Advances in Phytochemistry, Textile and Renewable Energy Research for
Industrial Growth – Nzila et al. (Eds)
© 2022 Copyright the Author(s), ISBN: 978-1-032-11871-0
Open Access: www.taylorfrancis.com, CC BY-NC-ND 4.0 license
Purification and upgrade of biogas using biomass-derived adsorbents:
Review
Elshaday Mulu ∗
Department of Mechanical, Production and Energy Engineering, School of Engineering, Moi University,
Eldoret, Kenya
Faculty of Mechanical and Production Engineering, Arba-minch University, Arba-minch, Ethiopia
African Centre of Excellence in Phytochemicals, Textile and Renewable Energy. Moi University, Eldoret,
Kenya (ACE II PTRE)
Milton M. M’Arimi
African Centre of Excellence in Phytochemicals, Textile and Renewable Energy. Moi University, Eldoret,
Kenya (ACE II PTRE)
Department of Chemical and Process Engineering, School of Engineering, Moi University, Eldoret, Kenya
Ramkat C. Rose
African Centre of Excellence in Phytochemicals, Textile and Renewable Energy, Moi University, Eldoret,
Kenya (ACE II PTRE)
Department of Biological Science, School of Sciences and Aerospace Studies, Moi University, Eldoret, Kenya
ABSTRACT: The contaminants in biogas, which include carbon dioxide and hydrogen sulfide, limit its application as engine fuel because they reduce its energy content and cause corrosion to metals. The aim of this
study was to review the applications of biomass materials in the purification and upgrading of biogas. The CO 2
adsorption capacity of activated carbon is dependent on the surface area and pore size of the adsorbent. Biochar
has a high adsorption capacity of H 2 S, which is dependent on the media alkalinity and the surface chemistry. The
capture of CO 2 and H 2 S by biomass adsorbent occurs through both physisorption and chemisorption. An increase
in adsorption temperature decreases the adsorption capacity of CO 2 but increases the adsorption capacity of H 2 S
for biomass adsorption. Published data indicate that modification with KOH adsorbents improves CO 2 uptake
significantly. Furthermore, impregnation of biomass adsorbents with agents like amine compounds can increase
the adsorption capacity of H 2 S.
1 INTRODUCTION
Fossil fuel has a high contribution to global warming.
Therefore, the use of renewable energy is an attractive alternative source. Biogas is among the renewable
energy sources that are currently used as replacements
for fossil fuels. In Europe, the biogas potential is
estimated at 18 billion M
3 produced per year from animal manure with an average power capacity between
315–515 kWe (Scarlat et al. 2018). Biogas is one of
the best alternative renewable energies which can be
used for generating electricity, heating, and fueling
engines. In addition, it is cost-effective and reduces
the environmental effects of waste materials.
Biogas can be produced from various organic
compounds by anaerobic digestion. Anaerobic digestion is a process that breaks down organic matter
in the absence of oxygen. It consists of four main
∗ Corresponding author
steps: hydrolysis, acidogenesis, acetogenesis, and
methanogens. Hydrolysis is the breakdown of complex
organics material (carbohydrate, protein and lipid) into
simple monomers (monosaccharide, amino acid, long
chain fatty acid) by hydrolytic enzyme. Acidogenesis bacteria convert simple monomers into volatile
fatty acids. Acetogenesis bacteria convert the volatile
fatty acid into acetic acid, carbon dioxide, and hydrogen. The methanogenesis bacteria convert acetates into
methane and carbon dioxide (Murphy J. & Thamsiriroj
2017).
