<div>Dear Kyle,</div>
<div>I apologise for all the unwanted advice contained in this message, but I feel that people working on biogas generally ignore the biological aspect of biogas technology and work on it only from the engineering point of view. The consortium of biogas producing microbes lives in the guts of animals and therefore they eat what the animals eat. This statement is supported by my own observation that substances having a high in vitro dry matter digestibility also give high biogas yield. In the case of ruminent herbivores, the excreta consist mainly of lignin (from the midribs and veins of leaves), a load of micro-organisms, and mucus which lubricates the dung. Thus only the microbes and the mucus represent the digestible matter in dung. Even freshly fallen dry leaves from avenue trees yield more biogas than dung. Therefore, we advocate the opinion that cattle dung should be used only as an inoculum but not as feedstock for producing biogas. Dung can be dried into dung cakes and burned. Forty kg dung, which you are using daily in your biogas plants would yield about US$1 in India if it were converted into dung cakes and sold as fuel. 1 kg dung cakes would yield about 3600 kcal energy if burned. This represents a higher calorific value than the mineral coal that is being used in India by our thermal electricity generating plants. If converted into biogas, 1kg (dry weight) dung would yield only 600 kcal. </div>
<div> <br>Yours</div>
<div>A.D.Karve<br></div>
<div class="gmail_quote">On Tue, Nov 13, 2012 at 1:14 PM, Takamoto <span dir="ltr"><<a href="mailto:kyle@takamotobiogas.com" target="_blank">kyle@takamotobiogas.com</a>></span> wrote:<br>
<blockquote style="BORDER-LEFT:#ccc 1px solid;MARGIN:0px 0px 0px 0.8ex;PADDING-LEFT:1ex" class="gmail_quote">
<div style="WORD-WRAP:break-word">Dear Biogas List,
<div><br></div>
<div>I have been testing a plastic (LLDPE) floating drum digester with cow dung and found that the biogas production was lower than expected (pH 7, 19˚C) at around 0.5 cubic meters of biogas per day at 67% methane. The reactor volume is 3.2 cubic meters. I discovered that our dung supplier had recently used the antibiotic Tetracycline for a few of his cows so there is a chance of contamination, though at this point, I feel like the antibiotic concentration would be very low and should not affect gas production. Does anyone have experience with the effect of antibiotics? Also, what gas production should I expect from a 3.2 cubic meter reactor that I add 40 kg of cow dung to per day (plus 40 kg of water)? If I assume 15% TS and 80% of TS are VS then the Organic Loading Rate is around 1.5 kg -VS/m3/day and our specific methane yield is 0.07 m3 CH4/kg-VS and our digester efficiency is 0.1 m3 CH4/m3 reactor/day. Does this sound reasonable?</div>
<div><br></div>
<div>I have also been reviewing research articles on gas production from cow dung but the results vary widely and sometimes I am not sure if the reported results are accurate. Also, research papers often use CSTR (continuously stirred tank reactors?) at 37˚C which makes comparing their results to my results rather difficult. We are getting a new load of non-contaminated cow dung today to see if that makes a difference. I'll let you know.</div>
<div><br></div>
<div>I am sure this topic has been discussed before, so I am sorry if I have repeated the topic. I am newish to the forum so I haven't seen anything on this yet.</div>
<div><br></div>
<div>Thanks for your advice,</div>
<div><br>
<div><span style="TEXT-TRANSFORM:none;TEXT-INDENT:0px;BORDER-COLLAPSE:separate;FONT:medium Helvetica;WHITE-SPACE:normal;LETTER-SPACING:normal;WORD-SPACING:0px"><span style="TEXT-TRANSFORM:none;TEXT-INDENT:0px;BORDER-COLLAPSE:separate;FONT:medium Helvetica;WHITE-SPACE:normal;LETTER-SPACING:normal;WORD-SPACING:0px">
<div style="WORD-WRAP:break-word">Kyle<br>Managing Director<br>Schutter Energy Ltd.</div>
<div style="WORD-WRAP:break-word"><a href="http://www.takamotobiogas.com/" target="_blank">www.takamotobiogas.com</a><br><br><br></div></span></span></div><br></div></div><br>_______________________________________________<br>
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<br><br></blockquote></div><br><br clear="all"><br>-- <br>***<br>Dr. A.D. Karve<br>Trustee & Founder President, Appropriate Rural Technology Institute (ARTI)<br><br><br>