Bioethanol is one alternative energy fuel that can be produced from different types of biomass. Second generation bioethanol comes from fermentation of Lignocellulosic material and can be seen as a more environmental friendly alternative as e.g. forest residues and agricultural by-products are used. To be able to use Lignocellulosic biomass in ethanol production, it has to be subjected to different treatments first. In this study, aspen sawdust was used as Lignocellulosic material.

Ethanol produced from Lignocellulosic biomass has the potential to become a promisingalternative to gasoline. In this work the simultaneous saccharification and fermentation (SSF)technology was applied for ethanol production from hardwood with focus on cell growth,ethanol production and contamination.The SSF was performed at PH 5.5 and 35°C for different suspended solid concentrations(8%, 10% and 12%) of pretreated birch slurry which contained 16 % total suspended solids.Two different hexose fermenting yeast strain (Ethanol Red) and pentose fermenting yeaststrain were used.Quantifying the concentration of chemical components and metabolites in the fermentationmedium demonstrated that glucose and xylose are the major fermentable sugars in the slurry.The higher load of slurry (12%) represents a higher content of carbohydrates and potentiallyhigher end concentration of ethanol. Moreover, more lactic acid is produced with the lowerload of slurry (8 % or 10 %), presumably due to a result of a less inhibitory environment forbacterial growth. In this context, acetic acid sticks out as the most important inhibitor withconcentrations of 15.2 and 12.5 and 9.7 g/l respectively in the 12 %, 10 % and 8 % (ofsuspended solids) trials. Using pentose fermenting yeast may lead to higher ethanolproduction, lower xylose uptake and lower lactic acid formation.

The goal of this master thesis project was to develop computer models of some plausiblepretreatment techniques and to assess the potential benefits/costs of using pretreatment andanaerobic digestion for waste management of organic waste from a system perspective. Forthis purpose a computer program called ORWARE has been used. ORWARE (organic wasteresearch) is a program for making life cycle assessments of waste management. As the mainpart of the project work the ORWARE system has been provided with three new models ofpretreatment techniques. The additions consist of: One model of pretreatment with ultrasound,one model of thermal hydrolysis and one model of a screw press.