Reusing ALS2 Non-Metallic Residues as Construction Aggregates
Australia generates hundreds of thousands of tonnes of electronic waste each year, and the country has steadily expanded its capacity to recover valuable materials from discarded devices. Printed circuit boards, mobile phones, laptops, and industrial control units contain gold, silver, palladium, and copper that justify dedicated refining. Ikoi S.p.A.'s ALS2 acidless separation technology sits within this recovery landscape, extracting precious metals from e-waste and WEEE streams without the hazards of aqua regia or cyanide leaching. The process leaves a non-metallic fraction historically sent to industrial landfills, but engineers are now examining whether this material can serve a more productive purpose.
The Australian construction sector consumes roughly 200 million tonnes of aggregates annually, making it one of the country's largest material markets. Sand, gravel, and crushed rock feed concrete, road base, and asphalt production. With major infrastructure programs underway in Sydney, Melbourne, and Brisbane, demand for aggregates outpaces new quarry development in some regions. Alternative sources that displace virgin extraction are both an environmental priority and a practical supply chain consideration.
When precious metals are stripped from circuit boards and connectors, the remaining material is a complex mixture of ceramics, fibreglass, plastics, and flame-retardant resins. For years, this residue has been regarded as a troublesome by-product with limited downstream applications. The ALS2 approach, by avoiding aggressive acids, produces a residue stream that is comparatively stable and easier to characterise. Researchers supported by Horizon 2020 funding have been investigating whether this non-metallic fraction can meet the technical specifications for use as a secondary aggregate, either as a direct substitute for crushed stone or as a blend component in lower-specification applications.
The landfill diversion potential of these residues matters for several reasons. Australian landfills are increasingly constrained, with state governments in New South Wales, Victoria, and Western Australia introducing levies and restrictions that make disposal of industrial by-products more expensive. At the same time, the federal government has signalled support for circular economy reforms that prioritise material recovery over disposal. Repurposing ALS2 residues as aggregates would address both pressures simultaneously, creating a new revenue stream for recyclers while reducing the quarrying footprint of the construction industry.
Characterising the Non-Metallic Fraction
The composition of ALS2 residues depends on the feedstock, but typical outputs include fibreglass-reinforced laminate, ceramic substrates from capacitors and resistors, and various engineering plastics. Particle size distribution, chemical stability, and heavy metal leachability all need to be assessed before any aggregate application can be considered. European testing under the Horizon 2020 programme has shown that the material is largely inert when properly processed, with leach values well within the thresholds required for construction use in member-state jurisdictions.
The mechanical properties of the residue are different from those of natural stone. Bulk density tends to be lower, reflecting the presence of plastics and hollow ceramic components. Crushing strength is adequate for non-structural applications, and the angular particle shape produced by the separation process actually improves interlock in bound aggregate applications. These characteristics make the material suitable for pipe bedding, drainage layers, and road sub-base, where high compressive strength is not essential.
Consistency is a challenge when scaling up. Unlike quarried stone from a single geological formation, e-waste residues vary in composition from batch to batch depending on the devices processed. Quality assurance protocols must account for this variability, drawing on sorting and grading techniques familiar to the recycling sector. Approaches used in related manufacturing quality control, such as automated component inspection, demonstrate the type of continuous monitoring that could ensure aggregate grades remain within specification.
Performance Compared to Virgin Aggregate
Standard aggregate tests measure parameters such as Los Angeles abrasion, aggregate impact value, and water absorption. Early ALS2 residue characterisation suggests the material performs adequately in lower-impact categories but is not yet suitable for high-stress applications such as structural concrete or wearing surfaces. Blended with conventional crushed rock at 20 to 30 percent, the mixture retains most of the performance of the virgin material while reducing the volume of natural aggregate required.
A side-by-side parameter overview illustrates the trade-offs involved:
| Parameter | ALS2 Non-Metallic Residue | Crushed Basalt (Typical) | Recycled Concrete Aggregate |
|---|---|---|---|
| Bulk Density (kg/m³) | 1,400–1,700 | 1,500–1,800 | 1,300–1,600 |
| Los Angeles Abrasion (%) | 28–35 | 15–22 | 25–32 |
| Water Absorption (%) | 4–8 | 1–3 | 5–9 |
| Leachate Heavy Metals | Within EN 12457 limits | Negligible | Variable, often compliant |
| Suitable Applications | Sub-base, drainage, pipe bedding | General construction | Sub-base, low-grade concrete |
For Australian contexts, the relevant comparison is often with locally sourced materials such as Sydney sandstone-derived crusher dust, Melbourne's basalt-based products, or the lateritic gravels common in Western Australia. Performance benchmarks differ by region, but the general pattern holds: ALS2 residues work well in non-structural roles and offer benefits in lighter-weight applications where reduced dead load is desirable.
