• Energy Research

Abstract Under conditions of low funding for the production of “green energy” in Poland, it became necessary to search for other – cheaper sources of biomass and the development of more efficient technologies. The maize straw is waste material arising in the production of grain. Therefore currently has no wider application and the cost of acquisition is several times lower than in case of maize silage. This paper presents the results of research on biogas efficiency of the maize straw silage, the dynamics of the fermentation process and the decomposition time of biomass under the meso- and thermophilic conditions. Moreover, the exploitation costs of a biogas plant working on this substrate and maize silage have been compared. It has been proved that thermophilic fermentation is significantly shorter (17%) than mesophilic and permits to increase biogas production (8.6%) and methane content (9.3%). In turn, mesophilic fermentation has more stable pH changes in comparison with the thermophilic technology. However, it is related to inhibition of the propionic acid, which can be of great importance in case of continuous fermentation. On the basis of energetic calculations it was shown that the substitution of the maize silage with the maize straw silage allows for nearly three-fold costs reduction and thus increase of the biogas plant profitability.

Abstract Primary energy sources have limited deposits and their exploitation has a negative impact on the environment. Biofuels production is an efficient and profitable method of environmentally-friendly energy production in terms of economic reasons. In recent years use of renewable energy sources (RES) in the Polish energy balance can be noticed. The main sector in which can be observed a dynamic growth is the biomass market, with the solid biofuel market in particular. The aim of this research was to perform an economic and energy analysis of briquettes and pellets production. The obtained results of economic analyzes have shown that the individual production of solid biofuels from digestate is more profitable than using sawdust as a substrate. The costs of producing solid biofuels from solid fraction of digested pulp, as well as their calorific value, make the discussed substrate to be used to produce energy. The calorific value of the solid biofuel produced from the digested pulp solid fraction (DSF) can be compared to the calorific value of biofuel generated from sawdust. The digested pulp can be considered as an alternative to the sawdust in the production of solid biofuels.

Abstract The paper presents the use of classical statistical methods and methods based on neural modeling in short-term forecasting of electric energy from photovoltaic conversion. A detailed analysis of the input data measured in central Poland (Poznan, 52°25′ N, 16°56′ E) showed that some variables like air pressure and the length of the day are statistically insignificant. The values of kurtosis, skewness and results of applied tests, to check the normality of the distribution of dependent variable in the form of daily electricity production, indicate that the linear regression models should not be the only method in forecast process. The result of neural modeling using implemented network designer is RBF 6: 6-5-1: 1 model with quality test approximately 93% and the RMS error of 0.02%. The input parameters necessary for the operation of proposed ANN model are: number of sunny hours, length of the day, air pressure, maximum air temperature, daily insolation and cloudiness.

In modern agricultural biogas plants, the biowaste are increasingly used for biogas production. Food waste are also widely used in larvae breeding. This is important because, based on biowaste, its proper management and green energy production is possible. This study aims to determine the biogas and methane efficiency of Hermetia illucens larvae that were fed using food waste. In the research on biogas and methane efficiency, Hermetia illucens larvae were used. The total solids (TS) of the substrate equals 30.35%, and volatile solids (VS) content was 92.31% of TS. The larvae were fed only by plant origin food waste. The obtained substrates were homogeneous. The experiment was carried out under mesophilic anaerobic digestion conditions – 39°C in the 21-chamber biofermentor set in the Institute of Biosystems Engineering in Poznań University of Life Sciences. The anaerobic digestion process in the batch reactor ran correctly. Fermentation inhibition was not detected. Biogas efficiency for larvae amounted to 198.75 m3∙Mg-1 fresh mass (FM). On the other hand, methane efficiency, amounted to 127.73 m3∙Mg-1, at methane concentration of 64.27%. Based on the research, it was found that the larvae feeding food waste can be used directly as anaerobic digestion in the bioconversion process.

