The biomethanation trial was conducted at a high gas feed rate to GRT of 24.9 and 16.7 min and the results are shown in Figure . On average PC was 8.51 ± 0.56 Nm 3 /m 3 d at GRT of 24.9 min, which was 21% higher than the PC of 7.0 ± 0.17 Nm 3 /m 3 d achieved at a similar GRT of 25.7 min but had N2 the feed gas. This showed the effect of partial pressure of the reacting gases that leads to higher absorption and conversion in the absence of the inert component. The average PC further increased to 9.44 ± 0.50 Nm 3 /m 3 d at GRT of 16.7. During the biomethanation trial, there was unreacted H 2 and CO 2 at the reactor outlet, RE was 96.1% and 67.6% at GRT of 24.9 and 16.7 min, respectively. This indicated that the feed gases were available over the whole length of the packing in the reactor, hence the CH 4 formation was not limited by the unavailability of the substrate. This also means that the PC value achieved at GRT of 16.7 was the maximum possible for this size and type of packing material and reactor, considering that the whole packing contained an active biofilm of hydrogenotrophic methanogens. The reason for unconverted H 2 and CO 2 at the same GRT compared to when the feed was H 2 , CO 2 , and N2, is the increased H 2 and CO 2 flow due to the same GRT.