Advances in microbial and enzymatic phosphate precipitation for sustainable biocementation in civil and geoenvironmental engineering applications

In the past 20 years, biocementation processes have emerged as effective techniques used for ground improvement, crack healing and restoration of building materials or heritage stones. To-date most researchers have studied biocements based on calcite precipitation using the urea-hydrolysis metabolic pathway. This pathway produces undesirable ammonia by-products that need to be treated or removed, limiting the large-scale and sustainable applicability of microbially-induced carbonate precipitation (MICP) or enzymatically induced carbonate precipitation (EICP). Moreover, carbonate precipitation has poor durability in acidic environments. Different biocementation mechanisms and biocements other than calcite are known but have been very little researched. This comprehensive review focuses on phosphate biomineralisation as a novel, ammonia-free, and potentially more sustainable alternative bio-cementation technique. It discusses microbially and enzymatically induced phosphate precipitation (MIPP and EIPP respectively), with particular focus on ground improvement (soil stabilisation and remediation) and construction material applications. The environmental advantages of phosphate biocement, such as lower pH sensitivity, absence of harmful by-products, and potential compatibility with green chemistry principles and the UN Sustainable Development Goals are critically examined to assess their viability as sustainable materials in civil and geoenvironmental engineering. • MIPP/EIPP reviewed as novel, sustainable biocementation approaches . • MIPP/EIPP biocement soils (UCS 1.5 – 4.3 MPa) and seal concrete cracks . • MIPP/EIPP reduce ammonia emissions by ∼96 % and ammonium release by ∼57 % . • Phosphate mineralisation achieves 99.6 % heavy metal immobilisation . • MIPP recovers 90 – 97 % of nutrients from waste streams .