Indigenous Microbe Biocementation for Uniform Calcite Distribution
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Solution Overview
Problem
Existing methods for microbial biocementation face issues such as uneven calcite distribution, clogging, loss of microorganisms, and disruption of the local ecological framework due to the injection of exogenous microorganisms and reagents, which limits their practicality for various applications.
Innovation Solution
Utilizing indigenous urea-hydrolyzing microorganisms present in geomaterials, promoting their growth with nutrients and calcium ions, and allowing them to convert urea into calcium carbonate, thereby avoiding the need for exogenous microorganism addition and optimizing environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If exogenous microorganisms and reagents are injected into the starting material, then calcite formation and cementation occur rapidly, but calcite formation concentrates at or near the injection point causing uneven distribution and clogging
Solution Approach 1:
Instead of injecting microorganisms and reagents simultaneously to achieve rapid cementation (conventional approach), the patent inverts the sequence by first injecting only the reagents (urea and calcium chloride solution) and allowing them to distribute uniformly throughout the porous material. The microorganisms are then applied separately to the surface or injected afterward, enabling them to colonize the material and gradually produce calcite throughout the entire volume, resulting in uniform distribution while maintaining practical cementation rates.
2Productivity
If exogenous microorganisms are injected into the starting material, then cementation can be initiated, but microorganisms are lost and the local ecological framework is disrupted
Solution Approach 1:
The patent utilizes the principle of self-service by relying on indigenous microorganisms already present in the starting material rather than introducing exogenous ones. These native microorganisms are already adapted to the local environment and ecological framework. When urea and calcium chloride are injected, the indigenous microorganisms naturally utilize these reagents to produce calcite, eliminating the problems of microorganism loss and ecological disruption while maintaining reliable cementation.
3Reliability
If microorganisms are fixed in the starting material before cementation, then microorganism loss is reduced, but the process complexity increases with sequential steps
Solution Approach 1:
The patent applies the extraction principle by separating the microorganism application step from the reagent injection step. Instead of fixing microorganisms in the material before adding reagents (complex sequential process), the method extracts the microorganism component and applies it separately—either by surface application or delayed injection—after the reagents are already distributed in the material. This simplifies the overall process while maintaining microorganism retention and effectiveness.
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
This approach ensures uniform calcite distribution, reduces clogging, maintains the local microbial ecosystem, and enhances the robustness and simplicity of the biocementation process, making it more practical for real-world applications.
Implementation Method 1
Many naturally occurring microorganisms present in soils, especially bacteria of the family Bacillacae such as bacteria of the genera Bacillus, Sporosarcina, Sporolactobacillus, Clostridium and Desulfotomaculum are able to hydrolyze urea (NH2)2CO in the presence of water to ammonium and carbonate ions
Implementation Method 2
The carbonate ions combine with the calcium ions to form calcium carbonate
Implementation Method 3
Calcite bridges adjacent soil particles, cementing soil grains together to form a cemented sand or sandstone
Data Source
AI summary
A method for increasing the concentration of calcium carbonate in a geomaterial that contains indigenous microorganisms capable of hydrolyzing urea to ammonia, which method includes enriching the geomaterial with a source of nutrients, adding urea to the geomaterial which is hydrolyzed to ammonia and which raises the pH of the geomaterial, and adding a source of calcium ions to the geomaterial. Carbonate ions obtained by the hydrolysis of the urea combine with calcium ions to form calcium carbonate.