household biogas digesters
TRANSCRIPT
Evaluation of Household Biogas Digesters
Content
1. Introduction 2. Designs 3. Constructions 4. Evaluations and Comparisons 5. Conclusions
1. Introduction
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
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
2. Design
2.1 KT 31 design
1. Digester
2. Gas holder
3. Inlet
4. Outlet
5. Gas outlet
6. Compensation tank
2.2 KT1 & KT2 design
KT1 KT2
2.3 Composite design
400
1000mm 1000
400
R= 2600
Inlet: 800 Outlet: 900
1300
600
80
400
200
Gas outlet
Gas holder
Digester
2.4 Nylon bag
2. Construction
3.1 Construction of KT31
3.2 Construction of KT1 &KT2
3.3 Construction of Composite
3.4 Construction of Nylon bag
3. Comparison and Evaluation
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)
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)
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
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)
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
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)
5. Conclusions
5.1 KT31 digester
Pros:
Durable and long lifetime.
Cons: High Investment cost More complicated to transport Less availability. Need trained masons.
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.
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.
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.
Contact: Tran Hai Anh – Renewable Energy Specialist [email protected]