Acid gas cleaning activity of bio-adsorbent prepared by waste shell of different shellfish species was investigated in a fixed bed reactor to evaluate its feasibility as an acid gas cleaning agent. The physicochemical properties of prepared adsorbents were measured using ICP, BET, SEM-EDX and XRD. The results showed that active chemical species of bio-sorbent are comparable to that of commercial limestone and lime. SO2/NOx removal capacity of waste shell of shellfish was higher than that of commercial limestone due to the enhanced physical properties. In particular, the desulfurization activity of clam based adsorbent was the best among the tested waste shells because of both higher calcium content and more specific surface area. These lead to the conclusion that commercial limestone can be substituted for bio-sorbent prepared by waste shell of clam.