household biogas digesters
TRANSCRIPT
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Evaluation of Household Biogas Digesters
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Content
1. Introduction 2. Designs 3. Constructions 4. Evaluations and Comparisons 5. Conclusions
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1. Introduction
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1.1 Background
The most Vietnam common household biogas digesters:
Household biogas digester which is made from brick and composite (KT31)
Household biogas digester which is made from composite
Household biogas digester which is made from brick (KT1 & KT2)
Household biogas digester which is made from nylon bag
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1.2. Evaluation Criteria
1. Construction material (10 scores max.)
2. Convenient of construction method (20 scores max.)
3. O&M (30 scores max.)
4. Return on Investment (30 scores max.)
5. Sanitation (10 scores max.)
Total: 100 scores
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2. Design
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2.1 KT 31 design
1. Digester
2. Gas holder
3. Inlet
4. Outlet
5. Gas outlet
6. Compensation tank
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2.2 KT1 & KT2 design
KT1 KT2
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2.3 Composite design
400
1000mm 1000
400
R= 2600
Inlet: 800 Outlet: 900
1300
600
80
400
200
Gas outlet
Gas holder
Digester
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2.4 Nylon bag
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2. Construction
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3.1 Construction of KT31
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3.2 Construction of KT1 &KT2
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3.3 Construction of Composite
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3.4 Construction of Nylon bag
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3. Comparison and Evaluation
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4.1 Comparison in terms of construction materials
8.586.79
5.00
10.00
7.58
4.79 5.00
9.55
-
2.00
4.00
6.00
8.00
10.00
12.00
KT31-Northern
part
Composite-Northern
part
Nylongbag-
Northernpart
KT1 KT31-southern
part
Composite-Southern
part
Nylongbag-
Southernpart
KT2
Total score (10 maximum) Availability (5 maximum) Strength (5 maximum)
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4.2 Comparison in terms of Convenient of construction
8.01
17.03
20.00
4.005.53
14.0616.17
0.500.00
5.00
10.00
15.00
20.00
25.00
KT31 - Thenorth
Composite- thenorth
Nylong bag -the north
KT1 KT31- thesouth
Composite- thesouth
Nylon bag - thesouth
KT 2
Total score (20 maximum) Soil excavation (5 maximum)Easy to contruct (5 maximum) Manday (5 maximum)
Score for construction method (5 maximum)
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4.3 O&M Comparison
20.0
24.0
10.3
20.5 20.022.5
9.8
22.0
0.0
5.0
10.0
15.0
20.0
25.0
30.0
KT31 - thenorth
Composite-the north
Nylong bag-the north
KT1 KT31-thesouth
Composite-the south
Nylong bag -the south
KT 2
Total (30 maximum) Safety of the structure (6 maximum)Safety of end user (6 maximum) Gas productivity (6 maximum)
Easiness for O&M (6 maximum) Easiness to dectect failure and to repair
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4.3 Comparison of ROI
12.2610.01
16.6619.40
12.4811.23
16.6617.89
0.00
5.00
10.00
15.00
20.00
25.00
KT31 - thenorth
Composite- thenorth
Nylon bag KT1 KT31- theSouth
Composite- thesouth
Nylon bag - thesouth
KT 2
Total score( 30 maximum) Total investmetn csot (10 maximum) Average Anual investmetn cost (10 maximum)
Payback period (3.33 maximum) NPV (3.33 maximum) IRR ( 3.33 maximum)
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4.4 Comparison of Sanitation
No. Model Smell bad (5 maximum)
BOD 5, COD, coliforms (5 maximum)
Total (5 maximum)
1 KT31 5.00 5.00 10.00 2 Composite 5.00 5.00 10.00 3 Nylon bag 5.00 5.00 10.00 4 KT1-KT2 5.00 5.00 10.00
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4.5 Overall Comparison
58.85
67.8361.96 63.90
55.5962.58
57.63 59.94
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
KT31 - thenorth
Composite-the north
Nylon bag- the north
KT1 KT31- thesouth
Composite-the south
Nylon bagthe south
KT 2
Total (100 maximum) Construction material (10 maximum) Construction (20 maximum)
O&M (30 maximum) Cost (30 maximum) Environment (10 maximum)
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5. Conclusions
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5.1 KT31 digester
Pros:
Durable and long lifetime.
Cons: High Investment cost More complicated to transport Less availability. Need trained masons.
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5.2 Composite digester
Pros:
Easy to install and O&M
Higher gas productivity and longer lifetime
No need trained masons
Cons:
High investment cost
More complicated to transport.
Applicability:
Week soil foundation with high ground water level.
Places without trained masons, brick and cements.
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5.3 KT1 & KT2 digesters
Pros:
Higher gas productivity and longer lifetime.
Medium initial investment cost.
Easy to operate.
Cons:
Need trained mason.
Not easy to maintain.
Need trained masons, bricks and cements.
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5.2 Nylon- bag digester Pros:
Lowest initial investment capital
Easy to install, no need trained mason.
High availability of construction material.
Cons:
Inconvenient O&M
Less durable and short lifetime
Applicability
Poor households.
No long term plan of raising animal.
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Contact: Tran Hai Anh – Renewable Energy Specialist [email protected]