Portugal’s gas pipeline operator Redes Energéticas Nacionais (REN) has begun upgrading its network to enable it to carry blends of at least 10% hydrogen with fossil gas, ahead of a new rule that will force gas companies to include at least 1% of green H2 or biomethane.

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REN has started adapting 16 chromatographs — devices that measure the exact chemical makeup of the gas — across its 1,400km network, known as the National Gas System.

The chromatographs work by using an inert “carrier gas” to pass the mixture through the machine to analyse the quantities of hydrogen and gas.

The machines are typically used to assess the purity of methane, but will now also be used to measure the exact quantities of hydrogen in the mix.

In addition, the adapted chromatographs will allow REN’s scientists to reduce their use of relatively scarce helium as a carrier gas and use argon instead.

Later this week the Portuguese government is expected to announce the details of its long-awaited green hydrogen tender, which will see around renewable H2 and biomethane producers bid to supply a new state-backed wholesale trader with 3,045 tonnes per year under ten-year contracts.

Green hydrogen will sell for no more than €127/MWh ($139/MWh) while biomethane auctions will be capped at €62/MWh.

Controversially, the state-backed trader will then sell the hydrogen and biomethane on to the gas suppliers, who will be forced to include blends of at least 1% renewable H2 or biomethane with the fossil gas they deliver to customers.

It is not yet clear when the new rule will be enforced.

Portugal recently scrapped environmental permitting for green hydrogen projects, in a bid to bring more capacity on line as quickly as possible.

But blending hydrogen into the natural-gas grid is highly controversial, with several studies showing that it is expensive and results in relatively few emissions savings.