However, to be able to meet the demand for bioethanol in the near future, other raw materials must be utilized. When lignocellulosic materials are used to produce a sugar-rich substrate, some difficulties appear. Since much of the material consists of lignin (about 50% after pretreatment in many cases) high dry-matter contents must be used during hydrolysis or simultaneous saccharification and fermentation (SSF) to reach reasonable ethanol concentrations (above 4%).

It is a challenge to reach such high concentrations since mixing problems can be severe and inhibitor concentrations are higher. At the start of the hydrolysis the material may appear almost solid, while in later stages the slurry is much less viscous. Preliminary studies using steam-pretreated spruce resulted in ethanol concentrations 65- 70 g/l. The study is on-going and results will be presented.