It was the huge island windfarm that promised to pump millions into the local economy but after more than a decade the project has divided the community as hundreds call for it to be scrapped.

As reported in yesterday's The Herald, more than 800 Shetlanders have banded together in a bid to stop the proposed windfarm, which could be the UK's third biggest if approved, to be built across the archipelago, voicing concerns over the islands' fragile bio-diversity and plans to desecrate ancient peatlands.

If given the go-ahead, Viking Wind Farm could span 129 sq km of the islands leaving many islanders living close to or within the wingspan of the 103, 155 meter turbines.

A partnership between Scottish and Southern Energy and the council-owned Viking Energy Shetland, signed in 2005, the windfarm is to largely be built on peatlands, raising fears over carbon release.

The installation of the turbines and the infrastructure required to support them can fatally damage the peat through extraction, drainage and drying.

Scottish peatlands are vital in climate change mitigation, acting as a sink for greenhouse gases, supporting biodiversity and regulating water quality and flow.

While peatlands cover only 3% of the world's land area they contain nearly 30% of all carbon stored on land.

Read more: 'The green energy debate: the case for onshore wind'

Campaigners and experts warn that damage to the peatlands could be irreversible with degraded peat losing the ability to absorb carbon and potentially releasing thousands of tonnes back into the atmosphere.

Renewable energy sources, such as wind, are seen to be inexhaustible, creating energy that can be harnessed for heating, electricity and transport.

Scotland's wind turbines produced enough electricity between January and June 2019 to power almost double the amount of homes - around 4.5 million - it already does, according to WWF Scotland.

New research has revealed that onshore windfarms in Europe have the capacity to generate 100 times the energy currently produced. By building a further 11 million turbines, the entire world could be powered until 20150.

With Scotland's current greenhouse gas emissions target set to meet net-zero in 2045, windfarms are said to be a key tool in reaching the goal. But if the building and maintenance of these windfarms and their de- or recommission 25 years later destroys one of our greatest natural assets in the flight against climate breakdown, as well as others, what are their true cost?

Richard Lindsay, head of environmental and conservation research the University of East London said: "There is a delicious irony in the fact that we build wind farms to reduce our carbon emissions. But some of the best places to build wind farms are peatlands, which are our biggest carbon store.

"Just 30cm of peat over a hectare holds the same amount of carbon as the same area of tropical rainforest. They have been capturing and storing carbon for up to 8000 years so when you damage them, you release this long-term carbon store."

Read more: The green energy debate: why wind power will never be the answer

Peat is lost when the foundations for the turbines are dug out but it is the building of the roads that are the biggest risk to the peatlands, said Mr Lindsay, as they cut across their natural water functions, causing them to dry out.

Mr Lindsay said: "As soon as you stop peat being water logged it will begin releasing carbon dioxide. Long term, we actually don't know what the effect is going to be."

Other concerns, particularly in Shetland, include peat slides which occur after the peat has been destabilised through disturbance. In 2002, in Galway, around 2km of peat slid off the hillside and travelled for 20km down the river system narrowly missing buildings.

Both SSE and Scottish Power build 'floating roads' at their sites to minimise damage to the peat, but this may have little to no benefit.

Mr Lindsay said: "Actually, they are just slowly sinking roads.What they need to be doing is constantly building the road surface up again. The windfarm industry is not been very forthcoming on the extent of that issue."

In terms of what is being done by energy companies to offset damage to the peat, the future remains unclear. Mr Lindsay said: "Maybe they're restoring some very damaged peatland but what are the long term effects of what they're doing on the windfarm? Nobody can answer that question because we're looking at potential carbon release over decades. There are a whole series of issues that have never really been investigated."

And it's not just an issue in Scotland. On the ridges of Northern Spain's Cantabrian Mountains windfarms have been constructed on blanket bog, bisecting almost every one.

But there could be an alternative: building onshore windfarms on agricultural land that is currently not being used to its full potential.

In America and Europe, some windfarms are built on leased farmland, allowing farming, crops and grazing, to continue around them.

Mr Lindsay said: "There is incredible reluctance to turn agricultural land into multi-use but there is huge potential there."

Scottish government planning policy now requires the use of a carbon payback calculator, developed by The James Hutton Institute and Aberdeen University, that assesses the carbon impact of windfarm developments by comparing the carbon costs of the developments with the carbon savings made.

David Miller, Knowledge Exchange Coordinator for The James Hutton Institute who helped develop the calculator, told the Herald on Sunday: "The starting point was to rely on modelling of the carbon costs ... after a few years you could begin to refine the models to say the carbon payback would take a certain number of years, originally calculated to be one estimate and then subsequently recalculated today."

Calculations can vary from seven to 33 years which far exceeds the 25-year life span of turbines, influencing the carbon calculations when considering the impact of re-turbining or reinstatement of the site.

Mr Miller said: "This is something still being worked on in Scotland because we recognise that protecting our peatland is a core element of Scotland's contribution to mitigating greenhouse gas emissions."

Onshore wind is playing its part meeting Scotland's climate targets, said Mr Miller, but more questions need to be asked.

He said: "After 25 years, as each of the developments come up for reconsideration, are there any which might have been put in the wrong place and might not be renewed because other sources [of energy] are becoming effective.

"We have an opportunity in the second half of the next decade for reconsidering whether some of the earlier developments are as efficient for production as originally intended. Hypothetically, it might turn out [that windfarms] are not as negatively impacting to landscapes as feared or there might be other areas where the impacts are greater than has been expected but it does mean that the story is not finished."

Nothing comes without a cost, said Mr Miller, especially not our energy

He said: "Energy isn't created, it's just transferred. So it's hard to imagine that genuinely, there is environmental and cost free energy. It's not just the magnitude but where and the nature of the trade-off. That explains why we're felling trees instead of planting them as we did 30 years ago because of the understanding of the significance of the peatlands for carbon storage."