Applications of black salt in biogas production and effects on biogas impurities

The goal of the research is to spread information about how black salt can be used to make biogas. Black salt helps to improve anaerobic digestion and reduce hydrogen sulphide in the biogas. It needs to be added as an additive. There are several chemical compositions in the black salts that help to improve the quality of raw biogas. It will not only reduce the concentration of hydrogen sulphide in raw biogas but also reduce ammonia.

The rate of production of biogas is dependent on the type of organic waste and variable temperatures.

The typical composition of biogas is depicted below.

Methane is the useful gas in biogas. It is the only combustible gas in biogas, which is also clean in nature. The smell of rotten eggs comes from biogas; it is due to the presence of hydrogen sulphide in biogas. Hydrogen sulphide is poisonous and harmful for metallic parts.

Black salt: It consists of primarily sodium chloride and trace impurities of sodium sulfate, sodium bisulfate, sodium bisulfite, sodium sulfide, iron (I, II) sulfide, and hydrogen sulfide.

• Iron (I, II) sulfide helps to reduce the concentration of hydrogen sulfide by following reaction:

FeS + H2S→ FeS2 +2H

• Sodium bisulfate is used primarily to lower pH. This can be used to reduce the pH in a biogas digester. Generally, 6.5-7.5 is the ideal pH range required for biogas produc- tion.

In the poultry industry, sodium bisulfate is used a lot to reduce the amount of ammonia and bacteria in the litter.

• Sodium bisulfite is a common reducing agent; it readily reacts with dissolved oxygen.

2NaHSO3+

O2→ 2NaHSO4

Sodium sulfide is a desulfurising and dechlorinating agent.

Also, black salt can be used to help digestion and improve the anaerobic process. In other words, adding black salts to digestive slurries aids in the production of high-quality raw biogas with low levels of hydrogen sulphide and oxygen, as well as in the acceleration of the digestion process.

How

In India, people use kala namak for medicinal purposes, like for digestion problems; ‘Hajmola’ is the most common digestive tablet widely used in India. It also contains black salt. In our body, when digestion is not proper, it releases smelly gases; that’s the smell of hydrogen sulphide. In our body, aerobic digestion (the presence of oxygen) takes place because we breathe oxygen.