This paper compares the main stillage disposal methods from the point of view of technology, economics and energetics. Attention is paid to the disposal of both solid and liquid phase. Specifically, the following methods are considered: a) livestock feeding, b) combustion of granulated stillages, c) fertilizer production, d) anaerobic digestion with biogas production and e) chemical pretreatment and subsequent secondary treatment. Other disposal techniques mentioned in the literature (electrofenton reaction, electrocoagulation and reverse osmosis) have not been considered, due to their high costs and technological requirements.Energy and economic calculations were carried out for a planned production of 120 m3 of stillage per day in a given distillery. Only specific treatment operating costs (per 1 m3 of stillage) were compared, including operational costs for energy, transport and chemicals. These values were determined for January 31st, 2009. Resulting sequence of cost effectiveness: 1. – chemical pretreatment, 2. – combustion of granulated stillage, 3. – transportation of stillage to a biogas station, 4. – fertilizer production, 5. – livestock feeding. This study found that chemical pretreatment of stillage with secondary treatment (a method developed at the Department of Process Engineering, CTU) was more suitable than the other methods. Also, there are some important technical advantages. Using this method, the total operating costs are approximately 1 150 ??/day, i.e. about 9,5 ??/m3 of stillage. The price of chemicals is the most important item in these costs, representing about 85 % of the total operating costs.
Anaerobic Digestion of Vegetable, Fruit and Cafeteria Wastes with Cow Dung by Chemical Pretreatment for Biogas Production in Batch Digester
