Tuesday, May 3, 2011
The demand for renewable and sustainable energy sources is increasing due to the ascending greenhouse gas emissions and the prospect of scarcity of fossil fuel in a near future. The transport sector especially in Europe needs to find alternative feedstock’s for fuel production to meet the set target from EU of 10% transportation fuel coming from renewable sources by 2020. One source that has to be considered as feedstock is residual lignocellulosic materials from agriculture. The benefit of using agricultural residuals is the possible less competition with food production. Wheat straw is one such potential residue produced in great amount and with high energy content. The cellulose and hemicellulose fractions in the straw are suitable for production of bioethanol and biogas in a joint process. The remaining lignin can be utilized to provide heat and electricity for the process, which makes the integrated process feasible both in terms of energy efficiency and economics. It is also crucial to make the process as environmental friendly as possible.
This study investigates the outlook of combining weak organic acids with steam explosion to pretreat wheat straw. Ethanol is produced from the material by simultaneous saccharification and fermentation using hexose fermenting yeast. The residual sugars and other organic materials, including the acid used in the pretreatment, are used for biogas production by anaerobic digestion. An evaluation of different process configurations in terms of energy efficiency of the produced bioethanol and biogas will be presented.