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Although cow manure is a valuable natural fertilizer, it is also a source of extreme greenhouse gas emissions, mainly methane. For this reason, this study aims to determine the impact of investments in a biogas plant on the energy and economic aspects of the operation of a dairy farm. A farm with a breeding size of 600 livestock units (LSU) was adopted for the analysis. In order to reach the paper’s aim, the analysis of two different scenarios of dairy farm functioning (conventional–only milk production, and modern–with biogas plant exploitation) was conducted. The analysis showed that the investment in biogas plant operations at a dairy farm and in using cow manure as one of the main substrates is a more profitable scenario compared to traditional dairy farming. Taking into account the actual Polish subsidies for electricity produced by small biogas plants, the scenario with a functioning biogas plant with a capacity of 500 kW brings €332,000/a more profit compared to the conventional scenario, even when taking into account additional costs, including the purchase of straw to ensure a continuous operation of the installation. Besides, in the traditional scenario, building a biogas plant allows for an almost complete reduction of greenhouse gas emissions during manure storage.

Maize has great potential, especially as a substrate for biofuels production. The aim of this paper is to analyze the possibility of usage in methane fermentation maize straw harvested in different weather conditions, which had an influence on different physical parameters, mainly the dry mass content. The research has shown that maize straw harvested in Central-Eastern Europe can have a broad spectrum of dry mass content, which is related to diverse weather conditions during autumn. However, independently from moisture content, maize straw can be a good (for more wet material) or very good (for more dried straw) substrate for the biogas plant. With the methane productivity reaching 201–207 m3/Mg of fresh mass, this material is a significantly better substrate than that typically used in Europe maize silage (approximately 105 m3/Mg FM). It was noted that the retention time for maize straw (36–42 days) is longer than in the case of maize silage (less than 30 days). However, this difference is quite small and can be accepted by the biogas plant operators.

and Sosnowica. The present paper uses the data from the surveys conducted in these communes in 2016. On average, 88% of the population used the water supply system in the communes surveyed, while 48% of the inhabitants were connected to a sewerage system. Parczew District had 12 collective mechanical and biological wastewater treatment plants with a capacity exceeding 5 m 3 /d. The households which were not connected to the sewerage network discharged the wastewater mainly to non-return tanks. In the communes surveyed, 1,115 households had domestic wastewater treatment plants. All of them were systems with infiltration drainage, which do not ensure high efficiency of removing pollutions and may even contribute to the degradation of the groundwater quality. In order to solve the existing problems of sewage and water management in the communes of Parczew District, it is necessary to further develop the collective sewerage systems and equip the areas which have a dispersed development layout with highly efficient domestic treatment plants, such as constructed wetlands.

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