From Waste to Bioethanol - A Feasibility Study on Animal Bedding

Abstract: For the year 2020, the European Union has set common goals to aim for regarding the environment. One of them being to reduce the green house gas (GHG) emissions by 20 percent. The world population is increasing, consequently increasing the demand for energy and food. Since the use of fossil sources is neither sustainable nor environmentally friendly, new techniques of meeting the energy demand need to be found, starting with one of the biggest contributors to GHG – the transportation sector. Alternative fuels such as bioethanol need to substitute today’s fossil fuels. Bioethanol in particular can be made from materials such as sugar- or starch-based crops, referred to as first generation (1G) bioethanol. It can also be produced from lignocellulosic substrates, which in this case is referred to as second generation (2G) bioethanol. In case of 2G bioethanol, the sugar components that are necessary for the production of bioethanol are difficult to access. This drawback makes the process of 2G bioethanol production more challenging. However, 2G ethanol does not compete with the food market, per se. The aim of this thesis was to investigate different fermentation configurations using animal bedding as the raw material. Bioethanol from animal bedding, can be referred to as 2G bioethanol. The investigation was conducted experimentally at the Department of Chemical Engineering at LTH. The animal bedding was collected at a farm in Køge, Denmark. It was once washed with water and later soaked in 0.4 wt-% sulfuric acid. The animal bedding was pretreated in a steam explosion reactor at 190°C for 10 minutes. Results showed that it is possible to produce bioethanol from animal bedding. When using simultaneous saccharification and fermentation (SSF), an ethanol yield above 0.47 g ethanol/g glucose can be obtained. A slightly higher yield (0.51 g ethanol/g glucose) was achieved when using fed-batch instead of batch. Since it was desired to utilize as much sugar as possible from the animal bedding, simultaneous saccharification and co fermentation (SSCF) was also tested with the genetically modified yeast strain KE6-12B. No significant amount of ethanol was produced when using SSCF.