Page 49 - Biofuels Refining and Performance

32 Chapter One

insurmountable, but may help us to orient our future course of action,
research, and development.
1. Dehydrated cow dung is a popular fuel and does not need special or
expensive containers for keeping throughout the year.
2. Untended herds make the collection of dung laborious and cost
intensive.
3. Installation of community biogas plants is not easy. Due to the frag-
mentized small households, individual plants are also difficult to erect.
Most families cannot provide the minimum 50-kg average dung input
to the plant. About 50 L of water should also go with it. Fifty percent
of the settlements are located in drought-prone areas. The remaining
50% face water shortage during the 5 months of dry season.
4. Temperature fluctuations throughout the year are significant and
affect the rate of biogas production.

Disfunctioning and malfunctioning of some of the plants, due to the
lack of proper maintenance and servicing, create poor examples to neigh-
bors. This reduces the fresh installation potentialities and leads to an
unwillingness to invest funds. The increasing cost of installation is
another reason for the negative attitude.
The Chinese use mostly underground designs, and their outlays have
been more successful because they have already undergone a genera-
tion of restructured social order. As per Neelakantan’s (1974–1975)
report, the wet-dung yield of a cow is on an average 11.3 kg ( 3.6 to 18.6 kg)
and of a buffalo is 11.6 kg ( 5.0 to 19.4 kg). The daily output of dung from
an average of five cattle (a minimum of four) may suffice for a house-
hold with a miniature gobargas plant. When underground ambient con-
3 3
ditions (30 C), are favorable, at least 2.7 m of gas (50 m /ton of wet dung)
per day is expected out of the plant. This gas has a minimum of 9500
3
kcal (3500 kcal/m ) of heat value (equivalent to 1.5 L of kerosene), which
may serve the daily need of a five-member family. It is estimated that
the average daily requirements of the gas per adult per day are 0.3 m 3
3
for cooking and 0.2 m for lighting purposes.
3
Installation of a 3 m digester (gobargas plant), partly embedded in the
earth, or preferably constructed underground, as per improved versions
of several designs, suffices for one standard household (see Fig. 1.11). At
the present cost, it comes to about Rs. 10,000 (approximately US $200),
depending on the remoteness of the house or the community. Attractive
cost figures have been developed by competent engineers and social
workers who have estimated an annual savings to the tune of Rs. 1000
(approximately US $20) per family, and the initial investment is likely to
be paid off within 3 years. The estimated average lifetime of a gobargas