SNP ministers have been left with a “gaping chasm” in their net zero blueprint after almost halving the amount of harmful emissions expected to be removed from the atmosphere by 2030 through controversial technologies such as carbon capture.

The Scottish Government has been previously warned about over-reliance on unproven methods, known as negative emissions technologies (NETs) to meet climate ambitions – but has so-far pushed ahead with its ambitious strategy.

NETS include carbon capture, which prevents burned carbon dioxide being released into the atmosphere and is instead injected deep into the seabed.

But there are concerns about the viability of the technology being used at commercial scale, with the majority of projects allowing fossil fuels to continue to be burnt and not a single project up and running in Scotland so far.

Under the last climate change plan, the Scottish Government forecast that 5.7Mt of carbon dioxide could be removed by 2032 by NETs – the equivalent of almost one third of Scottish emissions reductions, while the forecast for 2030 was 3.8Mt of carbon dioxide - almost 20% of reductions.

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But a stark new study published by the Scottish Government “estimates that the maximum negative emissions technologies potential achievable in Scotland in 2030 is 2.2MtCO2”, adding that “this is significantly lower than the stated NETS ambition” in the latest climate change strategy.

The admission leaves questions over where the Scottish Government will make emission reductions instead to meet its legal 2030 target of cutting 1990 levels of pollution by 75%.

The next climate change plan was promised to be published by the end of last month, but has been delayed by the Scottish Government – blaming changes by the UK Government to key net zero policies such as rolling back a ban on the sale of petrol and diesel cars.

The Scottish Government has now committed to publishing the new climate change plan “next year”.

The rolling back of confidence in technologies such as carbon capture comes after Rishi Sunak visited Aberdeenshire in July to announce funding for the Acorn carbon capture and storage project, a venture by fossil fuel giant Shell and Storegga, and other partners.

But on is visit, the Prime Minister acknowledged that the technology does not yet work.

He told journalists that “if we can get that technology to work, and to bring the cost down” it “can be hugely helpful for us to transition to net zero”.

The Acorn carbon capture project has been used as a political football over recent years after it missed out on the first round of UK Government funding – delaying the project getting up and running.

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The Scottish Government has blamed the downgrade on how much carbon capture and other NETs can contribute, in part, on the UK Government’s delays in getting the Acorn project up and running as well as “various shifts in evidence” on the technology.

The Acorn project hopes to begin operations by the end of the decade and is now unlikely to be able to contribute significantly to Scotland’s 2030 target – meaning more drastic cuts to emissions will be required in other sectors such as agriculture, industry and transport in the next seven years.

The Scottish Government has vocally backed the Acorn project, with Storegga one of around 20 selected businesses that made up Humza Yousaf’s delegation to COP28.

At the time, questions were raised about the delay meaning the key energy project could not contribute to the crunch 2030 target – previously described by the chief executive of the independent Climate Change Committee as “on the fringes of credibility” before the latest blow..

Bringing a carbon capture project to the North East, which could help prolong the life of the North Sea oil and gas sector and help with the transition to hydrogen, has been a costly journey.

Around £100 million was spent by the UK Government on a competition to bring a £1 billion carbon capture project to either Peterhead or North Yorkshire before being scrapped - before the current funding round was pressed ahead with.

The UK Government has pledged a combined £1 billion to the Acorn project and a similar project for the Humber, while £80 million has been earmarked by SNP ministers for the Aberdeenshire proposals.

Scotland has failed to hit eight of its last 12 annual carbon emissions reductions targets, with concerns raised the 2030 target may be slipping out of reach.

Last month, Zero Carbon Buildings Minister Patrick Harvie confirmed a target for 1 million homes to be decarbonised by 2030 has been axed, adding to fears that progress is stalling.

Climate campaigners have warned there is now a huge gap of cuts to emissions needed in order to keep legal targets on track.

Friends of the Earth Scotland’s climate campaigner, Alex Lee, said: “Reality is finally dawning on ministers that the promises of negative emissions technology are little more than hot air.

“For too long the Scottish Government has been distracted by carbon capture and these other dangerous schemes resulting in a gaping chasm in plans to meet climate commitments.

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“Ministers have been repeatedly warned about their over-reliance on these rogue technologies and the time and money they have poured into the sinkhole of carbon capture rather than being deployed in working climate solutions.”

They added: “Ministers should instead put the needs of people and the planet first, and scale up investment in public transport and home insulation that will improve lives and bring down climate pollution.

“Scotland’s energy future should be focused on readily available and more affordable options such as wind, solar, renewable heat and energy efficiency measures.

“Carbon capture is little more than greenwash from industries who are fighting to the deny the reality of the changes needed in energy generation, land use and how we reduce waste.

“Politicians in Scotland can no longer ignore the clear warnings about carbon capture and storage as a technology that could put our environment and climate at real risk of danger.”

The Centre for International Environmental Law published a report last month, warning about the risks of offshore carbon capture and storage.

The research concluded that “injecting CO₂ under the seabed will not fix the problem of fossil fuel pollution”, adding that the technology “is poised to introduce new threats to the ocean, the climate, human rights, and the coastal and frontline communities”.

The study added that “the false promise of CCS only prolongs reliance on these dirty energy sources, delaying the necessary transition to a fossil-free future”.

The report also claims that focusing on carbon capture “provides cover for fossil fuel expansion projects”.

Nikki Reisch, CIEL’s climate and energy program director and report co-author, said: “Carbon capture and storage's track record is riddled with failures and warning signs about the technology’s feasibility and safety.

"Proposed offshore CCS ‘hubs’ are enabling big polluters to amplify the myth that we don’t need to phase out fossil fuels, we can just ‘manage’ their emissions.

“The last thing we should do is trust the same industry that has pushed the world’s oceans and climate to the brink to bring us back from it. “The accelerating efforts to build ever more dangerous, unnecessary, and expensive infrastructure offshore should be abandoned, and subsidies for CCS should be eliminated.”

The companies behind the Acorn project say that it will still be expected to store at least 5Mt of CO2 by 2030 and is expected to be “operational by the late-2020s”.

Acorn chiefs insist that before 2030, the Scottish Cluster could include nine different UK CO2 sources, including industrial sites and power generation plants, as well as new hydrogen generation plant technology.

The Acorn projects early sources of CO2 could include two of the gas terminals at the St Fergus Gas Complex in Peterhead, SSE and Equinor’s proposed Peterhead carbon capture power station, a new blue hydrogen plant supplying Ineos and Petroineos sites at Grangemouth and ExxonMobil and Shell’s facilities at Mossmorran.

Dr Nick Cooper, CEO of Storegga, said that the project “will be a major contributor towards meeting the UK and Scotland’s carbon reduction targets”.

A Scottish Government spokesperson said that "negative emissions technologies in Scotland can deliver at scale in due course, but not at the pace assumed in the CCPu".

They added: “This is due to various shifts in evidence since the publishing of the CCPu in 2021 including – critically - the UK Government’s decision to not allocate the Scottish Cluster as a track-1 cluster for delivery in the mid-2020s.

“This decision has had a clear impact on when the carbon storage underpinning NETs will be available, jeopardising Scotland’s net zero targets.

“NETs are an emerging field of technologies that remove carbon dioxide from the atmosphere. This feasibility study was not specifically designed to assess existing NETs performance against CCPu targets.

“It is an independent analysis incorporating recent developments to set out a deployment potential for NETs which use carbon capture and storage infrastructure to sequester carbon permanently.

“The study was commissioned by the Scottish Government to help increase our evidence-base on negative emissions technologies as we develop policy ahead of the new draft climate change plan being published next year.”