M. ARSHADI, Swedish University of Agricultural Sciences, Sweden and H. GRUNDBERG, Processum Biorefinery

Initiative AB, Sweden

Abstract: Bioethanol can be produced from different sources of biomass including biological material from agricultural products and forest raw materials. The chapter first discusses the different biomass feedstock available for both first and second generation bioethanol production. It then discusses the various process technologies including pre-treatment, acid hydrolyses, enzymatic hydrolyses and fermentation steps to convert the various feedstock to bioethanol. The chapter includes a description of a pilot plant for production of bioethanol from lignocellulosic materials. Environmental aspects and future trends of bioethanol production have also been discussed.

Key words: biomass (lignocellulosic) feedstock, enzymatic hydrolyses, acid hydrolyses, bioethanol process tecnology, fermentation.

9.1 Introduction

For many years transport systems have relied on fossil fuels such as petrol, diesel and natural gas but these fuels are not sustainable in the long term. Petroleum prices have increased steadily over recent years which has caused much interest and investment in biofuels production. Emissions of greenhouse gases such as CO2, CH4 and N2O from the combustion of fossil fuels in the engines of motor vehicles have had negative impact on human health and also caused weather changes related to global warming. The Kyoto Protocol demands that the European Union cut CO2 emissions by 8% between 1990 and 2012. In 2007, the 27 European Union member governments approved a new target to cut their collective greenhouse gas emissions by 20% from the 1990 level by 2020.

The health and environmental problems together with increasing worldwide demands for energy and the depletion of fossil fuels in the near future call for sustainable production of fuels for the transport sector. At the same time, developing motor vehicles which increase efficiency and reduce fuel consumption has been urged. Therefore, the development of fuel systems that are based on renewable sources has been the topic of frequent international discussion.

Different transport fuels have different physical and chemical properties and they may exist as liquids or gases in many cases, e. g. biodiesel, biogas and bioethanol (ethanol derived from biological sources). The production of these from renewable resources has increased during recent decades. Liquid fuels are easily handled and possess a high energy content. The global production of bioethanol was 51 billion litres (13.5 billion gallons) in 2006 (Balat, Balat, and Oz, 2008; Sanchez and Cardona, 2008).

Bioethanol as a fuel has both advantages and disadvantages depending on the type of engine (Otto engine or diesel engine) using the fuel and there are some physical obstacles to bio-ethanol use. Bio-ethanol can be produced from different sources of biomass including biological material from agricultural products and forest raw materials, etc. The biomass feedstock can also be divided into several groups depending on the type of chemical structure of the raw material, e. g. sugar, starch or cellulosic materials. In a future bio refinery process the production of bioethanol should be integrated with the production of other value added chemical compounds and biofuels in order to be able to utilise the feedstock in an optimum way (Demirbas, 2009).