The effect of ensiling and alkaline pretreatment on anaerobic acidification of Napier grass in the leached bed process

The characteristics of feedstock are important to the biocatalyst-based processes. Herein the effect of ensiling and alkaline pretreatment on acidification of Napier grass in anaerobic leached bed reactors was investigated. The results depicted clearly that grass preparation affected its chemical properties and leaching ability differently. After pretreatment in 3.0% of NaOH, lignin was reduced significantly by 50.1% to 68.0%, while less deterioration was found for ensiling. About 18.9% to 54.1% of the produced soluble chemical oxygen demand (SCOD) of these biomasses was increased subsequently compared to 0.102 kg SCOD or 0.56 kg SCOD/kg VSadded of raw grass digestion. However, about 3.3% of SCOD was reduced after the ensiling. An extension of biomass soaking time and heat supplementation under alkali-thermal conditions of raw grass promoted more production of SCOD for 18.9% to 29.9% and 54.1%, respectively. While about 45.5% to 54.4% of SCOD was increased for alkali-thermal pretreated residue. The solid content and lignocelluloses were changed differently and accordingly with treatment conditions. Similar profiles of leachates contained mainly acetic acid were obtained. These results confirm the beneficial application of alkaline soaking and ensiling as a pretreatment method to enhance the solubilization of grass biomass under the leached bed acidification process.