Experimental Study of Increase of Biogas Production from Lagoon Station's Sludge by Alkaline Pretreatment

Abstract

The present research focuses on the experimental study of the effect of alkaline pretreatment with NaOH on biogas production. Different concentrations of NaOH, i.e. 1, 2.5 and 5% (w/w), were tested on the lagoon station's sludge (dry basis) at room temperature for 24 h. The results obtained after 60 days of digestion, through the cumulative volume of biogas recorded, clearly indicate a positive effect of the chemical alkaline pretreatment on the anaerobic digestion since the amount of biogas produced increased by 42.6% when the NaOH concentration was close to 2.5%. This concentration is considered optimal under the chosen conditions. Indeed, inhibition of the methanogenic activity and a blockage of the digestion process are observed beyond this concentration. These results suggest that the alkaline pretreatment can improve the energy efficiency of the obtained biogas (CH₄ content) and reduce the residence time.