Lignocellulosic Biomass—Thermal Pre-treatment with Steam

With the ever rising demand for more energy and the limited availability of depleted world resources, many are beginning to look for alternatives to fossil fuels. Liquid biofuel, in particular, is of key interest to decrease our dependency on fuels produced from imported petroleum. Biomass pre-treatment remains one of the most pressing challenges in terms of cost-effective production of biofuels. The digestibility of lignocellulosic biomass is limited by different factors such as the lignin content, the crystallinity of cellulose and the available cellulose accessibility to hydrolytic enzymes. A number of different pre-treatment methods are known to enhance the digestibility of lignocellulosic biomass by affecting these limiting factors. Some of them are: milling, thermal pre-treatment with steam or hot water, acid pre-treatment, and alkaline pre-treatment. This chapter will focus on one of the more promising technologies; thermal pre-treatment with steam. The Norwegian company Cambi developed a process for treatment of sludge from waste water treatment plants, and the idea was based on the experience that cooking sludge under pressure at temperature from 150 °C to 180 °C improved the digestibility and at the same time increased the dewaterability of the sludge. If Cambi's process is to be used for treatment of biomass, it will have to compete with other processes on market. The strongest competitor at present is the integrated biomass utilisation system process of DONG Inbicon which is used for pre-treatment of straw. Both processes are being described and discussed in this chapter.