Researchers from the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS; www.ikts.fraunhofer.de) and the Fraunhofer Institute for Electron Beam and Plasma Technology (FEP; both Dresden, Germany; www.fep.fraunhofer.de) are introducing an eco-friendly, biologically induced method of producing biogenic construction materials as part of the BioCarboBeton project. The process does not emit any carbon; instead, it binds CO2 inside the material.
The centerpiece of the new method are cyanobacteria (blue-green algae) — bacterial cultures that are capable of photosynthesis. As light, moisture and temperature interact, they form limestone structures known as stromatolites. These rock-like biogenic structures have existed in nature for 3.5-billion years, which attests to the resilience and durability of this material. As part of the mineralization process, CO2 is captured from the atmosphere and then bound in the biogenic rock.
The Fraunhofer researchers have succeeded in mimicking this natural process, by first cultivating the cyanobacteria, then adding a calcium source (such as CaCl2), CO2 and sand to enable mineralization into stromatolite-like structures. The bacterial mixture can be shaped in molds, or through spraying, foaming, extrusion or additive manufacturing into a form in which the final stages of mineralization take place. Alternatively, porous substrates can also be produced and subsequently treated with the cyanobacteria culture. The bio-based construction materials made from cyanobacteria (photo) do not contain any toxic substances.
Targeted selection of fillers and management of process and mineralization parameters allow for manufacturing of products for a wide range of different application scenarios. Potential applications include insulation material, brick, formwork filling and even mortar or stucco that cures or hardens after it is applied.
The researchers are working to scale the volumes and determine the desired solid properties. The goal is to enable manufacturers to produce the ecofriendly bio-based construction materials in the necessary volumes, quickly and cost-effectively.