Crop diversity for mixed first and second generation ethanol production

ABSTRACT

Thermohydrolysis at low temperatures achieves lower conversion compared to high temperatures. However, the process consumes less energy. We tried to make this pretreatment process more efficient by adding triticale grist to the fermentation and use the positive effect of the protein content and the increased ethanol concentration. The concept is made for rebuild of grain distilleries and reuse of the large equipment. The concept was evaluated for several crops with an attempt to crop diversity in the fields. This work presents thermohydrolysis (155°C, 45 min) with subsequent steam explosion combined with an enzymatic hydrolysis and the addition of triticale grist in the fermentation process. All substrates achieved improved cellulose hydrolysis, except for the silages. Over 90% of the cellulose in hemp straw and Jerusalem artichoke stalks was converted to glucose. Analysis for inhibitors showed high amounts of organic acids solely in Jerusalem artichoke mashes, corn and wild plant silage. The chosen conditions are suitable for a great variety of crops, also as intercrop scenario. However, silages need pH adjustment. The high loads of organic acids clearly suppress amylase activity, but cellulase activity seems to be unaffected. The switch to mixed first and second generation ethanol production in distilleries is possible.

KEYWORDS:

• Cellulose
• starch
• thermohydrolysis
• enzymatic hydrolysis
• co-fermentation

Acknowledgements

We gratefully thank DBFZ (Deutsches Biomasse Forschungszentrum, Leipzig, Germany) and BMU (Bundesministerium für Umwelt, Naturschutz, Bau und Reaktorsicherheit, Bonn/Berlin, Germany) for financial support. We acknowledge German Hasselbeck (Erbslöh®, Geisenheim, Germany) for the supply of enzymes.

Many thanks for proofreading to Sandra Schläfle (Institute of Food Science and Biotechnology, Universität Hohenheim, Stuttgart, Germany) and Bastian Fleitz (Institute of Food Science and Biotechnology, Universität Hohenheim, Stuttgart, Germany) for development of an applicable enzyme activity test.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Bundesministerium für Umwelt, Naturschutz, Bau und Reaktorsicherheit