Bio Gas System

Biogas is mixture of gases which are produced by the natural decomposition of organic matter in the absence of oxygen. i.e. anerobic conditions.

Biogas is generated through decomposition of natural and organic substances. Any organic waster can be used as raw material for decomposition and formation of biogas.

Raw Material such as the agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste can be added in the digestor for fermentation.

Biogas is a renewable energy. It is also termed as the Green Gas due to its very low carbon emission properties resulting in very small carbon footprint to nature.

Composition

Biogas primarily is a Methane based gas.

1. Methane (CH4) - 54 - 70 %

2. Carbon Dioxide (CO2) - 27 - 45 %

3. Nitrogen (N2) - 03 - 05 %

4. Hydrogen (H) - 01 - 10 %

5. Carbon Monoxide (CO) - 00 - 0.1 %

6. Hydrogen Sulfide (H2S) - Negligible

Methane, Hydrogen, and Carbon Monoxide can be burnt with oxygen to release energy. Due to this energy biogas is used as fuel. Variably utilize for heating purpose, for cooking. It is also used in gas engine to convert gas energy into electric power.

Biogas can be compressed like Natural Gas to CNG, and can be used to power IC engines in motor vehicles. Biogas can be cleaned and upgraded to natural gas standards, when it becomes bio-methane.

Production

Biogas is produced by the natural decomposition / breakdown of Biodegradable organic waste in a confined chamber devoid of oxygen (Anerobic Chamber). This anerobic chamber is termed as Biogas Plant which holds the organic waste for decomposition. These plants are fed with biodegradable wastes including sewage sludge and food waste.

During the process, the microorganisms feed on the waste material and leave out biogas (methane & carbon dioxide) and digestate. The digestate is the remaining inorganic matter that was not transformed into biogas. This digestate is not a waste but it is a high quality fertilizer which is also again as a fertilizer for agriculture.

What happens in the disgestor ?

In anaerobic digestion process there are two sub key processes: mesophilic and thermophilic digestion which are dependent on temperature. But temperature is not only important for microbial metabolic activities but also for the overall digestion rate, specifically the rates of hydrolysis and methane formation.

Anaerobic digestion can occur in a wide range of temperature. This temperature range is broadly divided into two groups:

Mesophilic 30 to 42 degree centigrade.

Thermophilic 43 to 55 degree centigrade.

In practice, most of the digesters are designed to operate at mesophilic range, between 30 to 38 degree.

Some are designed for thermophilic range between 50 to 57 degree. Here, heating arrangement has to be made for temperature control.

Thermophilic digestion processes potentially allow higher loadings with lower hydraulic retention times (HRT), higher conversion efficiencies and pathogen disinfection.

Mesophilic digestion is more stable, less at risk from ammonia nitrogen toxicity and it operates on ambient temperatures so it does not require additional heating system.