting (creating zinc fume — a serious health hazard requiring ventilation) and contaminates the melt. Best processed at facilities equipped for zinc fume management or de-galvanised before melting.³⁶
• Automotive scrap (mixed): Vehicle bodies contain multiple steel grades plus copper wiring, zinc coatings, and other contaminants. Suitable for construction-grade applications (rebar, general fabrication) where copper contamination up to approximately 0.3–0.4% is tolerable — this range is above the nominal hot-shortness threshold but acceptable for cast and non-wrought products.³⁷ Automotive scrap is not suitable for wire rod, cold-formed sheet, or any application requiring hot rolling without dilution from low-copper stock. The actual copper content of shredded auto scrap in NZ is estimated at 0.15–0.25% depending on how thoroughly wiring harnesses have been stripped before shredding; complete copper stripping is labour-intensive and not always feasible at scale.³⁸
• Cast iron: Engine blocks, brake drums, pipe fittings, machine bases. Identifiable by brittleness, grey fracture, and short dull sparks. Sorted for foundry use (Doc #93).
• Stainless steel: Sorted by magnet test (non-magnetic = 300 series) and spot test. Kept completely separate from carbon steel. Valuable for chemical equipment, food processing, marine applications.
• Tool steel and spring steel: High-carbon steels from springs, files, saw blades, tools. Identifiable by bright spark bursts. Valuable for blacksmith forging stock (Doc #92) — too valuable to melt indiscriminately.
• Rail steel: High-quality carbon-manganese steel. Excellent forging stock. Sorted separately.

Non-ferrous:

• Copper: Wire, tube, sheet, motor windings. Sorted by colour and non-magnetic response. Kept strictly separate.
• Aluminium: Castings, extrusions, sheet. Very light, non-magnetic. Sorted into casting alloys (engine components, generally high-silicon) and wrought alloys (extrusions, sheet, generally lower-silicon) where possible.
• Brass and bronze: Yellow-coloured copper alloys. Sorted for foundry casting stock.
• Lead: Batteries, sheet, pipe (old buildings). Handled with appropriate safety precautions (lead is toxic).
• Zinc: Die castings, some plumbing. Relatively rare as a separate scrap stream.

5.2 Processing at collection points

Scrap must be processed before it can be charged to a furnace:

• Sizing: Cut to dimensions that fit the furnace charge opening. For Glenbrook’s EAFs, this means pieces no larger than approximately 1 metre in the longest dimension.³⁹ For foundry induction furnaces, pieces must fit the crucible — typically 200–500 mm.
• Cleaning: Remove non-metallic contamination — rubber, plastic, wood, soil. Motor scrap must have copper windings removed (or be sorted into the copper-contaminated stream). Galvanised material should be flagged.
• Cutting equipment: Oxy-acetylene torch (preferred for heavy structural steel), mechanical shears (for plate and sheet up to ~10 mm), angle grinders with cutting discs (for lighter material), and plasma cutters where available. Oxy-acetylene gas is a consumable with a significant dependency chain: oxygen supply requires either an imported air separation unit (cryogenic ASU) or high-pressure electrolyser — neither of which NZ can manufacture domestically; acetylene requires calcium carbide feedstock, which is produced by smelting lime and coke at approximately 2,000°C in an electric arc furnace, a process NZ does not currently have in operation. Existing gas cylinder stocks are finite and should be managed as strategic reserves (Doc #89). Plasma cutters require electricity, imported electrodes/nozzles, and a compressor — also finite in consumable supply. Abrasive cutting discs have finite NZ stock and no domestic manufacturing capability. Mechanical shearing — which requires no gas and no abrasive consumables — should be the preferred method for plate and sheet wherever equipment permits, conserving gas and disc stocks for cuts that shears cannot make.

5.3 Transport logistics

Scrap metal is heavy. A single shipping container weighs 2.2 tonnes. A car body weighs approximately 1 tonne. Moving scrap in useful quantities requires heavy vehicles — trucks, trailers, or rail.

Under fuel rationing (Doc #53), scrap transport must compete for fuel allocation with food, medical, and other essential transport. This means:

• Prioritise high-density collection points: Scrap merchants, container depots, and auto dismantlers already have concentrated stocks. Collect from these first.
• Co-locate processing with collection: Sort and size scrap at the collection yard, not at the melting facility. This ensures only usable, sorted material travels to the furnace.
• Use rail where possible: Rail transport is far more energy-efficient than road for bulk materials. Scrap depots near rail sidings should be prioritised.
• Accept regional processing: Not all scrap needs to go to Glenbrook. Regional foundries with induction furnaces or cupolas can melt scrap locally for casting, eliminating long-distance transport entirely.

