Biocementation Method Using Non-Urease Proteins
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Solution Overview
Problem
Conventional enzyme-induced carbonate precipitation (EICP) methods for biocementation require high concentrations of urease enzyme and multiple cycles to achieve desired compressive strength in soils, leading to high costs and undesirable byproducts like ammonium chloride, and often result in low unconfined compressive strength.
Innovation Solution
A biocementation method involving a solution of urea, urease, calcium ions, and non-urease proteins, with an enzyme stabilizer like non-fat milk powder, which reduces the need for high enzyme concentrations and byproduct production, achieving enhanced compressive strength with lower carbonate content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional EICP methods use high concentrations of urease enzyme and multiple treatment cycles, then the compressive strength of soil can be improved, but the cost increases significantly and undesirable byproducts like ammonium chloride are produced
Solution Approach 1:
The patent introduces a biocatalyst system comprising urease enzyme and urea as intermediaries to achieve calcium carbonate precipitation. The urease catalyzes urea hydrolysis to produce carbonate ions, which then react with calcium ions to form calcium carbonate cement. This intermediary biochemical pathway enables controlled cementation while reducing harmful byproducts compared to direct chemical precipitation methods.
Solution Approach 2:
The patent optimizes multiple parameters including urease enzyme concentration (5-50 IU/mL), urea concentration (0.1-1.0 M), calcium ion concentration (0.01-0.1 M), and pH (7.0-9.0) to achieve effective biocementation. By carefully controlling these parameters, the system achieves desired compressive strength while minimizing ammonium chloride production through balanced stoichiometry and controlled reaction kinetics.
2Strength
If multiple cycles of EICP treatment are applied to achieve desired compressive strength, then the soil strength improves, but the time and cost of the process increase
Solution Approach 1:
The patent employs preliminary actions by pre-mixing the biocatalyst solution containing urease, urea, and calcium ions before application to the soil. This pre-preparation ensures that all necessary components are present in optimal concentrations from the start, enabling effective cementation in a single treatment cycle rather than requiring multiple sequential applications.
Solution Approach 2:
The patent maintains continuous useful action by using a biocatalytic system where urease continuously catalyzes urea hydrolysis throughout the treatment period. This continuous enzymatic activity ensures sustained carbonate ion production and calcium carbonate precipitation, achieving desired strength gain in one continuous treatment process rather than intermittent cycles.
3Strength
If high concentrations of substrate and enzyme are used in EICP treatment, then the compressive strength increases, but the cost of the process becomes prohibitive for field applications
Solution Approach 1:
The patent uses inexpensive, readily available materials including commercial urease enzyme preparations, urea (a common fertilizer), and calcium salts. These low-cost reagents can be applied in field conditions without requiring expensive specialized equipment or materials, making the biocementation process economically viable for large-scale geotechnical applications.
Solution Approach 2:
The biocatalytic system exhibits self-service characteristics where the urease enzyme continuously catalyzes urea hydrolysis to generate carbonate ions in situ, which then react with calcium ions to form cementing calcium carbonate. This self-sustaining chemical-biological process eliminates the need for external energy input or complex control systems, reducing overall process costs.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method achieves unconfined compressive strengths of 0.5 MPa or more with lower carbonate content, reducing the amount of substrate and enzyme required, decreasing byproduct production, and making the process more cost-effective and environmentally friendly.
Implementation Method 1
Carbonate precipitation via hydrolysis of urea is one technique that has been investigated by geotechnical researchers. This technique utilizes the urease enzyme to catalyze the hydrolysis of urea in an aqueous solution
Implementation Method 2
This technique utilizes the urease enzyme to catalyze the hydrolysis of urea in an aqueous solution
Implementation Method 3
causing alkalinity and forming carbonate ions that leads to calcium carbonate precipitation in presence of calcium ions
Data Source
AI summary
The present disclosure provides a method of biocementation comprising contacting a granular, cohesionless soil with a solution, wherein the solution comprises urea, urease, a source of calcium ions, and a source of non-urease proteins, wherein the urea, urease, source of calcium ions, and source of non-urease proteins are provided in effective amounts suitable to cause crystallization of calcium carbonate.