For many years the research on bioethanol production was based on laboratory scale experiments but since the demand for commercial bioethanol production from lignocellulosic feedstock it has become necessary to use and test the present knowledge of the process of ethanol production on a larger scale; a pilot scale (100 times larger scale than laboratory scale) before it can be applied on a large industrial scale (100 times pilot scale) production. There are several practical and technical challenges that need to be solved before industrial scale bioethanol production can be established. A continuously operated pilot plant for ethanol production from lignocellulosic feedstock was inaugurated in Sweden in May 2004. It is a complete pilot plant from a raw-material intake of wood chips in truck carried containers to a distillation column producing ethanol with a concentration up to 94%. In between, there are stages for rinsing the wood chips, steaming, impregnation, digesting, filtration and fermentation. The pilot plant is operated 24 h/day, 7 days a week and processes up to 2000 kg of dry raw material producing up to 400 litre of ethanol/day. The reactor system is continuously operated and at high pressures. This means that the wood chips have to be transported from atmospheric pressure in the raw material intake to the pressurised reactors without interrupting the material flow.

The feedstock in this plant is spruce wood chips at the moment but other feedstocks such as bagasse and other agro-based feedstock will be tested in the future. The pilot plant has two thermo-chemical reactors giving the possibility to either perform a two-stage dilute acid hydrolysis or a pre-treatment for enzymatic hydrolysis. In the plant, possibilities for both SHF and SFF are available. Also, recycling of liquids is possible in order to reduce the amount of fresh water usage. Fermentation and enzymatic hydrolysis is performed in five bioreactors with the size of 10 m3. A flow chart of possible steps in bio-ethanol production from lignocellulosic feedstock shown in Fig. 9.7.