**4. Conclusions**

The performance of three types of syngas cleaning systems using wood shavings as the filter medium was evaluated. Tar removal efficiencies of the three treatments were: wood shavings filter (10.28%) < wood shavings filter with heat exchanger (60.30%) < wood shavings filter with oil bubbler (97%). Even though the heat exchanger reduced the syngas temperature and led to increased condensation of tars, the vegetable oil bubbler was more effective in the removal of tars because of the oil's ability to absorb tar. Tar deposited at the top and around the periphery of the wood shavings filter was the highest when the heat exchanger was used.

**Acknowledgments:** The authors would like to acknowledge Oklahoma State University Research Foundation and Oklahoma Agricultural Experiment Station for their support.

**Author Contributions:** All authors significantly contributed to the scientific study and writing. Thapa performed tests and collected data, whereas, Bhoi, Kumar and Huhnke supervised the project, and all authors contributed to writing the manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.
