Advances in biogas desulfurization using organic and inorganicsorbents: A review

Abstract

Access to clean and affordable energy is a key enabler of development. Biogas is anessential renewable and sustainable energy that has great potential in meetingenergy requirements, especially in areas with limited access to the grid. However, thepresence of impurities such as hydrogen sulfide limits its application by corrodingequipment parts and reducing the calorific value. Biogas desulfurization is thereforeimportant; however, there are limited studies available. The current study criticallyevaluated existing biogas sweetening technologies applied on an industrial scale inthree main categories: pre-digestion, during digestion, and post-digestion. Theremoval of H 2S using sorption processes employing a variety of organic and inorganicsorbents was comprehensively reviewed. The effectiveness of inorganic materialssuch as red rock, ash, and zero-valent iron as well as organic sorbents including sweetpotato leaves, organic solvents, and water hyacinth was assessed. The effect of pro-cess conditions such as pH and moisture content especially for organic sorbents wasevaluated. The study proposed new ways of increasing the performance of the sor-bent materials through functionalization, recovery, regeneration, and reuse as well asbiogas pre-treatment to remove moisture. While most studies previously reportedfocused on H 2S during removal post-digestion, the current study evaluated the entireprocess train from pre-digestion, during digestion, and post digestion thereby provid-ing a more concise approach to biogas desulfurization.