## 5 Discussion  
### Implications for Field-Scale Implementation  
The LCSA results presented above, which model the impacts of meter-scale column testing performed in the laboratory, were upscaled to estimate the environmental impacts of MICP for two field-scale implementation scenarios (see \"Methods for Upscaling LCSA Results\" Section in the Supplementary Materials). The upscaled scenarios assume that solution transport in these treatment volumes would be similar to that observed in the performed one-dimensional column experiments. While this may not be strictly true, the scenarios provide important practical comparisons through which the relative differences between the studied treatment approaches can be better understood. Scenario 1 considers the impacts of MICP treatment at a hypothetical project site consisting of loose saturated sandy soils that require the mitigation of earthquake-induced soil liquefaction. The zone of improvement is approximately 30 m \(\times\) 30 m \(\times\) 11 m deep (100 ft \(\times\) 100 ft \(\times\) 35 ft). The functional unit is defined as the improvement of approximately 9900 m\({}^{3}\) of soil such that shear wave velocity is increased by 150 m/s (i.e., \(\Delta\)V\({}_{\text{s}}\) = 150 m/s). Scenario 1 assumes a two-dimensional triangular well configuration for all three MICP treatment approaches, with an injection-to-outlet well spacing of 3.5 m, similar to the treatment distance present at Vs location 4 (Supplementary Figure S1). In this scenario, MICP treatment is followed by the use of the optimal rinsing technique described earlier (i.e., injection of 1.8 PV of rinse solution). The results for primary energy consumption and global warming potential are shown in Table 2. For this scenario, the low-ureolytic-rate stimulation approach (Column 2) is the most sustainable. Relative to low-ureolytic-rate stimulation, the impacts of high-ureolytic-rate stimulation and augmentation are about 21% and 30% greater on average, respectively. One limitation of these findings is the limited scope of analysis; results consider impacts from materials use and process emissions but exclude impacts associated with energy consumption from pumping and several other life cycle phases, including equipment mobilization, materials transportation, well construction, and effluent management. It is expected that the impacts from these latter three categories would significantly decrease for the spacing of 3.5 m (Scenario 2) compared to the spacing of 1.3 m (Scenario 1), showing a further benefit of Scenario 2. These exclusions are the result of a lack of data and cannot be estimated by simply scaling laboratory experimental processes and results (e.g., pumps used during field applications may be very different than those used in the laboratory setting) and will be addressed in future work. Scenario 2 considers the same project site and well layout as considered in Scenario 1. However, in this case, the functional unit is the improvement of 9900 m\({}^{3}\) of soil such that Vs is increased by 400 m/s. Because the augmented column (Column 3) did not achieve this performance criterion during the laboratory experiment, only the high-ureolytic-rate stimulation (Column 1) and low-ureolytic-rate stimulation (Column 2) approaches were considered as viable treatment options. It was assumed that in order to achieve these