Polyethylene tube digester: Difference between revisions

Revision as of 00:44, 1 December 2012

Polyethelene Tube Digesters, also known as balloon biogas plants, are a type of biodigester quickly gaining popularity in applications throughout the world. Due to their simple construction, easily understandable mechanics, widely available inexpensive material, and versatile structure, polyethelene tube digesters are ideal for inital "test" conversions in small-scale applications.^[1].

A flexible plastic (polyethelene) type biodigester. [1]

A polyethelene tube biodigester is typically characterized by a raised inlet trough, a long, flexible fermenting reservoir with a gas vent tube, and a slurry output.

The exceedingly simple design and low cost of a PET digester and its lack of moving parts means that the system is inherently reliable and cost effective. However, the design may be shortlived in comparison to more traditional digesters (Fixed dome digester,Floating Drum Biogas digestor)due to its construction from polyethelene plastic, which will degrade over time. However, the low cost and easy installation of the digester bag means that the main chamber is simple to replace in the event degredation begins to affect the system's performance. Though the gas inside is being pushed out only by the pressure of the other methane gas inside the digester, the flexible reservoir allows the flow rate to be modified simply by applying additional pressure to the bag- say by placing a rock on it.^[2].

Pros

Simple setup
Low cost
Shallow installation, ideal for areas with high groundwater table
Easy to see how much gas is available
Easily warmed, ideal for warmer climates

Cons

Not as durable as traditional digesters
Low gas pressure
Production time highly dependent on ambient temperature

Comparisons to other digester types

vs. Floating drum digesters

Lower gas output (depending on size)
Lower pressure consistency
Similarly easy to gauge amount of gas available for use
Less insulated
Easier to maintain
Less expensive

vs. Fixed-dome biodigesters

Lower gas output (depending on size)
Similar pressure consistency
Easier to gauge amount of gas available for use
Less insulated
Easier to maintain
Less expensive

Notes and references

Template:Reflist

@@ Line 1: / Line 1: @@
-'''Polyethelene Tube Digesters''' are a type of biodigester quickly gaining popularity in applications throughout the world. Due to their simple construction, easily understandable mechanics, and <ref>
+'''Polyethelene Tube Digesters''', also known as '''balloon biogas plants''', are a type of biodigester quickly gaining popularity in applications throughout the world. Due to their simple construction, easily understandable mechanics, widely available inexpensive material, and versatile structure, polyethelene tube digesters are ideal for inital "test" conversions in small-scale applications.<ref>
-http://www.biogassa.co.za/digesters.html
+https://energypedia.info/index.php/Types_of_Biogas_Digesters_and_Plants#cite_note-TBW-0
-</ref>. [[Image:Digester.GIF|thumb|right|A fixed-dome type biodigester. [http://www.fao.org/docrep/T0541E/T0541E0E.GIF]]]Due to their relative simplicity and use of readily available materials both as fuel and in construction, fixed dome digesters have become increasingly popular throughout the world. The typical structure of a fixed dome digester consists of an inlet trough, a lower fermenting reservoir with a rigid, immovable collection dome capping it, and some type of overflow relief. Several different types of fixed dome digesters exist, but by far the most popular is the Chinese design, which is typically built of gas-sealed brick and mortar or cement.
+</ref>. [[Image:TubularPlasticBiodigester.gif|thumb|right|A flexible plastic (polyethelene) type biodigester. [http://www.build-a-biogas-plant.com/images/tubularPlasticBiodigester.gif]]] A polyethelene tube biodigester is typically characterized by a raised inlet trough, a long, flexible fermenting reservoir with a gas vent tube, and a slurry output.
-The simple design of a fixed-dome digester and its lack of moving parts means that if constructed well, the structure will last for many years. However, the design is by nature inaccessible due to its (usually) underground construction, and its lack of moving parts means that access to the interior of the digester (say for cleaning and maintenance purposes) is extremely difficult. Since the methane gas inside the collection chamber is being pushed out only by the pressure of other methane, the gas pressure coming out of the collector is subject to large fluctuations, making it unsuitable to use for cooking, or other applications requiring a steady stream of gas flow, without an additional regulating device<ref>http://fastonline.org/CD3WD_40/BIOGSHTM/EN/APPLDEV/DESIGN/DIGESTYPES.HTML</ref>.
+The exceedingly simple design and low cost of a PET digester and its lack of moving parts means that the system is inherently reliable and cost effective. However, the design may be shortlived in comparison to more traditional digesters ([[Fixed dome digester]],[[Floating Drum Biogas digestor]])due to its construction from polyethelene plastic, which will degrade over time. However, the low cost and easy installation of the digester bag means that the main chamber is simple to replace in the event degredation begins to affect the system's performance. Though the gas inside is being pushed out only by the pressure of the other methane gas inside the digester, the flexible reservoir allows the flow rate to be modified simply by applying additional pressure to the bag- say by placing a rock on it.<ref>http://fastonline.org/CD3WD_40/BIOGSHTM/EN/APPLDEV/DESIGN/DIGESTYPES.HTML</ref>.
 == Pros ==
+*Simple setup
+*Low cost
+*Shallow installation, ideal for areas with high groundwater table
+*Easy to see how much gas is available
+*Easily warmed, ideal for warmer climates
 == Cons ==
+*Not as durable as traditional digesters
+*Low gas pressure
+*Production time highly dependent on ambient temperature
 == Comparisons to other digester types ==
 '''vs. [[Floating drum biogas digestor|Floating drum digesters]]'''
+*Lower gas output (depending on size)
+*Lower pressure consistency
+*Similarly easy to gauge amount of gas available for use
+*Less insulated
+*Easier to maintain
+*Less expensive
-'''vs. [[Polyethelene Tube Digester|Polyethelene Tube Digester]]'''
+'''vs. [[Fixed dome biodigester|Fixed-dome biodigesters]]'''
+*Lower gas output (depending on size)
+*Similar pressure consistency
-==Types of Polyethelene Tube Digesters<ref>https://energypedia.info/index.php/Types_of_Biogas_Digesters_and_Plants#cite_note-TBW-0</ref>==
+*Easier to gauge amount of gas available for use
-*'''Chinese fixed dome''': The original. Some five million have been built in China since the 1930s.
+*Less insulated
-*'''Janata model''' (obsolete): An Indian-built fixed-dome digester. Discontinued due to flawed construction methodology consistently leading to cracks in the gas-holding dome and subsequent leakage.
+*Easier to maintain
-*'''Deenbanhdu model''': Successor to the Janata model, simplifies the silo-shape of the Chinese fixed dome fermentation chamber/gas collector down to a hemispherical dome.
+*Less expensive
-*'''CAMARTEC''': Simplest design of the fixed-dome digesters. Hemispherical fermentation chamber/gas collector with a rigid base.
 == Notes and references ==
@@ Line 32: / Line 42: @@
 * [[Biogas]]
 * [[Floating drum biogas digestor]]
-* [[Polyethelene Tube Digester]]
+* [[Fixed dome digester]]
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