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High gravity hydrolysis and fermentation of lignocellulosic material for production of bio-fuels


With the diminishing availability of oilbased fuels, new energy solutions are called for. There is a large interest of using bioethanol as a transportation fuel, however, using raw materials that compete with food production is not a sustainable and acceptable solution. Therefore we will work with the 2nd generation biofuels, making use of lignocellulosic raw materials. 


To meet the requirement of an economically feasible process, we will develop the process towards high gravity, i.e. operating at as high raw material concentrations as possible. Biobutanol is an alternative to bioethanol that has received increasing attention in later years, due to that it has several advantages over bioethanol, however, its production via a fermentation pathway faces a number of challenges. 


In the project we will develop and compare ethanol produced via a high gravity path with butanol production using bacteria and yeast. Life cycle analsysis will be used to assess the environmental performances. The focus area will be to optimise the enzymatic hydrolysis and the fermentation process. i.e. how are these two process steps interacting and integrated in a high gravity process. In addition, the project aims at solving and understanding fundamental challenges that arise when operating at high gravity. 

Project goals


The major objectives and deliverables in the project are: 

  • Advance the technology for production of 2nd generation liquid biofuels (ethanol and butanol) at very high gravity by improving process integration, hydrolysis procedures, developing novel robust fermentation organisms and optimising fermentation conditions 
  • Expand the knowledge-base on yeast and bacterial growth and physiology under industrially relevant (and challenging) conditions using various Nordic lignocellulosic feedstocks. Both Nordic wood and agriculture residues pretreated with hydrothermal pretreatment and steam pretreatment will be used.
  • Use LCA as a tool to evaluate, from an environmental point of view (i) yeast based ethanol production under high gravity conditions and (ii) to assess research steps necessary to make butanol conceivable as a biofuel in addition to ethanol.

The Top-level Research Initiative contributes 6 Million NOK (out of a total budget of 8 Million NOK)


Result summary

During the course of the project we have worked with two Nordic raw material streams, (i) steam-pretreated spruce yielding 20 % WIS from SEKAB E-Technology and (ii) hot water extracted wheat straw from Inbicon A/S. We have addressed specific possibilities and challenges arising from working at high gravity conditions. 


The results cover:

  • Pre-treatment technology for high gravity conditions
  • Evaluation of different process set-ups at high gravity, including evaluation of different process equipment and development of novel process schemes using separate and simultaneous saccharification and fermentation
  • Understanding the role of LPMO enzymes at high gravity
  • Addressing high gravity ethanol fermentation by evaluation of nutrient supplementation, detoxification strategies, adaptation during propagation, strain development to improve fermentation.
  • Addressing high gravity butanol fermentation showed that inhibitors is a major obstacle and that in situ recovery of butanol is a process solution necessary for high level butanol fermentation


  • LCA showed that high gravity conditions lead to a higher environmental impact due to inherently lower yields. However, in the case of straw this can be counteracted by reducing the impact of enzyme production and use. In the case of spruce, washing the pretreated spruce slurry appears to be the best detoxification strategy from an environmental point of view.

More information


HGBioFuel's final report will be published in 2015

Click here for a list of  HGBiofuel publications


Participating organisations



Project leader


Lisbeth Olsson, Professor

Department of Chemical and Biological Engineering

Chalmers University of Technology, Sweden

+46 3 1772 3805

Project team


  • Lisbeth Olsson, Chalmers, Sweden
  • Christer Larsson, Chalmers, Sweden
  • Anne-Marie Tillman, Chalmers, Sweden
  • Mathias Jansen, Chalmers, Sweden
  • David Cannella, University of Copenhagen, Denmark
  • Henning Jørgensen, DTU, Denmark
  • Hans Kristian Kotlar, Statoil, Norway
  • Børre Tore Børresen, Statoil, Norway
  • Jan Larsen, Inbicon A/S, Denmark 
  • Martin Dan Jeppesen, Inbicon A/S, Denmark
  • Sune Wännström, SP, Sweden
  • Roberth Byström, SEKAB E-Technology, Sweden
Contact person

Programme Secretary

Inger Karni, Nordic Energy Research


Phone: +47 9548 0329