Difference between revisions of "Experience with Polyethylene Biogas Digester (PBD)"

From energypedia
***** (***** | *****)
***** (***** | *****)
m
 
(9 intermediate revisions by 4 users not shown)
Line 1: Line 1:
'''<span style="font-size: 14pt;">International experience with polyethylene tube digesters (PTD)</span>'''
 
  
&nbsp;
+
[[Portal:Biogas|►Back to Biogas Portal]]
  
'''Overview'''
+
= Overview<br/> =
  
<span>Polyethylene biogas digesters have been used in several countries since the 1990s. In some areas they have been abandoned after unsuccessful introduction but their usage has never stopped completely. Reports show that the lifespan of the plastic tubes is always a main issue. However, dependable </span><span>data about the lifespan and reliability of digester bags is rare.</span>  
+
[[Types of Biogas Digesters and Plants|Polyethylene biogas digesters]] have been used in several countries since the 1990s. In some areas they have been abandoned after unsuccessful introduction but their usage has never stopped completely. Reports show that the lifespan of the plastic tubes is always a main issue. However, dependable data about the lifespan and reliability of digester bags is rare.<br/>
  
<span>PTDs can only function properly if the farmers take good care of the digesters. This needs intensive training and raised responsibility amongst the farmers.&nbsp;</span><span>If they do, experiences show that most problems are easy to handle and can be fixed by farmers themselves.</span>
+
PTDs can only function properly if the farmers take good care of the digesters. This needs intensive training and raised responsibility amongst the farmers. If they do, experiences show that most problems are easy to handle and can be fixed by farmers themselves.
  
<br>  
+
<br/>
  
<span>Below some information is summarized from GIZ projects and from the internet regarding the experiences with plastic tube digesters in different countries.</span>
+
Below some information mainly summarized from [http://www.giz.de/en/html/index.html GIZ] projects and from the internet regarding the experiences with plastic tube digesters in different countries.
  
== Bolivia  ==
+
<br/>
  
See what GIZ&nbsp;Endev is doing in Bolivia: [[Low-Cost Polyethylene Tube Digesters in Bolivia|click here]]<br>  
+
= International Experience with Polyethylene Tube Digesters<br/> =
  
<br>  
+
== Bolivia<br/> ==
  
== ''Honduras''  ==
+
► See what [[Energising Development (EnDev)|GIZ EnEev]] is doing in [[Bolivia Energy Situation|Bolivia]]: [[Low-Cost Polyethylene Tube Digesters in Bolivia|Low-Cost Polyethylene Tube Digesters in Bolivia]]<br/>
  
<span>In Honduras, the distribution of polyethylene plastic tube
+
<br/>
digesters faces several problems: They must be purchased in large
 
quantities. Need of a third party to act as a distributor to farmers.</span> Flooding for digesters laid in trench
 
  
''<span>(Emerging Biodigester Technology in Honduras:</span>'' Biophysical Process and Operation ''<span>by N. Stuart Green; Montana</span>'' Tech of the University of Montana, 1999)<br>  
+
== Honduras<br/> ==
  
<br>  
+
In [[Honduras Energy Situation|Honduras]], the distribution of polyethylene plastic tube digesters faces several problems: They must be purchased in large quantities. Need of a third party to act as a distributor to farmers. Flooding for digesters laid in trench<br/>
  
== ''Kenya''  ==
+
► [http://www.sswm.info/sites/default/files/reference_attachments/GREEN 2005 Emerging Biodigester Technology in Honduras.pdf Emerging Biodigester Technology in Honduras: Biophysical Process and Operation, N. Stuart Green; Montana Tech of the University of Montana, 1999)]<br/>
  
<span>After a false start in promoting this energy source in Kenya
+
<br/>
in the mid 1990s, it was successfully reintroduced by KARI-Embu in
 
2005. According to Erastus Kiruiro from KARI-Embu there are around 300
 
tubular digesters in use, mostly in Central Kenya but also around
 
Nairobi</span>  
 
  
''<span>(The Organic Farmer, The Magazine for</span>'' sustainable agriculture in Kenya, Nr. 45 February 2009)
+
== Kenya<br/> ==
  
&nbsp;
+
After a false start in promoting this energy source in [[Kenya Energy Situation|Kenya]] in the mid 1990s, it was successfully reintroduced by KARI-Embu in 2005. According to Erastus Kiruiro from KARI-Embu there are around 300 tubular digesters in use, mostly in Central Kenya but also around Nairobi.
  
