Hydrocarbon and Ammonia Production from Catalytic Pyrolysis of Sewage Sludge with Acid Pretreatment

Sewage sludge is the major byproduct generated in wastewater treatment plants and a potential resource for biofuel production. This study investigated the catalytic pyrolysis (CP) of sewage sludge with HZSM-5 (CBV2314) in a microfurnace pyrolyzer for the production of hydrocarbons and ammonia. Pyrolysis temperature had a significant role in the production and selectivity of aromatic hydrocarbons, olefins, and alkanes. Acid pretreatments including infusion and washing were employed to alleviate the catalytic effects of ash content in sewage sludge and improve the hydrocarbon production of CP. Both acid-infusion and acid-washing enhanced hydrocarbon production but acid-infusion yielded higher hydrocarbon production than acid-washing. At 650 °C the optimal acid infusion loading was 1 mmol·g^-1 sewage sludge and hydrocarbon yields reached to 51.4%. CP of acid-pretreated sewage sludge enhanced the denitrogenation of volatiles by releasing nitrogen as ammonia which could be recycled as fertilizer. These findings demonstrated that CP with acid pretreatment is a promising approach to converting sewage sludge into valuable fuels and chemicals.