• Energy Research
• 2025-2025close
• Open Access close
• Embargo close
• ETH Zurich close

Earth materials are subsoils used in construction due to their natural cementing properties. These properties originates from its clay fraction, which becomes cohesive during drying. Unlike common cement, earth materials are recyclable and have no CO2 emission apart from manufacturing. Unfortunately, earth materials containing the abundant clay mineral smectite exhibit large swelling and shrinkage strains. Such earth materials are considered unsuitable for construction unless a stabiliser is added, which is commonly Portland cement or quicklime. This study explored the use of MgO-based cementitious Binder (MB) as alternative with a focus on the mineralogical effect of MB on smectite during hydration. A series of MB/smectite blends and MB components/smectite was cured up to six months to investigate the mineralogical changes and the formation of magnesium (alumino) silicate hydrate. The results showed that MB transformed smectite into Mg-hydroxy-interlayered smectite (Mg-HIS) within hours. The reason is the dissolution of MgO, a main constituent of MB. The dissolved Mg precipitates as Mg-hydroxy in the interlayer and transforms the smectite to Mg-HIS in this process. This is causing a pH increase and may prevent a complete HIS formation as the MgO dissolution mechanism will change once the pH is above the point-of-zero charge of MgO. An advantage of the smectite to Mg-HIS transformation is the strongly reduced the swelling/shrinkage properties of the clay. This suggests that adding MB to smectite could be a superior binding approach compared to quicklime, which primarily causes clay particle flocculation. Applied Clay Science, 265 ISSN:0169-1317

Decentralized multi-energy systems (MESs) are a key element of a future low-carbon energy supply. Here, we address the crucial role of grid-connected and off-grid MESs in achieving a low-carbon future, particularly relevant for regions like the Mediterranean with high renewable energy potential and carbon-intensive grid networks, using a mixed integer linear program for optimal economic and environmental MES design considering location-specific regulations. The results reveal that substantial cost (up to 30%, potentially saving 1.6 million) and greenhouse gas (GHG) emission reductions can be reached in Mediterranean regions with sufficient solar and wind energy resources currently relying on fossil fuel-based generators. However, our case study shows that the actual cost and emission reductions are most likely limited due to location-specific regulations (limiting cost savings to 0.8 million), especially those that constrain solar photovoltaic and onshore wind. Off-grid energy systems might be suitable decarbonization options in Mediterranean regions, to avoid absorbing current GHG-intensive power from the local power grid, under marginal cost increase (15%) compared to grid-connected cost optimization. However, off-grid MESs require substantial upfront investments and exhibit some environmental trade-offs, especially on material utilization, which could be overcome by balanced autonomy. Overall, truly sustainable and secure decentralized energy systems can only be reached by considering life cycle environmental impacts, social acceptance, and regulations during the design phase. Applied Energy, 377 ISSN:0306-2619 ISSN:1872-9118