## 4 Results
### Effects of Increasing Cementation Treatments  
Figure 4 illustrates the increases in global warming potential associated with obtaining higher Vs values and Vs increases (\(\Delta\)Vs) in all three columns. Soil Vs increases were measured during the application of successive cementation treatments, which ranged from 0 to 9 injections during the experiment. Results are shown for Vs improvements measured at locations 2 (V\({}_{82}\), Figure 4a) and 4 (V\({}_{84}\), Figure 4b), which were located 1.33 m and 3.37 m from the injection source, respectively, as shown in Figure 1. All columns received treatment injections in a single direction in this experiment and were expected to be representative of a single injection-to-outlet well alignment. It should be mentioned, however, that during field-scale applications, treatment wells will likely be placed in more complex two-dimensional patterns and treatments may also be applied bidirectionally, thereby affording the potential for larger well spacings to be used. An example of a possible two-dimensional triangular well pattern with the same injection-to-outlet well distances present between the injection source and Vs locations 2 and 4 in the meter-scale column experiments is shown in Supplementary Figure S1. As evident in the experimental results, increasing the number of applied cementation treatments increased Vs due to the higher magnitudes of biocementation that were achieved. However, the level of improvement varied between treatment approaches and with distance from the injection well. The high-ureolytic-rate stimulation approach (Column 1) obtained more rapid and localized improvement near the injection well, resulting in large increases in V\({}_{82}\) (greater than 1000 m/s) but minimal increases in V\({}_{84}\) (only 168 m/s) after nine cementation injections. The low-ureolytic-rate stimulation approach (Column 2) achievedsmaller Vs improvements than Column 1 near the injection source but achieved the greatest uniformity and extent of biocementation when compared to the other two approaches, increasing V\({}_{\text{s2}}\) and V\({}_{\text{sat}}\) values by 698 m/s and 406 m/s, respectively. In the augmented column (Column 3), small increases in V\({}_{\text{s2}}\) and V\({}_{\text{sat}}\) values of 72 m/s and 166 m/s were measured, respectively, reflective of more localized improvement near the injection well and poor ureolytic activity and biocementation at larger treatment distances [19]. Increasing the number of cementation treatments required more material and energy consumption and thus increased environmental impacts and cost. While global warming potential is the only impact indicator presented in Figure 4, all other indicators exhibited similar trends with increasing cementation treatments. For all columns, each additional cementation injection increased total global warming potential linearly by about 5 kg CO\({}_{\text{2}}\) equivalent (eq.) but had nonlinear effects on the realized engineering improvements, as indicated by V\({}_{\text{s}}\). To appropriately compare the life cycle impacts and costs of the three MICP treatment approaches, each column must achieve the same level of biocementation. In this study, the LCSA results were compared for two different performance criteria, namely obtaining a \(\Delta\)V\({}_{\text{s}}\) increase of 150 m/s at locations 2 and 4. While this change in shear wave velocity is relatively small in comparison to the Vs improvements observed at shorter treatment distances (i.e., location 1), recent centrifuge modeling and laboratory element testing have shown that biocementation-induced Vs increases near 100 m/s can significantly increase liquefaction triggering resistances.