Payback Time

From Climate Scepticism


There was a bit of a discussion in the comments on For Peat’s Sake about the “carbon” payback time associated with windfarms, including some helpful links supplied by commenter “Ryelands”. At around that time, an interesting article appeared on the Shetland News website (of which, more below).

I have decided it is time to look at it again in rather more detail, not least as the issue regained my attention when I became aware of an objection last month by the John Muir Trust to the Shetland Energy Isles wind farm proposal, which reminded me of the Shetland News article.

I think it is interesting that the John Muir Trust has lodged an objection, given that the Trust is largely supportive of the net zero agenda:

The John Muir Trust supports the Scottish Government’s bold and ambitious net zero by 2045 target and understands the role that renewables, including onshore wind, have in meeting this target. We also support the expansion of community renewables for local benefit and therefore the intention of Energy Isles Limited to retain benefits within Shetland.

But then they go on to say this:

However, we believe that the Proposed Development would have an unacceptable impact on an area within the top 10% of wildest areas of Scotland, and the essential nature-based solutions it provides to both the climate crisis and biodiversity loss. As such, we must maintain our objection.

For my purposes in discussing “carbon payback”, however, this is the crux of their objection:

It is claimed that the Proposed Development will have a pay-back period of 1.7 years. This assessment has been made using the Scottish Government’s carbon calculator. However, since being published in 2008 many have recognised that there are significant issues with the calculator. This includes Professor Jo Smith of the University of Aberdeen who was part of the team which created the calculator who said that “[t]here’s now more information available that could help reduce two uncertainties: the extent of drainage, and the efficacy of restoration of peatlands. Therefore, I’d completely agree with reviewing it.” Clifton Bain, advisor of the IUCN UK Peatland Programme, said:

[t]here’s a risk that impact is being significantly underestimated. I think that’s highly possible, because it’s based on assumptions, based on outdated data, there’s no oversight of how the model is used’ .The commitment by the Scottish Government to provide adequate tools and guidance to inform the assessment of net carbon impacts of development proposals on peatland (Onshore Wind Policy Statement, page 65) appears to suggest a recognition that the Carbon Calculator in its current form does not adequately do this. Without the tools to provide an accurate picture of the emissions being released from constructing wind developments on peat, the pay-back period and the greenhouse gas emission estimates for the Proposed Development should be considered with caution.

The Scottish Government Carbon calculator for wind farms on Scottish peatlands factsheet is said:

…to support the process of determining wind farm developments in Scotland. The tool’s purpose is to assess, in a comprehensive and consistent way, the carbon impact of wind farm developments. This is done by comparing the carbon costs of wind farm developments with the carbon savings attributable to the wind farm.

So far, so simple, though not surprisingly the carbon calculator tool goes into a fair amount of detail. The opening questions are:

Will the site be drained on construction of the windfarm?

Is the soil at the site highly organic?

Does windfarm construction require a significant amount of deforestation?
i.e. is removal in excess of keyholing the turbines within the forest boundary?

There follow three sections dealing with core input data, forestry input data and construction input data, with the core input data alone comprising twelve pages that must be completed. In fairness, this goes into significant detail, with everything from the number and type of turbines, length of access road, depth of peat, size and number of borrow pits, and much more information having to be supplied. There is even a section asking questions about restoration of the site on decommissioning. It is all very impressive-looking.

On 30th June 2021 Ryelands commented:

The Scottish Wind Power Assessment Project published three reports on the destruction of peatland associated with wind-power development back in 2005-2007 and a fourth, “A guide to calculating the CO2 debt and payback time for wind farms” in collaboration with Dr Mike Hall, then of REF. You might find them of interest.

Of these, I think the fourth one referred to, namely the 17 years old report by Dr Mike Hall for the Renewable Energy Foundation, was particularly relevant when looking at the “carbon payback” time for wind farms built on peat. It predates the Scottish government calculator, and covers much of the same ground. It notes that:

Several papers from the wind industry in Denmark and the UK have addressed the first two points with estimates of payback time ranging from about six to 30 months.

Those first two points are:

Emissions arising from fabrication (steel smelting, forging of turbine columns, the manufacture of blades and the electrical and mechanical components);

Emissions arising from construction (transportation of components, quarrying, building foundations, access tracks and hard standings, commissioning)

Then Dr Hall notes:

However, the industry rarely, if ever, considers the last two. This is a fundamental omission as their contribution to the overall CO2 debt, in particular the last, can be far greater than all the others put together. This paper outlines a procedure for quantifying it.

The last two points being:

The indirect loss of CO2 uptake (fixation) by plants originally on the surface of the site but obliterated by construction activity including the destruction of active bog plants on wet sites and deforestation; Emissions due to the indirect, long-term liberation of CO2 from carbon stored in peat due to drying and oxidation processes caused by construction of the site

In fairness, the Scottish Government calculator (developed since publication of Dr Hall’s paper) does ask questions about these aspects of a wind farm development.

