seeking inoculant for methanogens
Moderator:Bob
Hi. Besides the swamp muck mentioned in earlier posts, what other products can be used as an inoculant for methanogens?
Sewage sludge, (contact your local municipal WWTP), septic tank sludge (contact a local septic tank pumping service), material taken from bottom of barnyard or manure pit (if you are on or near a farm?)
In short, any well-rotted, organically rich, liquid-saturated source. If you can wait long enough, make your own. Get a pile of leaves, grass-clippings, manure, kitchen and/or garden scraps, put them in a bucket, cover with water, put in a nice warm place and wait. Stir occasionally, trying not to mix in any more air than necessary. The main thing is to not let the mix get too acid, and to wait long enough. Check the pH periodically, add bicarbonate of soda (slowly & carefully) as required to keep it around 6.5-7.0.
What are you planning to digest?
In short, any well-rotted, organically rich, liquid-saturated source. If you can wait long enough, make your own. Get a pile of leaves, grass-clippings, manure, kitchen and/or garden scraps, put them in a bucket, cover with water, put in a nice warm place and wait. Stir occasionally, trying not to mix in any more air than necessary. The main thing is to not let the mix get too acid, and to wait long enough. Check the pH periodically, add bicarbonate of soda (slowly & carefully) as required to keep it around 6.5-7.0.
What are you planning to digest?
Hi Bob. In my email to you I attached a proposed design for a 55 gallon single stage digester. I will be digesting seperated solid cattle manure. The design includes an electric blanket wrapped around the barrel with a voltage regulator to adjust the blanket temperature. There is also a thermocouple inside a glass tube which has been inserted into the slurry. The thermocouple is attached to a small data logger which records the slurry temp and the ambient temp. The barrel is insulated on the top, bottom and sides with either fiberglass or styrofoam. The purpose for all of this is to maintain the slurry temp at 98 deg F, in what may sometimes be sub-freezing ambient temperatures. In my initial (unsuccessful) attempt, I did not make these efforts to monitor and control the slurry temp and I suspect the bacteria fell victim to low overnight temps. I have a few questions:
Would adding an inoculant (possibly more manure) to my existing slurry kick-start the gas production process?
Are bacterial septic tank additives generally methane producing or methane limiting?
My slurry consists of 45 gallons of water + 90 lbs of seperated solid manure, which I estimate to be a bit under 20% solid by mass. Is this an acceptable ratio for a single stage digester of this size?
Is the pH only a concern when preparing the slurry or must it be monitored throughout the process?
When using cattle manure, is the carbon to nitrogen ratio a concern?
Are there any inherent problems with the proposed design?
Thanks.
Would adding an inoculant (possibly more manure) to my existing slurry kick-start the gas production process?
Are bacterial septic tank additives generally methane producing or methane limiting?
My slurry consists of 45 gallons of water + 90 lbs of seperated solid manure, which I estimate to be a bit under 20% solid by mass. Is this an acceptable ratio for a single stage digester of this size?
Is the pH only a concern when preparing the slurry or must it be monitored throughout the process?
When using cattle manure, is the carbon to nitrogen ratio a concern?
Are there any inherent problems with the proposed design?
Thanks.
Hi Irvin,
The first thing I'd comment on is the electric blanket/voltage regulator idea. You also mentioned insulation and ambient temperature which may drop below freezing.
Of course these are all interrelated. Whether or not the electric blanket will be able to maintain the desired temperature under worst case conditions all depends on the design (worst case) ambient temperature, and how well you insulate it. You can use this design tool to determine what you need. (See instructions at bottom of page.)
Next, I'm not sure why you would use the thermocouple and datalogger -- unless it is just for your experimental interest. There are cheaper and easier ways to monitor temperature. And I would control the electric blanket with a line voltage thermostat instead of a voltage regulator. (I have never used an electric blanket for heat, so I'd be interested in hearing how it works for you.)
re kick-starting the process with inoculant, yes. If you browse through some of the other more recent discussions here in the forum, there is some info about it.
