Influence of silage additives on methane yield and economic performance of selected feedstock

Ensiling is an appropriate way of preserving feedstock for anaerobic digestion. Biological and chemical silage additives were used to improve silage quality and to prevent silage losses due to aerobic instability. Lab-scale experiments were conducted using alfalfa, grass and maize. Silages without additives and with chemical and biological additives were compared to the fresh material as well. The effect of silage additives was investigated using batch anaerobic digestion tests and comparing the results on an organic dry matter basis as well as on a hectare basis. In an economic assessment the costs of silage additives were compared to the additional proceeds which can be achieved from improving digestability and preventing silage losses. There seems to be some evidence that there is a correlation between organic acid content of silages and methane yield on organic dry matter basis. Considering aerobic instability of opened silos the additional income can over-compensate the costs of the application of chemical additives