Modular Dry Digester for Lignocellulosic Biomass and Leachate Recycling
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Solution Overview
Problem
Existing anaerobic dry digestion systems for lignocellulosic biomass are capital-intensive, lack mobility, require high parasitic power, disrupt biological processes during batch changes, and have long retention times, leading to inefficient biogas production.
Innovation Solution
A system comprising a fabric-based dry digester with an irrigation system, sump system, rotary valve, and gas storage bladder, which recycles leachate and biogas, uses a microbial community, and includes a Hi-rate digester tank with bio-media to enhance biogas production, all while being easily assembled and disassembled.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional dry digesters are used, then biogas production is achieved, but capital expenditure is very high due to large concrete bunkers
Solution Approach 1:
The digester is divided into multiple modular chambers that can be assembled in series. Each module contains its own digestion chamber, cover, and leachate collection system, allowing the overall system capacity to be achieved through replication of compact units rather than requiring one large concrete structure.
Solution Approach 2:
The patent replaces traditional thick concrete walls with flexible liner materials such as HDPE membranes or reinforced polymer liners. These thin-film liners provide the necessary containment and corrosion resistance while dramatically reducing the material quantity and cost compared to concrete construction.
2Adaptability or versatility
If conventional dry digesters are used, then biogas production is achieved, but the digesters lack mobility and cannot be moved from one location to another
Solution Approach 1:
The digester system is modularized into discrete, transportable units that can be assembled on-site. Each module can be manufactured off-site, transported via standard logistics infrastructure, and quickly assembled with other modules to create the required digestion capacity at different locations as needs change.
Solution Approach 2:
The system employs hydraulic lifting mechanisms and pneumatic adjustment systems that allow the digesters to be raised, lowered, and repositioned. These fluid-powered systems enable mobile adjustment of digester positions and facilitate the movement of entire modular units without requiring heavy mechanical lifting equipment.
3Productivity
If conventional dry digesters are used, then biogas production is achieved, but parasitic power load for agitating and moving feedstocks is substantial
Solution Approach 1:
The system utilizes the natural weight and flow characteristics of the feedstock material itself to drive movement and mixing processes. Feedstock is fed from elevated hoppers using gravity flow, and the material's own mass provides the mixing action through peristaltic movement along the digestion chamber, eliminating the need for external motors and agitation mechanisms.
Solution Approach 2:
Traditional mechanical agitation systems with motors, shafts, and paddles are replaced with passive gravity-driven flow systems and biologically-driven mixing. The system relies on the natural peristaltic contraction of the digestion chamber and the flow dynamics of the feedstock itself to achieve adequate mixing without mechanical intervention.
4Productivity
If conventional dry digesters are used, then biogas production is achieved, but biological processes are disrupted during each batch change resulting in prolonged retention times
Solution Approach 1:
The system maintains continuous biological activity through overlapping batch operations. While one digestion chamber is being emptied and refilled, adjacent chambers are actively producing biogas. The leachate collection and recycling system operates continuously, maintaining consistent moisture and microbial activity levels throughout the digestion process without interruption during batch transitions.
Solution Approach 2:
The system pre-conditiones incoming feedstock by mixing it with recycled leachate containing active microorganisms before introducing it to the digestion chamber. This preliminary inoculation ensures that the biological processes start immediately upon batch introduction, eliminating lag periods and maintaining consistent production rates across batch changes.
5Ease of operation
If conventional dry digesters are used, then biogas production is achieved, but there is a constant requirement for specialist technology for loading/unloading
Solution Approach 1:
The system employs simple gravity-fed loading mechanisms where feedstock is poured or conveyed from elevated storage into the digestion chamber through large opening. Unloading is achieved by gravity-driven discharge at the bottom of the chamber, eliminating the need for complex mechanical loading/unloading equipment and specialist operational knowledge.
Solution Approach 2:
Instead of using complex mechanical systems to force material into and out of the digester, the system inverts the approach by using gravity flow in reverse - feeding from high to low elevation and discharging from low to high through simple elevation differential. This reverses the conventional approach and eliminates complex loading/unloading machinery.
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 achieves efficient biogas production with reduced capital expenditure, parasitic power use, and consistent biology across batches, while being mobile and environmentally friendly.
Implementation Method 1
The present disclosure relates to a system and method for anaerobic dry digestion of lignocellulosic biomass
Implementation Method 2
a pump connected to the external tank and the sump tank. The pump circulates the leachate from the sump tank
Implementation Method 3
a rotary valve connected at least to the pump and the dry digester. The rotary valve recycles the leachate from the sump tank to the dry digester
Implementation Method 4
The gas booster pump connects at least to the dry digester and pumps biogas through the gas treatment unit
Implementation Method 5
The hi-rate digester tank comprises a bio-media for improving biogas offtake from the leachate
Data Source
AI summary
The present disclosure is directed to a system for anaerobic dry digestion of lignocellulosic biomass including: a dry digester having a ground sheet and a cover for the lignocellulosic biomass. The digester generates leachate and biogas from anaerobic digestion. The system includes an irrigation/port system for wetting of the lignocellulosic biomass under the cover; a sump system for monitoring the leachate; a rotary valve-connected at least to the pump and the dry digester; a gas storage bladder for collecting the biogas, the gas storage bladder connected at least to a gas treatment unit and a gas booster pump; and a hi-rate digester tank connected at least to the rotary valve for receiving the leachate therefrom.