Anaerobic capacity of solid pulp and paper mill waste

Aqueous suspensions of solid paper mill waste, fortified with nitrogen supplements, were effectively biodegraded into CO2 and CH4 under anaerobic conditions, with the major portion of the gas production occurring within 25-35 days. The procces was operated as a batch culture seeded with mesophilic methanogenic granular sludge. NH4CI, NH4NO3 or Urea at initial C:N ratios of 125:1, 125:1, or 150:1, respectively, sopported the best bioconversion rates. Other nitrogen sources at higher and lower concentrations as well as mixtures of nitrogen salts and trace mineral supplements were less effective in promoting methanogenesis and substrate reduction. The productive incubation temperatures ranged between 21-48oC. Reduction of bulk was 60-70 o/o of organic content, depending on the nitrogen supplement and incubation temperature. Digesters supplemented with NH4CI, Urea, or NH4NO3 produced an average of 100 L, 95 L or 77 L of CH4/kg of organic solid waste, respectively. The potential commercial value of the methane gas produced was calculated to be an average of $315 per ton of organic content of the solid waste or $150 per ton of total solid waste