Biogas technology in developing countries:
Vietnam case
study
Bui Xuan An
University of Agriculture
and Forestry
Thu Duc, Ho
Chi Minh City, Vietnam
Abstract
This report includes a short
review on the present status of biogas in developing countries and a review on
the introduction of polyethylene digesters in Vietnam. Biogas dissemination in
developing countries needs high investment for plant construction, well-trained
technicians and good post-installing services. Its generation has gone only
under subsidy systems from government or from overseas. The introduction of polyethylene tube
digesters on small farms in Vietnam has had good impact because of
the low costs, the simplicity of construction and operation and positive
effects on the environment.
The conclusions of this study
point to the importance of farmers’ participation and that dissemination needs
real farmers as demonstrators and the support of a credit system for the poor
farmers. The low-cost plastic digester technology has not been well developed
yet, so studying it in different natural and social conditions is necessary.
Research based on farmer participation is proposed as the model for further
activities.
Key words: Biogas, biodigesters, technology transfer
Introduction
The increasing population and the development demands in the Third World have caused an increasing demand on traditional fuels. The fast rate of forest
destruction and low rate of reforestation has simultaneously reduced the
availability of firewood. To arrest the environmental and agricultural
deterioration it is imperative to introduce other sources of renewable energy,
such as hydro-power, wind and solar energy and biogas. Biogas is considered one
of the cheapest renewable energies in rural areas in developing countries.
Production of biogas would not only save firewood but also be beneficial for
integrated farming systems by converting manure to an improved fertilizer for crops or ponds for
fish and water plants. Other benefits of biodigestion include the reduction of
manure smell, elimination of smoke when cooking and
the alleviation of pathogens and thereby improving hygiene on farms.
The environmental aspects and the need for
renewable energy are receiving interest and considerable financial support in
both developed and developing countries, leading to an increase in research and
development in this area. Many systems using biodigestion have been constructed
in different countries. Despite the potential benefits, the expansion of biogas
technology has gone slowly, especially in countries where there has been no
financial support (subsidy) from governments or development agencies. The main
constraint has been the high cost of the biogas plant for people in rural areas
with limited financial resources.
In recent years a low-cost biodigester,
constructed from polyethylene tubular film, has been promoted in
many developing countries aimed at reducing the
production cost by using local materials and simplifying installation,
operation and maintenance
(Preston 1985 unpubl.; Chater 1986; Botero and Preston 1987; Hieu et al 1994; Sarwatt 1995; Soeurn 1994; Solarte 1995; Khan
1996). This technology was evaluated in Vietnam beginning in 1992. More than 20.000 units have been
developed in Vietnam within the last 10 years. There
were different results from many countries
when introducing biogas technology to production. The objectives of this report
are to identify experiences, effects, constraints and problems associated with
this technology.
Biogas in developing countries
China
China has learned many lessons during the recent past. After 1975,
slogans such as “biogas for every household” led to the construction of 1.6
million digesters per year, mainly being concrete fixed-dome digesters, which
were cheap but of low
quality. Up to 1982, more than seven million digesters were installed in China (Kristoferson and Bokhalders 1991). In 1980, more than 50% of all digesters
were not in use (Marchaim 1992). The consequence was
that in 1979, construction activity slowed to less than one third of the
previous one. Marchaim (1992) reported there were
about five million family sized plants operating in China in 1992, many of them redesigned to avoid leaking. According
to some figures, only about three million digesters were in operation in 1991 (Kristoferson and Bokhalders
1991). This was because they were so crudely built and lack of the well-trained
personnel needed to fix them. These weaknesses have been the consequences of
the concrete digester construction. Attention has recently been paid to combine
quantity with quality of plants and to match the technology with local
conditions. Climatic as well as social and cultural conditions are being
studied first before digesters are being introduced (Marchain
1992).
The rapid development of biogas in China received strong government support and
sometimes, subsidies from local government and village government were up to
75% (Gunnerson and Stuckey 1986).
