Improvements in Bioethanol Production Process from Straw

Motivation: An efficient production of sustainable, carbon-neutral, renewable fuels like bioethanol and biogas from straw and other agricultural by-products has to be developed to guarantee mobility. The scientific focus is the improvement of the bioethanol production using straw as an alternative energy source. Methods: The ethanol production process is already established on a laboratory scale. The process involves the following steps: the pretreatment of straw with called steam explosion and cellulose becomes accessible for enzymatic hydrolysis. Subsequently, yeast ferments the obtained glucose to ethanol. Unfortunately, inhibitors such as weak acids, furans and phenolic compounds are generated during the pretreatment and hydrolysis process, thereby reducing the glucose concentration and ethanol yield. Results and limitations: Glucose concentration was raised up to 140 g/l and ethanol content up to 7% by means of optimization of the process (washing steps and recirculation). Diverse substances inhibit the fermentation and reduce the ethanol content. Washing steps prior to hydrolysis clearly reduced the inhibitory substances. Conclusion: The ethanol and glucose yield was improved due to optimization of the bioethanol production. Now an efficient procedure to reduce the inhibitors has to be established to plan a pilot plant