What is Anaerobic digestion

Anaerobic digestion is the process in which the organic material (Biomass) breaks down in the absence of oxygen into methane gas (CH4) and Carbon dioxide (CO2).

The anaerobic digestion or anaerobic fermentation, we can say either.

Anaerobic fermentation can only possible within a closed vessel or container, which is called digestor.

From anaerobic digestion, other raw materials also can be obtained such as fertilizer as shown under

anaerobic fermentation process mostly occurred at industries to manage their waste properly.

In a broad sense, anaerobic digestion is defined as it is the series of some process which will convert biomass into biogas without oxygen.

The end product of Anaerobic digestion is biogas (CH4) a carbon dioxide (CO2).

Biogas generally utilizes for several purposes like the generation of electricity, heating and for transportation after the process.

Other byproduct carbon dioxide can be utilized for several industries like soft drink industries, extinguisher maker industries, refrigeration industries, etc.

This process mostly occurs naturally at the places like bogs area, lake sediments, Oceans, and digestive tracts.

Anaerobic Digestion Process

This process mostly occurs at a suitable digester which has sufficient requirements for the process.

Anaerobic fermentation involves four stages which performed simultaneously in an anaerobic digester.

This four-process categorized as under.

step No 1: Hydrolysis

This is the most important step of anaerobic digestion in which large molecules convert in small molecules by adding some solution.

initially, the biomass(feedstock) have a very big size and structure which is not applicable to the anaerobic fermentation process.

These large organic molecules must be broken into small constituents to perform anaerobic digestion process.

Through hydrolysis process, these complex structured molecules are converted into the small molecules like, sugar, amino acid, fatty acids which can be easily digested by bacteria’s.

step No 2: Fermentation or Acidogenesis

Acidogenesis is the second process of anaerobic digestion in which the fatty acids and amino acids again convert in small structured

molecules by attacking acidogenic bacteria’s.

In this process, several compounds including VFAs (volatile fatty acids), H2S (Hydrogen Sulfide), CO2, H2, alcohols, carbonic acids, etc. as well as trace number of other byproducts are formed.

Acidogenesis process exactly similar to the milk sour process.

step No 3: Acidogenesis

Acidogenesis is the 3rd main step of anaerobic digestion in which acetate born from CO2 and other compounds like, H2, CO, etc. by attacking of anaerobic bacteria.

Mostly acidogenesis is the creation of acetate, by acetogenesis.

step No 4: Methanogenesis

Methanogenesis is the final step of anaerobic digestion in which the acetic acid and hydrogen convert into biogas (methane) and bulk amount of carbon dioxide.

Reaction:

CO2 + 4H2 ——> CH4 + 2H2O

CH3COOH ——-> CH4 + CO2

diagram of Anaerobic digestion process

Feedstock for the Anaerobic Fermentation

There are the various feedstocks (Biomass) for digestion which are available naturally and we can use it to produce biogas.

The feedstock includes.

Animal waste

Crops residues

Restaurant waste

Waste food

Poultry waste

Fats

Oil

Grease

Municipal waste

Agricultural waste

hospital waste

Etc.

feedstock will break more rapidly, produce more biogas and will be more efficient.

The feedstock which takes time to break down, produce less biogas and will be less efficient.

Animal waste, poultry manure, and waste food are sufficiently use for anaerobic digestion.

Advantages of Anaerobic digestion

• Produce renewable energy which can be utilized again and again

• Environment-friendly produce less emission of carbon dioxide

• Anaerobic fermentation produce the required product from infected biomass

• Anaerobic fermentation Reduce the volume of landfills because it reduces the amount of waste food, municipal waste etc.

• The digested waste can be utilized for fertilizing purposes, which have the ability to protect plants from several diseases

It can reduce the waste from urban and rural areas

• It Reduces the emissions of greenhouse gases

• Improves the water quality, helps us to remove phosphorous and other harmful constituents from water.

• It removes the pathogens from manure which will prevent diseases from plants.

• Less expensive as compared to other sources of energy.

• Reduce the cost of waste management.

• Reduce energy crisis because it can produce and supply electrical energy to the local grid.

• Decrease odors from livestock manure.

You will find a lot of topics on the waste management system and producing useful energy from that waste like; hospital waste management, solid waste management etc.

Disadvantages of Anaerobic digestion

• anaerobic digestion requires a large area to construct a plant.

• According to the EPA (environmental protection agency of USA), the anaerobic plants are only applicable for the large firms, which should have at least 300 cows.

• Difficult to maintain it require proper maintenance.

• It requires more time for maintenance.

• PH of the process must be maintained along with monitoring of volatile fatty acids.