In the near future, renewable energy sources will replace fossil energy. To allow full carbon utilization of renewable biomass, we have demonstrated a possible integration between a biogas reactor, an electrolysis unit, and a catalytic methanation reactor. Stringent removal of all sulfur contaminants in raw biogas is required to enable this integration. We demonstrate how existing bulk sulfur removal solutions, like a biotrickling filter loaded with Acidithiobacillus thiooxidans and impregnated activated carbon, are unable to meet this requirement. Only the main sulfur contaminant hydrogen sulfide (H ₂S) can effectively be removed. Contaminants carbon disulfide (CS ₂), dimethyl sulfide (DMS), and carbonyl sulfide (COS) will leak through the carbon filter, long before hydrogen sulfide can be detected. Utilization of surplus oxygen from the combined system is proven problem free and allows sulfur removal without introducing contaminants. Provided that a recommended sulfur guard is included, the proposed design is ready for full-scale implementation.