+Centre for Application of Science & Technology to Rural Areas (ASTRA) Indian Institute of Science Bangalore 560 012, India Tel: 91-080-309 2447 / 309 2762 Fax: 91-080 - 3600085/3600683 Email :hnc@astra.iisc.ernet.in              Chanakya@astra.iisc.ernet.in              hncbiogas@astra.iisc.ernet.in