Microbial induced carbonate precipitation (MICP) is a new geotechnical engineering technology used to strengthen soils and other materials. Although it is considered to be environmentally friendly, there is a lack of quantitative data and objective evaluation to support conclusions about its environmental impact. In this paper, the energy consumption and carbon emissions of MICP technology are quantitatively analyzed by using the life cycle assessment (LCA) method. The environmental effects of MICP technology are evaluated from the perspectives of resource consumption and environmental impact. The results show that for each tonne of calcium carbonate produced by MICP technology, 1.8 t standard coal is consumed and 3.4 t CO₂ is produced, among which 80.4% of the carbon emissions and 96% of the energy consumption come from raw materials. Comparing using MICP with cement, lime, and sintered brick, the current MICP application process consumes less non-renewable resources but has a greater environmental impact. The major environmental impact that MICP has is the production of smoke and ash, with secondary impacts being global warming, photochemical ozone creation, acidification, and eutrophication. In five potential application scenarios of MICP, including concrete, sintered brick, lime mortar, mine cemented backfill, and foundation reinforcement, the carbon emissions of MICP are 3 to 7 times greater than the emissions of traditional technologies. The energy consumption is 15 to 23 times. Based on the energy consumption and carbon emissions characteristics of MICP technology at the current condition, suggestions are given for the future research of MICP.

Microbially induced carbonate precipitation (MICP) has been proposed as a sustainable approach to solve various environmental, structural, geotechnical and architectural issues. In the last decade, a ubiquitous microbial metabolism, nitrate reduction (also known as denitrification) got attention in MICP research due to its unique added benefits such as simultaneous corrosion inhibition in concrete and desaturation of porous media. The latter even upgraded MICP into a more advanced concept called microbially induced desaturation and precipitation (MIDP) which is being investigated for liquefaction mitigation. In this paper, we present the findings on MICP through denitrification by covering applications under two main titles: (i) applications solely based on MICP, such as soil reinforcement, development of microbial self-healing concrete, restoration of artwork and historical monuments, and industrial wastewater treatment, (ii) an application based on MIDP: liquefaction mitigation. After explaining the denitrification process in detail and describing the MICP and MIDP reaction system occurring through denitrification metabolism, the most recent advances in each potential field of application are collected, addressing the novel findings and limitations, to provide insights toward the practical applications in situ. Finally, the research needs required to deal with the defined challenges in application-oriented upscaling and optimization of MICP through denitrification are suggested. Overall, collected research findings revealed that MICP through denitrification possesses a great potential to replace conventionally used petrochemical-based, labour intensive, destructive and economically unfeasible techniques used in construction industry with a bio-based, labourless, low-carbon technology. This worldwide applicable bio-based technology will facilitate the sustainable development and contribute to the carbon-emission-reduction.

Compared to many other cemented geo-materials, such as concrete and natural limestone or sandstone sediments, the applications of microbial induced carbonate in-situ precipitation (MICP) bonded sandstones by Sporosarcina pasteurii in many civil strengthening works were limited due to their low strength. The established empirical correlation of the compressive strength parameter and the MICP yield was not satisfactory since little validation data was reported for the uniaxial compressive strength higher than 8∼10MPa. The present study was focused on producing MICP bonded sandstones under laboratory and field conditions with the high strength using advanced material and biological science approach. According to the previous studies carried out at Tsinghua University, the continuous 4 weeks biological treatment with the enzyme activity about 18mM urea hydrolyzed per min could lead to the cubic sandstone with the uniaxial compressive strength (UCS) no more than 5MPa. Coarse-grained and fine-grained sands were used, but little strength gain was observed. Strength improvement technologies were considered and investigated including the in-situ supply of cultivation culture and optimization of grouting route.