Main Biogas Upgrading Technologies

Abstract

Biogas is a combustible gas mixture, and its chemical composition depends on the conditions on the production unit. Biogas can be valued thus constituting a renewable energy source. This review article provides a comparative analysis of the main technologies used in the treatment and purification of biogas. Treatment methods, such as H 2 O and H 2 S removal processes from biogas are described. After treatment, biogas can be used directly to produce thermal and electrical energy. Biogas upgrading is possible through its purification, obtaining biomethane that can be used as a substitute for natural gas. This review article also highlights the main technologies for biogas purification through CO 2 removal processes. Among the various biofuels, biomethane is a versatile fuel, and is expected to play an essential role in the circular bioeconomy. The advantages and disadvantages associated with each of these biogas treatment and purification technologies are also discussed.

Biomethane Production and Applications

“…The first level involves production of biogas with, H 2 S concentration of below 500 ppm, and can reach as low as 100 ppm. The second level involves reduction in H 2 S concentrations less than 0.005 ppm, which are typical specifications and requirements for biomethane gas [4,24].…”

“…Therefore, in Situ is a biotechnology which works by direct injection of pure air or oxygen and causing bacteria to oxidize H 2 S leading to biological removal H 2 S, to produce sulfur (S) which exits the digester via the digested. These microorganisms are widely present in anaerobic environment in biodigesters [4].…”

“…In the bio filter technology biogas is passed through a column having a synthetic material, in the form of a biofilm. The parallel or countercurrent flow system is used to maintain the humidity and nutrients, that are essential for the microorganisms that degrade of H 2 S [4]. The purification system consists of a bioreactor where sulfur-oxidizing bacteria like the Thiobacillus, Pseudomonas and Acidothiobacillus are immobilized on a carrier.…”

“…iii. Biological gas scrubber In biological gas scrubber, a two-stage system is used to remove H 2 S. In the first stage H 2 S scrubbing column, applies sodium hydroxide solution while activated sludge is used in the second stage which is injected with injected with air, because the microorganisms used are aerobic, leading to the solution regeneration [4]. Bio scrubber system is applied in the removal of compounds like ammonia, amines, hydrocarbons, hydrogen sulfide and odorous contaminants.…”

“…Other than production in anaerobic digesters, biogas can also be produced from landfills and through biomass thermal pyrolysis and gasification processes. The mixture produced generally consists of 30-75% methane (CH 4 ), 25-55% carbon dioxide (CO 2 ) and other constituents or impurities like hydrogen (H 2 ), oxygen (O 2 ), nitrogen (N 2 ), hydrogen sulfide (H 2 S), water (H 2 O) and ammonia (NH 3 ), dust particles, siloxanes, aromatic and halogenated compounds, which are often in tiny quantities [4][5][6].…”