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6. PRIORITY RECOVERY TARGETS

6.1 Priority matrix

Recovery effort should be directed by the ratio of metal value to recovery cost. The highest-priority targets are those that yield the most usable, well-sorted metal per unit of fuel, labour, and cutting equipment expended.

Priority	Source	Estimated NZ stock	Alloy	Why it ranks high
1	Existing scrap merchant stocks	100,000–300,000 tonnes	Pre-sorted by grade	Already sorted, sized, and concentrated. Immediate availability.
2	Shipping containers	400,000–800,000 tonnes	Corten (low-alloy carbon steel)	Known alloy, concentrated at depots, processable with standard cutting equipment.
3	Disused rail	20,000–50,000 tonnes	High-carbon rail steel	Premium forging stock, concentrated along rail corridors.
4	Auto dismantler stocks	50,000–100,000 tonnes	Mixed but partially sorted	Already at processing facilities with cutting equipment.
5	Vehicle fleet (Cat 4 donors)	Millions of tonnes (phased)	Mixed	Enormous volume but requires parts stripping first (Doc #88).
6	Farm machinery graveyards	Unknown, likely large	Mixed	Dispersed and variable, but high per-farm accumulation.
7	Industrial and commercial scrap	Unknown	Variable	Dispersed but includes high-quality fabrication offcuts.
8	Building demolition	Several million tonnes	Structural steel, rebar	Available only as buildings reach end of life. Long-term.

6.2 Non-ferrous priority targets

Copper (highest priority non-ferrous metal): Primary recovery targets are scrapped electric motors, transformers designated for decommissioning, building demolition wiring, vehicle wiring harnesses. Every copper recovery operation should be planned — not incidental — because copper is NZ’s most constrained industrial metal.

Aluminium: Primary recovery targets are vehicle components (engines, transmissions), building cladding and window frames (as buildings are demolished), and defunct commercial kitchen and food processing equipment.

Lead: Vehicle batteries. NZ processes approximately 1.5–2 million batteries per year in normal times.⁴⁰ Under recovery conditions, battery recycling becomes essential for maintaining battery production for essential vehicles and solar energy storage.

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7. MELTING CAPABILITY AND CAPACITY

7.1 Glenbrook EAFs

Glenbrook’s two electric arc furnaces can melt scrap as part of their ironsand-based charge. At a 20–30% scrap addition rate and an annual production target of 200,000–300,000 tonnes, Glenbrook could absorb 40,000–90,000 tonnes of sorted scrap per year.⁴¹ This scrap must meet Glenbrook’s quality standards: sized, sorted, low copper content, and free of excessive non-metallic contamination.

7.2 NZ foundries

Existing NZ foundries (Doc #93) operate induction furnaces and, potentially, cupola furnaces. Their combined melting capacity is modest — probably 5,000–15,000 tonnes per year nationally, though this estimate requires census verification.⁴² Foundries consume scrap as their primary raw material: cast iron scrap for iron castings, steel scrap for steel castings, and non-ferrous scrap for copper-alloy and aluminium castings.

7.3 Blacksmith forges

Blacksmith operations (Doc #92) do not melt scrap — they heat it to forging temperature (typically 900–1,100°C) and reshape it by hammering. This is the most energy-efficient form of scrap recovery for tool production. A blacksmith working with rail steel or leaf spring steel can produce knives, chisels, agricultural tools, and hardware directly from scrap without any melting step. The scale is small (kilograms per day, not tonnes) but the value per kilogram is high because the products are finished tools, not feedstock.

7.4 Future capacity

As graphite electrode stocks at Glenbrook deplete, scrap-based steelmaking in induction furnaces — which do not use graphite electrodes — becomes the primary pathway for continued steel production. Induction furnaces have their own dependency chain: copper induction coils (long-lived but eventually need rewinding), power capacitors (imported, finite NZ stock), refractory crucible linings (consumed every 50–200 heats depending on alloy and lining quality),⁴³ and water cooling systems. These constraints are less acute than graphite electrode depletion but must be managed. Doc #93 addresses foundry expansion, including the construction of NZ-built cupola furnaces for iron production and the use of existing induction furnaces for steel and non-ferrous melting.

The long-term NZ steel cycle is likely: Glenbrook produces primary steel from ironsand for as long as its electrodes and refractories hold out; regional induction-furnace and cupola-based operations expand to supplement and eventually replace Glenbrook’s output using scrap as feedstock; and the entire system manages copper accumulation by blending scrap with whatever primary production remains available.

