Shockwave pre-treatment enhances the physicochemical availability and anaerobic mono- and co-digestion of highly concentrated algae

Abstract

The effect of shockwave pre-treatment of algae on biogas production and physical availability was elucidated by lab-scale experiments. The solubilization rate, dewaterability, drying performance, microcystin concentration, and anaerobic mono- and co-digestion (algae and livestock manure) efficiencies before and after shockwave application were compared to those of other pre-treatment techniques (ultrasonication and thermal hydrolysis). Dewaterability and drying efficiencies of algae pretreated with shockwaves were 5.2 and 2.1 times higher than those of non-pretreated algae. Non-pretreated algae improved solubilization from 12% to 47%. The shockwave pre-treatment enhanced the reduction of the extracted microcystin concentration from 391.9 to 350.9 μg/L without affecting the methane production rate. The cumulative methane yield increased from 197.6 to 414.5 mL/g-VS for mono-digestion of algae and from 290.1 to 375.0 mL/g-VS for co-digestion of algae (20%) and livestock manure (80%). Co-digestion with 3 kJ/g-VS revealed the highest energy efficiency of 482.8%. Overall, the shockwave pre-treatment significantly enhanced algal physicochemical availability and methane production rate.