4. 1.1 Background
The mostVietnam 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
5. 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
17. 4.1 Comparison in terms of construction materials
8.58
6.79
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
Nylong
bag-
Northern
part
KT1 KT31-
southern
part
Composite-
Southern
part
Nylong
bag-
Southern
part
KT2
Total score (10 maximum) Availability (5 maximum) Strength (5 maximum)
18. 4.2 Comparison in terms of Convenient of construction
8.01
17.03
20.00
4.00
5.53
14.06
16.17
0.50
0.00
5.00
10.00
15.00
20.00
25.00
KT31 - The
north
Composite- the
north
Nylong bag -
the north
KT1 KT31- the
south
Composite- the
south
Nylon bag - the
south
KT 2
Total score (20 maximum) Soil excavation (5 maximum)
Easy to contruct (5 maximum) Manday (5 maximum)
Score for construction method (5 maximum)
19. 4.3 O&M Comparison
20.0
24.0
10.3
20.5 20.0
22.5
9.8
22.0
0.0
5.0
10.0
15.0
20.0
25.0
30.0
KT31 - the
north
Composite-
the north
Nylong bag-
the north
KT1 KT31-the
south
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
20. 4.3 Comparison of ROI
12.26
10.01
16.66
19.40
12.48
11.23
16.66
17.89
0.00
5.00
10.00
15.00
20.00
25.00
KT31 - the
north
Composite- the
north
Nylon bag KT1 KT31- the
South
Composite- the
south
Nylon bag - the
south
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)
21. 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
22. 4.5 Overall Comparison
58.85
67.83
61.96 63.90
55.59
62.58
57.63 59.94
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
KT31 - the
north
Composite-
the north
Nylon bag-
the north
KT1 KT31- the
south
Composite-
the south
Nylon bag
the south
KT 2
Total (100 maximum) Construction material (10 maximum) Construction (20 maximum)
O&M (30 maximum) Cost (30 maximum) Environment (10 maximum)
24. 5.1 KT31 digester
Pros:
Durable and long lifetime.
Cons:
High Investment cost
More complicated to transport
Less availability.
Need trained masons.
25. 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.
26. 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.
27. 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.
