Review of green reinforcement technology for peat soil based on MICP–Mg-rich synthetic gypsum concrete waste synergistic mechanism

Abstract This narrative review evaluates green reinforcement technologies for peat soil based on the synergistic mechanism of microbially induced carbonate precipitation (MICP), magnesium-rich synthetic gypsum (MRSG) and concrete waste (CW). A systematic search of Scopus, Web of Science and Google Scholar from 1997 to 2025 using keywords related to peat stabilisation, MICP, MRSG and CW identified 67 experimental studies. The review first summarises the distribution and engineering characteristics of peat soils and the limitations of conventional physical and chemical improvements. It then explains MICP ureolysis and factors influencing calcite precipitation. The reviewed studies demonstrate substantial strength enhancements in treated peat soils. Ureolytic MICP treatment elevated the unconfined compressive strength (UCS) of tropical peat from approximately 5 kPa to about 82 kPa. Treatment with 5% Mg-rich synthetic gypsum (MRSG) by weight resulted in a fourfold increase in UCS, from about 15 kPa to 59 kPa. A notable synergistic effect was observed in a combined treatment incorporating 10% MRSG and 10% concrete waste aggregate (CW), which yielded the most significant gain by elevating the UCS from 36 kPa to 144 kPa. The microstructural analysis revealed calcite, ettringite, and C–S–H gel. The synergy arises because MRSG and concrete waste supply Ca 2+ /Mg 2+ and alkalinity, accelerating bacterial ureolysis and carbonate precipitation. Considering the environmental impact, urea hydrolysis produces NH 4 + , and excessive CaCl2 or high pH values can inhibit bacteria, posing a risk. Overall, MICP–MRSG–CW technology offers a promising, low-carbon alternative for stabilising peat soils.