Increased methane yield from dairy cow manure by co-substrate with Salvinia

Abstract

The objectives of this recent study were to examine the partial substitution of dairy cow manure (DCM) with aquatic weed Salvinia molesta (SM). The treatment consisted of replacing DCM with SM at four different levels of SM proportion in the combined substrate: 0%, 9.87%, 18.08%, and 25.02% in terms of volatile solid (VS), respectively. In addition, methane production of different parts of SM and biogas production of digested slurries were also evaluated. The result showed that methane production was increased significantly (p<0.05) by 21.89% and 22.73% in terms of substrate weight and active bio-digester volume with the highest proportion of SM (25.02%) in the combined substrate, with values of 11.86 L/kg and 0.54 L/L, respectively. The ultimate methane yield of the whole plant, shoot system (i.e., the above ground part), and roots of SM were 118.49, 141.14, and 108.76 L/kg VS, respectively. The shoot system of SM had the highest methane yield and crude protein and the lowest ash and lignin concentrations, when compared to the whole plant and root system. As the proportion of SM in the combined substrate increased, so did the biogas production of the digested slurry. Therefore, when SM is used as co-substrate with DCM, the application of post digestion will be beneficial to capture the remaining biogas production of the digested slurry.