Strašil Z., Kára J., 2010. Study of knotweed (Reynoutria) as possible phytomass resource for energy and industrial utilization. Res. Agr. Eng., This paper deals with the Reynoutria × bohemica and Reynoutria japonica under conditions of the Czech Republic. It evaluates the impact of soil, weather conditions and various terms of harvest (autumn, spring) on the yield, dry matter content, phytomass loss, ash content, and basic elements content change in plants. Heavy metals content was determined in soil where plants were grown and consequently in plants themselves. The average yield of dry matter at the fully closed stands of Reynoutria japonica were 9.06 t/ha in autumn, Reynoutria × bohemica from 13.23 to 21.41 t/ha, according to the site. The yield losses within the winter period were found on average 42% for Reynoutria japonica and 34% for Reynoutria × bohemica. The moisture decrease of Reynoutria japonica was found from 68% in the autumn to 24% in the spring, and of Reynoutria × bohemica from 67% to 23%, respectively. Decreased content of nitrogen, phosphorus, potassium, calcium, and magnesium in the knotweed phytomass was found during the latter (spring) harvest periods in comparison with the earlier harvest periods. Decreased elements content in phytomass during the latter harvest period (spring) increases the phytomass quality as a fuel from both aspects -technical and emissions generation. The ash content in plants varied according to the site, on average from 3.12% in Ruzyně to 4.6% in Chomutov. None of the heavy metals monitored in knotweed plants reached the maximum admissible values determined for the food or feed purposes in the Czech Republic. From the results of combustion experiments, it is evident that Reynoutria × bohemica is a good fuel. Energy sorrel shows the extreme CO concentration in flue gases in comparison with other monitored fuels. According to the ČSN EN 12809 (2001) standard it does not meet even the third class of requirements. On the contrary, knotweed and wood bark fulfill the requirements for the first class. The surprising fact is that both of these fuels show the lower level of CO emissions, than the wooden briquettes. Concentrations of nitrogen oxids are comparable with biofuels, except of wood, and probably are related to the nitrogen content in heating material.

The aim of this paper was to give an overview of the biogas market in five countries (Austria, Czech Republic, France, Germany, and Poland) and to compare the potential of renewable energy sources from the food and beverage (FAB) industry waste. The objective included the identification of the production of biogas from organic waste and the untapped potential of organic waste in various industries of FAB and to specify non-technological barriers that hinder development and use of renewable energy potential in each mentioned country. Therefore, an evaluation of the most important FAB waste streams was carried out, to calculate the biogas production potential. The map depicting the existing FAB waste streams was prepared. As the data shows, the biogas market is growing, despite the often unfavorable conditions. Difficulties in obtaining all of the necessary permits and too complex administrative and legal procedures are the main barriers that hamper the development of the biogas market. In fact, the biggest bottlenecks were too many formal requirements and financial barriers. The biggest methane potential of 680 million m 3 of CH 4 /year was calculated for FAB waste generated by 13 127 FAB companies in France. The main four branches of FAB industry generating waste being a suitable substrates for biogas production are dairy, meat, brewing, and fruit and vegetable processing industries. As clear from the research, more and more industrial organic waste is used in biogas plants, replacing the most popular but expensive maize silage.

Pastorek M., Kára J., Pastorek Z. (2015): Experimental research on phytomass suitable for production of biogas. Res. Agr. Eng., 61: 129-133.The structure of the dry material plant is made up of a cell tissues system. The walls of the cells are formed by cellulose and lignin, ingredients difficult to biodegrade. Therefore, the aim of the breeders performed a variety of energy plants, providing a high yield of dry matter in the green state. This applies particularly to herbs, grown on agricultural and arable land (for example cereals, maize, sorghum, hemp, amaranthus, mallow, sugar beet, potatoes, fodder crops on arable land, permanent grassland and other). The subject of the experiment was to evaluate selected varieties of maize and sorghum and to determine the suitability of the materials on the device model for anaerobic fermentation mixed with beef slurry, and ferment from the biogas plant. Among the varieties of maize there are the significant differences in the production of biogas in the same conditions. Of the three maize varieties (Fixxif, Saxxo, Benicia), the most powerful was Saxxo.

Kára J., Janča E., Herák D., 2010. Exploitation of anaerobic fermentation of bio-degradable wastes. Res. Agr. Eng., 56: 8-17.The paper deals with assessment of biogas yield from mixtures of Reynoutria substrates and livestock manure. The aim was to perform laboratory experiments and suggest suitable fermenter operating conditions (dry matter content, pH, share of substrate components, thermic regime) for metanogenic digestion, then to determine its quality and assess the usability of such produced biogas.

Sochr D., Adamovský R., Kára J., Hanzlíková I., 2014. Evaluation of the influence of fermentation input substrates preparation on biogas production intensity. Res. Agr. Eng., 60: 60-67.The article is aimed at verification of the effect of chaff length of fermented material and duration time of the contact of material with oxygen before dosing into the fermenter, on production and energy content of biogas. The results of the verification showed an effect of chaff length in the fermented material on production and energy content of the biogas at processing grass silage with high content of dry-matter and especially maize silage. When processing maize silage, optimal length of chaff in terms of production and energy content of biogas was 13 mm, with grass silage it was from 69 to 112 mm. Verification of the influence of time of grass silage and maize silage contact with air oxygen before dosing into the fermenter did not confirm our hypothesis. It was demonstrated that production and energy content of the biogas increase together with the length of duration of 7 days compared to fermentation of material after max. 3 h of contact with air oxygen.