In recent years, the number of plants built each year has fallen dramatically
because of the reduction in subsidies with a consequent switching from biogas
to coal as a fuel (Qiu et al 1990). The biggest
constraint in the biogas programs has been the price of the digesters. It was
also learned that the popularization of biogas would only be successful when
the direct benefits to the farmers were obvious (Kristoferson
and Bokhalders 1991).
India
According to Khandelwal
(1990), India had a long and varied experience in the field of
developing simple and easy-to-operate biogas technologies to suit different
climatic conditions and socioeconomic groups of users. He also noted that
various management models of implementation of the sizeable
biogas extension program had been developed and tried successfully. Sinha (1994) concluded that a top-down centralized
government initiative was recommended to promote the design and use of rural
energy interventions because there were few options for rural India to alter deteriorating biomass resources.
In many
respects, the same situation as in China prevailed in India where a rapid biogas digester implementation
policy exceeded the capabilities of India’s research and development organizations to
produce reliable designs and to optimize digester efficiencies. As a result,
earlier digesters in the country were expensive and inefficient (Kristoferson and Bokhalders
1991). This situation has been remedied somewhat in recent years. According to Kristoferson and Bokhalders
(1991), new developments and designs are not incorporated as rapidly as they
might, and an improved coordination and feedback will be required if
development is to be achieved. The poor performance of earlier biogas digesters can also be
attributed to poor backup services. The situation that is still largely
prevalent and has led to a relatively high breakdown rate (Kristoferson
and Bokhalders 1991). According to Marchaim (1992), problems can be classified as (a) design
faults; (b) construction faults (c) difficulty of financing; (d) operational
problems due to incorrect feeding or poor maintenance and (e) organizational
problems arising from the differences of approaches and lack of coordination.
Biogas production has been stimulated by popular
publicity campaigns and subsidized constructions of biogas plants by central
and local governments (Sinha 1992). Everyone in India installing a biogas plant has the right to an
allowance paid by the central government (Khandal
2002). The floating cover design digester introduced by the All-Indian
Coordinated Biogas Program is the most common system currently in use in India. This system is more expensive than the fixed
dome (Chinese) digester. Despite having the world’s second largest number of
installed biogas digesters, the biogas program has mainly concentrated on the
expensive systems capable of being installed only by the wealthier inhabitants
in the rural areas (Kristoferson and Bokhalders 1991). According to Bhalla
and Reddy (1994), India has placed far more emphasis on the survival of small-scale farmers
than ensuring their efficiency and growth in a competitive environment through
various policy instruments including biogas programs. The subsidies given to
biogas programs have
frozen the technologies, and created inefficient and fragile industries (Desai
1992).
Other developing countries
The situation is almost the same in
many other developing countries, as in the Philippines, Thailand, Nepal and Brazil (Ellis and Hanson 1989; Desai 1992; Marchaim 1992; Karki et al 1994). For example in Nepal, Pokharel (1994) considered that with the installation of
more than thirteen thousand biogas plants, the strategic plan and activity of
biogas program implementation was gaining more popularity and becoming a
developed example of technology dissemination in Nepal. The government has
provided up to Rs 7000 for a plant built in the
lowland and Rs 10000 in the hill areas (about 30-70%
of the cost for construction). According
to a report from the Consolidated Management Services Nepal (Karki et al 1994), although biogas was introduced in Nepal about two decades ago, the present
infrastructure seems so weak that there is still the dependency upon foreign
countries for supply of some biogas accessories and equipment. With subsidies
of more than 50% of the cost of a family size plant, many farmers who demanded biogas plants were more attracted to the
amount of available subsidies than the utility of the plant as such. Many
newly-formed private companies were finding their business quite profitable and
a considerable part of the government subsidy was taken by these companies as a
profit (Karki et al 1994). Without subsidies the simple pay-back period varied
between 6 and 12 years in Nepal (Nes 1994).
Ellis and Hanson (1989) concluded that biogas
technologies in the Philippines were often not viable at the user level, and
only the fact that they were highly subsidized made them at all attractive. The
policies based on the subsidy are not sustainable in the long term. In
developing countries, these policies can only be maintained during short
periods. The concept of “comparative advantage” should be promoted in order to
use better our resources (Preston
and Murgueitio 1992).
