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.
The most frequently found metals in municipal sewage sludge are copper and zinc. The aim of this study was to the evaluate effect of these metals on anaerobic microorganisms during sewage sludge stabilization. Anaerobic fermentation tests were carried out in 24 batch fermenters with hydraulic retention time 21 days at mesophilic temperature conditions 38 °C ± 0.2 °C. Five different concentrations of metal ionts (100-1000 mg•l -1 ) were tested. Cumulative biogas and methane production were used as the comparative parameters of inhibition. Hypothesis, which predicted presence of inhibitory effect of zinc and copper on anaerobic microorganisms, mainly on methanogenic Archaea, was confirmed. The lowest concentration of zinc and copper which cause significant inhibition of biogas production was 400 mg Zn , which cause reduction of 10.3 ± 2.0 % and 82.8 ± 1.1 %, respectively. The lowest concentration of zinc and copper which lead to significant inhibition of methane production is 400 mg Zn 2+ •l -1 and 600 mg Cu 2+•l -1 , which caused to reduction of 16.1 ± 3.2 % and 17.4 ± 2.2 %, respectively. The reduction in methane production is higher than in biogas production.
Biogas is very promising renewable energy resource. The number of biogas plants increase every year. Currently there is a demand for new ways of organic waste treatment from production of different commodities. One of the technologies which produce waste is biodiesel production. One of the wastes from the biodiesel production is G-phase which is mainly consisted from glycerol and methanol. The aim of work was to find the effect of G-phase addition, to fermented material, on biogas resp. methane production. Two lab-scale batch anaerobic fermentation tests (hydraulic retention time 14 and 22 days) under mesophilic temperature conditions 38.5 °C have been performed. The positive effect of G-phase addition to methane production has been found. G-phase was added in three different amounts of inoculums volume 0.5 %, 1% and 1.5 %. The highest absolute methane production has been achieved by 1.5 % addition of G-phase. However it was also found difference in specific methane production due to use of different inoculum consisted of swine or cow manure. The specific methane production in hydraulic retention time of 14 days has been for the same G-phase dose 1.5 % higher for swine manure, 0.547 m3∙kg−1 of organics solids compare with cow liquid manure 0.474 m3∙kg−1 of organics solids.
Biogas production in the Czech Republic has expanded substantially, including marginal regions for maize cultivation. Therefore, there are increasingly sought materials that could partially replace maize silage, as a basic feedstock, while secure both biogas production and its quality. Two samples of rye grass (Lolium multifl orum var. westerwoldicum) silage with diff erent solids content 21% and 15% were measured for biogas and methane yield. Rye grass silage with solid content of 15% reached an average specifi c biogas yield 0.431 m
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.
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