showcasing the advantages and disadvantages too. It is concluded that the
recently innovated technologies have wide potential advantages than the conventional biogas upgrading technologies. Although innovated technologies are so far
better, detailed analysis, research and development is required for acquiring a
technology which is economically, environmentally, technologically, operationally and socially feasible and acceptable.
Keywords
Biomethane · Upgrading technologies · Desulphurization · Cryogenic · Biological
method · Scrubbing
9.1
Introduction
With increasing urbanisation and population growth, there has been a tremendous
increase in waste generation and there has been a renewed interest in using waste as a
resource for producing energy. Biogas is a valuable renewable energy produced by
the anaerobic digestion of organic materials with the major product of methane and
carbon dioxide along with traces of impurities like H 2 S, siloxanes, water vapour,
amines, ammonia etc. It is also a profitable solution for organic waste management,
fertiliser production, and reduction of greenhouse gas emissions. In general, cattle
dung, agricultural residues, food waste, organic fraction of municipal waste, sewage
sludge and energy crops are majorly used as a substrate for anaerobic digestion
process. However, the methane yield depends upon the type of feedstocks as well as
operational behaviour of the digester (Bauer et al. 2013a, b; Al Mum and Torii
2015). Thus, many types of anaerobic digester designs have been implemented such
as anaerobic sequencing batch reactor, anaerobic plug-flow reactor, continuous
stirred tank reactor and anaerobic contact reactor. The components of biogas, CH 4 ,
CO 2 , H 2 S, NH 3 and water vapour have different impacts on the basis of its
utilisation. For the reduction of these impacts, biogas components should be
removed (Petersson and Wellinger 2009).
The raw biogas contains approximately 55–70% of CH 4 , 35–45% CO 2 and
200–30,000% ppm H 2 S along with <5% traces of NH 3 , siloxanes and water vapour
(Sahota et al. 2018). The energy content of CH 4 described by lower calorific value
(LCV) is approximately 36 MJ/m
3 -CH4 (at STP conditions). Due to the fact that the
presence of components other than methane has no calorific value, this leads to
lowering down the LCV to 22–25 MJ/m
3 - biogas. Apart from energy prospective,
these components also lead to environmental pollution upon combustion. Thus,
biogas upgradation (Fig. 9.1) is needed for biomethane production as a replacement
of CNG.
Before going for biogas upgradation, first treatment is biogas cleaning. The
biogas cleaning step involves removal of H 2 S which is a hazardous and extremely
corrosive acid gas. H 2 S leads to damaging of engines and metal parts of the system
240
B. S. Dhanya et al.
recently innovated technologies have wide potential advantages than the conventional biogas upgrading technologies. Although innovated technologies are so far
better, detailed analysis, research and development is required for acquiring a
technology which is economically, environmentally, technologically, operationally and socially feasible and acceptable.
Keywords
Biomethane · Upgrading technologies · Desulphurization · Cryogenic · Biological
method · Scrubbing
9.1
Introduction
With increasing urbanisation and population growth, there has been a tremendous
increase in waste generation and there has been a renewed interest in using waste as a
resource for producing energy. Biogas is a valuable renewable energy produced by
the anaerobic digestion of organic materials with the major product of methane and
carbon dioxide along with traces of impurities like H 2 S, siloxanes, water vapour,
amines, ammonia etc. It is also a profitable solution for organic waste management,
fertiliser production, and reduction of greenhouse gas emissions. In general, cattle
dung, agricultural residues, food waste, organic fraction of municipal waste, sewage
sludge and energy crops are majorly used as a substrate for anaerobic digestion
process. However, the methane yield depends upon the type of feedstocks as well as
operational behaviour of the digester (Bauer et al. 2013a, b; Al Mum and Torii
2015). Thus, many types of anaerobic digester designs have been implemented such
as anaerobic sequencing batch reactor, anaerobic plug-flow reactor, continuous
stirred tank reactor and anaerobic contact reactor. The components of biogas, CH 4 ,
CO 2 , H 2 S, NH 3 and water vapour have different impacts on the basis of its
utilisation. For the reduction of these impacts, biogas components should be
removed (Petersson and Wellinger 2009).
The raw biogas contains approximately 55–70% of CH 4 , 35–45% CO 2 and
200–30,000% ppm H 2 S along with <5% traces of NH 3 , siloxanes and water vapour
(Sahota et al. 2018). The energy content of CH 4 described by lower calorific value
(LCV) is approximately 36 MJ/m
3 -CH4 (at STP conditions). Due to the fact that the
presence of components other than methane has no calorific value, this leads to
lowering down the LCV to 22–25 MJ/m
3 - biogas. Apart from energy prospective,
these components also lead to environmental pollution upon combustion. Thus,
biogas upgradation (Fig. 9.1) is needed for biomethane production as a replacement
of CNG.
Before going for biogas upgradation, first treatment is biogas cleaning. The
biogas cleaning step involves removal of H 2 S which is a hazardous and extremely
corrosive acid gas. H 2 S leads to damaging of engines and metal parts of the system
240
B. S. Dhanya et al.