Doesn't anyone have an answer for Kim? Keith
>Okay, I have read what is available in the journeytoforever library on >biogas. My question: Has anyone on this list ever built a biogas >digester? I have no problem finding the material to feed one, but I will >admit to be less than confident with the instructions given. > >Bright Blessings, >Kim > >At 12:47 PM 4/8/2004, you wrote: > >Keith, > > > >I am pleased to see you joining in on this discussion because I think > >this topic is right down you alley. > > > >I would like to suggest that the biogas energy be recovered in a small, > >slow speed, long life diesel generator such as a "Lister Engine" rather > >than a steam engine. Diesel engines deliver about three times the KWHr > >per /BTU than steam engines due to higher operating efficiency. Biogas > >needs to be combusted in a diesel engine rather than a gasoline engine > >because the diesel has a higher compression ratio (biogas needs about 12 - > >14:1 compression ratio for best combustion). The waste heat from the > >water jacket on the Lister engine is more than sufficient to maintain > >thermophilic temperatures of the biogas reactor and you still have the > >heat from the engine exhaust for other higher energy uses as well. About > >25% of the biogas energy will be recovered as electricity and the > >remainder as heat energy at various temperatures. > > > >It is important to look at the monthly and seasonal energy consumption > >profile to determine how much energy should be recovered in each form > >(summer vs winter usages). Do you need 5 KWHr per day as electricity and > >50,000 BTU's as space heat and 6,000 BTU's for cooking gas and 30,000 > >BTU's for hot water, etc. Then you can lay out the size of each the > >components necessary to convert the biogas into the appropriate form of > >energy. Perhaps some of the biogas will bypass the diesel engine and be > >fed directly into a water heater burner because your needs are for greater > >amounts of hot water for example. > > > >One of the nice features is that the biogas system produces energy fairly > >uniformly 24 hours per day. So with a small amount of batteries and > >insulated tanks, you can easily handle typical surges in demand >during the day. > > > >Of, course it also helps if you have a way to continuously supply the > >wastes needed to feed the biogas reactor. Having a herd of pigs, cows or > >horses helps alot. You might find yourself supply limited and need to > >import other wastes such as grass clippings or grain wastes or food > >wastes, etc to make up for a feedstock supply deficiency. > > > >One thing is certain - ALL of these efforts should be made to maximize the > >return of organic matter to soil as a mature soil amendment. Then the > >discussions about sustainability can begin. > > > >Art Krenzel > > > > > > ----- Original Message ----- > > From: Keith Addison > > To: biofuel@yahoogroups.com > > Sent: Thursday, April 08, 2004 10:01 AM > > Subject: Re: [biofuel] Rejoining list with a question > > > > > > Hi Kim > > > > Good to see you back. > > > > >Keith, I told you I would be back <grin> > > > > I thought it was going to be a year or two, glad you made it sooner. > > > > >Greetings, > > > > > >I was a member of this list for several years, but quit to have time to > > >learn other things. I hope all the regulars are doing well, >and I hope to > > >get to know all the new people. > > > > > >My husband and I own 20 acres in Texas and we are trying to >live and farm > > >sustainably. For now we are on the grid, but hope to change that one > > >day. We practise alternative building, such as paper adobe >and cordwood. > > > > > >The question: This months issue of Backwoods Home Magazine has an > > article, > > >by Rev. J.D. Hooker, on burning manure. It states that they >get 'somewhat > > >greater heating value than seasoned hardwood.' By using the ashes > > in the > > >garden, after several years of application have reach a rate >of 'more than > > >40% higher' than the garden with either commercial fertilizer or spread > > >manure. > > > > What was higher? Yields? You'd want other indicators than that. > > > > Spreading manure is generally not a good technique. (But letting the > > livestock do the spreading can be a very good technique.) > > > > >He did not compare it to composted manure, so much testing of his > > >'findings' still needs to be done. > > > > Yes. > > > > >If one can get both heat and fertilizer > > >out of manure, > > > > You need to distinguish between "fertilizer" and "nutrients". > > > > >then one could use the manure to fire a wood fuel steam > > >generator and be totally sustainable. > > > > > >The author states he got the idea from a friend from Thailand. >There are > > >no flaws mentioned in the article, and the article is only >about heat and > > >the garden. The steam generator is my idea. This seems to easy and too > > >perfect, what is the flaw that I have missed? > > > > As Art said, no organic matter. Ash just leaves the minerals and will > > provide nutrients but not soil fertility - it could even harm soil > > fertility. The effect of such treatments depends very much on what > > condition the soil is in to start with. Too much ash on low-O/M > > acidic soils will make matters worse, not better (eg hardpan), and > > not very much might be too much. There's no substitute for humus > > maintenance, and ash can't do that. > > > > Howard developed the Indore compost process in India partly to > > address a shortage of manure caused by its use for cooking fires. > > Composting extended the manure supplies by five times, so there would > > be enough for both the fires and the soil. Weight for weight, compost > > turned out to be much more effective than pure manure, so the effect > > was better than five times. It can be extended even further by adding > > compost made without any manure, from water hyacinth for instance. > > Note "adding" though - for long-term fertility maintenance at least > > some organic matter has to pass through an animal gut on its way back > > to the soil, preferably via more than one species of animal. It's > > also a much better idea to add any ash to the compost rather than to > > the soil. > > > > Art's suggestion of anaerobic digestion for methane production for > > heating is one way, but, as he said, the sludge must then be > > aerobically composted (hot) before applying it to the soil. Generally > > that requires added "browns" (dry, carbonaceous stuff) to correct the > > moisture content and allow sufficient aeration; easiest to use it as > > one component in an ongoing aerobic composting operation. Aerobic > > composting also produces heat of course, which is usually wasted. We > > always have at least one compost pile here that's at 70-75 deg C > > (160-170 deg F). One way to use the heat is via a heat exchanger to > > maintain optimum temperatures in the anaerobic digesters. We've done > > some preliminary work on harnessing composting heat, we'll take it > > further as soon as we have the chance. There's the makings of a good > > integrated system in this, fits in well with rational use of 20 acres > > (or less). > > > > Best > > > > Keith > > > > > > > > >Bright Blessings, > > >Kim > > > > > >Keith, I told you I would be back <grin> Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuels list archives: http://infoarchive.net/sgroup/biofuel/ Please do NOT send Unsubscribe messages to the list address. To unsubscribe, send an email to: [EMAIL PROTECTED] Yahoo! 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