This study proposes the use of vinasse, an inexpensive and readily available waste biopolymer, as a fundamental component of a waste culture medium that can enhance the effectiveness and cost-efficiency of the microbial-induced calcite precipitation (MICP) method for sustainable soil improvement. Vinasse enriched with urea, sodium caseinate, or whey protein concentrate is employed to optimize bacterial growth and urease activity of Sporosarcina pasteurii (S. pasteurii) bacterium. The best culture medium is analyzed using Taguchi design of experiments (TDOE) and statistical analysis, considering the concentration of vinasse and urea as effective parameters during growth time. To test the best culture medium for bio-treated soil, direct shear tests were performed on loose and bio-treated sand. The results demonstrate a substantial cost reduction from $0.455 to $0.005 per liter when using the new culture medium (vinasse and urea) compared to the conventional Nutrient Broth (NB) culture medium. Additionally, the new medium enhances soil shear strength, increasing the friction angle by 2.5 degrees and cohesion to 20.7 kPa compared to the conventional medium. Furthermore, the recycling of vinasse as a waste product can promote the progress of a circular economy and reduce environmental pollution. As ground improvement is essential for many construction projects, especially those that require high shear strength or are built on loose soil, this study provides a promising approach to achieving cost-effective and sustainable soil microbial improvement using enriched vinasse.
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