During the last twelve years, animal production on small-scale farms in Northern Vietnam has developed rapidly. Biogas technology transfer has been an important element in these activities. Biodigesters made of polyethylene tube (cheap biodigester) and by brick - cement (solid dome) construction have been well accepted by small-holder farmers. The former are popular in upland areas; while the latter are favoured in the low-lying delta where farms are smaller and space is limited. The most effective way to set up introduce these biodigesters in Northern Vietnam has been through pilot demonstrations followed by training and extension.
Key words: Bjodigsters, small-scale farm, polyethylene tiube, solid-dome
The aim of the project is to find simple ways to install biodigesters
made of polyethylene tube and brick - cement in small farms in North Vietnam. In the last 12 years the
animal production sector has developed rapidly in Vietnam due to the government policies in
supporting the farmers. The annual growth rate of animal production in
North Vietnam is estimated to be
from 4.5 to 5% (Statistical yearbook 2001). Most farms in North Vietnam have only small numbers of
animals: from 2 to 5 pigs and 1 to 2 cattle or buffaloes. About 10% of the farms
keep 6 to 15 pigs or 3 to 10 cattle or buffaloes. In some intensive farms there
are as many as 50 to 200 pigs or 20 to 50 cattle or 5 to 10 dairy cows or 1000
to 2000 chickens. The untreated waste from animal enterprises is a major source of
pollution of the environment. On the other hand, the demand for fuel wood and
energy for household use has steadily increased due to the booming population
especially in rural areas.
Biogas technology was introduced into North Vietnam in the 1970s when a few large biodigesters of the Indian design were installed in some cooperative farms. However, the cost of these digesters was very expensive therefore the poor small scale farmers could not adopt the technology. From 1990 onwards, emphasis on biogas technology received a new impetus with the introduction of low-cost tubular plastic biodigesters as a component of the technical assistance programmes supported by SAREC and FAO-TCP. More recently, models of brick- cement construction have also been introduced in some households.
The objective of the NIAH biodigester program is to find simple ways
for installing biodigesters on small farms.
Typical animal farms were selected in different regions to install
low cost polyethylene tube biodigesters to act as demonstration models. After 3
and 6 months, these units were evaluated in order to find the most suitable
technology and the installation costs that farmers could accept. Meetings were
held with farmers in order to have their recommendations. After
that, training courses on installing biodigesters have been implemented.
These training courses have been organized in the provinces of Ha Tay, Tuyen
Quang, Thai Nguyen, Vinh phuc and in the suburbs of Hanoi City. From 1995, biodigesters made of bricks
and cement (Chinese fixed dome, liquid displacement model) began to be
installed.
In 1990 the first polyethylene tube biodigesters were installed in small-scale farms in Northern Vietnam (see table 1)
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Table 1: Some information on polyethylene tube biodigesters on demonstration farms in Northern Vietnam |
||||
|
|
Number of farms |
Numbers/specie of animals |
Gas usage (hr/day) |
|
|
Pig |
Buffalo or cattle |
|||
|
Suburb Hanoi |
30 |
8-15 |
- |
3.0-3.5 |
|
Ha Tay |
35 |
5-8 |
1-2 |
4.0-4.5 |
|
Tuyen Quang |
28 |
4-6 |
2-5 |
3.5-4.0 |
|
Vinh Phuc |
24 |
6-10 |
1-2 |
4.0-4.5 |
In general, the gas is enough for cooking. The cost of each biodigester was about 500,000 VND (» 35 USD). The size of these biodigesters is from 9 to11 meters long and their capacity 5 to 6 m3. These polyethylene tube biodigesters can work well if the farmers have enough water and manure and there is good protection from animal and mechanical damage.
After the neighbours saw the polyethylene tube biodigesters working efficiently, many of them came to see and learn how to set them up. Afterwards, several hundred biodigesters were installed with the help of NIAH staff. Although the price of polyethylene tube biodigesters is low, this system brought some disadvantages such as:
· Time of using polyethylene tube was limited due to it being easily damaged by sunlight and also from mechanical actions.
· Installing the system requires quite a large land area so some small-scale farmers cannot apply it.
Because of these factors, some farmers accepted to make the biogas system with bricks and cement.
Over 100 brick and cement biodigesters (concrete biodigester) have been installed by NIAH staff. The design of these biodigesters was based on the Chinese model (Chendu biogas research institute of China, 1992). Details are in Table 2.
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Table 2: Details of brick and cement biodigesters installed by NIAH | |||
|
Capacity (m3) |
Farm size (pigs per farm) |
Cost (million VND) |
Time for cooking (hr/day) |
|
5-6 |
5-10 |
2.0-2.4 |
5-6 |
|
8-10 |
10-20 |
3.0-3.5 |
8-11 |
|
12-15 |
20-40 |
5.0-5.5 |
12-15 |
Most small-scale farms in Northern Vietnam preferred to install brick-cement biodigesters with a capacity of 5 to 6m3, because this digester supplies enough gas for daily cooking and the cost for installation is lower. The costs of these biodigesters is rather high but with this system, the farmer can use it for a longer time. After using it for 3 to 4 years, the money saved from buying fuel could be enough for the cost of this system. Many farmers said that they spent 50,000-80,000 VND per month for fuel (about 750,000 VND per year). The positive impacts on the environment of biodigesters are clear. The use of biogas also makes the work of women easier as discussed by Bui Xuan An et al (1994).
Most farmers use pig manure for their biodigesters. However, manure from buffalo and cattle can also be used although it produces less gas per unit of dry matter as compared to pig manure. Farmers having biodigesters reported that the effluent has positive effect on crop yields and in fish ponds as discussed by Preston (1994).
Conclusion
· The transferring of biogas technology in smallholder farms in Northern Vietnam by the National Institute of Animal Husbandry (NIAH) has had a good impact. The biodigesters have positive effects on the environment and supply a cheap fuel for farmers.
· Smallholders in mountainous and hilly areas accepted polyethylene tube biodigesters due to the low cost and being easy to install.
· Small farms in delta region and suburbs of Hanoi prefer biodigesters made with brick-cement as available areas are limited.
·
The biogas technology can be transferred through
the demonstration sites combined with training and evaluating with the farmers,
then farmers can learn from others.
The authors wish to thank SidaSAREC for financial support and the
farmers for their cooperation. We also wish to thank Dr T R Preston and Dr B
Ogle who gave us useful suggestions.
Bui-Xuan An, Ngo-Van-Man, Duong Nguyen-Khang, Nguyen-Duc-Anh and Preston T R 1994 Installation and performance of low-cost polyethylene tube biodigesters on small-scale farms in Vietnam. Proceeding of National Seminar-workshop on “Sustainable Livestock production on Local Feed Resources” Agriculture Publishing House, p.81-90.
Chendu Biogas Research Institute of China 1992. The biogas technology in China. Agr. publishing house, Beijng, p.1-79; 157-166.
Preston T R 1994 Renewable energy from tropical agriculture; the respective roles of biodigestion and gasification. Proceeding of National Seminar-workshop on “ Sustainable Livestock production on Local Feed Resources” Agriculture Publishing House, p.75-90.
Statistical yearbook of Vietnam 2001