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8. HEALTH AND SAFETY

8.1 Hazards in scrap recovery

Scrap metal operations involve serious occupational hazards:

• Zinc fume: Melting or cutting galvanised steel releases zinc oxide fume, which causes “metal fume fever” — flu-like symptoms that are self-limiting but debilitating. Repeated exposure has cumulative health effects. Galvanised material should be identified and processed separately, with adequate ventilation or respiratory protection.⁴⁴
• Lead exposure: Handling lead-acid batteries and melting lead-containing scrap creates lead exposure risk. Lead dust and fumes are toxic and cumulative. Use gloves, respiratory protection, and wash facilities.
• Asbestos: Older industrial equipment (boilers, pipe lagging, brake linings, electrical panels) may contain asbestos. Scrap workers must be trained to identify and isolate asbestos-containing materials.
• Cadmium plating: Some older fasteners and aerospace components are cadmium-plated. Cadmium fumes are extremely toxic. Identify and sort cadmium-plated items separately.
• PCBs: Older transformers and capacitors may contain polychlorinated biphenyls. These should be identified and handled according to hazardous waste protocols.
• Physical hazards: Crushing, cutting, and falling metal injuries. Standard industrial safety practices apply: PPE, safe lifting, exclusion zones during cutting and crane operations.

8.2 Environmental considerations

Large-scale scrap processing generates emissions (fumes from cutting and melting), runoff (oil, rust, and soil contamination from outdoor scrap storage), and noise. Processing sites should be sited and managed to minimise community impact. Under recovery conditions, environmental standards may be relaxed from peacetime levels, but basic protections — ventilation for furnace workers, containment of hazardous materials, separation of processing from residential areas — are not luxuries. A poisoned workforce is a workforce that cannot recover.

Māori land and waterways: A significant proportion of NZ’s industrial scrap is located on or adjacent to Māori-owned land, and many proposed processing sites will be near waterways subject to Māori customary authority (wāhi tapu, awa, and moana with particular cultural significance). Siting decisions for scrap sorting yards and processing operations must engage the relevant iwi and hapū before committing to locations. Acid runoff from battery processing, zinc oxide fume from galvanised steel cutting, and oil-contaminated stormwater from scrap yards are all capable of contaminating waterways and damaging the ecosystems that underpin both customary food gathering and local water supply. These are not compliance formalities — the affected communities will be partners in the recovery effort, and poisoning their resources is both morally indefensible and operationally counterproductive.

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CRITICAL UNCERTAINTIES

Uncertainty	Impact if Wrong	Resolution Method
Total NZ scrap metal stock by category	Cannot plan recovery rates or project supply duration	National scrap census (Doc #8)
Copper content of NZ scrap stream	If higher than assumed, recycled steel quality degrades faster	Sampling and testing of representative scrap batches
Scrap merchant current inventory levels	If lower than assumed, immediate supply is shorter	Direct inventory — first week priority
Shipping container numbers in NZ	If lower, a major assumed source is smaller	Port and depot census
Glenbrook’s practical scrap acceptance rate	May be lower than the 20–30% assumed if scrap quality is poor	Technical consultation with NZ Steel metallurgists
NZ foundry induction furnace capacity	Determines distributed melting capability	Foundry census (Doc #8, Doc #53)
Fuel availability for scrap transport	If fuel rationing is severe, scrap collection is slow	Coordinate with fuel allocation framework (Doc #53)
Portable XRF instrument count in NZ	Fewer instruments means more reliance on manual methods	Equipment census
Feasibility of de-galvanising at scale	If zinc removal before melting is impractical, galvanised scrap is lower-value	Process development trials

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CROSS-REFERENCES

• Doc #1 — National Emergency Stockpile Strategy (scrap as controlled resource; scrap merchant operations under national oversight)
• Doc #2 — Public Communication (communicating the scrap recovery programme)
• Doc #53 — Fuel Allocation and Drawdown (fuel allocation for scrap transport)
• Doc #6 — Vehicle and Transport Asset Management (vehicle fleet as metal reservoir)
• Doc #8 — National Skills and Asset Census (scrap inventory; metallurgist and scrap grader identification)
• Doc #33 — Tires (scrap vehicles as tire donors before metal recovery)
• Doc #88 — Spare Parts Triage and Cannibalisation (parts stripping precedes metal recovery; integrated workflow)
• Doc #89 — NZ Steel Glenbrook (primary steel production; scrap as supplementary EAF feed; dilution of tramp elements)
• Doc #91 — Machine Shop Operations (clean scrap as bar and plate stock for machining)
• Doc #92 — Blacksmithing (rail steel and spring steel as premium forging stock)
• Doc #93 — Foundry Work and Metal Casting (scrap as foundry charge material; induction furnace and cupola melting)
• Doc #94 — Welding Consumables (oxy-acetylene for scrap cutting; welding for scrap processing equipment fabrication)
• Doc #102 — Charcoal Production (charcoal as cupola fuel for scrap iron melting)
• Doc #138 — Wire Drawing (scrap steel as feedstock for wire rod via Glenbrook)
• Doc #138 — Sailing Vessel Design (ship plate and marine hardware from scrap or recycled steel)
• Doc #145 — Workforce Reallocation (scrap industry workforce expansion)
• Doc #150 — Treaty of Waitangi and Governance (Treaty obligations in site selection, resource allocation, and engagement with iwi over scrap on Māori land)
• Doc #157 — Accelerated Trade Training (spark testing and scrap grading as training priorities)

