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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Dear Friends of BioGas<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I have received a complex reply from David House (Author of the Biogas Handbook) on the question of charcoal in the digester and have separated the relevant parts below for your perusal. It was mixed with a longer communication so it is paraphrased here and there. The point in presenting it to this list is that stovers should know not to change feed stocks willy-nilly and expect the gas unit not to notice. Charcoal might be used in an inoculation zone only meaning not nearly so much of it is required (i.e. you don’t have to fill up or coat the whole chamber). <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Crispin<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'>Paraphrased From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'> David [mailto:david@h4c.org] <br><b>Sent:</b> October-06-11 1:39 PM<br><br></span><span style='font-family:"Georgia","serif";color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal>The high production rate for the ARTI digester really about the rate of gas production times the amount of gas production per unit weight from highly labile, easily digested food wastes. It is topologically equivalent to a number of previous efforts, such as work done or reported by FAO in the mid-'80s, and work done as early as 1920 had shown such inputs would have the effect described. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I think it is quite probable that the proper addition of the right kind of charcoal to a digester will have a beneficial effect, although I doubt that in most cases the effect would be as dramatic as described. After all, the biology is likely to be rate-limited by steps that are unlikely to be impacted by the addition of charcoal. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I plan to put a mesh bag filled with a certain kind of charcoal near the inlet of the digester, and perhaps scattered in other places therein, if I can figure out a proper anchoring system. My primary purpose is to encourage immediate inoculation of the incoming material, and to insure that there is a large, robust and stable reservoir of slow-growing methanogens such that process stability is better assured (i.e. wash-out is far less likely).<br><br>However, I would suspect that the proper kind of charcoal-- that is, with the proper structure, with many open cells, a honeycomb-- would encourage colonization of a vigorous methanogenic biofilm, and provide greater surface area for reactions. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Further, it may well be that certain kinds of charcoal tend to selectively absorb (and/or perhaps adsorb) and present nutritive chemicals for utilization by the biota, or perhaps functionally neutralize toxic chemicals. It may even act, in effect, to further buffer the organic acids in the slurry. In sum, regardless of the mode or modes of action, I would not be surprised to find it has a beneficial effect-- although again under the proper circumstances, etc.<br><br>d.<o:p></o:p></p><div><p class=MsoNormal>-- <o:p></o:p></p><div><p class=MsoNormal><span style='font-size:13.0pt'>David William House</span><o:p></o:p></p><div><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:9.5pt'>"The Complete Biogas Handbook" </span><code><span style='font-size:10.0pt'><a href="www.completebiogas.com">www.completebiogas.com</a></span></code><span style='font-size:9.5pt'><br><em>Vahid Biogas</em>, an alternative energy consultancy </span><code><span style='font-size:10.0pt'><a href="www.vahidbiogas.com">www.vahidbiogas.com</a></span></code><span style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p class=MsoNormal>"Make no search for water. But find thirst,<br>And water from the very ground will burst." <o:p></o:p></p><div><p class=MsoNormal><span style='font-size:9.5pt'>(Rumi, a Persian mystic poet, quoted in <em>Delight of Hearts</em>, p. 77) <br><br><a href="http://bahai.us/">http://bahai.us/</a><o:p></o:p></span></p></div></div></div></div></div></body></html>