Research on the Use of Selected Macrophytes in the Process of Methane Fermentation

Energy consumption increases globaly. Simultaneously demand for so called „clean energy“ escalates. Scientists are looking for new, more efficient technologies and alternative energy sources. Among the renewable energy sources a large potential of biomass is indicated. The aim of this study was to analyze macrophytes such as Phragmites australis, Typha latifolia, Acorus calamus, Ceratophyllum demersum as potential substrates in the process of methane fermentation. Research presents the results of the quantity and quality of biogas production using different load variations of reaction chamber with organic compounds. The study was divided into three stages depending on the range of the work. The first stage consisted of obtaining and preparation of raw materials for study. The second stage included physico-chemical analisis of substrates selected regarding hydration, dry matter content and organic compounds. The third stage was to prepare right quantities of substrates and conduct first stage fermentation, using measuring devices allowing to monitor the composition and quantity of the biogas. The experiments were conducted under laboratory conditions. Te study used plants collected from 3 lakes in Olsztyn. Investigations of biogas production were based on the respirometric method, using Oxitop Control – respirometric kit produced by WTW Company. This method allows to determine the activity of anaerobic sludge as well as the susceptibility of organic substrates to biodegradability with the possibility to estimate the quantity and composition of gaseous products of metabolism. A single kit consisted of: a reaction tank with a volume of 0.5 L connected tightly with a measuring-recording device. The process was carried out by microorganisms under anaerobic conditions and the resulting biogas caused changes of partial pressure in the measuring chamber. Changes of pressure were monitored by the measuring equipment. Reaction kits were placed in a thermostatic cabinet with hysteresis not exceeding ± 0,5°C. The process was run at a temperature of 36°C. Reaction chamber was charged with three loads: 1 kg VSS/m3d, 2 kg VSS/m3d, 3 kg VSS/m3d. The measurement was conducted in 5 replications for each variant of load applied in reaction chamber and each type of substrates,. The highest yield of biogas production was obtained for 1 kg VSS/m3d load, for each substrate used. With increasing charge of reaction chamber with load of organic compounds, the efficiency of biogas production decreased, except when the substrate was Ceratophyllum demersum. In this variant the resulting biogas quantity was constant, regardless of the applied load. The best substrate was the Phragmites australis. Average quantity of biogas in this variant was between 271 L/kg VSS to 344 L/kg VSS, depending on the applied load. The lowest yield of biogas production was observed for Acorus calamus. It oscillated from 132 L/kg VSS to 204 L/kg VSS depending on the applied load. The average percentage of methane in the biogas varied in the range of 51.1% to 61.7%, regardless of the applied load and substrate