Pathways into the Australian Market
Introducing a new aggregate source into the Australian market requires more than technical performance. Specifiers, contractors, and procurement officers need confidence in supply continuity, and the regulatory framework for recycled materials varies between states. In New South Wales, the NSW EPA recognises recovered materials under specific resource recovery exemptions, and Victoria's EPA operates a similar framework. Queensland has its own end-of-waste code system, which could accommodate ALS2 residues once characterisation data is available.
The logistics of moving material from e-waste processing sites to construction projects also need to be worked out. Most major ALS2 processing facilities in Europe are located near electronics manufacturing or recycling clusters, and Australia would likely develop its own hub-and-spoke model. A facility in Perth could supply infrastructure projects in the resource-rich Pilbara and Goldfields regions, while a Sydney- or Melbourne-based operation could serve urban renewal and transport projects. Brisbane's preparations for the 2032 Olympic and Paralympic Games are already generating demand for sustainable construction inputs, creating a potential early market for recycled aggregates.
Industry engagement will be critical. The Cement, Concrete, and Aggregates Australia peak body, along with state-level construction material associations, regularly updates guidance on alternative materials. Securing endorsements from these groups, alongside compliance with Australian Standard AS 2758.1 for aggregates and rock, would help mainstream adoption. Pilot projects with local councils, particularly those with explicit sustainability mandates such as the City of Melbourne and the City of Sydney, could provide case studies that build confidence in the wider market.
Environmental and Carbon Considerations
Quarrying, crushing, and transport collectively account for a meaningful share of construction-related emissions, yet the carbon footprint of aggregate production is often overlooked. Replacing some of this material with ALS2 residues avoids the extraction and processing emissions of virgin stone, while also avoiding the methane potential of sending organic-rich industrial waste to landfill. In Australian conditions, where transport distances between quarries and major projects can be substantial, the avoided transport emissions of a locally produced recycled aggregate are significant.
Water usage is another consideration. Aggregate washing at quarries consumes large volumes of water, and Australian operations in Murray-Darling basin catchments face scrutiny over consumption levels. Dry processing of e-waste residues, by contrast, uses minimal water and can be conducted in enclosed facilities. For inland regional centres such as Dubbo, Wagga Wagga, or Toowoomba, where water security is a recurring concern, the lower water intensity of recycled aggregate production is a meaningful advantage.
Life cycle assessment work carried out under Horizon 2020 has begun to quantify these benefits, but Australian-specific studies are still needed. Local researchers, potentially through the CSIRO or university partnerships in Adelaide, Perth, or Hobart, could refine the carbon and water accounts using Australian grid electricity mixes and transport assumptions. Such studies would give policymakers and procurement officers the data they need to justify preferential sourcing rules for recycled aggregates.
Regulatory Alignment and Future Steps
Australia's regulatory environment is moving steadily toward circular economy principles. The federal ban on e-waste exports, combined with state-level landfill restrictions, has created a stronger pull for in-country recycling infrastructure. Within this context, ALS2 technology and its non-metallic residue stream fit well into the broader strategy of maximising material value before any disposal occurs. The challenge is to align the technical characterisation work, which is largely European in origin, with Australian standards and expectations.
Translating European test data into Australian compliance frameworks will require targeted investment. Sampling programs need to reflect Australian e-waste streams, which include different device types and consumption patterns compared to European inputs. Pilot aggregate production runs should be tested under Australian Standard protocols, with results shared through industry bodies and academic channels. The work being done in Europe provides a strong foundation, but local validation is essential for market acceptance.
For the ALS2 project, the next step is identifying Australian partners willing to host demonstration trials. Universities with strong materials engineering programs, such as UNSW, Monash, or the University of Western Australia, could provide the technical rigour needed. Local councils and state transport agencies would then trial the aggregate in real projects, generating performance data that drives wider adoption. With e-waste generation continuing to climb and aggregate demand remaining strong, the alignment between the two material streams offers a practical route to genuine landfill diversion at scale.
If you are involved in WEEE processing, construction material sourcing, or circular economy research, there is a clear opportunity to explore how ALS2 non-metallic residues can fit into your operations. The project consortium welcomes engagement from Australian recyclers, aggregate producers, councils, and research institutions interested in pilot trials or collaborative characterisation work. Reach out to the ALS2 project team to discuss how your organisation can participate in turning e-waste residues into a tangible contribution to sustainable construction.