SCOTLAND’S densely populated central belt is awash with millions of tonnes of carbon dioxide spewed out by the country’s worst climate polluters, the Sunday Herald can reveal.

The latest pollution inventory from the Scottish Environmental Protection Agency (Sepa) shows that 12 of the country's top 20 polluters are in the central belt, with emissions totalling 7.7m tonnes. Five of the plants at Grangemouth and Mossmorran in Fife are run by three of the world’s biggest fossil fuel companies: Ineos, ExxonMobil and Shell.

Sepa’s inventory also reveals that discharges from the plants have been increasing in recent years, despite international efforts to reduce them to avoid catastrophic climate change.

The companies have been condemned as “dinosaurs” by environmentalists, who are demanding that they cut their pollution. But the firms insist that they are working hard to increase efficiencies and reduce their emissions. Sepa has just released 2016 data on pollution from all industrial plants in Scotland. By far the highest carbon emitter was the Grangemouth petrochemical giant, Ineos, which has three plants in the top ten.

The Petroineos oil refinery spewed over 1.6 million tonnes of carbon dioxide into the air last year, more than in 2015 or 2014. Ineos infrastructure and chemical plants at Grangemouth each emitted nearly half a million tonnes.

The third highest emitter was ExxonMobil’s ethylene plant at Mossmorran in Fife. Its carbon emissions have risen for the last four years to reach 885,580 tonnes in 2016, the highest for at least 14 years. On Friday ExxonMobil disclosed that the plant had suffered an unspecified “upset” and was being shut down. This would result in the burning of waste gas in flares for 48 hours, it warned.

Shell operates two plants among the high carbon emitters. Releases from the company’s St Fergus gas terminal in Peterhead have risen for the last four years to more than 356,000 tonnes, the level they were at in 2002.

Carbon emissions from Shell’s gas plant at Mossmorran also increased sharply in 2016, to reach the highest for 14 years. Another high carbon emitter was Tarmac’s cement works at Dunbar in East Lothian, which saw releases rise between 2015 and 2016).

Total carbon emissions from Scotland’s 200 plus industrial sites were 29 per cent lower in 2016 than in 2015. But this was because the huge coal-fired power station at Longannet, which has dominated emissions for decades, closed down in March 2016.

Friends of the Earth Scotland criticised companies for failing to cut climate pollution. “In many cases emissions are as high or higher than they were five years ago,” said the environmental group’s director, Dr Richard Dixon. He labelled Ineos as “Scotland’s biggest industrial polluter”, with emissions much greater than others. “None of these companies are doing anything significant to reduce their carbon emissions,” he argued.

“With the companies showing no interest and the government’s useless plans for the sector it is clear that big industry is a major problem for meeting our climate ambitions. The government needs a proper plan to help or force industry to reduce emissions.”

The Scottish Green Party called on companies to improve their record. “These dinosaurs are firmly stuck in the fossil age,” said the party’s environment spokesperson, Mark Ruskell MSP. “After Brexit, regulation and market mechanisms to cut carbon need to be strengthened, not abandoned. We need the right carrots and sticks so investment happens to deliver more industrial output from far less energy input.”

Dave Watson head of policy at the trade union, Unison Scotland, urged businesses to cut carbon emissions. “It is shocking to see them increasing in the last few years,” he said. “The companies should be explaining what they will do to reverse this.”

The international climate campaign group, 350.org, demanded that public sector pension funds withdrew their investments from fossil fuel firms. “This new data shows that the fossil fuel industry cannot be trusted to play a role in fighting climate change and the transition to a safe, clean future for Scotland,” said the group’s campaigner, Danielle Pafford. “Transparency is not enough. We need real action on polluters and support for a just transition for fossil fuel workers.”

Ineos pointed out that 1,350 people were employed at Grangemouth. Its crude oil refinery was the only one in Scotland, avoiding imports by producing 4.5 million tonnes of “clean” transport fuels every year, the company said. “We are constantly looking at ways to drive efficiencies, reduce our energy usage and thereby be more able to compete in the global oil and fuels market,” said an Ineos spokesperson.

“2016 was actually our most energy efficient year in the history of the refinery, with considerable effort made on energy conservation and how we operate our equipment.”

ExxonMobil stressed its commitment to maximising energy efficiency and minimising emissions. The cost of emissions under the European Union’s trading scheme was also an incentive to seek reductions, it said.

Emissions from the Mossmorran plant were “consistent with site production,” according to a company spokesman. “The largest figures correspond to years in which planned maintenance has taken place, such as 2016, as these maintenance activities contribute to a temporary increase in emissions,” he said. “These maintenance programme events are essential to ensure the plant’s continued safety, operational efficiency and reliability as an important supplier of ethylene to international markets.”

Shell highlighted its commitment to reducing climate pollution. “Shell is committed to reducing our emissions intensity and continuing efforts to improve the energy efficiency of our operations as well as ending continuous flaring,” said a company spokesperson.

The company’s chief executive, Ben van Beurden, has recently described climate change as “one of the biggest, long-term risks to the global economy”. He promised that Shell would innovate to cut emissions.

Tarmac also said that cutting carbon emissions was a key priority. “The 2016 statistics reflect that emissions levels can fluctuate from year to year in line with changes in economic activity,” said a company spokesperson.

“Producing more cement for the domestic market at Scotland's only cement plant reduces dependency on imports. The net effect is to remove the carbon and sulphur emissions associated with shipping.”

Sepa said it was encouraging that total carbon emissions were falling, but companies needed to go further. “It won’t be easy, but it will result in more powerful protection for Scotland’s environment,” said the agency’s head of environmental quality, Martin Marsden. “Whilst recognising that small annual fluctuations are often linked to production cycles, Sepa is working collaboratively with industry and partners to explore environmental innovation that reduces emissions and achieves better resource efficiency.”

The Scottish Government stressed that business emissions overall were falling. “Small fluctuations can be expected given these are working sites,” said a spokeswoman.

“The European Union emissions trading scheme provides businesses with access to the EU carbon market, ensuring a level playing field that allows industry to determine how to decarbonise in a cost effective way.”

She added: “We are delivering practical support to business in line with Scotland’s manufacturing action plan. This includes providing advice on energy efficiency improvements, and re-using heat that is produced from industrial processes.”