The two-tower method is a biological technique to remove sulfur from biogas. In this work the applicability of a numerical model for the absorption tower was validated. The model takes into account ionization equilibrium of H(2)S, gas/liquid saturation equilibrium, gas to liquid mass transfer and packing material properties. As packing material magnetic raschig rings and polypropylene rings were considered. In a transient (one-way) sprinkle experiment, the change of the H(2)S absorption rate due to liquid-to-gas (L/G) ratio was examined. It was verified that numerical absorption rates agree with the experimental data. In another series of recirculation experiments, the effect of L/G on the H(2)S absorption rate was investigated for neutral and basic water with pH 7 and 9, respectively. It was shown that our numerical calculations give the correct absorption rates. Hence it has become possible to design the absorption tower and to specify inlet, outlet and pH conditions for the downstream biological reactor.