Electromethanogenesis Process for Stable CO2 Conversion
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Solution Overview
Problem
Existing processes for converting carbon dioxide to methane in bioelectrochemical systems face stability issues and declining energy efficiency over time, especially when operated for prolonged periods.
Innovation Solution
The process involves contacting an aqueous solution with a high pH (above 7.5) and containing sodium and potassium cations, along with more than 20 mM phosphate ions, with an electron charged packed bed of activated carbon granules and microorganisms under anaerobic conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the process is operated for prolonged periods with existing processes, then carbon dioxide conversion to methane is achieved, but energy efficiency drops and process stability deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the aqueous solution composition with specific concentrations of sodium cations (0.3-4 M), potassium cations (0.3-4 M), and phosphate ions (>20 mM), along with maintaining pH above 7.5. These parameter adjustments create optimal conditions for halophilic microorganisms, resulting in stable operation and sustained energy efficiency of around 60% over prolonged periods
Solution Approach 2:
The patent implements feedback mechanisms through continuous monitoring and adjustment of process parameters including pH, salt concentration, and phosphate levels. This feedback control ensures that the system maintains optimal conditions for halophilic microorganisms, preventing efficiency degradation over time and maintaining stable methane production
2Reliability
If phosphate ion concentration is increased to improve stability, then process stability improves, but solution complexity increases
Solution Approach 1:
The patent simplifies the solution composition by establishing specific parameter ranges: phosphate ions >20 mM, sodium cations 0.3-4 M, potassium cations 0.3-4 M, and pH >7.5. Within these defined parameters, the system achieves both high stability and relatively simple operation, avoiding the need for complex compositional adjustments
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 results in a more stable process with improved energy efficiency, achieving values around 60%, compared to previous efficiencies of 25% and 40%, while maintaining stability over prolonged operation times.
Implementation Method 1
carbon dioxide is converted to methane in the presence of an electron charged packed bed comprising of a carrier and microorganisms under anaerobic conditions
Implementation Method 2
the aqueous solution comprises more than 20 mM phosphate ions
Data Source
AI summary
The invention is directed to a process to convert carbon dioxide to methane by contacting an aqueous solution comprising dissolved carbon dioxide with an electron charged packed bed comprising of a carrier and a biofilm of microorganisms under anaerobic conditions wherein the pH of the aqueous solution is above 7.5 and wherein the aqueous solution comprises between 0.3 and 4 M sodium cations or between 0.3 and 4 M sodium and potassium cations and more than 20 mM phosphate ions.