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1. NZ ferrous scrap exports: NZ has historically exported 400,000–600,000 tonnes of ferrous scrap per year, primarily to steelmakers in South Korea, Indonesia, Bangladesh, and other Asian countries. Exact figures are available from Stats NZ trade statistics. https://www.stats.govt.nz/ — The export volume indicates the scale of annual scrap generation but not the total accumulated stock in the NZ economy.↩︎

2. NZ steel consumption data: NZ’s apparent steel consumption has been approximately 800,000–900,000 tonnes per year in recent years, comprising NZ Steel (Glenbrook) domestic production plus imports. See: HERA (Heavy Engineering Research Association), NZ steel industry data; Steel & Tube Holdings Ltd annual reports; Stats NZ trade statistics. The accumulated stock figure of 15–30 million tonnes is a rough estimate based on decades of net consumption; the wide range reflects uncertainty in service life, disposal, and export of end-of-life products.↩︎

3. Copper removal from steel: Copper is thermodynamically more noble than iron and cannot be oxidised out of molten steel by conventional refining processes (oxygen blowing, slag treatment). The only practical method for managing copper in steel is dilution with low-copper virgin metal or careful sorting to avoid copper-bearing scrap entering the furnace in the first place. See: Savov, L. et al., “Problems of recycling in steelmaking,” Journal of the University of Chemical Technology and Metallurgy; Fruehan, R.J. (ed.), “The Making, Shaping and Treating of Steel — Steelmaking and Refining Volume,” AISE, 1998.↩︎

4. NZ scrap metal industry: Major operators include Sims Metal (part of Sims Limited, global scrap recycling company, with multiple NZ locations), Ward Recycling, Metalman Recycling, and numerous regional operators. NZ’s scrap metal industry is primarily export-oriented under normal conditions, with ferrous scrap shipped to Asian steelmakers. See: Sims Limited corporate information, https://www.simsltd.com/ ; NZ scrap metal industry directory listings.↩︎

5. Scrap addition to EAF charge: Electric arc furnaces globally typically use scrap as their primary feedstock. EAFs that process DRI (like Glenbrook) commonly blend 20–40% scrap with DRI to improve melting efficiency and reduce energy consumption. The scrap acts as a coolant and provides metallic iron that melts rapidly, supplementing the DRI charge. See: Fruehan (note 3); Worrell, E. et al., “Energy efficiency improvement in the world steel industry,” Energy Policy, 2001.↩︎

6. NZ scrap industry employment: Precise employment figures for NZ’s scrap metal sector are not readily available from public sources. Sims Metal alone operates multiple NZ sites, and numerous smaller operators exist in most NZ towns and cities. An estimate of several hundred workers nationally is based on the number of known operations and typical staffing levels for scrap processing facilities.↩︎

7. NZ vehicle fleet: Approximately 4.4 million registered vehicles as of 2023–2024, including passenger vehicles, light commercial vehicles, and heavy vehicles. See: NZ Transport Agency (Waka Kotahi) Motor Vehicle Register. https://www.transport.govt.nz/statistics-and-insights/fle...↩︎

8. Vehicle metal content: Typical passenger vehicle material composition data from various automotive engineering sources. A modern passenger vehicle contains approximately 60–70% ferrous metals (by weight), 8–12% aluminium, 1.5–2.5% copper, and smaller percentages of zinc, lead, magnesium, and other metals. Exact composition varies significantly by vehicle make, model, and year. See: Sakai, S. et al., “An international comparative study of end-of-life vehicle recycling systems,” Journal of Material Cycles and Waste Management; European Automobile Manufacturers Association (ACEA) vehicle composition data.↩︎

9. NZ shipping container stock: The number of shipping containers in NZ at any given time is difficult to determine precisely — containers flow in and out with trade, many are repositioned empty, and a significant number have been retired from shipping service and are used for storage on farms and commercial properties. The estimate of 150,000–300,000 is based on NZ’s annual container throughput, typical dwell times, and the known stock of retired containers. Port company statistics and container leasing company data would provide better figures.↩︎