Abstract In recent years, constructed wetland systems are used widely for the purification of small amounts of wastewater because they provide very high effects of removing impurities. The existing research results show that constructed wetland systems can be used not only for highly efficient wastewater treatment, but at the same time in order to produce biomass for energy purposes. The aim of this paper was to determine the possibilities of energy use of the plants: common reed, willow, Jerusalem artichoke, giant miscanthus, obtained from constructed wetland system. The yield of common reed was the highest compared to the other plant species used in analyzed object and amounted to 13.6 Mg DM ha −1 and then 8.7 Mg DM ha −1 for willow. The lowest dry matter yield was 5.9 Mg DM ha −1 in the case of Jerusalem artichoke. High Heating Value was similar in all analyzed plants (17.9–19.2 MJ kg −1 ), the highest results were obtained from willow. Biomethane production during anaerobic digestion was the highest from common reed (108 m 3 Mg −1 FM) and the lowest from Jerusalem artichoke (66 m 3 Mg −1 FM). The methane concentration in biogas was rather low (50.9–54.9) comparing to other typical substrates for biogas production.

Sector of animal production is growing strongly in Poland within last years. This concerns especially poultry sector (first position in Europe with more than 900 million animals per year) bit also swine and cattle. This sector generates dynamic growth of meat export. However, this sector is responsible also for large scale production of slaughter waste which very often creates problem with its proper management and recycling. This paper describes the possibility of the energetic usage of slaughter waste as the substrate for biogas production. The biogas efficiency analysis of different waste like: waste category II, blood, feathers, soft waste category III and solid waste category III have shown its good usefulness for methane production. The calculations showed the energetic potential for analyzed slaughter house as 700 kWe.

The biogas production constitutes one of renewable energy sources (RES) . In addition, wastes are preferred for energy production. In the case of some wastes, e.g. poultry manure, it is difficult to conduct anaerobic digestion in monofermentation. The aim of this work was to plan the biogas plant, in which the main substrate is the waste from a poultry farm. The scope of work included: preparation of a biogas plant technological project, determining the amount of biogas and methane that can be produced annually on the example of the selected poultry farm, performing the energy and financial calculations for the current conditions prevailing on the renewable energy market in Poland. The installation project assumed the location of a biogas plant at an existing poultry farm – the source of the substrate. The micro-biogas plant includes a fermentation tank with a capacity of 500 m3 and storage of digestate pulp with a capacity of 700 m3. The assumed power biogas plant will generate 112 kW of electricity and 120 kW of heat. The installation will operate in a single-stage mesophilic technology (39ºC), which will avoid incurring additional costs related to heating and the construction of additional fermentation tanks. The use of poultry manure by anaerobic digestion provides benefits through biogas technology. It is necessary to examine the technology in terms of biogas production, which is carried out under better sanitary and environmental conditions. This work was undertaken to investigate the environmentally friendly removal of poultry manure through biogas technology to obtain the best economic effect, and employ it further, e.g. as a fertilizer.

Sewage sludge management is an important element of environmental protection. Composting and anaerobic digestion are the biological conversion methods for sewage sludge management. Mass and volume reduction is a result of a properly composted process. Solid fraction of digested pulp can be use as co-substrate, because it is good structural material. The aim of the study was to determine the possibility of composting sewage sludge with a solid fraction of digestate. The compost mix consisted of 25 kilograms of sewage sludge and 20 kilograms solid fraction of digestate in fresh mass. The experiment was carried out in laboratory conditions. Bioreactors of 165 dm3 volume were used. The experiment included two stages. Stage I took place in bioreactors and lasted until the cooling phase of the compost was complete. Stage II included compost maturation for a period of eight months (to 287 day of composting). The reduction of mass obtained at the end of Stage I amounted 30.2%. At the end of Stage II, it was 86.7% relative to the initial weight of the compost. The maximum value of temperature was 75.1°C. Studies have shown that sludge with a solid fraction of digestate can be a suitable substrate for composting with sewage sludge.