Waldemar Szaferski

Silage of Switchgrass ( Panicum virgatum ) as a Bioenergy Feedstock in Poland

The production of biogas from the waste materials and crops is one of the main ways of acquiring the renewable energy. The switchgrass (Panicum virgatum) is a plant with significant potential for energy utilization in terms of thermal utilization and bio-logical processing. The aim of that work is to indicate the level of biogas productivity of switchgrass. The research methodology has been done according to DIN 38414 p.8. The plant material was used in the form of silage. The effect of exposure of plant material to atmospheric air was tested in the studies. Results were compared with silage samples. Plant substrate samples were mixed with biologically active liquid substrates: inoculum and slurry. Studies were carried out on the mixture with a dry matter content of up to 8% m/m. The results were statistically analysed. The correct courses of the fermentation processes were observed for both tested cases of the plant materials. Results of the studies indicated that the productivity of biogas for silage switchgrass, which was exposed to atmospheric air, was increased by 20.7% v/v. At the same time, increased emissions of nitrogen oxides and hydrogen sulphide were observed. The average methane concentration in biogas was higher for the aerated plant sample and was equal to 56.11% v/v. Favourable results for the initial method of aeration should be attributed to initiate decomposition of biomass be-fore the actual fermentation process.

Reduction of Energy Consumption in Gas-Liquid Mixture Production Using a Membrane Diffuser and HE-3X Stirrer

Mechanical mixing of liquids in the presence of gas is used when it is necessary to exchange mass between the liquid and gas phase whose special case is aeration of liquid. Mixing of liquid-gas multiphase systems has been widely used in industrial absorption (purely physical and with chemical reaction) processes of hardly soluble gases and biochemical engineering. The rate of liquid mass transfer limits the whole process. By increasing the surface of the interphase contact and splitting large gas bubbles into finer ones, it is possible to significantly intensify the process. In this case, the barbotage itself is insufficient and the mechanical stirring apart from the increase in the interphase contact area and the shorter restoration time of the limiting layer, is responsible for even circulation throughout the apparatus. For this purpose, the modernization of the process has been introduced by introducing a membrane diffuser into the test apparatus, which is used to efficiently introduce the gas into the mixer and to guarantee the maximum dispersion of the air bubbles at low volume flow rates. In addition, the mixer is fitted with a modified HE-3X stirrer which is to increase the residence time of the air bubbles and reduce the energy consumption for creation of gas-liquid mixture.

Chemical Processing of Switchgrass ( Panicum virgatum ) and Grass Mixtures in Terms of Biogas Yield in Poland

Decomposition of waste biomass as a result of thermal, biological and chemical processing allows for the acquisition of energy and its carriers. Switchgrass (Panicum virgatum) and grass mixtures are a universal biological substrate for energy purposes. The digestibility of organic substrates in the fermentation process limits the presence of raw fiber. The aim of the work was to indicate the effectiveness of the method, which consists in pretreatment with the sodium hydroxide of the plant material. Processing conditions for low sodium concentrations (3.5 and 2% m/m) were determined. The study used the methodology of testing productivity of biogas in accordance with DIN 38414 p.8. Fresh vegetable substrate, slurry and inoculum were used to produce test mixtures. The results of the research have been developed statistically. Shapes of obtained characteristics of biogas productivity showed the correct course of the methane process. The total biogas productivity of switchgrass as a result of processing with sodium hydroxide gave better effect than with similarly processed grass mixtures. Cumulative biogas productivity of switchgrass mixtures as a result of chemical processing increased by about 10% v/v. Cumulative biogas productivity of grass mixtures, as a result of chemical processing, increased by approximately 17.5% v/v.