10. Shipping container weights: Standard 20-foot (6.1 m) container tare weight is approximately 2,200 kg; 40-foot (12.2 m) container tare weight is approximately 3,700 kg. These are ISO standard dimensions. See: ISO 668:2020, “Series 1 freight containers — Classification, dimensions and ratings.”↩︎

11. Corten / weathering steel: Shipping containers are predominantly manufactured from Corten-type weathering steel. The US specification is ASTM A588; the Australian and NZ equivalent for structural weathering steel is AS/NZS 3678 Grade 350L0 with atmospheric corrosion resistance (weathering) composition, or AS/NZS 3678 WR350. Note that containers are manufactured globally (primarily in China) to ISO standards rather than a single national specification — the precise steel chemistry varies by manufacturer, but all comply with ISO 1496 container structural requirements and use atmospheric corrosion-resistant steel meeting approximately ASTM A588 chemistry. The alloy typically contains 0.25–0.55% copper, 0.40–0.70% chromium, 0.25–0.40% nickel, and 0.01–0.04% phosphorus in addition to base iron and carbon. See: ASTM A588/A588M; AS/NZS 3678:2016, “Structural steel — Hot-rolled bars and sections”; ISO 1496-1, “Series 1 freight containers — Specification and testing.”↩︎

12. NZ structural steel grades: NZ structural steel is specified to AS/NZS 3679, “Structural steel — Hot-rolled bars and sections,” and AS/NZS 1594, “Hot-rolled steel flat products.” Common grades are 300 and 350 (minimum yield strength in MPa). These are basic carbon-manganese steels with controlled composition. See: Standards New Zealand; HERA (Heavy Engineering Research Association) structural steel information.↩︎

13. NZ rail network: KiwiRail operates approximately 3,700 km of track on the national rail network. Significant additional mileage exists in disused branch lines, industrial sidings, and port rail. See: KiwiRail annual reports; NZ Ministry of Transport. https://www.transport.govt.nz/↩︎

14. Rail steel composition: Standard rail steel (e.g., to AS 1085.1 or international equivalents) is a carbon-manganese steel with approximately 0.6–0.8% carbon and 0.7–1.2% manganese. The high carbon content provides the hardness and wear resistance needed for rail service, and also makes rail steel an excellent material for forging tools. See: AS 1085.1, “Railway track material — Steel rails”; general rail metallurgy references.↩︎

15. Disused NZ rail: NZ has a significant stock of disused rail on closed branch lines and industrial sidings. Many branch lines closed progressively from the 1950s through the 1980s. Some rail has been recovered; other sections remain in place. The exact tonnage available for recovery requires a specific survey. See: NZ Railway and Locomotive Society publications; KiwiRail disused corridor information.↩︎

16. NZ farm numbers: NZ has approximately 50,000–55,000 farms and agricultural holdings, though the exact number depends on the definition and size threshold used. See: Stats NZ Agricultural Production Statistics. https://www.stats.govt.nz/topics/agriculture↩︎

17. NZ copper stock estimate: NZ’s accumulated copper stock includes building wiring (the largest single category), power distribution infrastructure (cables, transformers), telecommunications cabling, plumbing pipe in older buildings, vehicle wiring, motors, and electronic equipment. A rough estimate of 200,000–400,000 tonnes is based on NZ’s annual copper consumption (approximately 15,000–25,000 tonnes per year, nearly all imported) accumulated over decades. The actual figure requires detailed stock analysis.↩︎

18. NZ aluminium stock estimate: NZ’s accumulated aluminium includes vehicle components, building cladding and window frames (aluminium joinery is standard in NZ residential construction), industrial equipment, and consumer goods. The Tiwai Point smelter remains operational (see footnote 36) with production of approximately 330,000–340,000 tonnes per year, though most output is exported; domestic NZ consumption of aluminium (excluding export) is estimated at 80,000–120,000 tonnes per year based on import and production data. The accumulated in-service stock is estimated at 500,000–1,000,000 tonnes based on decades of consumption and the long service life of building products (aluminium joinery typically 30–50 years). The upper end of the range is plausible given the penetration of aluminium joinery in NZ residential construction. See: Stats NZ trade statistics; Rio Tinto annual reports (Tiwai Point production figures); Ministry of Business, Innovation and Employment.↩︎

19. Tiwai Point aluminium smelter status: The Tiwai Point aluminium smelter (operated by New Zealand Aluminium Smelters, a joint venture of Rio Tinto and Sumitomo Chemical) has been operating since 1971 with an annual capacity of approximately 334,000 tonnes of primary aluminium. A planned closure announced in 2020 was averted by a renegotiated electricity contract with Meridian Energy, and the smelter continues to operate as of 2024–2025, though its long-term future remains subject to ongoing commercial negotiations. See Doc #109 for the full smelter assessment and decision framework. See: Rio Tinto media releases; NZ Ministry of Business, Innovation and Employment energy reports.↩︎

