Assessment of a mechanical pretreatment to enhance biogas production from the noxious weed eichhornia crassipes on industrial scale

The effects of a mechanical pretreatment were determined on the methane yield of water hyacinth. The feedstock was pretreated using a two stages dry milling process and the experiments were performed at a mass flow rate of about 750 kg h -1 . Untreated and pretreated materials were both anaerobically digested in batch reactors under mesophilic conditions for 28 days. The cumulative biogas production from pretreated hyacinth exceeded 141.8 Nm 3 tr -1 of volatile solids, showing a +44.5% gain compared to the raw material. Such a gain resulted above the known range for size reduction pretreatments and the energy consumption for treatment was only 14.5% of the electric energy output from the processed materials. The net primary energy output from pretreated hyacinth was enhanced by 28.7% respect the untreated feedstock, showing that the investigated pretreatment might be successfully used to improve anaerobic digestion of water hyacinth on an industrial scale.