Effects of Silage Pretreatment on the Anaerobic Digestion of Different Parts of Water Hyacinth

Abstract

Abstract. In this work, the influences of silage pretreatment on the anaerobic digestion of different parts of water hyacinth (leaves, stems, roots) were investigated respectively. The silage pretreatment at 30°C was processed within 4 days, then series of anaerobic batch digestion at 35°C were carried out. The results showed that silage pretreatment can improve the biogas and methane yield of water hyacinth leaves. With increasing ensilaging period from 1 to 4 days silage pretreatment of water hyacinth leaves, the biogas yield increased correspondingly. The cumulative biogas and methane yields produced by 4 days ensilaged water hyacinth leaves were 9.6% and 14.4%, more than the control group on 28th day at the end of the experiment. It seems that the total biogas yield from leaves trends to increase by prolongating the pretreatment period properly. In contrary to this, the biogas yields from water hyacinth stem decreased, but the methane yields were increase a little after silage pretreatment. The total solid (TS) and volatile solid (VS) values of water hyacinth leaves were decreased with increasing of the silage pretreatment time. The specific biogas and methane production of untreated water hyacinth stem was a little higher than of the untreated leaves. The untreated water hyacinth roots produced the least specific biogas and methane. The water hyacinth leaves still produced biogas on the 28th day, while the stems of water hyacinth stopped producing biogas on the 19th day, and the roots of water hyacinth even on the 12th day. The silage pretreatment needs no additives and less energy to keep the temperature during the summer, while the water hyacinth grows the fastest.