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
A review of low-cost materials for biogas purification
Nyambane Doricah, Sombei Dorcas, Jepleting Anceita & Achisa C. Mecha
Department of Chemical and Process Engineering, Moi University, Eldoret, Kenya
ABSTRACT: The increasing demand for energy for both household and industrial use has necessitated the
exploration of renewable energy sources such as biogas. Raw biogas contains 50–70% methane and impurities
which comprise 30–40% carbon dioxide, 5% moisture, 0.5% hydrogen sulfide, and other trace compounds. In
Kenya, biogas is used in households without purification. This poses challenges such as corrosion of equipment
and low biogas calorific value. In this study, we assess the various low-cost adsorbents that have been recently
employed for biogas purification. The materials evaluated include activated carbon from organic waste such
as coconut shells, and iron oxide from lathe machine iron chips. The performance of these materials in biogas
purification that has been reported in various studies is evaluated. The findings indicate that these materials
have great potential in biogas purification and can be readily applied in small-scale systems. Such systems are
expected to contribute significantly to increase the access to clean energy in rural areas.
Keywords: adsorption, biogas, energy, purification
1 INTRODUCTION
Biogas production is an important initiative aimed
at increasing access to clean and safe energy with
low environmental impact. The adoption of biogas
as a source of energy is therefore a major way of
contributing to the realization of Sustainable Development Goal 7: affordable and clean energy. Biogas
is produced by anaerobic digestion of biomass such
as plant and animal wastes. Raw biogas is composed
of methane (50–70%), carbon (IV) oxide (30–40%),
moisture (5%), hydrogen sulfide (0.5%), and other
trace compounds. The main impurities in biogas are
therefore CO 2 , H 2 S, and moisture (Vijay, Chandra,
Subbarao, & Kapdi, 2006). Large-scale production
of biogas in developed economies such as in Europe
employ biogas purification technologies such as chemical absorption, pressure swing adsorption, membrane
separation, and cryogenic separation among others
(Niesner, Jecha, & Stehlík, 2013). These technologies
are relatively expensive and suited for purification systems for these small-scale systems. Low-cost biogas
upgrading systems that use adsorption techniques can
be locally adapted for biogas purification at a smallscale level to address the challenge of corrosion of
pipes by H 2 S in biogas and to increase the heating value
of biogas by removing CO 2 and moisture. This study
therefore assesses potential candidates for adsorbents
that can be used to develop low-cost biogas upgrading
systems for small-scale use. The use of locally available materials that are less costly and easily available
such as waste iron chips and activated carbon from
organic waste is explored.
2 BIOGAS PURIFICATION TECHNIQUES
Biogas upgrading refers to the removal of contaminants in the raw biogas such as moisture, H 2 S, and CO 2
to produce a bio-methane stream of a certain desired
quality. The main technologies used are absorption,
adsorption, membrane separation, and cryogenic separation. However, most of these target large-scale
systems and little has been mentioned on technologies for small-scale applications (Awe, Zhao, Nzihou,
Minh, & Lyczko, 2017).
