Expandable Lagoon Cover for Methane Capture and Volume Control
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Solution Overview
Problem
Anaerobic digestion systems are often exposed to natural elements, making operation and monitoring difficult, and there is a need for improved systems to manage fugitive methane emissions and operational challenges.
Innovation Solution
A cover for a lagoon system featuring an expandable membrane with stretchable and restraining members, a skirt, and a gas processing unit, which can be retrofitted to existing slurry lagoons to control rainwater entry, minimize methane leakage, and facilitate gas processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional fixed cover is used for a lagoon, then the structure is simple and easy to manufacture, but it cannot adapt to volume changes of the lagoon contents and requires complex mechanical support structures
Solution Approach 1:
The cover system transitions from a fixed rigid structure to a dynamic flexible membrane that can change shape and volume in response to lagoon contents. The expandable membrane automatically adjusts its configuration as gas accumulates or is removed, eliminating the need for complex mechanical support structures while maintaining adaptability to volume changes.
Solution Approach 2:
The patent employs a flexible expandable membrane as the cover structure, which can deform and expand/contract to accommodate changes in lagoon volume. This thin film approach replaces rigid mechanical structures with a flexible barrier that naturally adapts to internal pressure and volume variations, reducing structural complexity while improving adaptability.
2Volume of stationary object
If the expandable membrane is allowed to expand freely vertically, then gas storage capacity increases, but the membrane becomes unstable and difficult to control
Solution Approach 1:
The compressible member acts as a counterweight or restraining force against the expanding membrane, providing downward pressure that balances the upward expansion force from gas accumulation. This creates a controlled equilibrium where the membrane can expand to increase storage volume while remaining stable and predictable in its behavior.
Solution Approach 2:
The system controls membrane expansion by changing the physical state or properties of the compressible member (such as its compression force or stiffness). By adjusting this parameter, the membrane's vertical expansion is regulated, maintaining stability while still allowing sufficient volume increase for gas storage.
3Reliability
If stretchable members are added to compress the membrane, then membrane stability improves, but the device complexity increases
Solution Approach 1:
The compressible member is designed to automatically perform its stabilizing function without external control or additional complex mechanisms. It self-adjusts to membrane expansion through its inherent compressibility, providing stability through its own physical properties rather than requiring active control systems or complex mechanical linkages.
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 system effectively captures 80-95% of fugitive methane, reduces nitrogen loss, minimizes slurry handling, and provides operational benefits such as reduced energy demands and greenhouse gas emissions, offering a reasonable return on investment for small- to mid-sized farms.
Implementation Method 1
an expandable membrane. The cover includes a plurality of stretchable members coupled to points on opposing sides within the expandable membrane and configured to compress the expandable membrane in a vertical direction
Implementation Method 2
The plurality of stretchable members comprise elastic material within the expandable membrane and connected to a top surface and a bottom surface of an interior of the expandable membrane
Implementation Method 3
The plurality of restraining members comprise rope within the expandable membrane and connected to a top surface and a bottom surface of an interior of the expandable membrane
Implementation Method 4
Anaerobic digestion is a process that can be used to convert a wide range of biomass materials into useable gas, such as a gas comprising mostly methane and carbon dioxide (CO2)
Implementation Method 5
a gas processing unit configured to process raw biogas from a gas outlet and to feed processed biogas into a gas inlet of the expandable membrane
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
A cover for a lagoon is provided. The cover includes an expandable membrane; a plurality of stretchable members coupled to the expandable membrane and configured to compress the expandable membrane; and a plurality of restraining members coupled to the expandable membrane and configured to limit expansion of the expandable membrane.