Silage pretreatment of green crops for 2nd generation bioethanol production

New methods of pretreatment and conversion of plant biomass for energy is a prerequisite for the bio-based society, as current technologies are energy-intensive and expensive. This project examined whether ensiling treatment, ie anaerobic wet solid state fermentation with lactic acid bacteria, could be a pretreatment method for grass for bioenergy purposes. The project was a collaboration between DLF Trifolium, Novozymes A/S and Department of Chemical Engineering DTU, and showed:

1) silage improves cellulose degradation of grassland biomass, but cannot stand alone as a pretreatment method for improving enzymatic cellulose degradation of grass biomass

2) that ensiling un-avoidably causes loss of carbohydrates in biomass, but

3) that ensiling can function as an initial pretreatment before heat treatment of the biomass (hydrothermal pretreatment) as the temperature of the heat treatment can be lowered.

For green grass the work showed that the effect of silage varies with harvest time of grass, mainly because grass biomass composition varies over the season and with the grass maturity. The overall conclusion is that silage can be a useful technology integrated with storage of biomass for further processing for energy purposes.