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Wednesday, August 24, 2011

India's58' consumption ofenergy today is at 6500TWha-1, but this is expected to double in the near future. Today, about 2.5 Mio biogas plants are running, with an average size of 3-10 m3 ofdigester volume. Depending on the substrate, the plants generate 3-10 m3 biogas per day, enough to supply an average farmer family with energy for cooking, heating, and lighting.
The national advisory board for energy in India has published a report forecasting the required quantity and the manner of supply of energy in the future. The board estimates that India has enough resources to sustain 16-22 Mio small biogas plants with 2 m2 reactor volumes, each to supply sufficient energy for a farmer family with 4 cows. The estimates suggest that the plants will together provide an energy yield that corresponds to 13.4 Mio Mg of kerosene oil. The amount of fertilizer is projected at 4.4 MioMg.
In plants in India, the substrate, cattle dung, and biogenous waste, are manually mixed with water in a ratio of 10% dry matter to 90% water. The mix is filled into the digester by simply pushing. The reactor is neither heated nor isolated, enabling the fermentation process to take place at temperatures in the the region of 14 °C during winter and 25 2 C during summer. In the reactor itself, the substrate is mixed by a simple mixer which is operated manually. After a dwell time of the substrate in the reactor of around 100 days the fermented residue is removed with buckets or scoops. Pumping systems are not used.
In general, such a small biogas plant costs around 5000 Indian rupees (about 120 US$) per cubic meter of digester. The plants are constructed with the help of local artisans who receive a daily wage of 50 rupees (1.20 US$).
The construction of more and more biogas plants has revealed several beneficial side effects, such as a significant reduction in the exhaustive cultivation of forests. Unexpected successes were noted in the medical sector also. Since respiratory systems and eyes were no longer exposed to aggressive wood smoke from fires, the number of cases of acute asthma and eye diseases was significantly reduced.
Overall, the use of biogas for energy supply provides economic but also ecological and hygienic advantages.
Figure 4.3 Biogas plants. China: cross section of a "four in one" plant in China (1st row, left), "Four in one" plant in China (1st row, right)
Green house in China, part of a "Four in one" plant (2nd row, left), pig pen with loophole to digester and digester cover in the floor (2nd row, right)
Figure 4.3 Biogas plants. China: cross section of a "four in one" plant in China (1st row, left), "Four in one" plant in China (1st row, right)
Green house in China, part of a "Four in one" plant (2nd row, left), pig pen with loophole to digester and digester cover in the floor (2nd row, right)
Plastic biogas reactor in South Africa (3rd row, left), Moderm biogas plant in Kerala, India, (Suntechnics GmbH) producing 6.75 kW to lighten street-lamps (3^ row, right), Feeding of a biogas plant in Peru (4* row, left), Bioreactors in the Ukraine (Elenovka/ Dnipropetrovsk).

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