Anaerobic Degradation Pattern of Urban Solid Waste Components

MATERIALS AND METHODS

Ten specific biomass wastes in the larger basket of fermentable fractions of urban solid waste in Bangalore were collected from IISc campus in Bangalore, India. We selected 5 vegetable wastes [cauliflower, onion, flat beans, radish and peas] and 5 fruits waste [banana peel, sweet lime (Mosamby), orange rind, papaya and watermelon] as shown in Table 1. Individual components were collected fresh, within 12 hours of generation.

The TS (total solids) and VS (volatile solids) content of individual samples were determined from fresh samples. Total solid was determined by drying wastes samples at 105±2°C till constant weight. One gram of dried powdered sample was placed in pre-weighed porcelain crucibles and placed in the muffle furnace at 550±5˚C for 3 hrs. Samples were allowed to cool and weighed. The percent weight loss on ignition gave the total of volatile solids or organic matter.

Biological methane potential (BMP) was determined by fermenting powdered dry individual feedstock and their typical mixtures of equal proportion (vegetables, fruits and vegetables-fruits). This test was carried out in 135 ml serum vials with 0.5% (0.25 g/vial) of feedstock with 49.75 ml of inoculum for 60d (Chanakya et al., 2007a). Inoculum was 334 collected from a working biogas digester enriched with methanogens. After addition of inoculum in vials, the air in the headspace was immediately displaced with biogas from a biomass fed biogas plant, the bottles capped. The headspace was flushed with nitrogen and incubated upside down. The head space gas composition was determined immediately and after reaching a stationary phase of gas production for all the vials using a gas chromatograph with a Porapak-Q column connected to thermal conductivity detector. These vials were incubated upside down at ambient temperatures (25±3˚C). The gas production in these vials was determined by downward water displacement at intervals of 1, 3, 5, 8, 11, 15, 20, 25, 30, 37, 45 and 60 days after start. Controls were included to estimate the biogas production evolved from feedstock without addition of inoculum. All incubations were carried out in triplicate, except for feedstock mixtures where one replicate was used for incubation.

The non-linear regression approach was used to estimate the anaerobic degradation pattern of different feedstock. The first-order rate constant (k) was used to determine the rate kinetics of decomposition.


Abstract	Introduction	Materials and methods	Results and Discussion	Conclusion	References	PDF