[Digestion] Hydrogen sulfide - Biogas

[Amy and Jim Rankin]

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  I am new on this list serve, I have a question regarding the danger of H2S, I have been reading about this gas and its dangers, I am developing a project in a rural community in Mexico, I'm helping to develop 5 tubular PE- biodigesters, I am still working on solve the Hydrogen sulfide issue, I don't want to put people's life on risk; so, any help on the manage or elimination  of Hydrogen sulfide on Bio-gas systems will be helpful, 
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  If you control the biogas appropriately, you will mitigate the risk of the hydrogen sulfide.  

  However, there are ways to scrub the biogas on the way out of the digester (exposure to rusty steel wool, lathe turnings,shredded sheetmetal etc) or it can be collected in the digester by admitting a small amount of oxygen to the digester which causes the Sulfur to collect as less dangerous forms within the digester, eventually passing out with the effluent.  Sulfur has become an important plant nutrient in these days of decreasing powerplant sulfur emissions here in the USA and elsewhere in the developed world.  The amount of oxygen would have to be regulated to stay below the level where the mixture becomes flammable.  Not quite so simple a technology as the poly tube digester you are working with.  

  As part of your training for the operators of the digesters, you must emphasize that the digester is a very dangerous place.  Not that a poly tube digester is somewhere a person might ever go.  This is not only because of hydrogen sulfide, but also because of the carbon dioxide and methane.  Every year or two, someone (and sometimes several "rescuers" as well)  is killed when they enter a pit or other place where the biogas/manure gas has accumulated or is being liberated rapidly enough to reach dangerous concentrations.

  Jim

  James R Rankin, DVM
  Cedarcrest Farms, Inc
  Faunsdale, Alabama USA
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