Soil microbial improvement using enriched vinasse as a new abundant waste

Area of Science:

• Geotechnical Engineering
• Environmental Science
• Biotechnology

Background:

• Microbial-induced calcite precipitation (MICP) is a promising technique for soil improvement.
• Conventional culture media for MICP are often expensive, limiting widespread application.
• Vinasse, a waste biopolymer from ethanol production, presents an opportunity for developing sustainable and cost-effective alternatives.

Purpose of the Study:

• To investigate the use of vinasse as a primary component in a novel culture medium for MICP.
• To optimize bacterial growth and urease activity of Sporosarcina pasteurii using enriched vinasse.
• To evaluate the effectiveness of the developed medium for sustainable soil improvement and ground stabilization.

Main Methods:

• Vinasse was enriched with urea, sodium caseinate, or whey protein concentrate to support bacterial growth.
• Taguchi design of experiments (TDOE) was used to optimize vinasse and urea concentrations.
• Direct shear tests were conducted on loose and bio-treated sand to assess soil shear strength.

Main Results:

• The optimized vinasse-urea medium achieved a significant cost reduction from $0.455 to $0.005 per liter compared to Nutrient Broth.
• Bio-treated sand exhibited enhanced shear strength, with a 2.5-degree increase in friction angle and 20.7 kPa cohesion.
• The use of vinasse promotes a circular economy by recycling waste products and reducing environmental pollution.

Conclusions:

• Enriched vinasse offers a highly cost-effective and sustainable alternative to conventional culture media for MICP-based soil improvement.
• This approach significantly enhances the mechanical properties of loose soils, making it suitable for various construction projects.
• The study demonstrates a viable strategy for waste valorization and pollution reduction in the context of ground engineering.