20. Vehicle metal content: Typical passenger vehicle material composition data from various automotive engineering sources. A modern passenger vehicle contains approximately 60–70% ferrous metals (by weight), 8–12% aluminium, 1.5–2.5% copper, and smaller percentages of zinc, lead, magnesium, and other metals. Exact composition varies significantly by vehicle make, model, and year. See: Sakai, S. et al., “An international comparative study of end-of-life vehicle recycling systems,” Journal of Material Cycles and Waste Management; European Automobile Manufacturers Association (ACEA) vehicle composition data.↩︎

21. Copper removal from steel: Copper is thermodynamically more noble than iron and cannot be oxidised out of molten steel by conventional refining processes (oxygen blowing, slag treatment). The only practical method for managing copper in steel is dilution with low-copper virgin metal or careful sorting to avoid copper-bearing scrap entering the furnace in the first place. See: Savov, L. et al., “Problems of recycling in steelmaking,” Journal of the University of Chemical Technology and Metallurgy; Fruehan, R.J. (ed.), “The Making, Shaping and Treating of Steel — Steelmaking and Refining Volume,” AISE, 1998.↩︎

22. Hot shortness from copper contamination: Copper in steel concentrates at grain boundaries during hot working and forms a liquid copper-rich phase at temperatures above approximately 1,100°C, leading to intergranular cracking. The threshold for hot shortness varies with other alloy elements but is generally around 0.2–0.3% Cu for unalloyed carbon steel. Nickel additions (in roughly equal proportion to copper) mitigate the effect, which is why Corten steel — which contains both copper and nickel — can be hot-worked despite its copper content. See: Melford, D.A., “The influence of residual and trace elements on hot shortness and high temperature embrittlement,” Philosophical Transactions of the Royal Society, 1980.↩︎

23. Copper accumulation across recycling generations: Each recycling pass concentrates copper because it cannot be removed during refining. Nakajima et al., “Thermodynamic Analysis of Contamination by Tramp Elements in Steel Recycling Cycle,” ISIJ International, 2011, model the progressive copper enrichment and show that without dilution from primary (virgin) iron, the copper concentration in recycled steel exceeds the 0.2–0.3% hot shortness threshold within 3–5 complete recycling generations, depending on the copper content of input scrap. See also: Ohno, H. et al., “Unintentional Flow of Alloying Elements in Steel during Recycling of End-of-Life Vehicles,” Journal of Industrial Ecology, 2014.↩︎

24. Copper content of Glenbrook ironsand-based steel: NZ ironsand contains negligible copper. Steel produced from ironsand at Glenbrook has very low tramp element levels, making it metallurgically “clean.” This is a significant advantage for NZ — primary Glenbrook steel can dilute copper-contaminated scrap. See: NZ Steel technical publications; general ironsand metallurgy references.↩︎

25. Global scrap-based steelmaking: Approximately 30% of global steel production (about 550 million tonnes out of approximately 1.9 billion tonnes total in recent years) comes from electric arc furnaces using primarily scrap feedstock. The proportion varies by country — the United States produces approximately 70% of its steel from scrap. See: World Steel Association statistical yearbooks. https://worldsteel.org/↩︎

26. Scrap addition to EAF charge: Electric arc furnaces globally typically use scrap as their primary feedstock. EAFs that process DRI (like Glenbrook) commonly blend 20–40% scrap with DRI to improve melting efficiency and reduce energy consumption. The scrap acts as a coolant and provides metallic iron that melts rapidly, supplementing the DRI charge. See: Fruehan (note 3); Worrell, E. et al., “Energy efficiency improvement in the world steel industry,” Energy Policy, 2001.↩︎

27. Scrap grading in the NZ and Australian context: NZ’s scrap metal trade has historically used grading definitions adapted from the ISRI (US Institute of Scrap Recycling Industries) Scrap Specifications Circular, with modifications for the Australian and NZ export market. The Australasian Institute of Scrap Metal Recyclers (AISMR) represents the industry in Australia and NZ. In practice, NZ exporters trade primarily to Asian steelmakers (South Korea, Indonesia) using grades negotiated bilaterally. Under recovery conditions, NZ Steel’s own acceptance specifications — developed through its existing commercial scrap purchasing — should be treated as the authoritative grading reference for Glenbrook input quality. See: ISRI Scrap Specifications Circular https://www.isri.org/ ; Australasian Institute of Scrap Metal Recyclers; NZ Steel technical purchasing standards (to be verified directly with NZ Steel).↩︎

