A model for calculating the maximal theoretical production of hydrogen from corn wastes is proposed. The model has been used to estimate the potential for hydrogen production from cereals wastes such as wheat, barley, and corn which are cultivated in Poland. The potentials for Pomorze and other regions of Poland are compared. The hydrogen produced from cereal wastes in Poland could potentially meet 47 % of national hydrogen demand.

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The biogas produced in municipal wastewater-treatment plants (WWTP) should be cleaned before it can be used as a fuel in internal combustion engines. Efficient running of such engines is possible only subject to using high quality biogas and lubricating oil. Otherwise, biogas impurities in course of complex chemical reactions may form deposits on various engine parts as well as seriously contaminate the lubricating oil. In this paper, mineral deposits containing high concentration of bismuth, silicon, sulphur, calcium and zinc are studied. Silicon deposits demonstrating strong friction properties are formed during combustion of volatile silica compounds. As these deposits build up, abrasion problems, ignition failure and even engine failure result. The bismuth containing deposits comes from bearings degradation, zinc and calcium were derived from the additives present in commercially available lubricating oil, while lead, aluminium, copper, nickel, iron and chromium were introduced by engine wear phenomena. The highest bismuth content was located at the engine cylinder heads and the lowest at the exhaust elements, whereas highest calcium content was registered on the pistons. Silicon containing deposits are highest in the exhaust and lowest at the engine head. Zinc deposits are highest at the piston.

In this article, the results of key lime fruit (Citrus aurantifolia) wastes and cabbage (Brassica L.) wastes anaerobic digestion are presented. Anaerobic digestion of the wastes was performed in batch process, neutral pH (key-lime 7.47 and cabbage 7.67) and substrate concentration of Volatile Suspended Solids (VSS) 10 gVSS/L. One of the aims of this research was to check the availability of these substrates to be the source of methane and hydrogen. Key lime wastes produced 32 times more methane than raw cabbage. However, hydrogen production from cabbage was 149 times higher than key lime. The percentage of methane production in cabbage was up to 81% and in key lime was up to 75%. This research showed from the substrates comparison that efficient hydrogen production is less dependent on low pKa, pH than on total solids of the substrates.

Municipal landfills generate a significant amount of high-energy biogas, which can be used as a renewable gaseous fuel. However, it is necessary to improve the quality of this biogas due to the presence of various chemical compounds. The most common pollutants in landfill biogas include volatile compounds of silicon, sulphur, phosphorus and chlorine. The aforementioned elements, as well as other metals, were found both in the deposits and in the engine oil. The paper presents detailed characteristics of the solid residues formed in selected parts of gas engines powered by landfill biogas. Its elemental composition and morphology were investigated in order to determine the structure and influence of these deposits. In order to better understand the observed features, selected analyses were also conducted for biogas, engine oil and the condensate generated during biogas dewatering. It was found that the content of individual elements in samples collected from the same part of the gas engine but sourced from various landfills vary. The occurrence of elements in deposits, e.g., Mg, Zn, P and Cr, depends on the location of sampling sites and the type of engine. It was also observed that the deposits formed in parts that come into contact with both biogas and engine oil contain Ca or Zn, which can be related to biogas pollutants as well as different oil additives. The presence of Al, Fe, Cu, Cr, Sn or Pb in selected motor oil samples can be explained by the penetration of metallic abrasives, which confirms the abrasive properties of the formed deposits. The analysis of the characteristic deposits may contribute to the selection of an appropriate landfill biogas purification technology, thus reducing the operating costs of energy cogeneration systems. Finally, we highlight challenges for biogas purification processes and anticipate the direction of future work.

Dark fermentation of textile wastes is discussed in the paper. In the experiment cotton wastes were fermented. Before fermentation the cotton was hydrolyzed using 0.1 M HCl acidic solution. The inoculum was pretreated by means of heat shock for 0.5 h at 105 °C. The fermentation was carried out under mesophilic conditions at a load of 5 g VSS/L, and pH 5. Oxygen was added in small quantities during fermentation. The oxygen flow rates (OFR) were between 0.3 and 1.0 mL/h. The fermentation was carried out for a few days at temperatures between 40 and 43 °C. Hydrogenesis prevailed at the lower temperature (40 °C) and methanogenesis at the higher (43 °C). Conversion of cotton waste to methane (3.4%) was slightly higher than conversion to hydrogen (2.6%). The highest hydrogen production was obtained for OFR 0.8 mL/h and the percentage of hydrogen in biogas was 43%. At higher temperatures (43 °C) no hydrogen production was observed

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