9.3.6 Hybrid Method
Due to the persistence of various pros and cons in the biogas upgrading technologies,
hybrid methods have been developed to rectify the problems and to meet maximum
efficiency. Hybrid methods are one or two methods integrated together to mitigate
the challenges, to develop novel methods and to innovate a profitable technology.
Currently, two hybridised methods have been developed:
(a) Hybrid cryogenic technology and polymeric membrane separation method.
(b) Hybrid polymeric membrane separation method and pressurised water scrubbing method.
9.3.6.1 Hybrid Cryogenic Technology and Polymeric Membrane
Separation Method
Integrating polymeric membrane separation method with the cryogenic technology
enhances the cost reduction and is energy intensive when compared to the cryogenic
technology. Various simulation studies were performed in hybrid methods for
increasing the energy requirements by comparing it with the chemical scrubbing
method (Belaissaoui et al. 2012). Temperature-membrane-cryogenic technology
method is hybridised to incorporate the techno-economic feasibility, and the novel
technology consumed less energy of 1.7 MJ/kg CO 2 when compared to 2.5 to
3.5 MJ/kg CO 2 (Song et al. 2017; Sahota et al. 2018).
9.3.6.2 Hybrid Polymeric Membrane Separation and Pressurised Water
Scrubbing Method
Integrating polymeric membrane separation method with the pressurised water
scrubbing can overcome the burden of upgrading costs when compared to the
conventional pressurised water scrubbing, and about seven different types of hybrid
membranes have been processed as apart of biogas enrichment (Scholz et al. 2013).
9.3.7 Chemical Hydrogenation Method
Sabatier reaction is the basis for chemical dehydrogenation method. Carbon dioxide
is reduced with hydrogen chemically by adding catalysts such as ruthenium and
nickel at high temperature of 300
C and pressure of 5–20 MPa (Xia et al. 2016).
The advantage of this method lies in its high selectivity option (Jurgensen et al.
2014), and the disadvantages include regular replacement of catalysts which is
degenerated by the presence of trace amount of gases (Guebitz et al. 2015), the
requirement for pure gases and a possible increase of energy-related costs
(Angelidaki et al. 2018).
9 Recent Trends in Biogas Upgrading Technologies for Biomethane Production
255
Due to the persistence of various pros and cons in the biogas upgrading technologies,
hybrid methods have been developed to rectify the problems and to meet maximum
efficiency. Hybrid methods are one or two methods integrated together to mitigate
the challenges, to develop novel methods and to innovate a profitable technology.
Currently, two hybridised methods have been developed:
(a) Hybrid cryogenic technology and polymeric membrane separation method.
(b) Hybrid polymeric membrane separation method and pressurised water scrubbing method.
9.3.6.1 Hybrid Cryogenic Technology and Polymeric Membrane
Separation Method
Integrating polymeric membrane separation method with the cryogenic technology
enhances the cost reduction and is energy intensive when compared to the cryogenic
technology. Various simulation studies were performed in hybrid methods for
increasing the energy requirements by comparing it with the chemical scrubbing
method (Belaissaoui et al. 2012). Temperature-membrane-cryogenic technology
method is hybridised to incorporate the techno-economic feasibility, and the novel
technology consumed less energy of 1.7 MJ/kg CO 2 when compared to 2.5 to
3.5 MJ/kg CO 2 (Song et al. 2017; Sahota et al. 2018).
9.3.6.2 Hybrid Polymeric Membrane Separation and Pressurised Water
Scrubbing Method
Integrating polymeric membrane separation method with the pressurised water
scrubbing can overcome the burden of upgrading costs when compared to the
conventional pressurised water scrubbing, and about seven different types of hybrid
membranes have been processed as apart of biogas enrichment (Scholz et al. 2013).
9.3.7 Chemical Hydrogenation Method
Sabatier reaction is the basis for chemical dehydrogenation method. Carbon dioxide
is reduced with hydrogen chemically by adding catalysts such as ruthenium and
nickel at high temperature of 300
C and pressure of 5–20 MPa (Xia et al. 2016).
The advantage of this method lies in its high selectivity option (Jurgensen et al.
2014), and the disadvantages include regular replacement of catalysts which is
degenerated by the presence of trace amount of gases (Guebitz et al. 2015), the
requirement for pure gases and a possible increase of energy-related costs
(Angelidaki et al. 2018).
9 Recent Trends in Biogas Upgrading Technologies for Biomethane Production
255