Dr Hall then went on to provide a worked example, in respect of the proposed Whinash development in Cumbria, which was described thus:

The Whinash site, which was refused consent following a Public Inquiry in 2006, would have occupied a rounded ridge between the Lake District and Yorkshire Dales National Parks. The total area of 763 hectares is composed of blanket bog in relatively poor condition, purple moor grass/rush pastures and upland heath. Compared to many sites in Wales and Scotland, it has a shallow peat covering and patchy areas of blanket bog. It is deemed to be a medium scenario site and the extent of peat degradation is thus assumed to be 50 metres.

The conclusion arrived at was that the carbon payback time, had the development proceeded, would have been 3.5 years.

Fast forward to the Viking Energy development on Shetland, which presumably used the Scottish government calculator to arrive at a conclusion about “carbon payback”, and we are told:

Updated carbon payback calculations for the wind farm were produced as part of the Environmental Impact Assessment underpinning the variation to the planning consent granted in 2019. The calculations show the expected carbon payback for the development to be less than two years, saving over 500,000 tonnes of carbon dioxide every year over the lifetime of the project.

In approving the Viking Energy development, the Scottish Government said:

Ministers are satisfied that the proposed varied development would provide carbon savings, and that these savings would be of an order that weighs in favour of the proposed varied development. There is no evidence to suggest that the proposed varied development would not offer substantial carbon savings.

Thus we see a worked example for a proposed development on a site of degraded peat with a payback time of 3.5 years, but the Viking Energy wind farm (where the developers made hay with the claim that the peat on that site was heavily degraded) with a supposed payback time of less than two years, or a little over half the time in Dr Hall’s worked example. This is despite the fact that pretty much everything connected with the Viking Energy development (including much of the workforce) had to travel (presumably via diesel-powered shipping) to Shetland from the UK mainland and despite the added complication of the undersea cabling required to bring the electricity from the windfarm to the UK mainland. The switchgear for the converter station was manufactured in Germany. The transformers for the converter station were manufactured in Sweden. And as a Viking Energy/SSE glossy brochure happily tells us (it seems that they have no shame), the turbine blades were manufactured by Vestas in Italy, so had to be transported from there to Shetland; the tower sections were manufactured in Spain; the nacelles/hubs/drives were manufactured (with what seems these days to be a sad inevitability) in China. Did the payback calculation take into account the emissions associated with transporting the components half-way round the world in some cases? Did it take into account that the Chinese components will have been manufactured using electricity mostly generated by coal-fired power stations? It seems that something doesn’t add up. At first sight, the Viking Energy development should obviously have a longer – perhaps significantly longer – carbon payback period than that at Whinash in Cumbria, yet – by quite some margin – the opposite is claimed to be the case. Could it be (as the John Muir Trust suggests) that the Scottish government carbon calculator cannot be relied upon?

The report on the Derrybrien bog slide with additional observations regarding blanket peat and windfarms also makes interesting reading. Many of the criticisms contained in the report, though interesting, can probably be disregarded for current purposes, since they are aimed specifically at the way that particular wind farm received planning approval in the Republic of Ireland over two decades ago. One hopes that lessons have been learned, and that such criticisms, though relevant at the time, are now of only historic interest. However, other aspects of the report remain directly relevant today:

Claims are made concerning carbon emissions which are incorrect and present only part of the story. It is suggested that there are no emissions from wind farms and that all carbon-balance issues are favourable. This is not so because vehicles are used to construct and maintain the wind farm and there are emissions associated with construction. While these should form part of the environmental audit, the most important issue at Derrybrien is the release of CO2 from the peat soil as it oxidises during construction and as a result of catastrophic failures. The losses from the October 2003 event alone are equivalent to the energy production of three or four turbines for the lifetime of the project.

The Viking Energy project has already witnessed some peat slides, admittedly minor when compared to the disaster at Derrybrien. However, do we know enough about the CO2 emissions associated with them? Do they have an impact on the development’s carbon payback calculation? The following statement from the report puts the issue very bluntly:

It is difficult to understand the logic of damaging long-term carbon stores to install devices whose purpose is to reduce emissions.

As the authors go on to say:

Even without the events of October 2003, it is too simplistic to talk of a 60 MW wind farm representing such a total saving of carbon emissions. If a true carbon balance is to be calculated, it should include the carbon released from peat excavated for the turbine bases or drainage activities, carbon released during the manufacture of raw materials and turbines components, in the hundreds of truck loads, regular maintenance journeys and in decommissioning the wind farm…

…The story that has unfolded in this report seems to cast doubt on the wisdom of wind farm development on any area of deep blanket peat. Whilst the prospect of a few 15 x 15m undrained holes accommodating turbine bases does not at first sight seem incompatible with the processes that maintain the peat blanket, the reality of wind farm construction and maintenance requires comprehensive disruption of a site’s hydrology through drainage and thus of the peat itself – either relatively safely through wastage or, as the residents of Derrybrien have discovered, through catastrophic failure.

