Calculating carbon savings from wind farms on Scottish peat lands: a new approach

This approach was developed to calculate the impact of wind farm developments on the soil carbon stocks held in peats. It provides a transparent and easy to follow method for estimating the impacts of wind farms on the carbon dynamics of peat lands.

Appendix 3: Report from the Stakeholder Workshop

A3.1. Introduction

The stakeholder workshop was held to explain the methodology and approach used in producing the guidance document and respond to any concerns or questions raised by stakeholders. The long-term objective is to gain consensus for adopting the revised Technical Guidance Document. A range of stakeholders was invited from Scottish government, the power industry, the forestry sector, and from sectors with environmental interests. The participants are listed below.

Clifton Bain, RSPB,
Nick Blyth, Institute of Environmental Management & Assessment,
Olivia Bragg, University of Dundee,
Andrew Coupar, Scottish Natural Heritage,
Mike Daniels, John Muir Trust,
Fergus Forsyth, South Ayrshire Council Education (Carrick Academy)
Bill Grainger, AMEC,
James McKenzie, Scottish Government, James.McKenzie
Richard Luxmoore, National Trust for Scotland,
Martin Mathers, Scottish Power,
Sandra Marks, Ecological Advisors unit - Scottish Government,
Anne McCall, RSPB,
Helen McDade, John Muir Trust Policy Officer & Scottish Environment Link,
David Miller, Macaulay Institute,
James Pendlebury, Forestry Commission,
Peter Singleton, SEPA,
Jo Smith, University of Aberdeen,
Howard Steele, Scottish Government, Energy Consents Unit, (sent apologies)
Philip Wilson, SEPA,
Guy Winter, Scottish Government,
Geeta Puri, Project Officer - Scottish Government,

A3.2. Background

Large scale wind farm development on organic (peat-based) soils has raised concerns about the reliability of methods used to calculate the time taken for these facilities to reduce greenhouse gas emissions. This project was commissioned to revise guidelines. It was generally agreed that revision of guidelines was needed.

Questions were raised as to how these revisions should be referred to: "new guidelines", a "toolbox", or "technical advice". This is of importance as it affects the way in which the guidance is used. This is an issue for Scottish Government. Action Point: Scottish Government participants - consider how you want to refer to the revised guidance.

The new guidance emphasizes that good development is about good practices as well as good site selection: this was seen as an advance in the guidance.

The new guidance attempts to reduce uncertainties, is modular (so allowing improved calculations to be inserted easily), and should be updated annually using new data / statistics as they become available. Action Point: Geeta Puri - consider mechanisms for updating the guidance.

There is no presumption that this will have an impact in planning. However, the SNH representative stated that they would hope to adopt the guidance.

The revision is significantly longer than 4 pages, and may be too complicated for a 4 page format. A simpler format (including less equations) should be used for the 4 page document. This extended guidance note, the spreadsheet and the longer report will then be downloadable from the web on request.

Carbon payback time is not currently included in the wider planning system, but may become material over the next few years. This would include a wide range of sectors.

In addition to the current information, the technical guidance note (or perhaps just the full report) should show the effects of including different factors in the examples. A simple sensitivity analysis would be a good way of demonstrating these effects.

The guidance should give a figure for the best and worst case scenarios for a range of factors. Factors that might be expressed as a range include restoration / habitat improvement, extent of drainage, capacity factors, fuel used for backup. The user should be encouraged to enter site specific factors in these cases.

The occasions when the guidance is needed should be clarified. If a site includes only 10% peat land, is this enough to require the guidance to be used?

The work should eventually be extended to include mineral soils to allow budgets on mixed soil types to be done. This would also allow the relative losses on sited a wind farm on a mineral soil or a peat land to be examined. Derivation of more general summary models will probably require application of ECOSSE to remove the noise from the data. Long Term Action Point: Scottish Government participants - consider the need for a set of guidelines with a wider target soil type.

A link should be included to methods used to express the importance of the habitat, and the avoidance of important habitats emphasized. Refer to government guidelines for designation of the importance of a habitat.

The treatment of other greenhouse gases should be emphasized in the technical guidance.

