Lignocellulosic biomass, including agricultural residues, wood and energy crops, is an attractive material for bioethanol production. Lignocellulosic biomass could produce up to 442 billion litres per year of bioethanol (Bohlmann, 2006), which is about 16 times higher than the current world bioethanol production (Kim and Dale, 2004). Furthermore, about 3.6% of the world’s electricity production and 2.6 x 1012 MJ of steam are also generated from burning lignin-rich fermentation residues, a co-product of bioethanol made from crop residues and sugar cane bagasse. Most potential electricity and steam production could be provided by burning fermentation residues in the utilisation of wheat straw (Sun and Cheng, 2002).

Conversion of cellulosic biomass is a future alternative of biofuel production. However, bioconversion of cellulosics and lignocellulosics to bioethanol is difficult due to the resistant nature of biomass to breakdown, the variety of sugars that are released when the hemicellulose and cellulose polymers are broken, the need to find or genetically engineer organisms to efficiently ferment these sugars and costs for collection and storage of low density lignocellulosic feedstocks (Balat et al, 2008). Provided that cellulases and pretreatment processes are expensive, genetically modified crops to reduce the needs for pretreatment processes are promising paths to solve this problem, together with other strategies, such as increasing plant polysaccharide content and overall biomass (Sticklen, 2008).

Forest and agricultural residues may be used to produce bioethanol. As an advantage, there would not be a strong competition between the use of land for food and for energy. Sorghum seeds can be used for food, while the stems could be optimised for different chemical platforms. Recent studies concluded that sweet sorghum is a very useful plant, whereby the complete plant can be used without leaving any waste (Smith and Buxton, 1993; DSD, 2005). Lignocellulosic biomass of cardoon can be used as a solid biofuel, while seed oil can be derived for biodiesel production (Fernandez et al., 2006). Lately, the production of ethanol fuel from cardoon stems and leaves has been proposed (Martinez et al, 1990).

New crops that have been evaluated as bioenergy crops over the last years include switchgrass and elephant grass. Provided they cannot be used for feeding purposes, they seem to successfully substitute cereals, such as corn, to produce bioenergy. Lignocellulosic perennial crops (e. g. short rotation coppices and inedible grasses), especially warm-season (plants with C4 carbon fixation) perennial grasses, are promising feedstocks because of high yields, low costs, good suitability for low quality land (which is more easily available for energy crops) and low environmental impacts (Cherney et al, 1991).

Another group of dedicated bioenergy feedstocks is woody plants, including hybrid poplar, willow and pines. Hybrid poplar is considered a model woody biomass feedstock because of its broad adaptation, available genome sequence and fast growth. The biomass accumulation of hybrid poplar is reported to be between 7 and 20 mg/ha/year depending on the nutrition and environmental conditions (Christersson, 2006; Yuan et al., 2008).