Evaluation of the chemical composition of raw common duckweed (lemna minor L.) and pulp after methane fermentation

English. The development of our civilization is associated with an increase in the energy consumption by the general population. Therefore, the energy sector is of strategic importance in the development of modern countries. That is why new technologies and raw materials for the production of renewable energy resources are being widely searched for. The aim of this paper was to assess the efficiency of methane fermentation of common duckweed. Another aim was to assess the chemical composition of substrates intended for methane fermentation and of digestates. Common duckweed biomass, which originated from carp ponds, was subjected to methane fermentation. Moreover, an analysis of the chemical composition of the batch and digestates was carried out. The nitrogen content in the studied samples was determined by the Kjeldahl method, whereas determination of the other elements was based on the ICP-OES method. The research on methane fermentation showed that the amount of biogas obtained from common duckweed is satisfactory. In terms of dry matter of the batch, the total yield of biogas recovered from the batch from common duckweed was higher than that generated by maize silage. Methane fermentation of common duckweed biomass resulted in an increase of most of the studied elements, with the exception of nitrogen. Digestates generated by methane fermentation of common duckweed biomass can be used for supporting plant cultivation, as they contain substantial amounts of calcium, nitrogen and phosphorus. If the studied digestates were applied in a dose of approximately 5 Mg ha-1, the amount of the incorporated calcium would be more than 200 kg Ca. The amounts of nitrogen and phosphorus would amount to 80 and 22 kg, respectively. The content of the other macroelements was lower than specified in the scientific literature for various natural fertilizers. In no case was the threshold heavy metal content for natural fertilizers exceeded in the studied material.

English. common duckweed; methane fermentation; digestates; fertilizer value

15

685-695

2