Enhanced biogas production at mesophilic and thermophilic temperatures from a slaughterhouse waste with zeolite as ammonia adsorbent

Abstract

Anaerobic digestion is a sustainable approach to deal with wastes with beneficial production of sustainable energy. In the anaerobic digestion processes, an increase in ammonia concentration hinders the efficacy of biogas production. The current study focused on minimizing the ammonia effect by the addition of zeolite as an adsorbent in a fluidized bed anaerobic reactor using poultry slaughterhouse waste as the substrate. The effects of zeolite dosage were investigated at mesophilic and thermophilic temperatures. Biomethane potential, volatile solids reduction, chemical oxygen demand, total volatile fatty acids concentration, ammonia–nitrogen levels, and pH were monitored. The initial biomethane potential test revealed that poultry slaughterhouse waste produces methane for up to 610 ml/g volatile solids (intestinal residues) and 200 ml/g volatile solids (feathers) at mesophilic conditions, 675 ml/g volatile solids (intestinal residues) and 276 ml/g volatile solids (feathers) at thermophilic conditions. The amendment with zeolite had significantly reduced chemical oxygen demand for up to 57%. Volatile solids reduction increased from 13 to 19%. Ammonia–nitrogen concentrations also decreased (15.5 mg/l) due to the application of zeolite. Enhanced biogas production of 700 ml/g volatile solids was observed after 25 days. It can be concluded that the addition of zeolite can significantly enhance biogas production by reducing the ammonia concentration in anaerobic digesters.