Biogas is composed of methane, carbon dioxide,
hydrogen sulfide, nitrogen, siloxanes, oxygen and
other minor components. The composition is mainly
determined by the substrate and the conditions in the
anaerobic digester, such as temperature and media
pH. The microbes in the culture may also influence
the composition of biogas. The main contaminants
in biogas include carbon dioxide and hydrogen sulfide, which limit the application of biogas, especially
286
DOI 10.1201/9781003221968-38
Industrial Growth – Nzila et al. (Eds)
© 2022 Copyright the Author(s), ISBN: 978-1-032-11871-0
Open Access: www.taylorfrancis.com, CC BY-NC-ND 4.0 license
Purification and upgrade of biogas using biomass-derived adsorbents:
Review
Elshaday Mulu ∗
Department of Mechanical, Production and Energy Engineering, School of Engineering, Moi University,
Eldoret, Kenya
Faculty of Mechanical and Production Engineering, Arba-minch University, Arba-minch, Ethiopia
African Centre of Excellence in Phytochemicals, Textile and Renewable Energy. Moi University, Eldoret,
Kenya (ACE II PTRE)
Milton M. M’Arimi
African Centre of Excellence in Phytochemicals, Textile and Renewable Energy. Moi University, Eldoret,
Kenya (ACE II PTRE)
Department of Chemical and Process Engineering, School of Engineering, Moi University, Eldoret, Kenya
Ramkat C. Rose
African Centre of Excellence in Phytochemicals, Textile and Renewable Energy, Moi University, Eldoret,
Kenya (ACE II PTRE)
Department of Biological Science, School of Sciences and Aerospace Studies, Moi University, Eldoret, Kenya
ABSTRACT: The contaminants in biogas, which include carbon dioxide and hydrogen sulfide, limit its application as engine fuel because they reduce its energy content and cause corrosion to metals. The aim of this
study was to review the applications of biomass materials in the purification and upgrading of biogas. The CO 2
adsorption capacity of activated carbon is dependent on the surface area and pore size of the adsorbent. Biochar
has a high adsorption capacity of H 2 S, which is dependent on the media alkalinity and the surface chemistry. The
capture of CO 2 and H 2 S by biomass adsorbent occurs through both physisorption and chemisorption. An increase
in adsorption temperature decreases the adsorption capacity of CO 2 but increases the adsorption capacity of H 2 S
for biomass adsorption. Published data indicate that modification with KOH adsorbents improves CO 2 uptake
significantly. Furthermore, impregnation of biomass adsorbents with agents like amine compounds can increase
the adsorption capacity of H 2 S.
1 INTRODUCTION
Fossil fuel has a high contribution to global warming.
Therefore, the use of renewable energy is an attractive alternative source. Biogas is among the renewable
energy sources that are currently used as replacements
for fossil fuels. In Europe, the biogas potential is
estimated at 18 billion M
3 produced per year from animal manure with an average power capacity between
315–515 kWe (Scarlat et al. 2018). Biogas is one of
the best alternative renewable energies which can be
used for generating electricity, heating, and fueling
engines. In addition, it is cost-effective and reduces
the environmental effects of waste materials.
Biogas can be produced from various organic
compounds by anaerobic digestion. Anaerobic digestion is a process that breaks down organic matter
in the absence of oxygen. It consists of four main
∗ Corresponding author
steps: hydrolysis, acidogenesis, acetogenesis, and
methanogens. Hydrolysis is the breakdown of complex
organics material (carbohydrate, protein and lipid) into
simple monomers (monosaccharide, amino acid, long
chain fatty acid) by hydrolytic enzyme. Acidogenesis bacteria convert simple monomers into volatile
fatty acids. Acetogenesis bacteria convert the volatile
fatty acid into acetic acid, carbon dioxide, and hydrogen. The methanogenesis bacteria convert acetates into
methane and carbon dioxide (Murphy J. & Thamsiriroj
2017).
Biogas is composed of methane, carbon dioxide,
hydrogen sulfide, nitrogen, siloxanes, oxygen and
other minor components. The composition is mainly
determined by the substrate and the conditions in the
anaerobic digester, such as temperature and media
pH. The microbes in the culture may also influence
the composition of biogas. The main contaminants
in biogas include carbon dioxide and hydrogen sulfide, which limit the application of biogas, especially
286
DOI 10.1201/9781003221968-38