Anaerobic Digestion Process

Anaerobic digestion is the decomposition of organic waste by the help of micro-organisms. These micro-organisms break down the organic structure of the waste in the absence of oxygen. The major product of this process is Bio-gas, which can be used to generate heat and electricity. The container used to carry out this process is usually termed as “Digester”. These digesters can be designed in various ways and commonly consists of an inlet of water and substrate (which is an organic bio-degradable material) and outlet for effluent of waste, bio-gas and sludge. Number of digesters use some mixing strategies to ensure better efficiency of the process. The size of a digester determines the quantity of the feed, which can be processed in unit time.

This means that the addition of certain bio-degradable substrates in the feedstock for digestion process with conventional type of substrate. This addition is carried out to increase the quantity of the bio-gas produced by the base substrate. Generally, the substrates added to the AD system have better production of biogas per unit mass than the base substrate. This is referred to as synergistic effect. The most commonly used base substrates for an anaerobic digestion process are sewage sludge (biosolids) and Food/agricultural waste (Municipal waste dung/manure and crops waste). Extra substrates can include crops wastes, cheese production wastewater, milking parlor wastewater and cheese whey etc. To conclude, the mixing of wide range of biodegradable organic food wastes with nutrient-rich sewage sludge is called “Co-digestion”.

There are number of benefits and hindrances for a co-digestion process. The gains of co-digestion are abundant and the existing accessibility and diversity of potential substrates can create multiple combinations. Major benefits include:

• Better efficiency as more biogas is

This is favorable for resource utilization and maximizing the gas production and signifies an essential part in the optimization of a biogas plant. Nevertheless, not all substrate combinations result in the positive effect on the system.

Unfortunately, when observing and analyzing possible substrates for co-digestion, most consideration is given to such qualities as biogas production and biodegradability. Additional characteristics of acute importance are quantities of K, organic nitrogen, sulfur, presence of chemicals and other cations, gross solids, phosphorus, pH, alkalinity and FOG. After the identification of the additional co-digestion substrate in compliance with the base substrate for the feed of the digestion process, the mixing, blending and feed proportions must be carefully analyzed to lessen process