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Inventory of Innovative Indoor Smoke
Alleviating Technologies in Nepal
Chapter Six
BIOGAS TECHNOLOGY
Biogas is a combustible gas produced by anaerobic
fermentation of organic materials by the action of
methanogenic bacteria. This odorless gas is 20 per cent
lighter than air and burns with blue flame as LPG. Biogas
contains methane and carbon dioxide and has the
proportion of methane (50 to 70 per cent), carbon dioxide
(30 to 40 per cent), hydrogen (5 to 10 per cent), nitrogen
(1 to 2 per cent), water vapor (about 0.3 per cent) and
traces of hydrogen sulphide. Retention time of
biodegradable material varies depending upon
temperature and type of materials used to feed in the
anaerobic digester. Generally biogas in Nepal refers to
the gas produced from animal excreta. However, it can
also be generated from human excreta, wastewater from
industries, byproduct of food wastes from food
industries, municipal wastes, energy crops like hyacinth
and other various organic products. The waste materials
of plants and animal origin consist mainly of
carbohydrates, lipids, proteins and small amounts of
metabolites generally insoluble in water. If biodegradable
organic materials are decomposed or fermented in
anaerobic condition, combustible methane gas is
produced by the bacterial action. The typical biogas plant
called GGC 2047 model is promoted in Nepal by Biogas
Support Programme (BSP) shown in Figure 6.1.
Livestock plays an important role in the Nepalese farming
system; with 2.7 million HHs owning cattle and buffalo
(estimate 2001). The technical potential of biogas plants
in Nepal is about 1.9 million; 57 per cent in plains, 37
per cent in hilly areas and 6 per cent in mountainous
regions (BSP 2004). There is a huge potential of biogas
production throughout the country which can generate
71,383 Giga Joules of energy considering the average
yield of 1.7 cum biogas per day from the types of plants
widely adopted in Nepal (1 Cum biogas = 22.1 MJ from
Source: SESAM/Rehling: Energy and Development, p. 18).
It is reported that 157,675 biogas plants have already
been installed in 67 districts by December 2006 under
BSP. Until 2005, BSP covered 2593 VDCs of the total
4000 VDCs. About 98 per cent of the constructed plants
are in operation. A total of 102,719 toilets were
constructed and is connected to biogas outlets. About
1 million people are directly benefiting and about 11,000
are employed. In order to provide financial assistance
for the establishment of biogas plants, 130 micro finance
institutions are mobilised. Likewise, 60 private biogas
companies are strengthened and 16 biogas appliances
manufacturing workshops are developed so far (BSP
2007).
The government is prioritising the importance for biogas
promotion in plan since seventh five year plan (1985 to
1990). The tenth five year plan (2002 to 2007) has taken
a long term approach for commercialisation of biogas
sector and has a target to install 200,000 (revised to
175,000) biogas plants.