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 (CaCO3) 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 CaCO3 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 CaCO3 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.