On the possibility of using bacteria for recycling finest fractions of concrete waste: a critical review

Introducing the principles of circular economy into the concrete industry would significantly contribute to the sustainability of this sector. Even though recycling ranks below waste elimination, the generation of concrete waste is inevitable, and modern recycling strategies cannot efficiently tackle waste concrete fines (WCF) that represent an enormous environmental burden. Inspired by recent advances in self-healing concretes and biocementation of loose soil, we propose harnessing bacteria for bonding WCF to form artificial rocks that could be used as construction material. The devised technology brings many obstacles that can be tackled based on extensive research offered in this critical review, focused mostly on different bacterial metabolic pathways resulting in calcite precipitation and their environmental impacts. The most frequently exploited pathway in materials engineering, ureolysis, was employed to demonstrate the technical feasibility of WCF recycling using Sporosarcina pasteurii. Despite promising results of this demonstration, an alternative approach must be sought to reduce the negative environmental impact associated with the use of ureolytic bacteria as it exceeds potential benefits. Such an approach could be based on the use of by-products from other industries to replace laboratory-grade chemicals, or on utilization of different metabolic pathways, such as carbonic anhydrase or methane oxidation.