Difference between revisions of "How to Build the Vacvina Biogas Digestor"

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This model was first introduced from Columbia to Vietnam in 1994 by doctor Reg Preston, Rector of the University of Tropical Agriculture. <br>
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==Introduction==
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Biogas obtained from the treatement of animal waste in order to produce energy can be very harmful for the environment if the exeeding  biogas is released in in the atmosphere. In fact the GWP (Global Warming Potential - a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming) of CH4 (Methane) is 21 times the one of CO2.
  
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The system consists of a long digestion bag or fermentation bag (Fig.2) and a gas reservoir bag. Both are made of two or three layers of polyethylene tubing, 21c thick and 1m in diameter. <br>
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VACVINA biogas is a technology introduced in 1998 by The Center for Community Research and Development (CCRD) belonging to the Vietnam Gardening Association. VACVINA stands for VAC ("Vuon"-Garden, "Ao"-Pond, "Chuong"-Stable) of VietNam. The VACVINA biogas model is developed based on two existing technologies in Vietnam: (1) The fixed dome model came from China and India, and (2)The plastic digestion bag model was firstly introduced from Columbia to Vietnam in 1994 by doctor Reg Preston, Rector of the University of Tropical Agriculture. The VACVINA model is an innovative technology chosen by EASE Vietnam Programme[http://ease-vn.org.vn] to promote in a commercialization approach from 2006.<br>
  
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The length of the main bag determines the total digestion chamber volume (a 10 m bag results in a 7 cubic meter digestion chamber). The digestion bag is half buried in a trench and is connected at one end to a small mixing and collection tank and at the other end to a slurry holding pit. The gas reservoir has a capacity of 1,8 m3 and is usually suspended either in the kitchen or the stable (Fig. 3).<br>
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==System==
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The system consists of a digestion tank (septic tank), nylon reservoir bag and inlet, outlet systems. The digestion tank is a flat-top rectangular underground digestion chamber. The external plastic gas reservoir is made of two to three layers of nylon bag. An ingenious system of inlet siphon allows the new material to be dropped into the surface of the fermenting liquid thus breaking any accumulated scum. The small outlet tank collect liquid waste from the digestion tank through a plastic tube.<br>
  
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As organic material is fed into the digestion bag, it slowly travels down the length of the tube while the fermentation process occurs and is then expelled at the other end as digested slurry. The biogas produced accumulates in the main bag and, through gravity as well as pressure, finds its way to the gas reservoirs. Thus biogas is stored partly in the digestion bag and partly in the gas reservoir. Users can easily judge the quantity of gas available by the level of inflation of the bags. <br>
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===The digestion tank:===
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The main digester is an underground rectangular tank made of bricks and mortar. However, the shape of the tank can be adjusted to the specific configuration and constraints of the family compound while retaining a sufficient volume. One of the great advantages of this model is that the concrete flat top of the digester can provide a clean and dry floor for the pigsty or stable. It also can be build as an integration of the toilet and the septic tank under the stable. <br>
  
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Plastic bag digesters are inexpensive, easy to install and operate and scum formation can be controlled easily by gently slapping the scum to make it sink to the bottom. On the other hand, the polyethylene bags are somewhat fragile they can be perforated or torn and their life expectancy is but 3-5 years. They must be protected from wandering animals and also from sunlight as UV rays will degrade the plastic. In addition, the model requires a large area of 10-15m2 near the animal stable.  
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===The inlet system:===
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The hole for the inlet pipe is 30cm diameter and starts from the top of the wall. It can be located on any wall of the digestion tank during the construction time. A siphon connect the mixing tank and the main digestion tank. The standard dimensions of the mixing tank are 0.2 m x 0.4 m with a depth of 0.3 m. This system prevents the formation of a scum layer by regularly wetting and mixing the surface with fresh input. (See picture 1)<br>
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[[Image:Siphon_VACVINA.jpg]]
  
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This is a problem for many households in the Red River Delta where household compound is not large enough to allow its installation. <br>
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===The outlet system:===
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The outlet pipe's length and position are important because they determine the level of slurry in the digester. The PVC pipe is 110 – 150 mm in diameter with a length equal to one third of the slurry height (80 – 100 cm). It must be positioned at a 45° angle, making sure it extends under the surface of the slurry the equivalent of one third of the height of the slurry. (See picture 2)<br>
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[[Image:Outlet_VACVINA.jpg]]
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===The reservoir bag:===
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The reservoir is made of two layers of 20-24μc polyethylene tubing, 100cm in diameter and 2.5 m in length capable of storing 1.8m3 of gas. One end of bag is tightly tied while the other is connected to the pipeline with φ21 plastic tubing.(See picture 3)<br>
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[[Image:Nylon_VACVINA.jpg]]
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In order to ensure a rapid production of gas for cooking, it is advisable to prepare 700-800 kg of fresh dung (to be collected and stored in a 7-day period) as initial input. The ratio to mix dung and water is 1/5. After 5-10 days, gas will appear and inflate in the reservoir bag.  
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<br>
  
 
[[Image:VACVINA Biogas model.jpg]]
 
[[Image:VACVINA Biogas model.jpg]]
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==Video link==
 
