Magnesium and bio-slurry enhance the properties of bio-tiles produced using an automated microbial calcium carbonate precipitation process

This study presents a novel, modular 3D printing system for the scalable production of microbially induced calcium carbonate (CaCO 3 ) precipitation (MICP) produced bio-materials. Through modular design principles and operation automation, the technique offers a biochemical route to cementitious materials with the potential for lower energy and carbon footprints compared to traditional kiln-fired ceramics. The bio-tiles produced using this technique exceed international standards of breaking strength and modulus of rupture. By leveraging freeze-dried urease-active bio-slurry powder, the process ensures uniform bacterial distribution within the sand matrix, enhancing reproducibility and scalability. To establish a technical baseline for this automated platform, the effect of CaCO 3 seed supplementation, magnesium-enriched cementation solution, and manual daily nutrient broth treatments was evaluated as a function of ureolytic activity and mineralization performance. Results revealed that magnesium addition paired with nutrient broth supplementation was a notable factor associated with the observed strength enhancement, achieving an average of 622 ± 84 N. While individual seed loadings showed variability consistent with gravity-driven infiltration, the aggregate performance of magnesium-supplemented tiles established a clear general technical trend, achieving strengths 3.3 times higher than bio-tiles treated without magnesium and only nutrient broth. However, nutrient broth treatments were found to be redundant as ureolytic requirements were likely satisfied by the bio-slurry itself. Additional CaCO 3 seeds minimally influenced strength but improved edge solidification. Despite challenges in achieving uniform solidification without specific additives, the automated system successfully integrated submersion and pumping methodologies. The bio-tiles exceeded strength standards for tiles with a water absorption of greater than 10%, underscoring their potential for sustainable construction applications. This proof-of-concept highlights the mechanical automation as a key enabler for scalable MICP-based manufacturing, reducing labour intensity and optimising bio-cementation for sustainable, high-performance materials. Future research should focus on enhancing solidification consistency and advancing MICP-based bio-materials for structural applications. The integration of automation, modularity, and optimised MICP conditions marks a significant advancement toward the commercial-scale production of materials with improved environmental profiles.