# Biodegradation of a Mixed Manure-Lignocellulosic System--A Possibility Study
## 1 Introduction  
Renewable and sustainable bioenergy production has received a great deal of attention over the last several decades because of increasing energy demand and popular awareness of global warming caused by greenhouse gases [1, 2, 3, 4]. Depletion of fossil fuels can be reduced with the use of renewable energy sources, such as biofuels and biogas [5]. In addition, from a waste management point of view, the conversion of bio-waste (including garden and agricultural waste, foliage, kitchen waste, different manures and sewage) to bioenergy is more acceptable and preferable to landfill disposal or other kind of waste treatment [6, 7]. Increasing demand for food is reflected in expanded poultry rearing operations, which produce large amounts of miscellaneous waste, including feathers, fats and chicken manure. Because of environmental concerns (odor, greenhouse gas emissions, pathogens spreading and pollution of water), chicken manure cannot be disposed of in landfill sites [8, 9]. Therefore, various approaches have been employed to solve this problem, including computing [10, 11, 12, 13], pyrolysis [14, 15, 16], combustion [17, 18], gasification [19, 20, 21], hydrothermal carbonization [22, 23] and aerobic fermentation [24, 25, 26]. Anaerobic fermentation is a renewable and sustainable process for biogas production. Chick manure can be used as a substrate in this process. When chickens are reared, sawdust is applied for litter. Anaerobic microorganisms are not capable of degradingthis lignocellulosic biomass; however, some kind of pre-treatment must be performed. Lignocellulosic residues are widely available and are mainly composed of cellulose, hemicelluloses and lignin. All of them are rich in carbohydrates, which can be converted into biomass during the anaerobic digestion of both cellulose and hemicelluloses. However, the presence of lignin is well known to limit the accessibility and, thus, the biodegradation of polysaccharides in lignocellulosic materials. Due to the complicated structure of the cell walls, lignin is difficult to hydrolyze. Pre-treatment techniques include physical, thermal, chemical and biological [3; 4; 27; 28; 29]. The use of white-rot fungi for pre-treatment of lignocellulosic biomass is gaining attention among researchers, because it is an environmentally acceptable biological process [4]. For instance, _Pleutrotus ostreatus_ has been used for the pre-treatment of rice straw [30; 31], corn stover [32], Miscanthus [33] and wheat straw [34]; _Trames versicolor_ for wheat straw, barley straw [35] and Miscanthus [36]; _Polyporus brumalis_ for wheat straw [37]; _Ganoderma lucidum_ for rice straw [38]. White-rot fungi are generally preferred, as these organisms are most efficient in delignification. Their unique enzymatic system gives them the capacity to attack phenolic structures and to transform lignin. Although other microorganisms than white-rot fungi can be of interest in a pretreatment step for anaerobic digestion, they do not appear to outcompete them. White-rot fungi also have a strong potential to increase methane or bioethanol production. The main purpose of this study was to check the ability of _Pleutrotus ostreatus_ fungi to degrade the lignin present in the mixture of chicken manure with sawdust and wheat straw in one case and in the mixture of chicken manure with sawdust and Miscanthus in another case. For the comparison, ordinary (without fungi pre-treatment) wheat straw and ordinary Miscanthus were used as co-substrates. The addition of plant raw materials to animal waste is desired to balance nutrients, increase buffer capacity and improve possible biogas production. _Pleutrotus ostreatus_ was selected for the pre-treatment of wheat straw and Miscanthus, because it has a high potential for delignification.