Hello Bob.
Here's the thing. Next year I'm going to be moving to the woods to renovate a cabin from scratch. Id' like to build a digester that can produce enough methane to run an instant water heater and my stove top. I'd also like it to heat the cabin too, but I'm sure that's asking for too much. I couldn't get the design tool to work. I will be surrounded by dairy farms with whom I could get a regular supply of manure from along with personal compost etc. Anyway I was considering using a 55 gallon drum and a truck or tractor tire as a bladder. I have a pretty good idea how to build a simple one time use digester, but if I could build one that I could run constantly, that would be ideal. I downloaded the design you posted last year for Guy Sellers (thank you for the visual) but admittedly I have a limited understanding of it. (my engineering skills are lacking) Let's see...
1) This is probably a stupid question but, does the CO2 vent 'T' off at the bottom or is it attached to a separator disc?
2) Is the effluent forced out by pressure alone? Or is a pump/siphon needed?
3)But the real questions I have relate to the pumps. The feed pump is on a timer, how will I know how often it will need to be set to pump in? On the other side, the diaphragm air pump. I know nothing about this. The pump is on a timer...but only when there is positive pressure. Does the pump measure for positive pressure or is this a manual thing.
I think that's everything. Pardon my ignorance of this, it's all a little out of my field. Thanks a lot.
anaerobic digesters for dummies
Moderator:Bob
Hi yggdrazl,
(Isn't that a name from Lord of the Rings?)
re. getting the design tool to work, I'm working on a new version that will be less problematic. In the meanwhile, I'd guess that you can produce enough methane for cooking and heating a small amount of water, with wastes from a family plus kitchen scraps,etc. But not much more than that. (Hauling in cowshit to heat your house sounds like a lot of hassle. I'd sure look at other options first. Unless there are other reasons/benefits to hauling cowshit.)
In the drawing I posted, the CO2 vent is just connected to a bulkhead fitting through the plate.
Yes, in my system, the influent pump provides the pressure. Just simple displacement, so that as you pump more in, an equal amount flows out.
Re feed pump questions, it all depends on your specific setup. The timer is set to maintain the desired retention time. For example, if your tank is 100 gallons, and you want a 12.5 day retention time, the pump should run enough to pump 100/12.5 = 8 gallons per day. If the pump is capable of pumping 4 GPM, that would be 2 minutes of runtime. You could set it to run for one minute, twice a day. But, you will probably need to add some other controls, like, say, a low level float switch to shut the pump off before it runs dry, and a high level float switch to prevent your holding tank from overflowing, and signal an alarm. etc. All depends on your setup, and what you are willing to do manually vs automatically.
The diaphragm pump is just a simple air pump, as sold for fish aquariums. It is used to recirculate the gas, just for mixing the contents of the tank. If you put a pressure switch on the gas line, you can wire it to run only when there is sufficient gas available.
(Isn't that a name from Lord of the Rings?)
re. getting the design tool to work, I'm working on a new version that will be less problematic. In the meanwhile, I'd guess that you can produce enough methane for cooking and heating a small amount of water, with wastes from a family plus kitchen scraps,etc. But not much more than that. (Hauling in cowshit to heat your house sounds like a lot of hassle. I'd sure look at other options first. Unless there are other reasons/benefits to hauling cowshit.)
In the drawing I posted, the CO2 vent is just connected to a bulkhead fitting through the plate.
Yes, in my system, the influent pump provides the pressure. Just simple displacement, so that as you pump more in, an equal amount flows out.
Re feed pump questions, it all depends on your specific setup. The timer is set to maintain the desired retention time. For example, if your tank is 100 gallons, and you want a 12.5 day retention time, the pump should run enough to pump 100/12.5 = 8 gallons per day. If the pump is capable of pumping 4 GPM, that would be 2 minutes of runtime. You could set it to run for one minute, twice a day. But, you will probably need to add some other controls, like, say, a low level float switch to shut the pump off before it runs dry, and a high level float switch to prevent your holding tank from overflowing, and signal an alarm. etc. All depends on your setup, and what you are willing to do manually vs automatically.
The diaphragm pump is just a simple air pump, as sold for fish aquariums. It is used to recirculate the gas, just for mixing the contents of the tank. If you put a pressure switch on the gas line, you can wire it to run only when there is sufficient gas available.
I finally got a revised on-line design tool working. I still want to do some refinements, and add to the help info, but try this.
[This message has been edited by Bob (edited 12-21-2001).]
[This message has been edited by Bob (edited 12-21-2001).]