| Herbage samples for small-scale batch digestion tests are often dried and milled to provide smaller representative sub-samples for analyses. Thermal drying, however, can change the chemical composition of a feedstock and these changes may impact on specific CH4 yield. Consequently, freeze drying is often the preferred system for drying grass samples. However, additional difficulties are encountered when evaluating silage samples as a result of the loss of volatile compounds during both thermal and freeze drying. As grass and grass silages are readily used as feedstocks for biogas production, the impact of drying method needs to be considered for herbages pre- and post-ensiling. This study investigated the effects of thermal (40ºC) and freeze drying on... |
