Steam treatment of digested biofibers for increasing biogas production

The aim of this study was to elucidate the effect of steam pretreatment on the biomethane potential of biofibers from digested manure. These biofibers were treated for 15 min with steam in a pressure vessel. The effect of steam treatment temperature, solids content, catalyst concentration and time of pre-soaking on the methane potential of the biofibers was determined. The highest increase of methane production from steam-treated biofibers compared to untreated biofibers was 67% and was achieved at 155 degrees C with addition of 2.1% w/w H2SO4. Also higher treatment temperatures (180 degrees C without addition of acid) improved the methane production, but only by 29% compared to untreated biofibers. Long pre-soaking treatment (24 h) and high acid concentration increased the risk of inhibition of the biogas process. The energy from the increased methane production after steam treatment was between 15 and 121 kW h (t WW)(-1) (wet weight of untreated biofibers).