9.2.3.4 Adsorption on Biomass-Based Sorbents
The requirement of high temperature for the preparation of activated carbon is the
major concern. In this regard, biochar can be a promising adsorbent that can be
prepared from readily available waste biomasses. Moreover, biochar waste
adsorbents are relatively cheaper and environment friendly than commercially
available activated carbon (Sahota et al. 2018; Zicari 2003). The most common
biomass waste adsorbents are biochar (leaf waste, peat and sludge waste, slurry
based, manure based)
9.2.4 Biological Desulphurisation
Microbes such as Thiobacillus and Sulfolobus are used to remove hydrogen sulphide
by undergoing the process of oxidation. Biological desulphurisation occurs only in
the presence of oxygen, and so a small amount of air should be added to the digester.
The microorganisms are immobilised in this process. Another solution to remove the
hydrogen sulphide is using the trickling filter method, where the biogas is allowed to
pass through the trickling filter after leaving the digester. The microbes are packed in
the trickling filter and the sulphur containing the compounds can be removed. The
main disadvantage in both the biological methods is that it cannot be applied if the
biogas is used for grid injection or as a vehicular fuel and it is due to the presence of
trace amount of oxygen gas. This problem is rectified by developing an alternative
method where the biogas is free of oxygen after the removal of hydrogen sulphide
gas (Petersson and Wellinger 2009).
9.2.5 Biofiltration of H 2 S
From available biological methods for hydrogen sulphide removal, biofiltration is a
potential cost-effective technique which utilises living material to capture acid gas.
Nowadays, some common sulphur-oxidising microorganisms mainly from the family of Thiobacillus, Thiomonas, Paracoccus, Acidithiobacillus, Sulfurimonas or
Halothiobacillus are used for biofilters. However, this technique is limited for
utilisation at high concentration of H 2 S containing biogas streams. Mainly two
commercially available methods are used for removal of high concentration: one is
Thiopaq process and second is Biopuric process (Kadam and Panwar 2017; Tomas
et al. 2009; Soreanu et al. 2008). The advantages of biological methods are low
energy requirement at mild conditions, and production of elemental sulphur as
by-product is the major advantage of the process. Better microbial attachment onto
biofilter bed needs higher specific surface area, less pressure drop and better water
retaining capacity.
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B. S. Dhanya et al.
The requirement of high temperature for the preparation of activated carbon is the
major concern. In this regard, biochar can be a promising adsorbent that can be
prepared from readily available waste biomasses. Moreover, biochar waste
adsorbents are relatively cheaper and environment friendly than commercially
available activated carbon (Sahota et al. 2018; Zicari 2003). The most common
biomass waste adsorbents are biochar (leaf waste, peat and sludge waste, slurry
based, manure based)
9.2.4 Biological Desulphurisation
Microbes such as Thiobacillus and Sulfolobus are used to remove hydrogen sulphide
by undergoing the process of oxidation. Biological desulphurisation occurs only in
the presence of oxygen, and so a small amount of air should be added to the digester.
The microorganisms are immobilised in this process. Another solution to remove the
hydrogen sulphide is using the trickling filter method, where the biogas is allowed to
pass through the trickling filter after leaving the digester. The microbes are packed in
the trickling filter and the sulphur containing the compounds can be removed. The
main disadvantage in both the biological methods is that it cannot be applied if the
biogas is used for grid injection or as a vehicular fuel and it is due to the presence of
trace amount of oxygen gas. This problem is rectified by developing an alternative
method where the biogas is free of oxygen after the removal of hydrogen sulphide
gas (Petersson and Wellinger 2009).
9.2.5 Biofiltration of H 2 S
From available biological methods for hydrogen sulphide removal, biofiltration is a
potential cost-effective technique which utilises living material to capture acid gas.
Nowadays, some common sulphur-oxidising microorganisms mainly from the family of Thiobacillus, Thiomonas, Paracoccus, Acidithiobacillus, Sulfurimonas or
Halothiobacillus are used for biofilters. However, this technique is limited for
utilisation at high concentration of H 2 S containing biogas streams. Mainly two
commercially available methods are used for removal of high concentration: one is
Thiopaq process and second is Biopuric process (Kadam and Panwar 2017; Tomas
et al. 2009; Soreanu et al. 2008). The advantages of biological methods are low
energy requirement at mild conditions, and production of elemental sulphur as
by-product is the major advantage of the process. Better microbial attachment onto
biofilter bed needs higher specific surface area, less pressure drop and better water
retaining capacity.
246
B. S. Dhanya et al.