''Based ''<span>on'' Promoting Biogas Systems in Kenya,&nbsp;'' </span>  
+
► [http://www.infonet-biovision.org/res/res/files/2133.feb2009.pdf The Organic Farmer, The Magazine for sustainable agriculture in Kenya, Nr. 45 February 2009]<br/>
  
<span>“Pioneer Technologies” (a Kenyan plastic company) has built 200 plants since 2006. </span>They improved the plastic tubes to be better sun and pressure resistant.
+
► [[Plastic Tube Digesters in Kenya|Plastic Tube Digesters in Kenya]]
  
It has not been a successful story yet due to:
+
<br/>
  
<span>-<span> T</span></span>here is no reliable back-up support.
+
Based on Promoting Biogas Systems in Kenya, “Pioneer Technologies” (a Kenyan plastic company) has built 200 plants since 2006. They improved the plastic tubes to be better sun and pressure resistant.<br/>
  
<span>-<span> </span></span><span>The digester seems to
+
<u>It has not been a successful story yet due to:</u><br/>
suffer from effects of variable temperature, and there is a possibility
+
*There is no reliable back-up support.
that the heat catalyses some reactions that produce other volatile
+
*The digester seems to suffer from effects of variable temperature, and there is a possibility that the heat catalyses some reactions that produce other volatile gases as well as methane.
gases as well as methane. </span>
 
  
&nbsp;
+
<br/>
  
<span>It is still a promising approach which is strongly driven
+
It is still a promising approach which is strongly driven by KARI. Currently there are many problems and referring to the feasibility study mentioned above 4 of 5 visited plants had some technical problems but most of them could have been solved easily.
by KARI. Currently there are many problems and referring to the
 
feasibility study mentioned above 4 of 5 visited plants had some
 
technical problems but most of them could have been solved easily.&nbsp;</span>
 
  
&nbsp;
+
<br/>
  
<span>“Development of the plastic tubular technology was initiated in August 2006. </span>  
+
Development of the plastic tubular technology was initiated in August 2006.<br/>
  
<span>The Plastic Tubular bio-digesters are designed for
+
The Plastic Tubular bio-digesters are designed for households with two to three animals although bigger ones have been installed. Capacity of the former is about 8-9 m3, with a gas holding chamber of 1-3 m3. A larger one that doubles this size has already been installed. The smaller Plastic Tubular Bio-digesters can give gas for six hours using one burner. Methane production is initially dependent on temperatures.
households with two to three animals although bigger ones have been
 
installed. Capacity of the former is about 8-9 m3, with a gas holding
 
chamber of 1-3 m3. A larger one that doubles this size has already been
 
installed. The smaller Plastic Tubular Bio-digesters can give gas for
 
six hours using one burner. Methane production is initially dependent
 
on temperatures. </span>
 
  
<span>Currently, Pioneer Technologies Ltd receives support from
+
Currently, Pioneer Technologies Ltd receives support from Land O’lakes and has entered into research collaboration with '''Jomo Kenyatta University of Agriculture and Technology (JKUAT)'''. Land O’Lakes gives financial support to the company in the production of biogas digesters. JKUAT is supposed to carry out investigations into issues arising from the use of the technology, with focus on how the technology can be improved, made more efficient etc. However, Pioneer Technologies Ltd gave the JKUAT one digester only, and so the university should acquire more digesters for any meaningful research to be done.<br/>
Land O’lakes and has entered into research collaboration with Jomo
 
Kenyatta University of Agriculture and Technology (JKUAT). Land O’Lakes
 
gives financial support to the company in the production of biogas
 
digesters. JKUAT is supposed to carry out investigations into issues
 
arising from the use of the technology, with focus on how the
 
technology can be improved, made more efficient etc. However, Pioneer
 
Technologies Ltd gave the JKUAT one digester only, and so the
 
university should acquire more digesters for any meaningful research to
 
be done. </span>  
 
  
&nbsp;
+
<br/>
  
<span>Pioneer Technologies Ltd has installed its bio-digester in
+
Pioneer Technologies Ltd has installed its bio-digester in various parts of the country including Nakuru, Meru, Kisumu, Kiambu, the coastal regions and the environs of Nairobi.<br/>
various parts of the country including Nakuru, Meru, Kisumu, Kiambu,
 
