Evaluation of technology structure based on energy yield from wheat straw for combined bioethanol and biomethane facility

The objective of this paper is to evaluate a combined bioethanol and biomethane production from wheat straw applying process network synthesis for maximised energy yield per ton lignocellulosic biomass input. Experimental results in combination with literature data were implemented in process synthesis software for energy optimisation. Wheat straw was steam exploded at different pretreatment conditions on laboratory scale. Glucose and ethanol yields as well as specific biogas yields of different solid and liquid fractions were determined via batch-experiments. Preferable pretreatment conditions differ between biogas and bioethanol production. The optimal process configuration was found to consist of direct biogas production from steam explosion pretreated straw at 170 °C for 20 min combined with bioethanol production from straw pretreated at 200 °C for 20 min. This process results in a purified methane yield of 7892 MJ and a purified ethanol yield of 964 MJ per ton untreated straw input.