Steam explosion and thermal hydrolysis for pretreating Eichhornia crassipes to enhance anaerobic digestion

Abstract

The pretreatment of Eichhornia crassipes by means of steam explosion and thermal hydrolysis were tested to enhance anaerobic digestion. Different conditions ranging from 120 to 210oC and from 10 to 60 min (severity factor up to 5.0) were tested to assess the pretreatments influence on the substrate and the anaerobic digestion operation. Initially both pretreatments showed similar behaviors however, pretreatments mechanisms showed different results during the anaerobic digestion. The best solubilization efficiency was obtained at the severity factor 4.2 condition (210oC for 10 min). On the other hand, the best methane yield result was found as severity factor 3.8 (170oC for 60 min). For a higher severity factor value, anaerobic digestion showed signs of inhibition. These results suggest that the pretreatment optimization can’t be based only on the solubilization but also needs to consider the generation of inhibitory compounds and the remaining solid fraction after performing the pretreatment.