Methods to include the impacts of climate change, land use change and degrade sites on the estimates of carbon loss should be considered further. This could be done by including a range of climate change scenarios and the impact on wetness and rate of decomposition of peat at the site. Long Term Action Point: Scottish Government participants - consider if you want to include this.

The best practice guidance should be integrated throughout the technical guidance note (eg for floating tracks, treatment of peats etc).

The guidance should be sufficiently flexible to allow regular revision. The Scottish Government should take the lead in brokering a revision, according to current knowledge. Industry should also participate. Long Term Action Point: Geeta Puri - to consider mechanisms for doing this.

The technical guidance must be affordable, workable and valuable. Otherwise, it will not be adopted by industry, or will discourage wind farm development in Scotland.

A3.3. Carbon emission savings from wind farms

It should be noted in the guidance that capacity factors should be specific to the country in which the guidance is being applied.

There is some debate still to run over exactly how the comparison should be made. For example, in future will anything ever be switched off or will demand / export soak up the capacity?

The counterfactual energy source should present a range of results (assuming different sources). Currently calculations using grid mix, coal fired mix and fossil fuel mix as the counterfactual are given in the spreadsheet.

However, the recommended counterfactual case should also be agreed, and the figure used should be updated annually.

A3.4. Loss of carbon due to production, transportation, erection, operation and dismantling of wind farm

It was agreed that losses of carbon due to production, transportation, erection, operation and dismantling of the wind farm are highly site specific, depending on the type of turbines, as well as the site infrastructure. Therefore, users should be encouraged to enter the site specific value for total loss, L life (t CO 2).

A best and worst case default values of the CO 2 emissions due to production, transportation, erection, operation and dismantling, E life (t CO 2 MWh -1) should be provided to help users without access to a site specific value. The total losses, L life (t CO 2) would then be calculated from these default values, the total annual energy output of the wind farm, e out (MWh yr -1), and the life time of the wind farm, t (years).

Mathematical Equation

A3.5. Loss of carbon due to backup power generation

Calculation of backup power should account for projections of wind energy contribution to renewables, Scottish Government targets for renewables, and the time of construction of the wind farm.

The interpretation of the extra capacity required from Dale et al (2004) may be incorrect.

New data will shortly become available (following publication of the report commissioned by Sue Kearns).

A3.6. Loss of carbon fixing potential of peat lands

For completeness, include the time taken for restoration in the carbon fixing potential of the bog, i.e.

Mathematical Equation

where L fix is the loss of carbon fixing potential of peat land (t CO 2), A direct is the area directly affected by wind farm development by removal of peat, A indirect is the area indirectly affected by drainage (ha), G bog is the annual gains due to the carbon fixing potential of the peat land (G bog = 0.92 t CO 2 ha -1 yr -1) and t restore is the time taken for restoration of the habitat from the development of the wind farm (years).

However, the statements recognising that plant restoration is very small should be strengthened (even if it continues for 100 years the contribution is likely to be less than 5% of the total CO 2 payback time).

A3.7. Changes in carbon stored in peat lands

A3.7.1. Loss of carbon from removed peat

The approach, step 1 assuming 100% loss from removed peats, and step 2 calculating the C savings when peats were restored was generally accepted.

A3.7.2. Loss of carbon from drained peat

Estimation of volume of peat affected by drainage

In the absence of detailed measurements at the site, an equation was derived to provide extent of drainage, e drain (m), for a level site dependent on hydraulic conductivity, H (mm d -1).

Mathematical Equation

Sites are rarely level, therefore this equation should be removed from the guidance and the extent of drainage should be entered directly as an input value.

Equations / estimates for the worst and best cases could be used instead. However, the difficulty of estimating worst case scenarios might preclude this.

There is an urgent need for a hydrological assessment of existing work on the extent of drainage in peat soils to allow the best and worst case scenario to be estimated. Long Term Action Point: Scottish Government participants - consider whether such an assessment could be done and the mechanism for updating the guidance as information becomes available.

