Step-By-Step Instructions

Method:

→ Biodigester Assembly

  • Using a wireless drill and the appropriate hole saw bits (5” and 3”), create three holes at the top surface of the rain barrel; one 5” hole (for the feed pipe) and two 3” holes (for the gas pipe and effluent pipe).
  • Arrange the holes in a straight line across the center of the top surface; the gas pipe will be in between the feed and effluent pipes.
  • Always wear leather gloves and safety glasses when using the hole saw.
  • Add silicone caulking to the lip of both the 4” and 2” uniseals and fit them into the appropriate holes. Leave to dry overnight.
  • Unscrew the nut and remove the washer from the 2” bulkhead fitting; add silicone caulking to the bottom lip of the body and replace the washer; reach through the adjacent 4” feed pipe hole to push the bulkhead fitting from the underside of the barrel surface and up through the central gas pipe hole; screw on the bulkhead nut and tighten. Leave to dry overnight.


  • Using a handsaw, cut a 2” PVC pipe so that, when topped with a 2” PVC ‘T’, it reaches 8” inches above the top surface of the rain barrel (roughly a total of ~42” with the PVC ‘T’); this has been found to be the optimal height for facilitating effluent outflow.
  • Additionally, cut a ~1.25”x1.25” square from the center of the effluent pipe (this is where the effluent outflow will begin leaving the biodigester). 
  • Cut another section of 2” PVC (~10”) and attach to the PVC ‘T’ (the hole parallel to the ground) and attach a 2” PVC ‘L’ to the end (this is where the effluent will flow out of the biodigester).
  • Before inserting the 2” PVC pipe into the 2” uniseal, use a metal file to sand down the sharp edges and lather with either dish soap or vegetable oil (this will aid in passing the pipe through the uniseal); repeat this process with the 4” feed pipe.


  • Cut the 4” PVC pipe so that it is higher than the effluent pipe. In this build, the feed pipe was made to be about a few inches taller than the effluent pipe (before attaching the rubber funnel). Using the handsaw, cut out a ~7”x4” section from the bottom of the feed pipe; this will allow organic matter to disperse into the bottom of the biodigester. 








  • The gas pipe is the tallest pipe and was constructed to convert from 2” to ½” diameters; this ensures that gas can still rise upwards even if debris accumulates at the 2” base of the gas pipe. 
  • Cut an 8” section of 2” PVC and fit onto the bulkhead fitting; in this order, attach to the 2” PVC section: a 2” PVC coupling socket, a 2” - 1 ½” bushing, and 1 ½” - ½” bushing (these pieces together allow for this 2” to ½” pipe conversion).
  • Cut in half a 6” section of ½” PVC pipe; in this order, attach to the 1 ½” - ½” bushing: one 3” section of ½” PVC pipe, a ½” PVC ball valve, the second 3” section of ½” PVC pipe, a ½” PVC slip-to-thread pipe adapter. Before attaching the ½” hose barb to the pipe adapter, wrap a couple layers of plumber’s tape around the threads of the hose barb to ensure no leaks. The hose barb is where the PVC tubing can be attached to transport the methane gas.




→ Digester “Floaters” Materials
→ Digester Floaters Assembly
  • Using a razor blade, cut ~0.75”x0.75”x0.50” cubes of polyethylene (PE) foam.
  • Combine PE foam cubes with glass pebbles together inside a plastic mesh produce bag.
  • Tie the mesh bag.
  • Test the buoyancy of the floater within a bucket of water; add and subtract foam cubes and pebbles until the floater is able to float within the water column.
  • The porous surface of the PE foam cubes and the mesh bag will increase the surface area within the biodigester thus enhancing the rate of anaerobic digestion.
  • The floaters can be dropped into to the biodigester through the 4” feed pipe.

















  • Paint the rain barrel black; this will aid in solar absorption to maintain the optimal temperature for digestion.
  • Using a wireless drill and any sturdy drill bit, create a hole just smaller than ½” at the base of the rain barrel; using force, screw a ½” metal hose faucet into the hole; this allows the biodigester to be drained and transported easily if necessary



Created by Sarah Long

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