In many
developing countries, frequent changes in the government policies in interest
rates and subsidies have also had negative impacts in biogas dissemination.
These changes have disappointed the investors in long-term biogas development.
The progressive farmers who would like to have biogas also become doubtful
about their long-term biogas investments.
Biogas technology in Vietnam
Concrete biodigester technology
More than 20 years ago, biogas production was
introduced into Vietnam as an alternative source of
energy to partially alleviate the problem of acute energy shortage for
household uses. Biodigesters of various origins and designs were tested in
rural areas under different national and international development programs
using household or farm wastes as fermentation substrates (RERIC 1990). Indian-type,
Chinese-type and ferro-cement-type digesters were
installed and evaluated in many
provinces but concentrated in urban areas, such as in Ho Chi Minh City (700), Bienhoa City
(400), Cantho City (200) (Thong et al 1989; Khoi 1989; Binh 1989). However, few farmers used them in
practice.
The poor acceptability of these concrete
digesters was mainly due to: (a) high cost of the digesters; (b) difficulty in
installing them; and (c) difficulty in obtaining spare parts for replacement. A
digester of a size adequate for the fuel needs of an average family would
normally cost VND 1.8 to 3.4 million (US$ 180 to 340). This scale of investment
is considered unaffordable by the average farm family. In addition, it would
take about 2.5 to 3.5 years to pay back the initial investment (Thong 1989; Khoi et al 1989). Besides, the replacement of worn-out
parts posed another technical problem aside from the fact that such spare parts
are not always locally available. Khoi et al (1989)
reported that 33% of biodigesters installed in Cantho City had stopped functioning while only 47% of those set up in
Quangnam-Danang Province were still operable, out of 17 digesters (Scientific Office of Quangnam- Danang 1989). There
were many projects trying to improve plant quality and to
reduce the cost (Luong and Khai
2002).
Vietnam is a nation with one of the lowest gross
national products per capita so getting support for any kind of environmental
programs is difficult. Without the support from the Vietnamese government or
from overseas, the concrete digester development goes slowly. Only the richest
farmers in rural or periurban areas can afford the
construction of concrete digesters. The development of concrete biogas
digesters is therefore not sustainable in rural areas. To disseminate the biogas
fermentation technology in rural areas, reducing the cost of digesters and simple
means of construction are necessary.
Low-cost polyethylene tubular digester
In the light of these constraints,
many developing countries, such as Colombia, Ethiopia,
Tanzania, Vietnam, Cambodia, Bangladesh, promoted the polyethylene tubular
digester technology aiming at reducing the production cost by using local
materials and simplying its installation and
operation (Chater 1986; Hieu et al 1994; Soerurn 1994; Solarte 1995;
Sarwatt 1995; Khan 1996). To this end it
was decided to use a continuous-flow flexible tube biodigester based on the
"Taiwan" model as described by Pound et al (1981)
and later simplified by Preston and co-workers (Botero and Preston 1987; Bui Xuan An et al 1994). The low-cost biodigester technology
has been well received by poor smallholder farmers in Vietnam for producing a clean fuel to replace firewood.
Within ten years, more than 20,000 polyethylene digesters were installed in Vietnam, mainly paid by farmers (Bui Xuan An 2002).
However, the biodigesters are still not fully integrated
into the farming system as there is only limited use of the by-product (the
effluent) as fertilizer for vegetables,
fruit trees, fish and water plants (
Bui Xuan An et al 1994). The use of the effluent from
biodigesters could be
studied as a resource for small scale farmers. The farmers always
put questions about quantities of manure fed to the digester, ratios between
manure and water, time of cooking, quantities of gas
produced and the useful life of biodigesters. The relevant data comes almost
from temperate countries and from concrete biodigester plants (Machain 1992).