==Video link==
 
Video clip: http://www.youtube.com/watch?v=ne3RdAmPIbw
 
Video clip: http://www.youtube.com/watch?v=ne3RdAmPIbw
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==Contact==
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[[Image:Logo_RCEE.jpg]] Research Center for Energy & Environment (RCEE)<br>
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Address: No. 33, Trung Yen 9 Road, Yen Hoa ward, Cau Giay district, Hanoi, Vietnam
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Tel: (+84-4) 6291 2407, Fax: (+84-04) 3786 8593, email: rcee.ease@gmail.com <br>
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Website : [http://ease-vn.org.vn http://ease-vn.org.vn] / [http://rcee.org.vn http://rcee.org.vn]
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==Related Articles==
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# [[Biomass (Technical Brief)]]
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# [[Biomass and Liquid Biofuel (Technical Brief)]]
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# [[How to Build the ARTI Compact Biogas Digestor]]
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# [[How to Build the Vacvina Biogas Digestor]]
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# [[How to Use Biogas]]
  
 
==Categories==
 
==Categories==
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[[Category:Agriculture]] [[Category:Biogas]] [[Category:Community]] [[Category:Ideas]] [[Category:Small Business]]
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[[Category:Difficult]] 
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[[Category:Global Technology]]
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[[Category:Between 50 and 200 US$]] 
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[[Category:One Person and more]]
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[[Category:Household]] [[Category:Village]][[Category:Neighbourhood]]
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[[Category:Application]] [[Category:Principles]]
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[[Category:Howtopedia requested drawings]] [[Category:Howtopedia requested images]]
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[[Category:Practical Action Spanish]] [[Category:Requested translation to Spanish]] [[Category:Requested translation to French]]

Latest revision as of 15:42, 10 December 2009

Introduction

Biogas obtained from the treatement of animal waste in order to produce energy can be very harmful for the environment if the exeeding biogas is released in in the atmosphere. In fact the GWP (Global Warming Potential - a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming) of CH4 (Methane) is 21 times the one of CO2.

VACVINA biogas is a technology introduced in 1998 by The Center for Community Research and Development (CCRD) belonging to the Vietnam Gardening Association. VACVINA stands for VAC ("Vuon"-Garden, "Ao"-Pond, "Chuong"-Stable) of VietNam. The VACVINA biogas model is developed based on two existing technologies in Vietnam: (1) The fixed dome model came from China and India, and (2)The plastic digestion bag model was firstly introduced from Columbia to Vietnam in 1994 by doctor Reg Preston, Rector of the University of Tropical Agriculture. The VACVINA model is an innovative technology chosen by EASE Vietnam Programme[1] to promote in a commercialization approach from 2006.

System

The system consists of a digestion tank (septic tank), nylon reservoir bag and inlet, outlet systems. The digestion tank is a flat-top rectangular underground digestion chamber. The external plastic gas reservoir is made of two to three layers of nylon bag. An ingenious system of inlet siphon allows the new material to be dropped into the surface of the fermenting liquid thus breaking any accumulated scum. The small outlet tank collect liquid waste from the digestion tank through a plastic tube.

The digestion tank:

The main digester is an underground rectangular tank made of bricks and mortar. However, the shape of the tank can be adjusted to the specific configuration and constraints of the family compound while retaining a sufficient volume. One of the great advantages of this model is that the concrete flat top of the digester can provide a clean and dry floor for the pigsty or stable. It also can be build as an integration of the toilet and the septic tank under the stable.

The inlet system:

The hole for the inlet pipe is 30cm diameter and starts from the top of the wall. It can be located on any wall of the digestion tank during the construction time. A siphon connect the mixing tank and the main digestion tank. The standard dimensions of the mixing tank are 0.2 m x 0.4 m with a depth of 0.3 m. This system prevents the formation of a scum layer by regularly wetting and mixing the surface with fresh input. (See picture 1)
Siphon VACVINA.jpg

The outlet system:

The outlet pipe's length and position are important because they determine the level of slurry in the digester. The PVC pipe is 110 – 150 mm in diameter with a length equal to one third of the slurry height (80 – 100 cm). It must be positioned at a 45° angle, making sure it extends under the surface of the slurry the equivalent of one third of the height of the slurry. (See picture 2)
Outlet VACVINA.jpg

The reservoir bag:

The reservoir is made of two layers of 20-24μc polyethylene tubing, 100cm in diameter and 2.5 m in length capable of storing 1.8m3 of gas. One end of bag is tightly tied while the other is connected to the pipeline with φ21 plastic tubing.(See picture 3)
Nylon VACVINA.jpg

In order to ensure a rapid production of gas for cooking, it is advisable to prepare 700-800 kg of fresh dung (to be collected and stored in a 7-day period) as initial input. The ratio to mix dung and water is 1/5. After 5-10 days, gas will appear and inflate in the reservoir bag.

VACVINA Biogas model.jpg

Video link

Video clip: http://www.youtube.com/watch?v=ne3RdAmPIbw

Contact

Logo RCEE.jpg Research Center for Energy & Environment (RCEE)
Address: No. 33, Trung Yen 9 Road, Yen Hoa ward, Cau Giay district, Hanoi, Vietnam Tel: (+84-4) 6291 2407, Fax: (+84-04) 3786 8593, email: rcee.ease@gmail.com
Website : http://ease-vn.org.vn / http://rcee.org.vn

Related Articles

  1. Biomass (Technical Brief)
  2. Biomass and Liquid Biofuel (Technical Brief)
  3. How to Build the ARTI Compact Biogas Digestor
  4. How to Build the Vacvina Biogas Digestor
  5. How to Use Biogas

Categories

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