28. Effect of zinc contamination in copper alloy castings: Inadvertent zinc additions shift a tin-bronze or gunmetal alloy toward red brass or yellow brass composition. For example, gunmetal (C90300: approximately 88% Cu, 8% Sn, 4% Zn) intentionally contains some zinc for improved castability; however, uncontrolled zinc additions beyond approximately 5–8% reduce corrosion resistance, increase susceptibility to dezincification in marine environments, and alter mechanical properties (typically increasing tensile strength but reducing ductility). For marine hardware and valve bodies — primary uses of NZ foundry bronze/gunmetal production — dezincification resistance is critical. See: Copper Development Association, “Copper and Copper Alloys” (CDA Publication 117); ASM Metals Handbook Vol. 2, “Properties and Selection: Nonferrous Alloys and Special-Purpose Materials,” 10th ed.↩︎

29. Application-based alloy identification: Knowing the original application of a metal object provides a strong basis for alloy identification. Standard engineering practice specifies particular alloys for particular applications — structural steel is carbon-manganese steel, vehicle springs are medium-carbon alloy steel, stainless kitchen sinks are 304 austenitic stainless, copper plumbing pipe is pure or nearly pure copper (C12200 or similar). This knowledge is taught as part of metallurgical and materials engineering education but is also practical trade knowledge held by experienced tradespeople.↩︎

30. Magnetic properties of metals: Ferromagnetism is limited to iron, cobalt, nickel, and their alloys (plus some rare-earth alloys). All common non-ferrous metals (aluminium, copper, zinc, lead, tin, magnesium) are non-magnetic. Among steels, ferritic and martensitic grades are ferromagnetic; austenitic grades (stabilised by nickel) are non-magnetic or weakly magnetic. See: any standard materials science text; Callister, W.D., “Materials Science and Engineering: An Introduction,” Wiley.↩︎

31. Spark testing: Spark testing is a long-established workshop method for identifying steel grades. The principle is that carbon in steel reacts with atmospheric oxygen as the spark cools, producing characteristic secondary and tertiary bursts whose number and intensity correlate with carbon content. Alloy elements modify the spark colour and stream characteristics. See: ASM International, “ASM Metals Handbook Volume 1: Properties and Selection” (spark testing section); Metals Handbook Desk Edition; various workshop trade references.↩︎

32. Spark testing training: Competence in basic spark testing — distinguishing mild steel, medium-carbon steel, high-carbon steel, cast iron, and stainless steel — can be achieved rapidly with supervised practice using known samples. Expert-level identification of specific grades requires months of practice and is typically held by experienced toolmakers, metallurgists, and scrap graders. See: ASM spark testing references (note 25); practical trade training materials.↩︎

33. Chemical spot testing for alloy identification: Dimethylglyoxime test for nickel and diphenylcarbazide test for chromium are standard analytical chemistry methods adapted for field use. Reagent kits for alloy identification are commercially available (e.g., from Koslow Scientific Company, Rex Gauge Company). These tests are described in standard analytical chemistry references and in metal identification field guides. See: ASM Metals Handbook; Piotrowski, T. and Rybarczyk, T., “Chemical spot tests for metal identification.”↩︎

34. Chemical spot testing for alloy identification: Dimethylglyoxime test for nickel and diphenylcarbazide test for chromium are standard analytical chemistry methods adapted for field use. Reagent kits for alloy identification are commercially available (e.g., from Koslow Scientific Company, Rex Gauge Company). These tests are described in standard analytical chemistry references and in metal identification field guides. See: ASM Metals Handbook; Piotrowski, T. and Rybarczyk, T., “Chemical spot tests for metal identification.”↩︎

35. Portable XRF for alloy identification: Handheld X-ray fluorescence analysers (manufactured by companies including Thermo Fisher/Niton, Olympus/Evident, Bruker, and others) provide rapid non-destructive alloy identification and quantitative composition measurement. These instruments are widely used in scrap metal sorting and quality control. NZ scrap yards and metal testing firms operate these instruments. See: manufacturer product literature; ASTM E2465, “Standard Practice for the Analysis of Metals, Ores and Related Materials by Energy-Dispersive X-Ray Fluorescence Spectrometry.”↩︎

36. Zinc fume from galvanised steel: Cutting or melting galvanised (zinc-coated) steel releases zinc oxide fume. Inhalation causes metal fume fever — symptoms include fever, chills, nausea, and muscle aches, typically appearing 4–12 hours after exposure and resolving within 24–48 hours. Chronic exposure has more serious effects. Ventilation and respiratory protection (P2 or equivalent particulate respirator) are required when working with galvanised material at high temperatures. See: WorkSafe NZ workplace exposure standards; any occupational health reference on metal fume fever.↩︎

