The purpose of this work was to find out if a corn stover can be used as a cosubstrate in biogas production. We were investigating if corn stover could be used as a replacement for other dedicated energy crops e.g. for corn silage. Economically corn stover is better choice since it is at almost no cost (it is a left-over after harvesting), and it is not a primary agricultural product. The experimental part was set in a way, that different mixtures (combinations) of animal manure, corn silage and corn stover were tested under the same thermodynamic conditions. All mixtures contained inoculum obtained from Slovenian biogas plant and substrates that are currently used in biogas plants Jezera and Draženci (Perutnina Ptuj d.d) with addition of corn stover. It was investigated if addition of corn stover improves biogas yield under different combinations. During the process the daily and cumulative yield and composition of biogas were measured. Since the quantity of produced biogas depends on the total content of carbohydrates, lignin and extractives, the analysis was made that gave us amounts of them present before and after anaerobic digestion. Fort his purpose, Klason method was applied. The hypothesis that in certain cases the addition of corn stover improves biogas yields was confirmed. On the other hand the hypothesis that nothing happens with the lignin during anaerobic digestion process was rejected because the reduction in mass of lignin was recorded.
F.14 Improvements to existing production methods and tools or processes
COBISS.SI-ID: 20302614Globally, the ever growing volume of waste continues to pose an increasingly serious problem, which is why it is essential to prevent and decrease the accumulation of waste, making continuous efforts to exploit it for making biofuels, i.e. biogas. In this way, we would be able to decrease pollution of the environment and reduce the production of greenhouse gases, which will in turn mitigate climate changes. Biogas is a renewable energy source. It is produced in the process of anaerobic digestion – which is considered to be the most cost-efficient biological conversion –in order to generate electric power and heat. Issues might arise if chicken manure is used in this process because such litter contains wood shavings and sawdust, and bacteria have a difficult time breaking down wood matter due to the lignin content. However, it can be decomposed by wood decay fungi which cause white rot decay. In the framework of this research paper, we exposed a mixture of chicken manure and giant miscanthus for various time periods to two white rot fungi –Trametes versicolor and Pleurotus ostreatus. The colonized substrate was inoculated with two different inocula. We monitored anaerobic digestion based on the emitted biogas. The results indicate that the fungus type, colonization period and the type of inoculum used all influence the amount of generated biogas. The most productive substrate was the one colonized by T. versicolor in combination with the inoculum from the Draženci Biogas Plant. This yielded 28 % more biogas than the substrate that was not exposed to wood decay fungi.
F.14 Improvements to existing production methods and tools or processes
COBISS.SI-ID: 8486009The focus, when applying the Pinch Analysis, is usually minimizing the hot utility requirement first and the cold utility requirement after. The main reason for this is the usually higher cost of a hot utility compared to a cold utility since the temperature of the cooling media is usually similar to temperature of the surroundings. However, when there are large cooling or freezing requirements at sub-ambient temperatures, they can represent a significant cost to company as well. Typical representative of an industry with high cooling demand is the food production industry and the food storage. A promising solution for cooling is the absorption chilling utilizing process heat for cooling instead of electricity. In this work, a thermodynamic approach for the evaluation of absorption chilling, integrated to a process, has been developed. First, the model for estimation of absorption chilling was developed. Deriving the streams can be done after obtaining the heat duties of each unit constructing the absorption chiller. The integration of absorption chiller is evaluated by application of Grand Composite Curve and the derived streams. Three different options of integration was analysed: i) above Pinch, ii) below the Pinch, and iii) across the Pinch. The analysis indicates that the best integration can be achieved, when an absorption chiller is placed across the Pinch releasing all the heat above the Pinch. There are still benefits, when integration is performed entirely below the Pinch. However, placement of an absorption chiller entirely above the Pinch or integrating the chiller across the Pinch so that only a small part of its heat is released or used above the Pinch is inappropriate, as it increases hot and cold utility consumption at expense of additional investment.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 19683350