Utilising urea from urine treatment for enzyme-induced carbonate precipitation: circularity of resources and sustainability in soil erosion control

• Grant number: 25/03693-4
• Support Opportunities: Regular Research Grants
• Start date: September 01, 2025
• End date: August 31, 2028
• Field of knowledge: Engineering - Sanitary Engineering - Water Supply and Wastewater Treatment
• Principal Investigator: Rodrigo Custodio Urban
• Grantee: Rodrigo Custodio Urban
• Host Institution: Instituto de Ciência e Tecnologia (ICT). Universidade Estadual Paulista (UNESP). Campus de São José dos Campos. São José dos Campos , SP, Brazil
• Associated researchers: Liane Yuri Kondo Nakada ; Marcos Yutaka Shiino ; Sandro Donnini Mancini

Abstract

Soil biocementation is a technique that is currently gaining in importance because it is environmentally friendly. It can be carried out by precipitating calcium carbonate through the action of microorganisms (MICP) or enzymes (EICP). CaCO¿ acts as a cementing agent, increasing the strength of granular soils and reducing their permeability, which helps to combat erosion, for example. However, although biocementation is considered to be a nature-based solution, the use of commercial inputs can increase the negative environmental impact during its lifecycle, as well as increasing the cost of implementing the solution, threatening the sustainability of the process. For this reason, the use of alternative inputs from waste or sub-processes can make a significant contribution to the circularity of the solution. The inputs required for EICP include urea, the enzyme urease and a source of inorganic calcium (usually calcium chloride (CaCl2)). This project proposes the use of human urine, watermelon seeds and egg shells as alternative inputs for EICP. Although some of these inputs have been studied separately, their use together is an innovation, especially with regard to the use of human urine. Urine is a liquid waste excreted by the human body that contains large amounts of nitrogen, also in the form of urea, and has the potential for economic use. In addition, the separate collection of urine from domestic wastewater can contribute to treatment efficiency. Within the principles of circular economy, we could consider using urine as a source of urea, watermelon seeds as a source of urease enzyme and egg shells as a source of inorganic calcium for the EICP process, thereby reducing the environmental footprint of the processes. Against this background, the aim of this project is to evaluate the treatment of human urine by alkaline stabilisation and adsorption in an activated carbon column as a source of urea for the enzyme-induced carbonate precipitation (EICP) process, with the aim of increasing the resistance and reducing the permeability of non-cohesive soils. (AU)