Due to the strict legislation currently in use for landfilling, anaerobic digestion has a strong potential as an alternative treatment for biodegradable waste. Coffee is one of the most consumed beverages in the world and spent coffee grounds (SCG) are generated in a considerable amount as a processing waste during making the coffee beverage. Chemical composition of SCG, presence of polysaccharides, proteins, and minerals makes from the SCG substrates with high biotechnological value, which might be used as valuable input material in fermentation process. The methane production ranged from 0.271-0.325 m 3 /kg dry organic matter.
This paper deals with the relationship between grain yield and grain losses during harvest. Measurements were carried out on a combine harvester with axial harvesting device allowing various adjustments to combine harvester parameter settings, such as rotor speed, gap between separator and rotor, fan speed, holes of the upper and lower sieves. Values of harvest losses in combine harvester with custom settings for the given crops were compared with values of losses obtained by a harvester with manufacturer's recommended settings. This paper observes the losses in grains of spring barley and winter wheat crops. All the measurements made showed lower grain losses when the combine harvester settings were customized. In general, custom settings provided quantitative losses lower by 0.198% than settings recommended by manufacturer.
In the field of electric power industry, renewable energy sources, fertilisers, reclamation, and waste management, biomass is widely studied and used. Minerals are present in every step of biogas transformation, but their forms, occurrence, and composition have not been studied yet. However, there is no comprehensive study research that would address the presence of mineral phases in the process of biogas production. This aim of the study is determination of the amount and composition of the mineral phases present in fermentation residues resulting from different production technologies. Digestate mineral composition was analysed using 46 samples from agricultural biogas plants and university testing biogas reactor. The majority of samples contained the amorphous phase. Minority phases consisted of quartz, albite, orthoclase, muscovite, and amphibole. Opal-CT was found in eleven samples (1.26 to 12.1% wt.). The elements present in gas-liquid fluids or in liquids, gases and aerosols within the biogas technology system may create mineral phases, namely the amorphous phase or the crystalline phase under certain conditions. Opal-CT may enter the fermenter as part of plant tissues referred to as phytoliths, or as an unwanted admixture of different origin. It may also originate from the present amorphous SiO2.
Biodegradable products of food industry represent input substrates of biogas plants. Of these, food waste, grape pomace and spent grain were the products of choice for analyzing which tested biogas production and quality. The latter being in particular determined by methane and hydrogen sulfide content. Anaerobic fermentation was underway 26 days at mesophylic temperature 42 °C in a batch labscale reactors with volume 120 dm 3 . The following values were measured in relation to specific yield of methane: food waste: 0.347 m 3 per kg, grape pomace: 0.238-0.246 m 3 per kg, spent grain: 0.283 m 3 per kg. The specific production of hydrogen sulfide: food waste 752 mg per kg, spent grain: 585 mg per kg, red pomace: 74 mg per kg and white pomace 98 mg per kg.
The thermal decomposition of wood chips from an apple tree is studied in a static air atmosphere under isothermal conditions. Based on the thermogravimetric analysis, the values of the apparent activation energy and pre-exponential factor are 34 ± 3 kJ mol−1 and 391 ± 2 min−1, respectively. These results have also shown that this process can be described by the rate of the first-order chemical reaction. This reaction model is valid only for a temperature range of 250–290 °C, mainly due to the lignin decomposition. The obtained results are used for kinetic prediction, which is compared with the measurement. The results show that the reaction is slower at higher values of degree of conversion, which is caused by the influence of the experimental condition. Nevertheless, the obtained kinetic parameters could be used for the optimization of the combustion process of wood chips in small-scale biomass boilers.
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