CO2-assisted gasification of carbon-based waste materials is one of the processes that both utilises waste carbon chemicals and produces CO, which is a highly sought after raw material. In this work, we aimed at finding and clarifying the synergistic effects of simultaneous potassium and Fe, Co, or Ni-driven catalysis. To reveal the behaviour of such systems, a series with different potassium loadings and a fixed second metal loading of 5 wt.% was prepared. The following methods were applied for this purpose: SEM, TEM, EDX, XRD, electron diffraction, and catalytic tests. The most active sample was found to be 3 wt.% K and 5 wt.% Co- or Fe-loaded hydrolysis lignin. The attained CO2 conversion was up to 92%, while the pure lignin sample demonstrated only 62% conversion under the same conditions.