Anaerobic digestion is the natural breakdown of organic molecules by bacteria. Organic refers to something that comes from or is manufactured by plants or animals. Anaerobic digestion takes place in enclosed places without the presence of oxygen. Animal manures, fats, greases, oils, food scraps, sewage sludge and industrial organic residuals are commonly regarded as organic. The process of anaerobic digestion or the built system, where anaerobic digestion takes place is known as a digester or anaerobic digester .
In anaerobic digester, when microorganisms break down these organic materials without the presence of oxygen, biogas is produced. Biogas has gained popularity as a “greener” fuel in recent years. Biogas is typically composed of 60% bio-methane, a renewable fuel, and 34% CO2. This CO2 produced from biogas is thought to have higher supply reliability and be a more sustainable product than CO2 produced from fossil fuels .
A Summary of the Steps to Produce Green CO2
1. Collection of Organic Material
Organic materials or bio-waste is collected from different resources for combustion in the anaerobic digester to produce biogas.
2. Crushing of Organic Material
To prepare bio-waste or organic material for anaerobic digestion, it is crushed into smaller bits and slurred. Slurring bio-waste involves adding liquid to make it easier to process and help for combustion with ease.
3. Combustion in Anaerobic Digester
All organic materials or bio-waste are placed in the anaerobic digester for combustion. To keep the bacteria working at the optimal temperature, the digester’s contents must be heated. Preheating the feedstock before it enters the digestion reduces the amount of heat required in the digester and improves the overall efficiency. It is heated to between 30 and 60 degrees Celsius, depending on the type of the material.
4. Production of Biogas
Anaerobic digestion to produce biogas takes place in massive tanks for around a three week period. The biogas produced is a type of renewable energy that can be used in a range of applications.
5. Separation of CO2 from Biogas
Once biogas is produced, CO2 is separated. Water scrubbing, also known as water washing, is a relatively simple CO2 removal technique in which biogas is pushed under pressure into water. The carbon dioxide is absorbed by the water, while the methane flows through.
CO2 produced by biogas has a higher supply reliability and is a more sustainable product than regular CO2 produced by fossil fuels.
This green CO2 can be used in a variety of ways i.e. industries such as food, beverage, industrial processes, fertilizer, oil and gas etc. It is also more environmentally friendly and considered eco-friendly compared to conventional process.