Cellulosic and starch-based raw materials in ethanol production.

In the last years, the production of ethanol from renewable energy sources has come to the fore because of its potential to reduce greenhouse gases, especially CO2. If cellulosic and starchy materials should be used efficiently for ethanol production, short distances are necessary to save energy during the transport of the raw materials because of the low density of cellulosic raw materials. Short distances stand for regional ethanol production. One possibility for regional ethanol production is described by a study of Senn (2002). In addition to this study, cellulosic material e.g. corn silage can be used in the distillery to produce bioethanol. Because of the different natural structures of cellulosic and starchy biomass two different methods of treatment have to be used to get fermentable sugars. The cellulosic material needs to be pretreated mechanically and thermally at temperatures up 240°C before enzymatic hydrolysis with technical enzymes can digest the structure. In recently performed experiments it was possible to digest the cellulosic biomass up to 70% within two days after a mechanical pretreatment with a homogeniser and thermal treatment with temperatures up to 160°C. To enhance the low dry matter of the cellulosic mash after enzymatic hydrolysis, the sweet mash is used as process liquid for the starch process. Contrary of cellulosic material the starchy material can be treated with usual distillery methods and temperatures lower than 100°C. Using the cellulosic material as an additional source for the ethanol production, it should be possible to improve the energy balance of the process because of a minimal energy input in cellulose pretreatment and the possibility to produce biogas from the non-converted cellulosic material.