Adsorption of CO2 using biochar - Review of the impact of gas mixtures and water on adsorption

Biochar produced from sources such as forestry, agricultural, and marine wastes has demonstrated an ability to adsorb CO2. The adsorption capacity is a function of biochar surface properties, which subsequently depend on biochar feedstock and production conditions. This is a comprehensive review on the use of biochar as a carbon capture adsorbent with a particular focus on the impact of the properties of biochar and feed gas composition CO2 adsorption. Applying biochar in carbon capture at the industrial scale requires detailed knowledge of the impact of co-adsorption effects of other gases. This is particularly true of water, biogas, syngas, and other gas streams. The study of these impacts is diffuse across the literature, where only one other gas is typically studied. This review brings these studies together to give a comprehensive picture of the impact of gas mixtures as a function of biochar properties on carbon capture. This review highlights the limited study in this area, where the bulk of research work is focused on gas mixtures, demonstrating more work is required on this topic. Examining biochar affinity toward various gases can also indicate if biochar has potential applications in gas separations to recover gases such as H2. Articles focused on H2 purification from gas mixtures using carbon-based adsorbents are also studied. This review indicates the potential for biochar to separate H2 from syngas, particularly using biochar produced during gasification to then purify syngas, making it a closed-loop system.