the coastal regions and the environs of Nairobi. The company has
 
capacity to install up to 3,000 units a year, but there are several
 
challenges including:</span>  
 
  
<span><span>-<span> </span></span></span><span>Most
+
<u>The company has capacity to install up to 3,000 units a year, but there are several challenges including:</u><br/>
households need some financial support to acquire the technology. At
+
*Most households need some financial support to acquire the technology. At cost, a Plastic Tubular Bio-digester goes for €322 only. However, this excludes the cost of transport – and so areas further away from Nairobi pay more money. In Meru, users paid up to €399. The cost of the technology, though coming down is prohibitive to most farmers, although when financial and economic analyses are made, especially taking into account opportunity costs vis a vis other energy technologies, it is very likely that bio-digesters will be economical and profitable.<br/>
cost, a Plastic Tubular Bio-digester goes for €322 only. However, this
+
*Training of technicians to support the technology is costly. Not all technicians trained will work on the digesters forever, some move on. There is need for the technology to be supported by some form of extension. Regular visits to households that have installed it are critical for longevity, good use and success of the technology.<br/>
excludes the cost of transport – and so areas further away from Nairobi
+
*<span>Many people are not aware of the existence of the technology, or if aware, do not have adequate information on how the technology actually works. This is a hindrance to large-scale adoption.</span><br/>
pay more money. In Meru, users paid up to €399. The cost of the
+
*At times, the technology fails because of unmet expectations. Even the Plastic Tubular Bio-digester has some technical problems – and these need to be sorted out. Without a reliable back-up support, small problems can lead potential users to shun away from it. But companies like Pioneer Technology Ltd cannot afford to have an extension/back-up support team because it already charges very low figures to install a unit.<br/>
technology, though coming down is prohibitive to most farmers, although
+
*Users need to be trained, and this is quite costly. This is where organisations like Land O’Lakes come in.<br/>
when financial and economic analyses are made, especially taking into
+
*There are many research needs on the technology<br/>
account opportunity costs vis a vis other energy technologies, it is
 
very likely that bio-digesters will be economical and profitable.</span>  
 
  
<span><span>-<span> </span></span></span><span>Training of
+
<br/>
technicians to support the technology is costly. Not all technicians
 
trained will work on the digesters forever, some move on. There is need
 
for the technology to be supported by some form of extension. Regular
 
visits to households that have installed it are critical for longevity,
 
good use and success of the technology. </span>  
 
  
<span><span>-<span> </span></span></span><span>Many people
+
Pioneer Technologies Ltd has trained 7 technicians to support the technology and at least 300 or so units have been installed country wide and despite small problems, all are now working.<br/>
are not aware of the existence of the technology, or if aware, do not
 
have adequate information on how the technology actually works. This is
 
a hindrance to large-scale adoption. </span>  
 
  
<span><span>-<span> </span></span></span><span>At times,
+
<br/>
the technology fails because of unmet expectations. Even the Plastic
 
Tubular Bio-digester has some technical problems – and these need to be
 
sorted out. Without a reliable back-up support, small problems can lead
 
potential users to shun away from it. But companies like Pioneer
 
Technology Ltd cannot afford to have an extension/back-up support team
 
because it already charges very low figures to install a unit. </span>  
 
  
<span><span>-<span> </span></span></span><span>Users need to be trained, and this is quite costly. This is where organisations like Land O’Lakes come in. </span>
+
[[File:Pioneer Biogas Technologies Kenya.JPG|thumb|center|258px|Pioneer Biogas Technologies Kenya|alt=Pioneer Biogas Technologies Kenya.JPG]]
  
<span><span>-<span> </span></span></span>There are many research needs on the technology
+
'''Construction and Operation''':
  
&nbsp;
+
Once the trench is excavated and the materials are readily available, the construction and installation of a PTD only takes several hours. To operate a PTD, the producer has to charge it day to day with 20kg of cattle dung, mixed with 60 litres of water. After 1-2 months the digester will start producing around 4-5 hours biogas daily (for cooking and other applications such as gas lamps). Furthermore, it produces about 80 litres of ecological fertilizer daily.
  
