# From Waste to Strength: Applying Wastepaper, Fungi and Bacteria for Soil Stabilization
## 3 Results and Discussion
### Properties of MICP-Treated Soil Samples with Wastepaper Additives  
In accordance with the experimental design (Figure 1), soil samples were prepared with varying wastewater contents and treated with bacterial or fungal biomass, along with the cementing solution. After 14 days of treatment, the resulting soil samples were thoroughly characterized. 1.1 Compressive Strength of Soil Samples with Different Wastepaper Contents Treated with Bacterial and Fungal Biomasses  
As shown in Figure 2, increasing the wastewater content in the soil resulted in a corresponding increase in strength for both the control and the samples treated with the bacterial suspension. The highest strength (277.2 kPa) was observed in the Bact soil sample containing 6% wastepaper. Among the Fng samples, the highest strength was recorded in the sample without wastepaper (236.6 kPa). However, the addition of wastepaper reduced the strength: a sample with 2% wastepaper had a strength of 140.1 kPa, while further increases to 4% and 6% wastepaper reduced the strength to 97.6 kPa and 62.2 kPa,respectively. The strength of soil samples treated with a mixture of bacterial and fungal biomasses increased compared to the control only at 0% and 2% wastewater contents. Notably, the Mix sample with 2% wastewater exhibited the highest strength among all samples with the same wastewater content. 1.2 Formation of Calcium Carbonate in Soil Samples with Different Wastepaper Contents, Treated with Bacterial and Fungal Biomasses  
The calcium carbonate content was measured at different soil samples layers (top, bottom and middle). The addition of wastewater did not increase the total CaCO\({}_{3}\) content (Figure 3A), but it significantly affected its distribution within the soil sample. In the Control, Fng, Bact (in the 0-4% range) and Mix (in the 2-6% range) samples, an increase in wastewater content was associated with a decrease in CaCO\({}_{3}\) in the bottom layer of the soil (Figure 3B). This observation is consistent with the findings of [PERSON] [27], who reported a similar effect in sand bioccmentation with the addition of wastewater fibers. They suggested that paper fibers help retain mineralizing bacteria in the top layers of the sample by binding them, preventing their settlement in the bottom layers. In soil, similar to sand, bacterial cells may be washed away from the top layer by gravity, but the presence of paper fibers can prevent their downward migration. It is important to recognize that, in addition to preventing bacterial leaching, the wastewater fibers significantly enhance soil strength due to their natural reinforcing properties. Several reports [24; 39; 40] have shown that the introduction of both synthetic and natural fibers leads to an increase in the compressive strength of soil. In untreated soil, the observed strength enhancement is primarily due to the increased calcium carbonate content precipitated by the microorganisms. Figure 2: Values for compressive strength (Rc) of MICP-treated soil samples with wastewaterpaper additives. Soil sample treated with cementation solution (without MICP) was used as control. * Significantly different (\(p<0.05\)). Figure 3: Percentages of calcium carbonate formed in MICP-treated soil samples with wastepaper additives: (**A**)—average calcium carbonate content; (**B**)—CaCO\({}_{3}\) contents derived from top, middle and bottom layers of the soil sample. Soil sample treated with CS (without MICP) was used as control. * Significantly different (\(p<0.05\)). As can be seen in Figure 3A, the treatment of soil with a _B. licheniformis_ suspension, without wastepaper, increased the total CaCO\({}_{3}\) content by 1.5 times (Bact vs. Control samples) and doubled the strength of the sample (Figure 2). In a previous study [29], treating soil with a mixture of bacteria (without additives) resulted in a similar 1.5-fold increase in precipitated calcium carbonate content.