Dissemination of the technology has had different
successes in different countries. It has been successful in Colombia, Vietnam, Cambodia (Hieu et al 1994; Soeurn
1994; Solarte 1995; Beteta
et al 1996) but there have been negative reports from other countries such as Bangladesh (Khan 1996), Nepal (Thakurgaon Training
Centre Report, Grameen Krishi
Foundation, unpubl.) and Tanzania (Corsen et al, 1996).
The same technology was used but different results were obtained. The
difference is not only between countries but also in different areas of a
country (Bui Xuan An et al 1996). Many authors presented the
advantage of low cost and easy installation of the plastic digesters (Gunnerson and Stuckey 1989; Bui Xuan An et al 1994; Soeurn 1994,
Sarwatt 1995), meanwhile some have been doubtful of
the digester life expectancy and the ability of repair of the digesters (Gunnerson and Stuckey 1989; Nazir
1991, Kristoferson and Bokalders
1992). There were several private units, NGO’s and governmental institutions
involved in this biogas type development but mainly in the South. In the North,
the Agriculture and Forestry Extension Department of MARD did not stimulate the
development of plastic biogas plants (Luong and Khai 2002).
It is necessary to study the constraints in each
area carefully and seek experiences from institutions with knowledge in this
field. All institutions and personnel who are involved in the biogas research
and development should be informed when possible experiences and results
obtained elsewhere. The electronic mail system is one of the most appropriate
means to this end (Preston 1995).
Introduction of low-cost polyethylene digesters to Vietnam
The polyethylene biogas technology was appealing
to the rural people because of its low investment, fast payback, simplicity and
positive effect on pollution. The investment for construction of a family sized
plant was from US$34 (1995) to 60 (2000). This is obviously one important feature which
makes the polyethylene digesters attractive and no farmer complained about the
price. Most of the digesters installed in the area were paid by the farmers
themselves. The important constraint for poor farmers was lack of investment
for raising animals to get manure.
About 40% of the digesters had technical problems but two thirds were repaired
by the farmers themselves. The farmers’ participation was essential in
maintenance, repair and education of other farmers. It is believed that the
dissemination of the technology requires farmers’ motivation by selecting true
farmers for demonstrations, a supporting credit system to poor people and
strengthening farmer-extension-scientist relations. Despite the good impact of
the technology, there were many
questions from the users concerning digester feeding, appropriate maintenance
and incorporation in farming systems. Future research should be focused on
studies under farm conditions.
Technical problems with the digesters
A
survey of 17 cases showed that the main causes of damage to the digesters were
sun, falling objects, people and animals. In cases when the digesters had been
totally exposed to the sun, the plastic film was broken after 2 years. Seven
digesters had films older than 2 years and four of them had been changed by
technicians or farmers. The material cost for changing was about 15 US$ and one
work-day was needed. Most digesters
installed during the last
year were protected by roofs made from local materials, mainly
palm leaves. Also, simple fences were made around the digesters to prevent
damage from animals or people.
Slightly
more than 40% of the biodigester plants had problems especially with the
plastic tubes. An interesting observation was that in 70% of the cases (12/17)
the farmers could correct the problems by themselves and only in 30% of the
cases did they needed help from a technician. The fixing was mostly easy and
farmers could teach each other. The first farmers who had digesters installed
more than 2 years ago needed help from technicians while farmers who had
installed their digesters within the last year could resolve their problems by
themselves. They had received information, experience and guidance from their
neighbours. With increasing age of the plants more problems would be expected.
Nevertheless, as more plants are installed in a village there would be more
experienced farmers to do repairs and the help of technicians would therefore
be less. Also if there are good written instructions synthesizing experiences
from users, demand
for the technical personnel will be less. This result shows that technical
problems with the polyethylene were resolved more easily than with other
materials, such as concrete, metals and red mud PVC. In
many
developing countries, the biogas programs have failed because of inefficient
maintenance such as lack of technical personnel (Kristoferson
and Bokhalders 1991). When the farmers do not take
care of the digesters, only a small problem can cause gas production to cease
making the farmers disappointed. The participation of the farmers has paid an
essential role in the dissemination of the technology. Some digesters not
counted were installed by farmers themselves in the district.
