Category: Chemical

All You Must Know about Hydrogen Sulfide Removal from Biogas

Hydrogen Sulfide or H2S present in biogas is an impurity that environmentally hinders the utilization of biogas as a source of energy. Also, the concentration of hydrogen sulfide varies according to the feedstock. The concentration in the biogas is a function of the inorganic sulfate content and digester feed substrate. High-protein wastes contain amino acids, which influences the H2S levels.

What is the need to remove the gas?

The inorganic sulfate in the feedstock during the digestion process gets reduced by the sulfate-reducing bacteria present in the digester. This way, it ends up contributing more to the sulfide level present in the biogas. The H2S contained in the gas causes corrosiveness, bad smell along with sulfur emissions after the gas gets burned. If the biogas is to be used in fuel cells, turbines and internal combustion engines, it is important to remove hydrogen sulfide from the gas to prevent damage to the equipment.

Techniques involved in the removal process of H2S

Here are several techniques for the removal of H2S gas.

  • Iron oxide pellets
  • Iron sponge
  • Water scrubbing
  • Sodium Hydroxide scrubbing
  • Activated carbon
  • Biological removal on filter beds

Commonly used methods to remove H2S

The concentration level of the different components of biogas impacts its usage. While internal combustion engines function well when H2S is managed below 100 ppm, boilers are capable of withstanding concentrations to up to 1000 ppm. The most common methods used for H2S removal from biogas are iron chloride dosing and oxygen/air dosing.

Iron chloride dosing – Iron chloride is fed to the digester slurry directly or given to the feed substrate in the pre-storage tank. The produced H2S reacts with iron sulfide to produce iron sulfide salt. The method is quite effective in lowering the H2S levels.

The method of iron chloride dosing can be treated as a partial removal technique process to avoid corrosion in the remaining part of the upgrading process equipment. It further needs to be contemplated with a removal down to 10 ppm.

Such a removal process costs less because you need a storage tank for holding the iron chloride solution along with a dosing pump. Yet, the operational costs would be expensive because of the price of iron chloride.

Oxygen/air dosing – Biological desulphurization or oxygen/air dosing of biogas is performed with the help of microorganisms. Almost every microorganism oxidizing sulfide belongs to the Thiobacillus family. For the oxidation of sulfide, it is important to add amounts of oxygen in specific ratios to the biogas.

This simplest method involves adding oxygen directly to the storage tank or digester. The micro-organisms strive on the surface of the digester, which provides necessary space and nutrients. Depending on the reaction time, temperature, place and amount of air added, the H2S concentration gets reduced to about 50 ppm.

Safety measures should be taken to prevent overdosing of oxygen. Keep in mind that biogas in oxygen causes explosion depending on the percentage of methane.


When choosing from the different techniques, you have to consider factors such as cost of the chemicals used, adsorption capacity, vacuum trucks to empty filters, disposal of wastes, and so on. Or else, there could be a risk of ignition of the used or spent adsorbent.

Chemical Products Industries Also Offers Following Services :

Scavenger Chemical
Hydrogen Sulfide Scavenger MSDS
Surfactant Manufacturers

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Chemical Products Industries, Inc.
Address: 7649 SW 34th St, Oklahoma City, OK
Phone: (800) 624-4356

H2 Removal From Biogas – Useful Information

H2 Removal From Biogas – Useful Information

It is known fact that there are trace quantities of hydrogen sulfide or H2 in biogas and it has to be removed. This is because it is harmful and could also be poisonous for health. Further, it also has a corrosive property that could damage the various mediums that are used to transport it. Hence, there is an important need to remove hydrogen sulfide from gas. This process is often referred to as desulfurization. There are a few ways and methods that can be used for removing it. As is the case with carbon dioxide, water scrubbing and caustic scrubbing are the methods that are generally used to remove H2 from biogas. We will learn more about it over the next few lines.

What Is Water Scrubbing

This is a commonly used and proven method for removing hydrogen sulfide from biogas. In this method, gas is passed through water. Water has the capacity of absorbing a part of the hydrogen sulfide removal. But according to some experts, this process may not be the best way forward for removing H2. It does work very well for CO2 removal. This is perhaps because of a few reasons. Low partial pressure is an inherent property of H2. This often results in low mole friction absorption as far as hydrogen sulfide in water is concerned. Hence, this could be one of the main problems of water scrubbing for removal of H2 or hydrogen sulfide from biogas.

Caustic Scrubbing

This is another effective method for removal of h2s from gas. It works on the principle that when a caustic solution reacts with CO2 gas streams, this results in many changes. It leads to a reversible carbonate forming a reaction that is followed by another change. It leads to the formation of a reaction that has its origins from irreversible potassium hydrosulfide. When this happens, it appears as a yellow precipitate.

There are reasons to believe that it is possible to remove hydrogen sulfide and also carbon dioxide with the use of other chemicals such as trisodium phosphate, ammonical solutions, sodium phenolate, and various other alkacid processes. However, they are not without their own share of problems and limitations. The costs of purification are quite high because in caustic scrubbing it is common to see hydroxides such as calcium, sodium, and potassium being used in the entire purification process.

Solid Chemical Absorption

This is a simple and practical method that is commonly used for the desulfurization of biogas. It is considered quite efficient for situations where there is no need for removal of other impurities. This method is about using or iron sponge. This is nothing but a combination of wood shavings and ferric oxide that are kept in a dry scrubber. When the reaction takes place, the gas also is purified.

The good thing about this method is that it is not very expensive and it is also easy to operate and maintain. Zinc oxide, in place of ferric oxide, can also be used for desulfurization. It comes with the added advantage of being in a position to remove organic sulfur compounds and these include mercaptans and carbonyl sulfide.

Contact US:

Chemical Products Industries, Inc.

Address: 7649 SW 34th St, Oklahoma City, OK
Phone: (800) 624-4356