The co-digestion of certified and non-certified feedstocks is challenging for the GHG calculation according to the Annex VI method. This is because all co-digested feedstocks must be included in the GHG calculation according to the RED II methodology. However, GHG information for those non-certified feedstocks is often not provided by the feedstock supplier. Presently, ISCC allows for the calculation of the GHG value to be conducted only with the certifiedfeedstocks. It must be made sure that only the fraction of biogas that results from certified biogas is forwarded as sustainable under ISCC EU.