Absorption can be achieved by physical or chemical means. Physical absorption using water scrubbing
is commonly used and relies on the separation of
CO 2 and H 2 S from the biogas due to their increased
solubility in water compared to methane. It uses pressurized water as an absorbent. Its advantages include
the simplicity and high efficiency of methane recovery. The limitations are high investment costs, high
operating costs due to high pressure pumping, possible clogging because of bacterial growth, foaming,
low flexibility towards variation of gas input, a lot of
consumption of water and energy as well as the need
for gas drying (Angelidaki et al., 2018). Chemical
methods of absorption work in the same principle as
physical absorption but chemical reaction takes place
between the solvent and the absorbed substances. This
makes use of CO 2 reactive absorbents such as alkanol amines (mono ethanol amine) or di-methyl ethanol
amine (DMEA), and alkali aqueous solutions such as
potassium hydroxide, sodium hydroxide, ferric chloride, and ferric hydroxide, among others (Lasocki,
Kołodziejczyk, & Matuszewska, 2015).The advantage
DOI 10.1201/9781003221968-30
225
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
A review of low-cost materials for biogas purification
Nyambane Doricah, Sombei Dorcas, Jepleting Anceita & Achisa C. Mecha
Department of Chemical and Process Engineering, Moi University, Eldoret, Kenya
ABSTRACT: The increasing demand for energy for both household and industrial use has necessitated the
exploration of renewable energy sources such as biogas. Raw biogas contains 50–70% methane and impurities
which comprise 30–40% carbon dioxide, 5% moisture, 0.5% hydrogen sulfide, and other trace compounds. In
Kenya, biogas is used in households without purification. This poses challenges such as corrosion of equipment
and low biogas calorific value. In this study, we assess the various low-cost adsorbents that have been recently
employed for biogas purification. The materials evaluated include activated carbon from organic waste such
as coconut shells, and iron oxide from lathe machine iron chips. The performance of these materials in biogas
purification that has been reported in various studies is evaluated. The findings indicate that these materials
have great potential in biogas purification and can be readily applied in small-scale systems. Such systems are
expected to contribute significantly to increase the access to clean energy in rural areas.
Keywords: adsorption, biogas, energy, purification
1 INTRODUCTION
Biogas production is an important initiative aimed
at increasing access to clean and safe energy with
low environmental impact. The adoption of biogas
as a source of energy is therefore a major way of
contributing to the realization of Sustainable Development Goal 7: affordable and clean energy. Biogas
is produced by anaerobic digestion of biomass such
as plant and animal wastes. Raw biogas is composed
of methane (50–70%), carbon (IV) oxide (30–40%),
moisture (5%), hydrogen sulfide (0.5%), and other
trace compounds. The main impurities in biogas are
therefore CO 2 , H 2 S, and moisture (Vijay, Chandra,
Subbarao, & Kapdi, 2006). Large-scale production
of biogas in developed economies such as in Europe
employ biogas purification technologies such as chemical absorption, pressure swing adsorption, membrane
separation, and cryogenic separation among others
(Niesner, Jecha, & Stehlík, 2013). These technologies
are relatively expensive and suited for purification systems for these small-scale systems. Low-cost biogas
upgrading systems that use adsorption techniques can
be locally adapted for biogas purification at a smallscale level to address the challenge of corrosion of
pipes by H 2 S in biogas and to increase the heating value
of biogas by removing CO 2 and moisture. This study
therefore assesses potential candidates for adsorbents
that can be used to develop low-cost biogas upgrading
systems for small-scale use. The use of locally available materials that are less costly and easily available
such as waste iron chips and activated carbon from
organic waste is explored.
2 BIOGAS PURIFICATION TECHNIQUES
Biogas upgrading refers to the removal of contaminants in the raw biogas such as moisture, H 2 S, and CO 2
to produce a bio-methane stream of a certain desired
quality. The main technologies used are absorption,
adsorption, membrane separation, and cryogenic separation. However, most of these target large-scale
systems and little has been mentioned on technologies for small-scale applications (Awe, Zhao, Nzihou,
Minh, & Lyczko, 2017).
Absorption can be achieved by physical or chemical means. Physical absorption using water scrubbing
is commonly used and relies on the separation of
CO 2 and H 2 S from the biogas due to their increased
solubility in water compared to methane. It uses pressurized water as an absorbent. Its advantages include
the simplicity and high efficiency of methane recovery. The limitations are high investment costs, high
operating costs due to high pressure pumping, possible clogging because of bacterial growth, foaming,
low flexibility towards variation of gas input, a lot of
consumption of water and energy as well as the need
for gas drying (Angelidaki et al., 2018). Chemical
methods of absorption work in the same principle as
physical absorption but chemical reaction takes place
between the solvent and the absorbed substances. This
makes use of CO 2 reactive absorbents such as alkanol amines (mono ethanol amine) or di-methyl ethanol
amine (DMEA), and alkali aqueous solutions such as
potassium hydroxide, sodium hydroxide, ferric chloride, and ferric hydroxide, among others (Lasocki,
Kołodziejczyk, & Matuszewska, 2015).The advantage
DOI 10.1201/9781003221968-30
225