Conservationists have doubled down on their determination to fight Woodside's plan to build the $16.5 billion Scarborough gas project over concerns about its projected greenhouse gas emissions.

The Conservation Council of WA (CCWA) this week launched its second legal action targeting the WA government's management of the project's approvals over a number of years — in particular, how greenhouse gas emissions were considered.

Just days before Christmas, the WA Supreme Court will hear another CCWA challenge, this time to Scarborough's environmental approvals, which it argues were unlawful because they did not adequately consider the project's impact on the climate.

But WA Premier Mark McGowan appears to want to shift this battle to a different arena.

Aside from his comments about the possibility of state intervention if the approvals were found to be invalid, he highlighted the importance of keeping "the lights on".

"We can't have scores of industries close down because of a court ruling, so the state government will do what it has to do to make sure industries stay open," Mr McGowan said when asked about the legal action.

"Other industries or other projects have received approvals that this might have an implication for.

"We want to keep the lights on and make sure our hospitals continue to function."

Projected domestic supply would exceed demand

So just how important is Scarborough — Australia's biggest oil and gas project in a decade — to keeping WA's lights on?

The Scarborough project involves piping gas from the Scarborough gas fields to an expanded Pluto facility on the Burrup Peninsula for processing. 

Scarborough is slated to start production in 2026, with most of its gas headed to overseas markets like Japan and South Korea.

But it will also produce domestic gas.

According to a new analysis by climate scientist Bill Hare, the extension of Pluto's Train 1 and construction of Train 2 will increase domestic gas production from 25 to 250 terajoules a day.

Of this, 125 Tj/day will be supplied to Perdaman's proposed urea plant on the Burrup Peninsula and 40 Tj/day to Woodside's planned H2Perth project, south of Perth, to create hydrogen and ammonia from gas.

"[The] project would effectively add 20 per cent to the domestic gas (DomGas) supply in WA, well above the projected demand throughout the next decade," his report said.

"These additional fossil gas resources lock in a significant new demand for gas that does not presently exist, adding substantially to state emissions."

But Woodside disputes Mr Hare's 250 Tj/day figure, saying the total domestic capacity for Pluto is 225 Tj/day.

Dr Hare, who received support from the CCWA for the study, said WA did not need Scarborough gas to keep the lights on because there would be more renewable energy options by the time it was available.

"We've got renewables, we've got battery storage and we've got coming availability of hydrogen," he said.

"So really on the time scale of a decade or so, we could be 100 per cent renewable in the electricity space by the early 2030s, as are other places.

The most current data from the Australian Energy Market Operator (AEMO) shows that gas supply is expected to meet forecast demand in WA until 2029.

This prediction does not include Scarborough — which was only given the final go-ahead last month — and will be updated in coming weeks.

Gas to play 'significant' role despite growth of renewables

Most of WA's domestic gas supply is used for industrial purposes, with only 12 per cent used for electricity generation.

The AEMO expects gas demand to grow by about 0.7 per cent each year, due to industry requirements, although demand from WA's main electricity network — the south-west Interconnected System — is tipped to fall by about 0.4 per cent annually. 

A federal government report published in October showed WA's electricity market emissions were expected to decrease by 2030 because it would be using more renewable energy, particularly rooftop solar.

But the report, titled 'Australia's Emissions Projections 2021', also said gas would continue to play a significant role, even as the share of renewables in electricity generation was tipped to increase from 15 per cent in 2019 to 45 per cent in 2030.

"Gas generation continues to support reliability in the [WA Wholesale Electricity Market], and is projected to be the single biggest fuel source throughout the decade," it said.

"Baseload gas generation is projected to be at a similar level by 2030 as 2019, while coal generation declines."

Grattan Institute energy program director Tony Wood said WA was the most gas-intensive state in the country due to the demands of industry and power generation. 

"We know that power generation can be solved with renewables but not completely because we haven't yet worked out what we do when the sun goes down," he said.

Mr Wood said gas would continue to play a role in the energy mix but this would diminish as renewables became cheaper.

"This need for gas is going to go on for some time," he said.

"Maybe the use of gas as the fundamental ongoing source of electricity most of the time is replaced by renewables, however you still need gas to back up the renewables until you've got a solution to the storage issue."