The Challenge

Cement is a major contributor to global carbon emissions. It accounts for roughly 7.1% of global CO₂ emissions and around 4% of the EU's (Marmier, 2023).  Most of this comes from producing clinker, cement's key ingredient, which requires heating limestone to extreme temperatures. About 65% of the resulting emissions come directly from that chemical reaction, calcination; the rest from the fossil fuels burned to drive it (Nikolakopoulos et al., 2024). Cement production has also been linked to elevated health risks in nearby communities, including respiratory and cardiovascular conditions, associated with the release of particulate matter and heavy metals (Bărbulescu & Hosen, 2025).

Aluminium production presents a related but distinct waste challenge. Extracting alumina from bauxite ore through the Bayer process produces a hazardous industrial by-product known as bauxite residue, red mud, or processed bauxite (da Silva et al., 2025). The EU generates an estimated 7 million tonnes of this residue annually, of which less than 100,000 tonnes are recycled. The remainder is stored indefinitely, as large-scale reuse options remain limited (European Commission, 2020).

Due to its alkalinity and heavy metal content, bauxite residue is costly and hazardous to store, handle, and transport (Evans, 2016). These risks materialised in October 2010, when a storage reservoir failure at an alumina refinery in Ajka, Hungary, flooded nearby villages and caused fatalities and chemical burns (European Parliament, 2010).

The scale of the challenge continues to grow. Global bauxite residue inventories are projected to reach 10 billion tonnes by 2050 ( International Aluminium, 2022), underscoring the urgent need for viable, large-scale approaches to reuse rather than storage, a need that spans both the cement and aluminium sectors.

The Circular Solution

St Loarn Group, a CIRCULÉIRE member, has developed a geopolymer cement (GPC), currently patent pending, that replaces Ordinary Portland Cement (OPC) entirely, using bauxite residue, a major by-product of aluminium production, as its primary raw material, although composition varies by application.

Bauxite residue contains high concentrations of silica and alumina. When activated with an alkaline solution, these dissolve and reconnect into a gel that hardens and binds the material together (da Silva et al., 2025). St Loarn Groups technology differs from this conventional route, in its specific blend of constituents requires only water to initiate the geopolymer reaction and produce a strong binder.

More broadly, geopolymer materials of this type have been shown to perform effectively in structural applications, with strength comparable to standard cement concrete (Saeed et al., 2022). St Loarn Group reports that the bauxite residue it uses is sourced with a lower pH than material straight from processing and is classified as inert by the EPA and equivalent EU bodies.

By using a material that would otherwise require costly and environmentally damaging disposal, St Loarn Group addresses two problems with a single product: valorising potentially hazardous industrial waste from the aluminium industry and eliminating the need for carbon-intensive Portland cement.

The product has achieved certification to ASTM C1157, a US international performance specification for hydraulic cement (St Loarn Group, 2025). Structural testing confirmed that St Loarn Group's geopolymer beam exceeded the structural performance of standard Portland cement. It reaches full compressive strength within 28 days and has minimal shrinkage (St Loarn Group, 2025).

The company has also completed demonstrator pours, including concrete beams and cattle slats, in partnership with Harrington Concrete and Quarries. St Loarn Group is also working with the International Aluminium Institute, the global body representing the aluminium industry, and the Jamaican Bauxite Institute.

Environmental, Social and Economic Impact

Geopolymer cements deliver substantial climate and environmental advantages compared to Portland cement. The production of OPC is energy-intensive and generates significant carbon dioxide emissions (Zaland et al., 2026). GPC can cut carbon dioxide emissions by up to 80% relative to OPC, while also being more cost-effective and making use of industrial waste streams (Singh et al., 2020). St Loarn Group reports that their geopolymer cement's carbon footprint reduction could be as high as 93%. The company is targeting the global cement industry, valued at $394.82 billion in 2026 and projected to reach $500.3 billion by 2034 (Fortune Business Insights, 2026), underlining the scale of the market this technology could reach.

Cement is among the EU's largest-emitting energy-intensive industries, while aluminium, highly electro-intensive and recognised as a strategic raw material, has demand projected to rise 33% by 2050. Across these industries, decarbonisation has lagged EU climate targets (European Commission, 2026). The Industrial Accelerator Act, proposed by the European Commission in March 2026, aims to build EU demand for low-carbon industrial products through faster permitting and Single Market measures, naming both cement and aluminium specifically among its target sectors, the same market St Loarn Group's technology is positioned to serve.

St Loarn Group's geopolymer cement not only mitigates harmful pollutants by utilising industry waste streams, but also significantly lowers the waste treatment burden for producers.

Replicability

St Loarn Group's approach reflects a wider shift toward low-carbon construction materials in Ireland and internationally, with organisations pursuing this goal through different routes.

Ecocem (Ireland) - produces GGBS (Ground Granulated Blastfurnace Slag), a by-product of iron manufacturing, as a low-carbon substitute for a portion of Portland cement in concrete. Replacement rates of up to 70% are permitted under EU concrete standards, giving GGBS concrete a lower carbon footprint alongside improved chemical resistance and finish.

Techrete (Ireland) - developed a new range of lower-carbon concrete products, targeting a 50% reduction in embodied carbon by 2025. The R&D programme, supported by Enterprise Ireland, incorporates lower-carbon materials such as GGBS, fly ash, and limestone filler.

Trinity College Dublin & FLI Precast Solutions (Ireland) - developed methods for incorporating biomass ash, a by-product of Bord na Móna's Edenderry Power Station, into low-carbon concrete. Edenderry, Ireland's largest dispatchable renewable energy facility, moved to 100% biomass generation in late 2024, giving this waste stream a productive use rather than disposal.

Kilsaran (Ireland) - adopted CarbonCure technology, which injects captured CO₂ into concrete during mixing. The CO₂ mineralises permanently within the concrete, reducing both the cement required and the product's overall carbon footprint.

Holcim’s (Switzerland) - Recygénie project demonstrated that social housing can be built using 100% recycled demolition concrete, diverting over 6,000 tonnes of construction waste from landfill while reducing reliance on virgin cement. Read the CIRCULÉIRE case study on Holcim here.