Process-based soil gas leakage assessment at the Kerr Farm: Comparison of results to leakage proxies at ZERT and Mt. Etna

•We use a process-based soil gas approach to evaluate CO2 leakage at the Kerr Farm.•The approach was validated using leakage proxies from a controlled-release and Etna volcano.•No evidence of CO2 leakage was found at the Kerr Farm.•Leakage proxies show a process-based method may facilitate leakage quantification.