Biosuszenie pofermentu z biogazowni rolniczych

Anaerobic digestion residue represents a nutrient rich resource which, if applied back on land, can reduce the use of mineral fertilizers and improve soil fertility. However, dewatering of digestate may be recommended in certain situation. Limited applicability of digestate as fertilizer may appear, especially in winter, during the vegetation period or in areas where advanced eutrophication of arable land and water bodies is developing. The use of digestate may be also governed by different laws depending on whether it is treated as fertilizer, sewage sludge or waste. The solution for thus problem may by application of biodrying process. The aim of this paper is to present the possibilities of digestate from agricultural biogas plant drying in biodrying process, and analysis of its kinetic and efficiency. Dewatered digestate from agricultural biogas plant, with initial moisture of 78%, was mixed with wood chips in proportion 45:55, respectively. The mixture was placed in container reactor, and aerated during 4 weeks. During the experiment the temperature in the reactor, weight of the digestate, and energy demand was measured. Due to biodrying process, with mean air flow rate 0.025 m3/kg.h, 502 kg mass loss was achieved, what consists 76% of the initial weight of the digestate. Mean temperature in the bioreactor during first 10 days, fluctuated between 55 to 60°C. After that, gradual decrease of the temperature to 40°C in the end of 3rd week was observed. During last week the intense cooling of the bioreactor to final temperature below 20°C was observed. It was determined, that digestate mass loss had I-order reaction character. The k constant rate value was estimated, which was on the level of 0.00068 [1/h]. Total energy demand was 14.792 kWh, what relates to 0.0295 kWh of used energy per kg of mass removed.