Can the Annex V method be used if the biomethane is liquified or converted to methanol and used in the transport sector?

No, under ISCC, the Annex VI method must be used for all products resulting from co-digestion, regardless of the final physical state or market. Therefore even if biogas is upgraded to biomethane, liquified and used in the transportation sector, the Annex VI method must be used to calculate the GHG emissions associated with the biogas.