The certification of biomethane is a fundamental system to guarantee the sustainability of this energy source. European legislation provides for two types of certificates: proof of sustainability and guarantees of origin. ERGaR, the European Renewable Gas Registry, works in the field of certifications to facilitate not only cross-border trade between different national registries, but also to create collaboration and information networks between companies and registries in this sector. We discussed the matter with Tim Hamers, Secretary General of ERGaR