37. Copper in automotive shredded scrap: Published data from EAF operators in Australia and North America indicates shredded automotive scrap (mixed ferrous shred) typically contains 0.15–0.30% copper when wiring is not pre-stripped, and 0.05–0.15% when wiring harnesses are removed before shredding. The hot-shortness threshold for plain carbon steel is approximately 0.2–0.3% Cu, but cast products are less sensitive than rolled or forged products because they do not undergo the solid-state hot-working at which copper embrittlement occurs. For non-wrought applications, up to 0.4% Cu is generally tolerable. See: Fruehan (note 3); Savov (note 3); Jonsson, L. et al., “Copper Contamination in Recycled Steel Scrap,” Scandinavian Journal of Metallurgy, 2004 (representative of the literature). The NZ-specific figures require verification from NZ steel scrap sorting and testing data — the actual figure depends heavily on the composition of the NZ vehicle fleet and the stripping practices of NZ auto dismantlers.↩︎

38. Copper in automotive shredded scrap: Published data from EAF operators in Australia and North America indicates shredded automotive scrap (mixed ferrous shred) typically contains 0.15–0.30% copper when wiring is not pre-stripped, and 0.05–0.15% when wiring harnesses are removed before shredding. The hot-shortness threshold for plain carbon steel is approximately 0.2–0.3% Cu, but cast products are less sensitive than rolled or forged products because they do not undergo the solid-state hot-working at which copper embrittlement occurs. For non-wrought applications, up to 0.4% Cu is generally tolerable. See: Fruehan (note 3); Savov (note 3); Jonsson, L. et al., “Copper Contamination in Recycled Steel Scrap,” Scandinavian Journal of Metallurgy, 2004 (representative of the literature). The NZ-specific figures require verification from NZ steel scrap sorting and testing data — the actual figure depends heavily on the composition of the NZ vehicle fleet and the stripping practices of NZ auto dismantlers.↩︎

39. Scrap sizing for EAF charge: EAF charge sizing depends on the furnace size and charge opening dimensions. For large EAFs like Glenbrook’s, scrap is typically sheared, baled, or cut to pieces no larger than approximately 1,000 mm in any dimension. Oversized scrap reduces charge density and can cause operational problems (bridging, slow melting). See: general EAF operating practice references; Fruehan (note 3).↩︎

40. NZ battery recycling: NZ processes lead-acid batteries domestically. Exide Technologies NZ (now part of various operations) and other recyclers process end-of-life batteries, recovering lead, acid, and plastic. NZ generates approximately 1.5–2 million spent lead-acid batteries per year from vehicles, industrial applications, and backup power systems. See: NZ battery industry information; Ministry for the Environment waste management data.↩︎

41. Scrap addition to EAF charge: Electric arc furnaces globally typically use scrap as their primary feedstock. EAFs that process DRI (like Glenbrook) commonly blend 20–40% scrap with DRI to improve melting efficiency and reduce energy consumption. The scrap acts as a coolant and provides metallic iron that melts rapidly, supplementing the DRI charge. See: Fruehan (note 3); Worrell, E. et al., “Energy efficiency improvement in the world steel industry,” Energy Policy, 2001.↩︎

42. NZ foundry melting capacity: The combined melting capacity of NZ’s commercial foundries is not comprehensively documented in public sources. The estimate of 5,000–15,000 tonnes per year is based on the known number of operating NZ foundries, typical furnace sizes (250 kg to 2 tonne per heat for induction furnaces), and typical utilisation rates. The actual figure requires census verification. See: Doc #8; Australasian Foundry Institute industry data.↩︎

43. Induction furnace crucible life: Refractory crucible linings in coreless induction furnaces are consumable — the lining erodes through thermal cycling, chemical attack from the melt, and mechanical stress. Typical lining life for steel melting ranges from 50–200 heats depending on refractory material (silica, alumina, magnesia), operating temperature, and alloy chemistry. Iron melting is less aggressive on linings than steel. NZ can produce basic refractory materials (silica from sand, alumina from imported stocks or potentially from NZ clays) but high-performance refractory formulations use imported materials. See: ASM International, “Induction Furnace Practice”; general foundry engineering references.↩︎

44. Zinc fume from galvanised steel: Cutting or melting galvanised (zinc-coated) steel releases zinc oxide fume. Inhalation causes metal fume fever — symptoms include fever, chills, nausea, and muscle aches, typically appearing 4–12 hours after exposure and resolving within 24–48 hours. Chronic exposure has more serious effects. Ventilation and respiratory protection (P2 or equivalent particulate respirator) are required when working with galvanised material at high temperatures. See: WorkSafe NZ workplace exposure standards; any occupational health reference on metal fume fever.↩︎