Advances in biogas desulfurization using organic and inorganic sorbents: A review

Abstract

Access to clean and affordable energy is a key enabler of development. Biogas is an essential renewable and sustainable energy that has great potential in meeting energy requirements, especially in areas with limited access to the grid. However, the presence of impurities such as hydrogen sulfide limits its application by corroding equipment parts and reducing the calorific value. Biogas desulfurization is therefore important; however, there are limited studies available. The current study critically evaluated existing biogas sweetening technologies applied on an industrial scale in three main categories: pre‐digestion, during digestion, and post‐digestion. The removal of H ₂ S using sorption processes employing a variety of organic and inorganic sorbents was comprehensively reviewed. The effectiveness of inorganic materials such as red rock, ash, and zero‐valent iron as well as organic sorbents including sweet potato leaves, organic solvents, and water hyacinth was assessed. The effect of process conditions such as pH and moisture content especially for organic sorbents was evaluated. The study proposed new ways of increasing the performance of the sorbent materials through functionalization, recovery, regeneration, and reuse as well as biogas pre‐treatment to remove moisture. While most studies previously reported focused on H ₂ S during removal post‐digestion, the current study evaluated the entire process train from pre‐digestion, during digestion, and post digestion thereby providing a more concise approach to biogas desulfurization.