<span>Pioneer Technologies Ltd has trained 7 technicians to
+
<br/>
support the technology and at least 300 or so units have been installed
 
country wide and despite small problems, all are now working.”</span><br>  
 
  
<br>  
+
<u>Scheme of the complete tube digester system:</u>
  
[[Image:Pioneer Biogas Technologies Kenya.JPG|center|333x500px|Pioneer Biogas Technologies Kenya.JPG]]  
+
[[File:Scheme of the biogas supply line tube digester.jpg|thumb|center|743px|Scheme of the biogas supply line tube digester|alt=Scheme of the biogas supply line tube digester.jpg]]
  
'''Construction and Operation'''  
+
'''Lessons Learnt''':<br/>
  
<br>  
+
Pioneer has noted the importance of user training from the very first visit. User training therefore constitutes one of the key factors of a sustainable tube digester system. Follow up activities are also crucial: after-sales service and visits can improve obtained results considerably. Another key factor is the adequate protection of the biogas systems to achieve a satisfactory life time. To protect the tube digester against animals a wire fence is a useful option. Additionally, a roof should be installed to increase the lifetime of the digester.<br/>
  
Once the trench is excavated and the materials are readily available, the construction and installation of a PTD only takes several hours. To operate a PTD, the producer has to charge it day to day with 20kg of cattle dung, mixed with 60 litres of water. After 1-2 months the digester will start producing around 4-5 hours biogas daily (for cooking and other applications such as gas lamps). Furthermore, it produces about 80 litres of ecological fertilizer daily.
+
<br/>
  
<br>
+
'''Available Pioneer Technologies:'''
  
Scheme of the complete tube digester system:
+
Until today Pioneer Technologies offers two system sizes in Kenya.<br/><br/>
  
<br>
+
{| cellspacing="1" cellpadding="1" border="1" style="height: 225px; width: 100%"
 
 
[[Image:Scheme of the biogas supply line tube digester.jpg|500x284px|Scheme of the biogas supply line tube digester.jpg]]
 
 
 
<br>
 
 
 
'''Lessons Learnt'''<br>
 
 
 
Pioneer has noted the importance of user training from the very first visit. User training therefore constitutes one of the key factors of a sustainable tube digester system. Follow up activities are also crucial: after-sales service and visits can improve obtained results considerably. Another key factor is the adequate protection of the biogas systems to achieve a satisfactory life time. To protect the tube digester against animals a wire fence is a useful option. Additionally, a roof should be installed to increase the lifetime of the digester.<br>
 
 
 
&nbsp;
 
 
 
'''Available Pioneer Technologies'''
 
 
 
Until today Pioneer Technologies offers two system sizes in Kenya.<br><br>
 
 
 
{| cellspacing="1" cellpadding="1" border="1" style="width: 558px; height: 225px;"
 
 
|-
 
|-
| <br>  
+
| style="background-color: rgb(204, 204, 204)" | <br/>
| width="30%" nowrap="nowrap" | '''Standard size'''  
+
| style="background-color: rgb(204, 204, 204)" | '''Standard size'''
| width="30%" nowrap="nowrap" | '''Large size'''
+
| style="background-color: rgb(204, 204, 204)" | '''Large size'''
 
|-
 
|-
| width="30%" nowrap="nowrap" | '''Lay flat measurements'''  
+
| style="white-space: nowrap;  width: 30%" | '''Lay flat measurements'''
| 1.4 m x 10 m  
+
| 1.4 m x 10 m
 
| 2.6 m x 10 m
 
| 2.6 m x 10 m
 
|-
 
|-
| width="30%" nowrap="nowrap" | '''Volume (Pioneer Indication)'''  
+
| style="white-space: nowrap;  width: 30%" | '''Volume (Pioneer Indication)'''
| 3 m³  
+
| 3 m³
 
| 6 m³
 
| 6 m³
 
|-
 
|-
| '''Weight'''  
+
| '''Weight'''
| 24 kg  
+
| 24 kg
 
| 45 kg
 
| 45 kg
 
|-
 
|-
| '''Volume Calculation'''  
+
| '''Volume Calculation'''
| <br>  
+
| <br/>
| <br>
+
| <br/>
 
|-
 
|-
| '''D'''  
+
| '''D'''
| 0.89 m  
+
| 0.89 m
 
| 1.66 m
 
| 1.66 m
 
|-
 
|-
| '''L/D ratio'''  
+
| '''L/D ratio'''
| width="30%" nowrap="nowrap" | 11.22 (should be between 5-10)  
+
| style="white-space: nowrap;  width: 30%" | 11.22 (should be between 5-10)
| width="30%" nowrap="nowrap" | 6.04 (should be between 5-10)
+
| style="white-space: nowrap;  width: 30%" | 6.04 (should be between 5-10)
 
