Design Specifics:
Intermediate Bulk Containers (IBC) tanks are the most cost effective modular liquid containers, simply because they are the most common. They are compatible with fork-lifts and typical shipping processes, an unfortunate necessity in our current system, and they benefit from the production of the economy of scale.
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This methane digester design features a flush toilet running to a (diagram soon-to-com) mixing tank where the waste is then metered into the digester at a regular rate.
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The beauty of the design is that all the in/out ports are stacked into one manifold and fit into the manufactured port on the top of the IBC. This means that this port-manifold can be made separately and "plugged-in" to any IBC anywhere. The needed pipes are the: feed tube, effluent out-pipe, gas outlet, mixer gas in-pipe, and the heater pipes: gas in, air in, and exhaust out.
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The gas produced by the digester is used both to mix the digester and also to heat it, utilizing a very efficient submerged combustion chamber.
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The images to the left illustrate this design. The black ring at the top is the screw-in cap of the IBC. The large central Blue pipe is the digestate feed tube (running from the mixing tank). The pipes carrying methane gas are yellow, and there are three of them: the digester-to-reservoir out-flow pipe (the shortest), the reservoir-to-combustion chamber pipe used to heat the digester, and the pipe (shown at back of the image) which pumps methane gas from the reservoir back into the digester to bubble up through it at regular intervals.
The white pipe provides the air to combust with the methane in the combustion chamber at the bottom (red). The red pipe runs from this chamber back up bringing the hot combusted gasses out. The green digestate out-flow pipe runs along side this exhaust pipe and is sterilized by the heat as it exits.
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The top view has different coloring, the red and green pipes on the far side are the exhaust and digestate out-flow pipe. The closest pipes are the short methane out-flow (to reservoir) pipe and the long combustion methane (reservoir to hot water heater) pipe. To the left of the combustion gas is the combustion air pipe, and the last pipe to the left of this is the methane bubble mixer.
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