BIOGAS PRODUCTION POTENTIAL OF UNEXTRACTED, NUTRIENT-RICH ELEPHANT-GRASS LIGNOCELLULOSE

In an extension of an earlier study of the formation of a mixture of m ethane, propane and carbon dioxide in the biodegradation of solvent-ex tracted elephant grass lignocellulose using pure microorganism culture s unextracted (crude) elephant grass stalk was used. The effects of mi xed microorganisms (instead of pure cultures), potato dextrose agar (P DA) and nutrients (PO43- SO42-, urea, D,L-asparagine) were studied. In addition, the effectiveness of mixed microorganisms harnessed directl y from the air on substrate samples was also investigated. The results showed good correlation with those of the earlier study. The extent o f biogas formation was found to depend on the concentration of elephan t grass and to be first-order with respect to the latter. PDA and all the nutrients enhanced biogas formation. Urea was most effective at th e lower concentrations. Systems with microorganisms harnessed directly on the substrate by prior exposure to air degraded practically as eff iciently as those treated with mixed cultures.