|-
 
|-
| '''Total volume'''  
+
| '''Total volume'''
| 6.24 m³  
+
| 6.24 m³
 
| 21.52 m³
 
| 21.52 m³
 
|-
 
|-
| '''Liquid volume'''  
+
| '''Liquid volume'''
| 4.67 m³  
+
| 4.67 m³
 
| 16.14 m³
 
| 16.14 m³
 
|-
 
|-
| '''Gasholder volume'''  
+
| '''Gasholder volume'''
| 1.56 m³  
+
| 1.56 m³
 
| 5.38 m³
 
| 5.38 m³
 
|-
 
|-
| rowspan="3" | '''Cost of installed digester'''  
+
| rowspan="3" | '''Cost of installed digester'''
| rowspan="3" | 24,200 KES (233 Euro)  
+
| rowspan="3" | 24,200 KES (233 Euro)
 
| rowspan="3" | 33,800 KES (325 Euro)
 
| rowspan="3" | 33,800 KES (325 Euro)
 
|}
 
|}
  
&nbsp;<br>  
+
<br/>
  
== Rwanda<br> ==
+
== Rwanda<br/> ==
  
The National Domestic Biogas Program's (NDBP) focus in Rwanda lies on disseminating fixed dome digesters. However, rising investment costs (about 1000€ per 6 m<sup>3</sup> plant in 2011) render the technology more and more problematic in a context of severe shortage of available costumers. Therefore, polyethylene tube digesters could become a feasible economic alternative in a future energy supply scenario for Rwanda. A pilote phase launched in June 2010 with two projects (Rubinizi and Busogo) is about to clarify the potential of tube digesters for the Rwandan farmers and whether these systems can substitute fixed dome digesters. It has been agreed that the Institute of Agriculture and Animal Husbandry (ISAE) is the most appropriate institution to test the PTDs. In line with the MoU signed between NDBP and the ISAE on bio-slurry the proposal has been approved and the contract negotiation is ongoing.<br>  
+
The '''National Domestic Biogas Program's (NDBP)''' focus in [[Rwanda_Energy_Situation|Rwanda]] lies on disseminating fixed dome digesters. However, rising investment costs (about 1000€ per 6 m<sup>3</sup> plant in 2011) render the technology more and more problematic in a context of severe shortage of available costumers. Therefore, polyethylene tube digesters could become a feasible economic alternative in a future energy supply scenario for Rwanda. A pilote phase launched in June 2010 with two projects (Rubinizi and Busogo) is about to clarify the potential of tube digesters for the Rwandan farmers and whether these systems can substitute fixed dome digesters. It has been agreed that the '''Institute of Agriculture and Animal Husbandry (ISAE)''' is the most appropriate institution to test the PTDs. In line with the MoU signed between NDBP and the ISAE on bio-slurry the proposal has been approved and the contract negotiation is ongoing.<br/>
  
Studies on Kenya's experience with PTDs are used to further determine the feasibility of the technology for Rwanda. See PTD&nbsp;in Kenya<br>  
+
Studies on Kenya's experience with PTDs are used to further determine the feasibility of the technology for Rwanda. See PTD in Kenya<br/>
  
<br>  
+
<br/>
  
In Rwanda, production costs for PE in different sizes with a thickness of 250 microns are estimated to be the following:  
+
<u>In Rwanda, production costs for PE in different sizes with a thickness of 250 microns are estimated to be the following:</u>
  
<br>
+
{| cellspacing="1" cellpadding="1" border="1" style="width: 100%"
 
 
{| width="400" cellspacing="1" cellpadding="1" border="1"
 
 
|-
 
|-
| '''Lay flat width'''  
+
| style="background-color: rgb(204, 204, 204)" | '''Lay flat width'''
| '''1,5 m'''  
+
| style="background-color: rgb(204, 204, 204)" | '''1,5 m'''
| '''1,75 m'''
+
| style="background-color: rgb(204, 204, 204)" | '''1,75 m'''
 
|-
 
|-
| '''Cost for serial meter'''  
+
| '''Cost for serial meter'''
| 200,7 KES<br>1499,4 RWF<br>1,93 €  
+
|  
| 233,75 KES<br>1748,0 RWF<br>2,25 €
+
*200,7 KES
 +
*1499,4 RWF
 +
*1,93 €
 +
 
