Preston et al did all the development work on the polyethylene bag digester system and put it on the map.
http://www.fao.org/WAICENT/FAOINFO/AGRICULT/AGA/AGAP/FRG/Recycle/biodi g/manual.htm Biodigester installation manual Lylian Rodriguez and T R Preston University of Tropical Agriculture Foundation Finca Ecologica, University of Agriculture and Forestry, Thu Duc, Ho Chi Minh City, Vietnam http://www.ias.unu.edu/proceedings/icibs/ibs/info/ecuador/install-polydig.htm HOW TO INSTALL A POLYETHYLENE BIOGAS PLANT By Francisco X. Aguilar Agronomic Engineer MSc Sustainable Agricultural Systems The Royal Agricultural College Cirencester This is an excellent resource, from the German Appropriate Technology and Ecoefficiency Programme (GATE): http://www5.gtz.de/gate/techinfo/biogas/toc.html AT Information - Biogas Digest: Index Biogas plants constitute a widely disseminated branch of technology that came into use more than 30 years ago in developing countries. There are hundreds of thousands of simple biogas plants now in operation, and each one of them helps to improve the living conditions of people in rural areas. Biogas systems are an efficient way of dealing with organic waste, dung and crop residues while making optimal use of their energetic as well as nutrient content. In addition to generating renewable energy, biogas systems help to stimulate ecologically beneficial closed-loop systems in the agricultural sector while improving soil quality and promoting progress in animal husbandry and farming. While the main focus is on biogas systems of simple design, the technology is nonetheless complex enough to warrant close attention to its proper application, planning and construction. Only a well-planned, carefully constructed and properly functioning biogas system will fulfill its purpose of improving living conditions in rural areas. You will find useful and detailed information about all aspects of biogas plant design and maintainance, biogas appliances, social, political, economic and ecological framework conditions, planning and dissemination of biogas systems and last but not least country- and project-specific information. HTH Best Keith >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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