Circularity: scrap is the cleanest input, and slag and dust are resources

8.1 Scrap is the most powerful lever the industry already has

worldsteel estimates that each tonne of scrap used to make steel avoids about 1.5 t of CO₂ [S02]. Around 630 Mt of scrap is used in global steelmaking each year, avoiding nearly 950 Mt of CO₂, according to the Bureau of International Recycling; consumption reported by its tracked countries rose by 4.5% to 480 Mt in 2025 [S68]. Under the accounting conventions described in Chapter 2, scrap enters a steelworks with no upstream emissions, and ferrous scrap (CN 7204) is outside the scope of the EU CBAM [S27].

For RC-1, the scrap share is the second-largest lever after the carbon content of purchased DRI. Figure 8.1 shows that, at the Phase 1 configuration and a grid factor of 226 g/kWh, raising the scrap share of the charge by 10 points (and lowering the DRI share accordingly) reduces the total intensity by about 0.09 t per tonne. A works melting 90% scrap would emit about 0.40 t per tonne including upstream iron units; one melting 50% would emit about 0.75 t.

Source: WP06 model on the Cameroon Steel reference configuration RC-1 (planning estimate) [S90]; DRI power penalty [S15].

8.2 Cameroon is short of scrap

Scrap availability depends on how much steel a country put into use decades ago. Cameroon’s stock of steel in use is small by international standards, and its scrap arisings are correspondingly limited. The only quantified study, by researchers at the national polytechnic school and the local materials research centre, estimated arisings of 53,000 to 61,833 t a year using 2006 data, of which about 53% was collected by recyclers, 29% by informal dismantlers and 15% by exporters [S88]. More recent industry statements indicate that local scrap covers only about 40% of the needs of Cameroon’s existing mills, the balance coming from imported billets [S89]. Africa as a whole is a net importer of ferrous scrap, with exports of about 1.2 Mt and imports of about 3.4 Mt in 2025 [S03].

Figure 8.2 sets RC-1’s scrap need against that evidence. Even allowing for growth in arisings since 2006, domestic scrap could supply only part of Phase 1 and a small share of the full build-out, and most of what is collected already feeds existing mills. The RC-1 planning case therefore assumes about 30,000 t a year of domestic scrap, with a range of 0 to 60,000 t [S90]. The balance would have to be imported scrap or a higher share of DRI or HBI, which, as Chapter 4 showed, raises the footprint.

Source: WP06 model on the Cameroon Steel reference configuration RC-1 (planning estimate) [S90]; Bidoung et al. (2007), 2006 data [S88].

Table 8.1 Scrap in Cameroon and in the RC-1 balance

Source: as listed.

Three implications follow. First, RC-1 will be a scrap importer as well as a buyer of domestic scrap, and its carbon performance depends on its ability to secure scrap of suitable quality on the international market. Second, a well-organised domestic collection system is worth developing for both carbon and economic reasons: it creates local jobs, keeps value in the country and lowers the works’ footprint. That system must meet international labour and safety standards, including checks against child labour in informal collection, which lenders will require under IFC Performance Standard 2 [S21]. Third, domestic scrap supply will grow over time as Cameroon builds: the reinforcing bar and sections that RC-1 and other mills supply to the country’s buildings and infrastructure today will be part of its scrap stock in the second half of the century.

A domestic scrap programme for RC-1 would draw on several streams: demolition and construction waste, end-of-life vehicles and machinery, industrial offcuts and turnings, and end-of-life public assets sold through tender. It would work through licensed collectors and dealers rather than through informal purchases at the gate, with weighbridges, traceable payments, safety training and personal protective equipment for collection partners. It would also need safeguards against the purchase of stolen material, such as power cables, rail fittings or road furniture, which is a recurrent problem wherever scrap prices rise. A programme of this kind takes years to build, and its benefits accumulate: each additional tonne of domestic scrap replaces an imported tonne of scrap or DRI, reducing both freight and the works’ footprint.

Scrap quality matters as well as quantity. Copper and tin from wiring and coatings cannot be removed in an electric furnace and accumulate in the steel; wire rod for drawing is particularly sensitive to them. A scrap-sorting and quality-control system at the yard, with radiation detection at the gate, is a standard requirement for an electric-arc works.

8.3 Importing scrap: the other half of the charge

On the planning case, Phase 1 would import about 224,000 t of scrap a year, in addition to about 109,000 t of DRI or HBI (derived). With consumables, port receipts would come to about 351,000 t a year [S90]. Africa as a whole is already a net importer of ferrous scrap [S03], and the world market is large: the countries tracked by the Bureau of International Recycling used about 480 Mt in 2025 [S68]. Buying a few hundred thousand tonnes a year is therefore feasible, but it has three consequences for carbon. First, ocean freight and handling of imported scrap add Scope 3 emissions that this paper does not count (Chapter 4); they are small per tonne but should be reported. Second, imported scrap competes with buyers whose own decarbonisation plans depend on scrap, so the price and availability of low-residual grades may tighten as electric steelmaking grows (Chapter 1). Third, ferrous scrap is not a CBAM good and enters the CBAM calculation with no embedded emissions [S27], so every tonne of scrap that replaces a tonne of DRI lowers the CBAM charge on an EU-bound tonne as well as the total footprint, by about €7 per tonne of product for every 10 points of charge (Chapter 5).

