Comparison of Biogas Output During Methane Fermentation of Selected Energy Plants

Efficient conversion of plant material in the biogas is a challenge due to the complex structure of the cell wall of plants. In order to facilitate rapid and effective hydrolysis of carbohydrates pretreatment of biomass [2] is required. Pre-treatment of lignocellulosic materials can be carried out in a physical, chemical, physical-chemical and biological way [3]. Finding the right method of conducting the process of conditioning before anaerobic digestion is the subject of numerous studies. They are looking for methods that help to obtain a gas with higher efficiency. The reported study was undertaken in order to determine the effect of preliminary hydrothermal depolymerization on the efficiency of methane fermentation process in terms of quantity and composition of biogas obtained from two grass species: Miscanthus giganteus and Miscanthus sacchariflorus. The substrate was mechanically fragmented using a shredding machine Robot Coupe Blixer, and then prepared the plant material underwent hydrothermal depolymerization. This process was conducted in a pressure reactor with a active volume of 2.3 dm(3). The reactor was fed with 600 g of Miscanthus biomass of hydration of 90% and organic matter content of 10% in fresh weight. The reactor with the plant material was incubated at 200 degrees C and a pressure of 17 Ba for 30, 60 and 120 minutes in a muffle furnace. The processed plant substrate was next subjected to mesophilic fermentation. Application of hydrothermal depolymerization led to an increase in biogas quantity and improve its quality, the longer the conditioning time, the better outcome of this process. Due to content of methane in the biogas and the calorific value of methane Miscanthus saccharifloru was found to be more efficient. The study showed the relationship between the time of thermal depolymerization plant substrate, and the amount and composition of biogas produced in the process of methane fermentation. With the time of thermal depolymerization of both species tested the amount of the resulting biogas increased. Comparing two of the studied plants for their use as feedstock in biogas farm had a higher potential for Miscanthus sacchariflor. Comparing the calorific value of the two grass species, we can see that a much better substrate proved to be the Miscanthus saccharifloru. This species also proved to be particularly vulnerable to heat. Taking into account the ratio of the energy value of the resulting biogas for thermal conditioning of the time proved to be effective biogas Miscanthus saccharifloru. Based on the survey it was found that the conditioning process improves the fermentation process. Better substrate in terms of quality and quantity of biogas has proved to be a Miscanthus saccharifloru. Miscanthus saccharifloru fermentation resulted in obtaining biogas methane content min 12% more than the Miscanthus giganteus fermentation.