Poultry Waste to Biogas: An Overview
Fresh poultry waste and animal manure is weighed and stored in a collection tank before its passage to the homogenization tank where the waste stream is diluted with fresh/recycled water and mechanically mixed to obtain a uniformly mixed waste stream.
The slurry is passed through a macerator to obtain uniform particle size of 5-10 mm and pumped into the primary anaerobic digester where stabilization of the waste takes place. The effluent from the primary digester is fed to the secondary anaerobic digester so as to ensure complete degradation of the waste stream.
Biogas from both the digesters are collected and sent to the biogas purification unit. Apart from water vapours, biogas contain significant amount of hydrogen sulfide (H2S) gas which needs to be removed due to its highly corrosive nature. The removal of H2S takes place in a biological desulphurization unit in which a limited quantity of air is added to biogas in the presence of specialized aerobic bacteria which oxidizes H2S into elemental sulfur.
Gas is dried and vented into a CHP unit to produce electricity and heat. The size and nature of the CHP system depends on the amount of biogas produced daily. The digested substrate is passed through screw press for dewatering and then subjected to solar drying and conditioning to give high-quality organic fertilizer.
The press water is treated in an effluent treatment plant based on activated sludge process which consists of an aeration tank and a secondary clarifier. The treated wastewater is recycled to meet in-house plant requirements.
A chemical laboratory is necessary to continuously monitor important environmental parameters such as BOD, COD, VFA, pH, ammonia, C:N ratio at different locations for efficient and proper functioning of the process.
The continuous monitoring of the biogas plant is achieved by using a remote control system such as Supervisory Control and Data Acquisition (SCADA) system. This remote system facilitates immediate feedback and adjustment, which can result in energy savings.
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