Design and operation of a bench-scale process development unit for the production of ethanol from lignocellulosics

E Palmqvist, Bärbel Hahn-Hägerdal, Mats Galbe, M Larsson, K Stenberg, Z Szengyel, C Tengborg, Guido Zacchi

Research output: Contribution to journalArticlepeer-review


A bench-scale unit for the development of an enzymatic process for the bioconversion of lignocellulosics to ethanol has been used to study the recycling of waste-water streams to minimize fresh-water requirements and reduce effluent streams. Willow, after impregnation with sulphur dioxide, was steam-pretreated, enzymatically hydrolysed, and the sugars produced were fermented using S. cerevisiae. The fermentation broth was distilled and the stillage was fractionated by evaporation into six separate condensate fractions and a residue. The overall yield of ethanol from willow was 65% of the theoretical yield based on total fermentable sugars. The inhibitory effect of the evaporation condensates was assessed by fermentation using S. cerevisiae. The non-volatile residue of the stillage was found to be inhibitory to fermentation. The ethanol yield decreased from 0.37 g/g in a pure sugar reference to 0.31 g/g in the residue and the average ethanol fermentation rate decreased fi om 6.3 g/(l h) to 2.7 g/(l h), respectively. The evaporation condensates, containing the volatile components, showed no negative effects on fermentation. The intermediate evaporation condensate fractions, fractions 4 and 5, had the lowest chemical oxygen demand (GOD), 1560 and 1120 mg/l, compared with 33 300 mg/l for the stillage. Therefore, these fractions can be released directly into the effluent without further treatment. Copyright (C) 1997 Elsevier Science Ltd.
Original languageEnglish
Pages (from-to)171-179
JournalBioresource Technology
Issue number2
Publication statusPublished - 1996

Subject classification (UKÄ)

  • Industrial Biotechnology
  • Chemical Engineering

Free keywords

  • ethanol production
  • enzymatic process
  • lignocellulosics
  • willow
  • steam
  • treatment
  • inhibitors
  • waste-water recycling


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