 +
|  
 +
*233,75 KES
 +
*1748,0 RWF
 +
*2,25 €
 +
 
 
|}
 
|}
  
<br>  
+
<br/>
  
(Report of the installation of plastic tube digesters in Rwanda: [http://www.energypedia.info/index.php/file:Low_Cost_Polyethylene_Tube_Digester_Rwanda.pdf download])<br>
+
► [[:File:Low_Cost_Polyethylene_Tube_Digester_Rwanda.pdf|Download the report of the installation of plastic tube digesters in Rwanda]]
  
== ''Tanzania''  ==
 
  
<span>It is concluded that the main reasons for failure was insufficient training of farmers and insufficient follow up by Surude. </span>
 
  
''<span>(Evaluation of small scale biogas digesters in</span>'' Turiani, Nronga and Amani, Tanzania by University of Aarhus, Denmark)
+
== Tanzania ==
  
<br>  
+
<span>It is concluded that the main reasons for failure in [[Tanzania_Energy_Situation|Tanzania]] was insufficient training of farmers and insufficient follow up by Surude.</span>
  
<br>  
+
► [http://agris.fao.org/agris-search/search/display.do?f=2000/DK/DK00026.xml;DK2000000892 Evaluation of small scale biogas digesters in Turiani, Nronga and Amani, Tanzania by University of Aarhus, Denmark]<br/>
  
== ''Vietnam''<br> ==
+
<br/>
  
<span>Over 30,000 Units have been installed over the past ten years in Vietnam and was widely accepted by the farmers</span>  
+
== Vietnam<br/> ==
  
''<span>(Presentation by Vo Lam, Takeshi Watanabe, College of Agriculture,</span>'' Cantho University. Vietnam)&lt;span /&gt;
+
<span>Over 30,000 units have been installed over the past ten years in [[Vietnam_Energy_Situation|Vietnam]] and was widely accepted by the farmers</span>
  
<br>  
+
<br/>
  
<br>
+
= Further Information =
  
<br>  
+
*[[Portal:Biogas|Biogas Portal on energypedia]]
 +
*[[Types_of_Biogas_Digesters_and_Plants|Types of Biogas Digesters and Plants]]
 +
*[[:file:Fact sheet 01 2010 low-cost polyethylene tube digester altiplano bolivia.pdf|Fact Sheet Low-Cost Polyethylene Tube Digester Altiplano Bolivia - (3.000 - 4.500 m above sea level)]]
 +
*[[:file:Fact sheet 01 2010 low-cost polyethylene tube digester valley bolivia.pdf|Fact Sheet Low-Cost Polyethylene Tube Digester Valley Bolivia - (2.000 - 3.000 m above sea level)]]<br/>
 +
*[[:file:Fact sheet 01 2010 low-cost polyethylene tube digester tropics bolivia.pdf|Fact Sheet Low-Cost Polyethylene Tube Digester Tropics Bolivia - (0 - 2.000 m above sea level)]]
 +
*[[:file:Low cost polyethylene tube installation.pdf|Installation manual for Low Cost Polyethylene Tube Digesters]]
  
== Documents on Energypedia  ==
+
<br/>
  
*[http://www.energypedia.info/index.php/File:Fact_sheet_01_2010_low-cost_polyethylene_tube_digester_altiplano_bolivia.pdf Fact Sheet Low-Cost Polyethylene Tube Digester Altiplano Bolivia - (3.000 - 4.500 m above sea level)]
+
= References =
*[http://www.energypedia.info/index.php/File:Fact_sheet_01_2010_low-cost_polyethylene_tube_digester_valley_bolivia.pdf Fact Sheet Low-Cost Polyethylene Tube Digester Valley Bolivia - (2.000 - 3.000 m above sea level)]<br>
 
*[http://www.energypedia.info/index.php/File:Fact_sheet_01_2010_low-cost_polyethylene_tube_digester_tropics_bolivia.pdf Fact Sheet Low-Cost Polyethylene Tube Digester Tropics Bolivia - (0 - 2.000 m above sea level)]
 
*[http://www.energypedia.info/index.php/File:Fact_sheet_01_2010_comparison_low-cost_polyethylene_tube_digester_bolivia.pdf Fact Sheet Comparison of the Low-Cost Polyethylene Tube Digester Types of GTZ / EnDev Bolivia]
 
*[http://www.energypedia.info/index.php/File:Low_cost_polyethylene_tube_installation.pdf Installation manual for Low Cost Polyethylene Tube Digesters]
 