The planning case is deliberately cautious. If domestic collection reached the upper end of the 2006 estimate, about 60,000 t a year, the works would still import about three-quarters of its Phase 1 scrap; if it found none, port receipts would rise by about 30,000 t. Either way, the carbon result depends on the share of scrap in the charge, not on where the scrap comes from. That is why the pathway in Chapter 10 treats more scrap in the charge, domestic or imported, as a single lever, and why a domestic collection programme is worth building for economic and social reasons as much as for carbon.

8.4 Slag: from residue to road aggregate

An electric-arc furnace leaves about 110 to 180 kg of solid residue, mostly slag, per tonne of product, according to the IFC’s guidelines for steel mills [S20]; RC-1 uses 140 kg of slag per tonne of liquid steel. That gives about 45,000 t a year in Phase 1 and about 149,000 t at full build-out (Figure 8.3). EAF slag is a hard, dense, angular material that, after crushing, metal recovery and weathering to stabilise free lime, is widely used as road base, asphalt aggregate and fill. The IFC guidelines note that slag from iron and steel making is sold as a by-product for civil engineering, road construction and cement [S20].

European practice shows what is possible. In 2024, of about 16.5 Mt of steelmaking slag produced in the EU, about 13.5 Mt (82%) was used, including about 9 Mt in road construction; including blast-furnace slag, 92% of ferrous slag was used, avoiding the extraction of about 40 Mt of natural stone [S67].

Source: Cameroon Steel reference configuration RC-1 (planning estimate): slag 140 kg/t, dust 15 kg/t, mill scale 20 kg/t [S90]; IFC benchmark for solid residue [S20]; zinc content range [S69]. Derived by Cameroon Steel.

The Kribi area offers a local market. Motorway, port and industrial-zone construction all need aggregate, and every tonne of slag used replaces a tonne of quarried stone. The condition is quality assurance: each slag product must be tested for volume stability and for the leaching of metals such as chromium and vanadium under recognised test methods, and approved by the road authority for its intended use. Cameroon Steel would seek a slag-product approval with the public works authorities before the first heat, so that slag leaves the site as a product rather than accumulating as a waste.

8.5 Furnace dust: a hazardous waste that contains zinc

The dust captured by an electric-arc furnace’s fume-extraction system carries zinc, lead and cadmium from the scrap [S20] and has to be managed as a hazardous waste. The planning range is 10 to 20 kg per tonne of liquid steel (the European reference document reports 10 to 30 kg) [S19]; RC-1 uses 15 kg/t, giving about 4,800 t a year in Phase 1 and about 16,000 t at full build-out. Its zinc comes mainly from galvanised scrap, and zinc contents above about 15% make recovery economically viable; typical dusts are at or above that level [S69]. At 20% to 30% zinc, RC-1’s dust would contain about 1,000 to 1,400 t of zinc a year in Phase 1 and about 3,200 to 4,800 t at full build-out (derived).

The established recovery route is the Waelz kiln, which volatilises zinc from the dust and recovers it as a zinc oxide concentrate for zinc smelting. About 98% of the EAF dust produced by European steelmakers is recycled [S69], and the largest operator alone processed more than 1.2 Mt of dust in 2024 [S70]. There is no Waelz plant in Central Africa. In Phase 1, RC-1’s dust would therefore be stored in a secure, covered facility and shipped to a licensed recovery plant abroad, following the prior-informed-consent procedures of the Basel Convention for transboundary movements of hazardous wastes [S71]. As volumes grow, or if other electric-arc works in the region generate dust, a regional recovery facility could become viable. Landfilling untreated dust is not an option a modern works should plan for.

Table 8.2 Main residues and co-products of the RC-1 works

Source: Cameroon Steel reference configuration RC-1 (planning estimate) [S90]; IFC EHS Guidelines for Integrated Steel Mills [S20]; EAF dust recovery practice [S69][S70]; Basel Convention [S71].

8.6 Water and energy loops

Circularity also applies to water and heat. RC-1 plans closed-loop cooling with a make-up of about 2.0 m³ per tonne of product (range 1.5 to 3.0) [S90], against worldsteel’s 2024 sector averages of 2.3 m³ consumed and 8.5 m³ withdrawn per tonne [S01]. With about 2,836 mm of rain a year, roof-water harvesting for cooling make-up is an obvious measure. Hot charging of billets from the caster to the mill reduces reheating energy; heat recovery from furnace off-gas and from reheating-furnace flue gas becomes worthwhile at the larger scale of Phases 2 and 3.

8.7 Circular by design

The principles that follow for RC-1 are straightforward:

• Maximise scrap within quality limits, through domestic collection partnerships and a disciplined import strategy, and report the scrap share every year alongside the carbon intensity.
• Sell slag as a product, with tests, approvals and a local market prepared before commissioning.
• Recover the zinc in the dust, through a contract with a licensed recycler from the first year and a regional solution as volumes grow.
• Close the water loop and harvest rainfall.
• Design products for long life and recovery. Steel reinforcing bar and sections are fully recyclable; worldsteel’s life cycle data assume a 95% end-of-life recycling rate for the credits reported in module D of an EPD [S44].

The next chapter turns from materials to money: what lenders, buyers and certifiers will ask a low-carbon steelworks to prove.