There is potential for a study site to be established at Whitelee or alternative site Arecleoch, S Ayrshire (not yet in place). Long Term Action Point: Scottish Government participants - consider whether a study at Whitelee or Arecleoch would be useful and the mechanism for updating the guidance as results become available.

Before floating roads can be considered to be undrained, the guidance should require evidence that the risks of the requirement for drainage are low.

Reference should be made to the SNH best practice guidance for floating roads (plus web-link).

A bond payment is established at planning stage for restoration of the site. This is reviewed every 5 years. If monitoring indicates that floating roads are sinking, this should be reflected in the size of the bond payment.

There are actually a range of reasons why different parties will be studying the hydrological characteristics of a site (eg. Scottish Water - quality of runoff; site engineers - positioning of turbines and roads). It may not be unreasonable to ask the industry to provide site specific estimates of hydrology and drainage.

Loss of carbon from drained peat if the site is not reinstated after decommissioning

The approach, assuming 100% loss from non-reinstated (restored) peats was generally accepted.

Loss of carbon from drained peat if the site is reinstated after decommissioning

The term reinstatement is used in the revised guidance to mean the recovery of hydrological conditions and habitat after the site is decommissioned. This is more normally referred to in the power sector as restoration, so the term "reinstatement" should be replaced by "restoration". The meaning of the term should be defined in the guidance.

A clear definition of reinstatement (restoration) should be included. For example, what is flooding?

The wording of the guidance should emphasize the need to demonstrate the quality of reinstatement (restoration). The importance of reinstatement (restoration) to the overall carbon budget should be emphasized (eg by showing scenario with and without reinstatement (restoration)).

There is a need to bring together peat research and data in Scotland to improve the evidence base. Long Term Action Point: Scottish Government participants - consider whether such a review should be done and how the results could be included in the revised guidance.

A3.7.3. Loss of carbon dioxide due to leaching of dissolved organic carbon

Losses of carbon dioxide due to leaching of dissolved organic carbon, L DOC (t CO 2), are calculated by multiplying the sum of the gaseous losses of carbon from the different sources in the soil, L gas (t C), by the percentage of the total gaseous loss of carbon that is leached as dissolved organic carbon, p DOC (%), and the percentage of the leached dissolved organic carbon that is eventually emitted as carbon dioxide , p DOC? CO2 (%).

Mathematical Equation

This figure is significantly lower than predicted from the work of Worral and others.

A3.7.4. Loss of carbon due to peatslide

It was accepted that the catastrophic effects, such as peatslide, can be neglected in the guidance because it is dealt with in the existing guidance.

Strong reference (plus web-link) should be given to the existing SPP6 guidance.

The guidance should be clarified to make it clear that paragraph 36 only refers to landslides.

Less catastrophic effects, such as the losses of particulates due to erosion of gullies should be included. These could be expressed as a risk factor. The experimental literature should be reviewed to determine the size / risk of particulate organic matter erosion losses.

A3.8. Loss/saving of carbon due to forestry clearance

The interaction between forestry and peat should be included. This is already included in that drainage of forested peat can be included, so the volume of peat affected by any subsequent drainage will be accounted for. Also, restoration of deforested areas by blocking drains can be accounted for. In the spreadsheet the description of forestry, specific soil conditions for the forested area, and the potential for restoration should be expanded so that a specific drainage depth for the forested area can be entered.

The nature of forestry being replaced should be considered in more detail. C losses from soils under forestry should be assumed to continue to zero if soil is not restored. This will increase the C savings associated with felling of plantations.

The forestry commission will provide comment on whether the longevity of products should be included in the calculation.

A3.9. Carbon dioxide saving due to restoration of peat land

The term restoration is used in the revised technical guidance to refer to the improvement of peat land during the lifetime of the wind farm. This term should be changed because in the power sector it is usually taken to mean the restoration of the site after the wind farm is decommissioned. Suggested term: improvement. The meaning of the term chosen should be defined in the guidance.

The guidance should emphasize the need to demonstrate the quality of restoration (improvement).

The importance to the overall carbon budget should be emphasized (eg. by giving example with and without restoration (improvement)).

The revised guidance should refer to the forest and peat guidelines document (plus weblink?).



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