Due to its slow and energy-demanding decomposition, waste sheep wool is becoming an ever-increasing environmental problem in Europe and around the world. The slow degradation is due to the high content of keratin in sheep wool, which is stabilized by a large amount of disulfide bonds. Keratin is an energy-rich protein that, due to its difficult breakdown, is rarely exploited as substrate for biogas production. In the assignment, we investigated the influence of microbial and enzymatic degradation of sheep's wool, which was then used as a substrate in biomethane potential tests. Sheep wool was exposed to different mixtures of six keratinolytic microorganisms (A. reticulisporus, S. coelicoflavus, B. mycoides, B. weidmanii, B. subtilis and B. altitunidis) or their rough enzyme extracts. The BMP tests were carried out in liter serum bottles under anaerobic and mesophilic conditions (37 °C), and they lasted for different lengths of time, depending on the biogas production. We monitored the volume of biogas produced and its composition, pH, content and composition of volatile fatty acids. The results of the experiments showed that autoclaving had the greatest positive impact on biogas production, while pretreatment slightly reduced the yield. The specific production of biogas was slightly higher in microbial pretreatment compared to enzymatic. The highest specific production of biogas and methane was measured in experiment BMP 3, in which twice autoclaved sheep's wool was used as substrate. In samples where sheep wool was pre-treated with a mixture of all six microorganisms or enzyme extracts, the production of biogas and methane was greater than in those where sheep wool was pre-treated with mixtures of a smaller number of microorganisms.
|
