Managing sewage sludge and pine needles through anaerobic co-digestion in a hilly terrain: a lost cost approach

The pine needles (PNs) and sewage sludge (SS) have a significant amount of biodegradables. Due to this they are highly susceptible to pollute the environment. Both the wastes can be managed via anaerobic digestion. However, the low ambient temperature in hilly areas can affect the digestion process. Therefore, to determine their anaerobic digestibility in a hilly terrain two digesters were examined: one with mono-anaerobic digestion of SS and another one with co-digestion of SS with PNs. It was found that co-digestion yielded 40.93% more biogas than that mono-digestion of SS. Cumulative methane yield of 158.6 mL g−1 VSadded and 268.45 mL g−1 VSadded was obtained from SS and co-digestion of SS-PNs, respectively. During the experiment, a reduction of 26.7% and 35% COD and VS for SS and 30 and 34% COD and VS for SS-PNs were reported, respectively. To study the anaerobic digestibility various mathematical models and one kinetic model were also used. This study concludes that PN and SS can be managed through anaerobic digestion however their co-digestion is highly recommended.