Problems in the dissemination of biogas technology
There
are some constraints and problems in the dissemination of biogas technology in
developing countries. The question is how to solve them and what priorities to
make. Some of the experiences in Bavi and Thu duc areas provide indications as to the reasons. In Bavi, the most important problem was unsuitable selection
of demonstration farms (where main income was not from farming activities)
which resulted in low feedback from farmers on technologies of installing,
maintaining and repairing the digesters. The selection of demonstration farms is important to
promote a high degree of farmer participation in digester introduction and
provide technical feedback. In the first year, the Thu duc
group installed
60 digesters with the orientation of “farmers pay” in order to strengthen their
motivation. True farmers (most activities are on-farm) with high demand
for fuel were selected as demonstrators. Several meetings between farmers and extensionists were held. Many small but important
innovations were learned from farmers when extensionists
spent time working and discussing with them. After 3 years more than 200 units
have been installed by the Thu duc group and the
technology has been improving.
Although
the biogas technology has been developing steadily around Ho Chi Minh City, there are still many
questions from farmers, such as amounts of loading of on-land and floating
digesters, how to prolong plastic life under farm conditions, how to use slurry
for crops if the fields are far from the digester, incorporation of fish ponds
and other uses of the gas. The other problems such as, investment problems of
poor farmers, variable animal production and plastic quality were also
mentioned. Many aspects involved in the technology should be studied carefully
under real farm conditions. Sustainable use of natural renewable resources will
be facilitated when the feed is grown, the animals are fed and the excreta are
recycled on the farm in ways that reduce the use of imported inputs including
energy (Preston
1995). This idea has
been displayed in integrated farming systems in many
developing countries in South Est Asia. In this
consideration, Dolberg (1994) pointed out the need to develop the ability of
researchers to be sensitive to the farmer’s perspective and convert feedback
from farmers into hypotheses for research and new possible solutions, which
would then have to go through the same iterative process of trial and error.
On-farm work will accelerate the research process and make it move faster than
if the scientists confine themselves to the research station and laboratory. In
order to realize this process, the professional agriculturists in developing countries
should be re-trained for sustainable tropical agriculture in their home
countries (Preston
1995).
Allowing
some time for the farmers to “digest” the biodigester technology is essential.
It took about 3 months from the time the first digester was installed as a
demonstration to the moment
when the first digester was purchased by a farmer. It took an additional 6
months for the first digester to be installed by a farmer by himself (Bui
Xuan An and
Preston
1995). It is indispensable to strengthen the relationship between farmers and
scientists in order to receive the feedback. According to Dolberg (1995), an
important condition for success of that approach is that the leading scientists
take it seriously and are prepared to spend time in the field with farmers,
showing how to deal with feedback from farmers and to convert that into
researchable problems.
It
should be noted that the technology of the polyethylene tubular digesters is
not fully developed and the technology depends very much on natural, as well as
socioeconomic conditions. Therefore, it is necessary to study on-farm
conditions in different areas to improve it. An exchange of experiences between
institutions should take place which should improve results. Communication
between the institutions and between technical personnel is not always sufficient.
A network of all institutions and people involved in the biogas technology
should be built over the country and overseas. Some recommendations for future
developments and research of biogas programs in Vietnam
based on foregoing criteria were pointed out by Dolberg (1995b).
Conclusions
Anaerobic fermentation is one of the most
potentially appropriate renewable energy sources for rural areas in developing
countries. Because of the process advantages, biogas disseminations in the
developing world have been promoted by many governments and organizations but its
generation has been slow. Among the constraints and problems, the high
investment for construction and difficult procedure and repair are the most
important. The low-cost polyethylene tubular technology has been resolving these
inhibiting factors but the dissemination of the technology requires farmers’
motivation. In order to promote the farmers’ participation, it is necessary to
select real farmers as demonstrators, create appropriate credit systems for
the poor and strengthen the farmer-extension-scientist relations. Research
based on farmer participation is proposed as the model for further activities.
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Hochiminh City, pp 66-69.
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