Methane Production from Feather Waste Pretreated with Ca(OH)2: Process Development and Economical Analysis

This study investigated the industrial application of feather waste as a substrate for anaerobic digestion. Feather was pretreated with 0-0.2 Ca(OH)(2) g/g TSfeather (total solids of feathers) for 30-120 min at 100-120 degrees C, in order to increase the digestibility, and to enhance the methane yield in a subsequent digestion at 55 degrees C. Based on the results of the batch digestion, an industrial process was developed, which can achieve 0.40 Nm(3)/kgVS(feather) (volatile solids of feathers) methane yield from the pretreated feathers, while it fulfills the animal by-product hygenization requirements as well. This base case of the industrial pretreatment process was designed using SuperPro Designer (R) for utilizing 2,500 tons of feathers per year, which is the waste stream from an average slaughterhouse with a capacity of 60,000 broilers per day. The production cost of the methane is estimated to be 0.475 EUR/Nm(3), while the investments on the pretreatment unit requires 0.97 million EUR as total capital investment, and 0.25 million EUR/year for operating cost. However, the process is sensitive to the plant capacity. Changing the plant capacity from 625 to 10,000 tons of feather per year, results in reducing the biogas production cost from 1.177 to 0.203 EUR/Nm(3). In addition, sensitivity analysis was performed on the base case to investigate the effect of the value of the incoming feather on the overall process profitability. The results showed that the proposed investment could be considered as being financially viable in the case of production of upgraded biomethane even without the current gate fee system.