An anaerobic digestion plant (or AD plant) is a decentralized energy system, which not only helps in sustainable management of organic wastes but also helps to attain self-sufficiency in heat and power requirements. The major components of an anaerobic digestion plant are waste collection system, anaerobic digester, effluent treatment plant, biogas holder, and power generating equipment.
Description of an Anaerobic Digestion Plant
The fresh organic waste is stored in a collection tank before its processing to the homogenization tank which is equipped with a mixer to facilitate homogenization of the waste stream. The uniformly mixed waste is passed through a macerator to obtain uniform particle size of 5-10 mm and pumped into suitable capacity anaerobic digesters where stabilization of organic waste takes place.
In an anaerobic digestion plant, organic material is converted to biogas by a series of bacteria groups into methane and carbon dioxide. The majority of commercially operating digesters are plug flow and complete-mix reactors operating at mesophilic temperatures. The type of digester used varies with the consistency and solids content of the feedstock, with capital investment factors and with the primary purpose of digestion.
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 combined heat and power (CHP) system to produce electricity and heat. The size of the CHP system depends on the amount of biogas produced daily. The digested substrate is then passed through screw presses for dewatering followed by 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.
Salman is a prolific environmental writer, and has authored more than 500 articles in reputed journals, magazines and websites. He is proactively engaged in creating mass awareness on renewable energy, waste management, sustainability and conservation all over the world.
Salman can be reached on salman@cleantechloops.com
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Originally posted 2014-12-22 22:54:54. Republished by Blog Post Promoter