# Recent Developments on Biomineralization for Erosion Control
## 2 Biomineralization Process and Efficiency Optimization
### Biomineralization Efficiency Optimization  
One of the major issues that needs to be solved in the application of MICP technology is the uniformity of cementation. Uneven cementation will lead to stress concentration and brittle failure of the reinforced ground when subjected to load. Many scholars have conducted research and analysis on this issue. As shown in Table 1, three methodologies were evaluated by [PERSON] et al. (2025) for MICP in silt cementation [117]. The mixing method, involving direct blending of bacterial and cementation solutions with silt prior to compaction, achieved optimal uniformity and strength (801.25 kPa UCS). This approach ensured even radial and longitudinal CaCO\({}_{3}\) distribution, effectively minimizing pore volume disparities. In contrast, the grouting method utilized pressure-driven injection,resulting in longitudinal inhomogeneity with declining CaCO\({}_{3}\) content (bottom-to-top gradients) and reduced strength (684.78 kPa UCS), attributed to pore channel clogging hindering upward slurry migration. The immersion method, which soaked silt in solutions, exhibited radial inhomogeneity as CaCO\({}_{3}\) precipitation decreased from outer to inner layers due to limited permeability, yielding the lowest strength (206.11 kPa UCS). While adjusting grouting pressure, solution concentration, or utilizing intermittent injection cycles could enhance solute distribution, the study identified mixing as the most effective strategy for uniform cementation. Structural analyses confirmed that mixing generated homogeneous pore networks with spatially consistent CaCO\({}_{3}\), whereas grouting and immersion produced strength variations dictated by solute transport limitations and gradient-dependent precipitation patterns. In addition to methodology optimization, material formulation can also be optimized. [PERSON] et al. (2025) developed a novel one-phase injection method integrated with polycarboxylic acid (PA) to optimize the uniformity and strength of MICP-treated sand (2018). By leveraging PA's dual functionality, delaying CaCO\({}_{3}\) nucleation through Ca\({}^{2+}\) chelation and acting as a non-bacterial nucleation template, this approach allows deeper penetration of solutions into pores before precipitation begins. Experiments demonstrated that 3% PA delayed initial CaCO\({}_{3}\) precipitation by over 2 h, enabling uniform reactant distribution, while calcium ion conversion rate curves confirmed complete Ca\({}^{2+}\) utilization within 24 h under optimal conditions (3% PA added), achieving a strength of 2.76 MPa after five treatment cycles. Comparative analyses revealed PA-MICP's superiority over traditional methods like grouting and immersion, which suffered from pore clogging and radial heterogeneity. The efficacy of PA shows progressively enhanced homogeneity and cementation coverage with increasing PA concentrations (0%, 1%, 3%, 5%) and extended treatment times, ultimately validating PA's role in bridging soil particle gaps for structural reinforcement. Yet, the impacts of ambient environmental conditions (such as temperature, salinity, oxygen availability, etc.) on optimization strategies should be further investigated.  
\begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Treatment Method** & **Soil Type** &
\begin{tabular}{c} **CaCO\({}_{3}\) Content** \\ **and Distribution** \\ \end{tabular} & **UCS** & **Pros and Cons** & **Reference** \\ \hline \multirow{4}{*}{Mixing} & \multirow{4}{*}{Silt} & 8–10\%, relatively uniform & \multirow{4}{*}{801.25 kPa} & Good uniformity, suitable for shallow reinforcement, difficult to use on large areas & [PERSON] et al., 2025 [117] \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: The soil reinforcement effects under different MICP treatment methods.