I'm not sure how the bacteria commonly sold for use in septic tanks would affect methanogenesis. I think they are probably rapid growing aerobic heterotrophs -- probably either wouldn't survive in anaerobic conditions, or would be acid-producers (generating 'food' for the methanogens). But I don't know how adding them would affect production of methane -- another interesting area for experimentation that I'd be interested in hearing about.
re slurry mixture, how are you going to operate your digester? batch feed? If so, try filling it with manure, and less water -- just enough to cover the solids.
yes, pH is always a concern. methanogens are pretty finicky, fragile little guys, easy to kill if it gets too acid.
re C/N ratio, yes it is always a factor. But cattle manure should be ok. (My sources list it at about 18:1).
re your proposed design, I have more questions than answers. The devil is in the details. How will you fill it? Mix it? Empty it? What will you do with the gas?
The first thing I'd comment on is the electric blanket/voltage regulator idea. You also mentioned insulation and ambient temperature which may drop below freezing.
Of course these are all interrelated. Whether or not the electric blanket will be able to maintain the desired temperature under worst case conditions all depends on the design (worst case) ambient temperature, and how well you insulate it. You can use this design tool to determine what you need. (See instructions at bottom of page.)
Next, I'm not sure why you would use the thermocouple and datalogger -- unless it is just for your experimental interest. There are cheaper and easier ways to monitor temperature. And I would control the electric blanket with a line voltage thermostat instead of a voltage regulator. (I have never used an electric blanket for heat, so I'd be interested in hearing how it works for you.)
re kick-starting the process with inoculant, yes. If you browse through some of the other more recent discussions here in the forum, there is some info about it.
I'm not sure how the bacteria commonly sold for use in septic tanks would affect methanogenesis. I think they are probably rapid growing aerobic heterotrophs -- probably either wouldn't survive in anaerobic conditions, or would be acid-producers (generating 'food' for the methanogens). But I don't know how adding them would affect production of methane -- another interesting area for experimentation that I'd be interested in hearing about.
re slurry mixture, how are you going to operate your digester? batch feed? If so, try filling it with manure, and less water -- just enough to cover the solids.
yes, pH is always a concern. methanogens are pretty finicky, fragile little guys, easy to kill if it gets too acid.
re C/N ratio, yes it is always a factor. But cattle manure should be ok. (My sources list it at about 18:1).
re your proposed design, I have more questions than answers. The devil is in the details. How will you fill it? Mix it? Empty it? What will you do with the gas?
The thermocouple and datalogger allow me to keep track of the temp while I?m away. A line voltage thermostat would be nice but I?ve been able to keep the temperature fairly constant so far. This is a single batch digester (perhaps later I will try batch feed). The slurry is prepared by adding 10 lbs of manure to 5 gallons of water and stirring with a boat paddle until the entire 90 lbs of manure is well mixed. The gas initially bleeds out through a bubbler. After some period when anaerobic conditions are reached and methanogenesis begins, the valve to the bubbler is closed and the valve to the collector is opened. I am using a large mylar balloon as the collector and my immediate goal is only to produce a flame using biogas. The ultimate goal is to operate a 1000 watt generator, though I?m not sure what I?ll use to collect the amount of biogas needed to operate the generator for 30 minutes, or how I?ll maintain a constant gas flow into the generator. I might regulate the flow rate by putting a restrictor nozzle at the output of the gas bag and a weight on top of the bag to maintain a constant pressure. I have a question concerning pH monitoring.
Isn?t it a requirement that an anaerobic digester remain sealed? I can use a pH meter with probes to monitor the pH but if it becomes necessary to balance it, I would have to open the digester temporarily. What effect would this have?
Isn?t it a requirement that an anaerobic digester remain sealed? I can use a pH meter with probes to monitor the pH but if it becomes necessary to balance it, I would have to open the digester temporarily. What effect would this have?
re pH monitoring & maintenance...
I'm not sure what you mean by "open the digester". Do you mean taking the lid off? Or just opening a valve on an access port? If the latter, it shouldn't be a problem. Just make sure the pipe extends down into the liquid, so that no gas escapes when you open it.
How will you stir the contents while it's digesting?
I'm not sure what you mean by "open the digester". Do you mean taking the lid off? Or just opening a valve on an access port? If the latter, it shouldn't be a problem. Just make sure the pipe extends down into the liquid, so that no gas escapes when you open it.
How will you stir the contents while it's digesting?