Those comments bring us almost full circle, to the interesting article on the Shetland News website, which I mentioned above. It builds on the story with which I opened this piece, namely the criticism by the John Muir Trust of the Scottish government carbon payback calculator and the limited reliance that should be placed on it. It is dramatically headlined “Experts warn wind farms should not be built on peatlands: With governments pledging to accelerate the construction of onshore wind power until 2030 to help meet climate targets, scientists call for an urgent review of the policy of building turbines on peatlands.

The problem with the Scottish government calculator is reiterated:

But the government calculator used to reach these figures is flawed, according to experts.

Professor Jo Smith, who led the Aberdeen university team which created the spreadsheet tool, said: “The science has moved forward. There’s now more information available that could help reduce two uncertainties: the extent of drainage, and the efficacy of restoration of peatlands.

Therefore, I’d completely agree with reviewing it.”

Clifton Bain, advisor of the IUCN UK Peatland Programme, said: “There’s a risk that impact is being significantly underestimated. I think that’s highly possible, because it’s based on assumptions, based on outdated data, there’s no oversight of how the model is used.”

One of the biggest factors in bringing down the carbon payback time from decades to just a few years is how far out the bog will drain as a result of tracks and turbine bases being built on it.

It can be given as low as 10 metres. In Shetland, Viking Energy’s calculations used ranges between 10 and 50m, while Energy Isles, in Yell, used 17-39m.

According to Dr Guadaneth Chico, who has studied peat bog erosion at wind farms in Spain, the impact varies for every peatland but can be “up to hundreds of metres”.

One of the problems is that drainage is hard to evaluate in the short-term, he added. “It’s a long-term habitat. Restoration tends to be monitored for a few years, then we forget about it. But in three years, it doesn’t change much.”

Promises of restoration are also crucial to reaching a short payback time. Degraded peatland emits greenhouse gases at an extraordinary rate – it’s estimated that Shetland’s peat, in poor condition from centuries of over-grazing, cutting and climate, is emitting hundreds of thousands of tonnes of CO2 equivalent every year.

Much (with regard to carbon payback times) depends on the rigour with which promises of peat restoration are carried through by the developer. And this carries its own problems:

Oversight is the job of the Scottish Environment Protection Agency (SEPA), and planning departments within local authorities are struggling with recruitment and workload.

I have seen estimates on the restoration potential using very high figures, whereas estimates on the damage seem to use low figures,” said Bain.

This illustrates there’s not consistency in carbon numbers and impacts, and it’s left to the developers’ judgement – there needs to be much clearer guidance on which numbers are used.”

He warned that “otherwise it is potentially possible to inflate numbers for restoration and reduce numbers for damage…”

Does the Scottish government, with its gung-ho attitude to wind farm developments, acknowledge the problem? Barely, and only in its usual weasly manner. A (rather desperate, it seems, in a clutching at straws sort of way) “Scottish Government spokesperson said they “note the limitations” of the payback calculations, but said the calculator still provided “the best available means” to get figures in a “consistent and comparable format”.” That’s not the same thing as saying that the calculator enables the provision of payback calculations that are accurate. It’s not a glowing vote of confidence. But never mind – those windfarms will be built, even on peat, regardless of the damage they cause to the environment.

In the last six months, a study titled Quantifying the land-based opportunity carbon costs of onshore wind farms was published on 20th August 2022. Its abstract tells us:

…the construction of 3848 wind turbines in Scotland generated 4.9 million tonnes of carbon dioxide (CO2) emissions from land use change. On average the emission intensity of land use change in peatland is 560g CO2 kWh−1, in forestry is 88g CO2 kWh−1, in cropland is 45g CO2 kWh−1, and in pastureland is 30g CO2 kWh−1. In the worst land use change scenario, the displacement of Dystrophic basin peat habitats generated 1760g CO2 kWh−1, which is comparable to the life cycle emissions of fossil-fuel technologies such as coal and gas-fired electricity generation.

Sadly, it also reminds us “that, out of the 21 terrestrial habitats identified in Scotland, 14 habitats were affected by the construction of onshore wind farms”, though that’s a different, albeit extremely bothersome, story.

A tabloid interpretation of that study can be found in the Scottish Mail on Sunday here.


Whatever the rights and wrongs of claims regarding “carbon payback” times for windfarms, it seems clear that the manufacturers of the turbines are struggling with financial payback. Vestas – one of the manufacturers for Viking Energy – has announced very poor financial results in its 2022 Annual Report. In announcing to shareholders that the board was recommending no dividend payment, its CEO said:

Vestas and the wind industry remained challenged in 2022 as external headwinds and industry immaturity hampered profitability and resulted in unsatisfying financial results for the full year.

As is the way with these things, the rest of his statement went on to put a positive spin on the results, but they are very downbeat. The reality is that revenue declined against the previous year; earnings before interest and tax were “hampered by supply chain disruptions, inflation, higher warranty provisions and offshore impairments”; turbine orders were down 19%; and the company’s strategy is to restore profitability in the “turbine segment”.

Tough times, it seems, with much to review, but that’s for another day.