*[http://www.energypedia.info/index.php/File:How_to_install_a_polyethylenedigester_sl.pdf How to Install a polyethylene Digester]
 
  
<br>
+
*GIZ project experience
  
<br>  
+
<references />
  
[[Category:Biogas]] [[Category:Kenya]] [[Category:Honduras]] [[Category:Bolivia]]
+
[[Category:Tanzania]]
 +
[[Category:Rwanda]]
 +
[[Category:Honduras]]
 +
[[Category:Kenya]]
 +
[[Category:Vietnam]]
 +
[[Category:Bolivia]]
 +
[[Category:Biogas]]

Latest revision as of 06:04, 14 November 2014

►Back to Biogas Portal

Overview

Polyethylene biogas digesters have been used in several countries since the 1990s. In some areas they have been abandoned after unsuccessful introduction but their usage has never stopped completely. Reports show that the lifespan of the plastic tubes is always a main issue. However, dependable data about the lifespan and reliability of digester bags is rare.

PTDs can only function properly if the farmers take good care of the digesters. This needs intensive training and raised responsibility amongst the farmers. If they do, experiences show that most problems are easy to handle and can be fixed by farmers themselves.


Below some information mainly summarized from GIZ projects and from the internet regarding the experiences with plastic tube digesters in different countries.


International Experience with Polyethylene Tube Digesters

Bolivia

► See what GIZ EnEev is doing in Bolivia: Low-Cost Polyethylene Tube Digesters in Bolivia


Honduras

In Honduras, the distribution of polyethylene plastic tube digesters faces several problems: They must be purchased in large quantities. Need of a third party to act as a distributor to farmers. Flooding for digesters laid in trench

2005 Emerging Biodigester Technology in Honduras.pdf Emerging Biodigester Technology in Honduras: Biophysical Process and Operation, N. Stuart Green; Montana Tech of the University of Montana, 1999)


Kenya

After a false start in promoting this energy source in Kenya in the mid 1990s, it was successfully reintroduced by KARI-Embu in 2005. According to Erastus Kiruiro from KARI-Embu there are around 300 tubular digesters in use, mostly in Central Kenya but also around Nairobi.

The Organic Farmer, The Magazine for sustainable agriculture in Kenya, Nr. 45 February 2009

Plastic Tube Digesters in Kenya


Based on Promoting Biogas Systems in Kenya, “Pioneer Technologies” (a Kenyan plastic company) has built 200 plants since 2006. They improved the plastic tubes to be better sun and pressure resistant.

It has not been a successful story yet due to:

  • There is no reliable back-up support.
  • The digester seems to suffer from effects of variable temperature, and there is a possibility that the heat catalyses some reactions that produce other volatile gases as well as methane.


It is still a promising approach which is strongly driven by KARI. Currently there are many problems and referring to the feasibility study mentioned above 4 of 5 visited plants had some technical problems but most of them could have been solved easily.


Development of the plastic tubular technology was initiated in August 2006.

The Plastic Tubular bio-digesters are designed for households with two to three animals although bigger ones have been installed. Capacity of the former is about 8-9 m3, with a gas holding chamber of 1-3 m3. A larger one that doubles this size has already been installed. The smaller Plastic Tubular Bio-digesters can give gas for six hours using one burner. Methane production is initially dependent on temperatures.

Currently, Pioneer Technologies Ltd receives support from Land O’lakes and has entered into research collaboration with Jomo Kenyatta University of Agriculture and Technology (JKUAT). Land O’Lakes gives financial support to the company in the production of biogas digesters. JKUAT is supposed to carry out investigations into issues arising from the use of the technology, with focus on how the technology can be improved, made more efficient etc. However, Pioneer Technologies Ltd gave the JKUAT one digester only, and so the university should acquire more digesters for any meaningful research to be done.


Pioneer Technologies Ltd has installed its bio-digester in various parts of the country including Nakuru, Meru, Kisumu, Kiambu, the coastal regions and the environs of Nairobi.

