Thursday, February 6, 2014

Biogas digester in Vietnam

4 in 1 biogas digester - piggery + toilet + greenhouse + digester

For colder regions, the “four-in-one” model with a greenhouse is recommended so the digester can “live through the winter.”

More info: http://www.ecotippingpoints.org/our-stories/indepth/china-biogas.html 
 

3 in 1 biogas digester - pigsty + latrine + digester

A slightly more elaborate model is the “three-in-one,” which includes a pigsty and latrine connected directly to the digester tank. In warmer regions, the fertilizer can be applied on an orchard in the “pig-biogas-fruit” model.

 More info: http://www.ecotippingpoints.org/our-stories/indepth/china-biogas.html 

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Biogas digester news

 

4 meter cubic fixed dome biogas digester plant

5 meter cubic floating dome biogas digester plant

Biogas digester videos



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Biogas digester photos



Wednesday, February 5, 2014

Biogas digester resources

Resources for biogas digester / methane generator:

  1. http://takamotobiogas.com/biogas/payg-biogas/
  2. http://textbook.s-anand.net/ncert/class-xii/biology/10-microbes-in-human-welfare
  3. http://biogas-technology.blogspot.com/2012/12/biogas-plant-photos.html
  4. http://bio-gas-plant.blogspot.com/2011/09/biogas-plant-construction-fixed-dome.html
  5. http://paksc.org/pk/biogas-plant-design/1144-design-construction-and-installation-of-biogas-plant
  6. http://biogas-technology.blogspot.com/2012/12/biogas-plant-wallpapers.html
  7. http://biogas-technology.blogspot.com/2013/06/homemade-diy-biogas-plant-digester-step.html
  8. http://biogas-technology.blogspot.com/2013/10/homemade-medium-size-biogas-plant-for.html
  9. http://www.homepower.com/articles/home-efficiency/equipment-products/home-cookin-homemade-biogas/page/0/1
  10. http://hestiahomebiogas.com/gallery-2/
  11. http://www.ecotippingpoints.org/our-stories/indepth/china-biogas.html
  12. http://takamotobiogas.com/biogas/how-biogas-works/
  13. http://paksc.org/pk/biogas-plant-design/item/1014-vacvina-biogas-model-construction-video.html
  14. http://www.ceres.org.au/greentech/Projects/Energy/howitworks.html
  15. http://www.habmigern2003.info/biogas/methane-digester.html 

 

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Biogas digester types

The two main digester types of digesters are the continuous and the batch.

Continuous digesters have a constant throughput of material, and

Batch digesters extract the gas from a contained batch of material, which is then emptied and a new batch added.

Want to construct your own biogas biodigester? Click here!
 

biogas digester system or components

The biogas digester is the system component where the animal, human and other organic wastes are introduced, usually as a slurry with water, to break down anaerobically.

A storage container is used to hold the gas produced, from which it is piped for burning as a fuel. Variable volume storage (i.e. flexible bag or floating drum) is easier, cheaper and more energy efficient than high pressure cylinders, regulators or compressors.

When the digester is emptied, the spent effluent is dried for later reuse as a fertilizer.

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Microbes in biogas digester

Biogas is a mixture of gases (containing predominantly methane) produced by the microbial activity and which may be used as fuel. You have learnt that microbes produce different types of gaseous end-products during growth and metabolism. The type of the gas produced depends upon the microbes and the organic substrates they utilise. In the examples cited in relation to fermentation of dough, cheese making and production of beverages, the main gas produced was CO2.

However, certain bacteria,which grow anaerobically on cellulosic material, produce large amount of methane along with CO2 and H2. These bacteria are collectively called methanogens, and one such common bacterium is Methanobacterium. These bacteria are commonly found in the anaerobic sludge during sewage treatment. These bacteria are also present in the rumen (a part of stomach) of cattle. A lot of cellulosic material present in the food of cattle is also present in the rumen. In rumen, these bacteria help in the breakdown of cellulose and play an important role in the nutrition of cattle. Do you think we, human beings, are able to digest the celluose present in our foods? Thus, the excreta (dung) of cattle, commonly called gobar, is rich in these bacteria. Dung can be used for generation of biogas, commonly called gobar gas.

The biogas plant consists of a concrete tank (10-15 feet deep) in which bio-wastes are collected and a slurry of dung is fed. A floating cover is placed over the slurry, which keeps on rising as the gas is produced in the tank due to the microbial activity. The biogas plant has an outlet, which is connected to a pipe to supply biogas to nearby houses. The spent slurry is removed through another outlet and may be used as fertiliser. Cattle dung is available in large uantities in rural areas where cattle are used for a variety of purposes. So biogas plants are more after build in rural areas. The biogas thus produced is used for cooking and lighting. 
 

Biogas digester energy

Each kilogram of biodegradable material yields around 0.4 m³ (400l) of gas.

So in practice, in small scale waste to energy systems, if you have some livestock, plus kitchen and human waste you can meet your cooking and lighting needs easily:

• 2 gas rings for a couple of hours a day will use between 1-2 m³

• Gas lights need around 0.1 m3 (100l) per hour.
 
Driving any kind of engine (eg a generator or a pump) is, however, way beyond the domestic-scale. (Better to go for algal biodiesel!)