The company has capacity to install up to 3,000 units a year, but there are several challenges including:

  • Most households need some financial support to acquire the technology. At cost, a Plastic Tubular Bio-digester goes for €322 only. However, this excludes the cost of transport – and so areas further away from Nairobi pay more money. In Meru, users paid up to €399. The cost of the technology, though coming down is prohibitive to most farmers, although when financial and economic analyses are made, especially taking into account opportunity costs vis a vis other energy technologies, it is very likely that bio-digesters will be economical and profitable.
  • Training of technicians to support the technology is costly. Not all technicians trained will work on the digesters forever, some move on. There is need for the technology to be supported by some form of extension. Regular visits to households that have installed it are critical for longevity, good use and success of the technology.
  • Many people are not aware of the existence of the technology, or if aware, do not have adequate information on how the technology actually works. This is a hindrance to large-scale adoption.
  • At times, the technology fails because of unmet expectations. Even the Plastic Tubular Bio-digester has some technical problems – and these need to be sorted out. Without a reliable back-up support, small problems can lead potential users to shun away from it. But companies like Pioneer Technology Ltd cannot afford to have an extension/back-up support team because it already charges very low figures to install a unit.
  • Users need to be trained, and this is quite costly. This is where organisations like Land O’Lakes come in.
  • There are many research needs on the technology


Pioneer Technologies Ltd has trained 7 technicians to support the technology and at least 300 or so units have been installed country wide and despite small problems, all are now working.”


Pioneer Biogas Technologies Kenya.JPG
Pioneer Biogas Technologies Kenya

Construction and Operation:

Once the trench is excavated and the materials are readily available, the construction and installation of a PTD only takes several hours. To operate a PTD, the producer has to charge it day to day with 20kg of cattle dung, mixed with 60 litres of water. After 1-2 months the digester will start producing around 4-5 hours biogas daily (for cooking and other applications such as gas lamps). Furthermore, it produces about 80 litres of ecological fertilizer daily.


Scheme of the complete tube digester system:

Scheme of the biogas supply line tube digester.jpg
Scheme of the biogas supply line tube digester

Lessons Learnt:

Pioneer has noted the importance of user training from the very first visit. User training therefore constitutes one of the key factors of a sustainable tube digester system. Follow up activities are also crucial: after-sales service and visits can improve obtained results considerably. Another key factor is the adequate protection of the biogas systems to achieve a satisfactory life time. To protect the tube digester against animals a wire fence is a useful option. Additionally, a roof should be installed to increase the lifetime of the digester.


Available Pioneer Technologies:

Until today Pioneer Technologies offers two system sizes in Kenya.


Standard size Large size
Lay flat measurements 1.4 m x 10 m 2.6 m x 10 m
Volume (Pioneer Indication) 3 m³ 6 m³
Weight 24 kg 45 kg
Volume Calculation

D 0.89 m 1.66 m
L/D ratio 11.22 (should be between 5-10) 6.04 (should be between 5-10)
Total volume 6.24 m³ 21.52 m³
Liquid volume 4.67 m³ 16.14 m³
Gasholder volume 1.56 m³ 5.38 m³
Cost of installed digester 24,200 KES (233 Euro) 33,800 KES (325 Euro)


Rwanda

The National Domestic Biogas Program's (NDBP) focus in Rwanda lies on disseminating fixed dome digesters. However, rising investment costs (about 1000€ per 6 m3 plant in 2011) render the technology more and more problematic in a context of severe shortage of available costumers. Therefore, polyethylene tube digesters could become a feasible economic alternative in a future energy supply scenario for Rwanda. A pilote phase launched in June 2010 with two projects (Rubinizi and Busogo) is about to clarify the potential of tube digesters for the Rwandan farmers and whether these systems can substitute fixed dome digesters. It has been agreed that the Institute of Agriculture and Animal Husbandry (ISAE) is the most appropriate institution to test the PTDs. In line with the MoU signed between NDBP and the ISAE on bio-slurry the proposal has been approved and the contract negotiation is ongoing.

Studies on Kenya's experience with PTDs are used to further determine the feasibility of the technology for Rwanda. See PTD in Kenya


In Rwanda, production costs for PE in different sizes with a thickness of 250 microns are estimated to be the following:

Lay flat width 1,5 m 1,75 m
Cost for serial meter
  • 200,7 KES
  • 1499,4 RWF
  • 1,93 €
  • 233,75 KES
  • 1748,0 RWF
  • 2,25 €


Download the report of the installation of plastic tube digesters in Rwanda


Tanzania

It is concluded that the main reasons for failure in Tanzania was insufficient training of farmers and insufficient follow up by Surude.

Evaluation of small scale biogas digesters in Turiani, Nronga and Amani, Tanzania by University of Aarhus, Denmark


Vietnam

Over 30,000 units have been installed over the past ten years in Vietnam and was widely accepted by the farmers


Further Information


References

  • GIZ project experience