17.10. Measures Adopted as Part of the Array

81. As part of the Array design process, a number of designed in measures have been proposed to reduce the potential for impacts on and from climate change (see Table 17.11   Open ▸ ). They are considered inherently part of the design of the Array and, as there is a commitment to implementing these measures, these have been considered in the assessment presented in section 17.11 (i.e. the determination of magnitude and therefore significance assumes implementation of these measures). These designed in measures are considered standard industry practice for this type of development.

Table 17.11: Designed In Measures Adopted as Part of the Array

17.11. Assessment of Significance

82. Table 17.7   Open ▸ summarises the potential impacts arising from the construction, operation and maintenance and decommissioning phases of the Array, as well as setting out the maximum design scenario against which each impact has been assessed. An assessment of the likely significance of the effects of the Array on and from climate change is given below.

17.11.1. GHG Effects

GHG Emissions Arising from disturbance to blue carbon stocks during the construction, operation and maintenance and decommissioning of the Array

83. Throughout the lifetime of the Array, during the construction, operation and maintenance and decommissioning phases, it is anticipated that there will be disturbance to seabed habitats. For the construction phase this will arise from the installation of anchors and mooring cables, OSP foundations, interconnector and inter-array cables, cable protection and scour protection. For the operation and maintenance phase this may arise from mooring cable movement during rough weather and storms. For decommissioning, disturbance is likely to be similar to construction.
84. Where seabed habitats are disturbed, this affects the habitat’s ability to store and sequester blue carbon. For example, when organic sediments are disturbed and enter the water column, stored blue carbon within these organic sediments can be converted to CO2 through a process called remineralisation (Cunningham and Hunt, 2023). The emissions associated with the disturbance from the Array are detailed below. This impact entails an assessment of the largest total Array footprint over all phases, representing the greatest potential for GHG emissions from disturbance to blue carbon stores.
85. However, not all blue carbon stocks that are disturbed will be remineralised to CO2 (Smeaton and Austin, 2022). As such, a range of emissions are presented, reflecting the likely range of remineralisation rates and resulting emissions (Smeaton and Austin, 2022; Cunningham and Hunt, 2023).

                        Construction phase

                        Magnitude of impact

86. Based on the MDS presented in Table 17.7   Open ▸ , the total area disturbed during the construction phase is 32.25 km2. As set out in volume 3, appendix 17.1, site-specific benthic surveys undertaken for the Array (volume 3, appendix 7.1, annex A) and published literature values (Smeaton et al, 2020) have been used to calculate the average blue carbon per hectare contained in habitats within the Array area. This figure has been calculated to be 5.00 tonnes of carbon per hectare, which corresponds to 18.35 tCO2 per hectare when converted from carbon to CO2. Literature values for rates of remineralisation in offshore sediments (Smeaton and Austin, 2022) were then used to calculate total emissions. Refer to volume 3, appendix 17.1 for more details.
87. The impact is predicted to be of international spatial extent, short term duration, intermittent and low reversibility. It is predicted that the impact will affect the receptor directly. The magnitude of impact is calculated to be between 11,813 tCO2 and 59,067 tCO2.

                        Sensitivity of the receptor

88. In accordance with paragraph 71, the receptor is deemed to be of high vulnerability, low recoverability and high value. The sensitivity of the receptor is therefore, considered to be high.

                        Significance of the effect

89. Overall, the magnitude of impact is deemed to be between 11,813 tCO2 and 59,067 tCO2, and the sensitivity of the receptor is considered to be high. Consistent with paragraph 73, the magnitude of emissions comprise less than 0.002% of the Fifth and Sixth UK Carbon Budgets (set out in Table 17.1   Open ▸ ). Further, the magnitude of emissions arising from disturbance to blue carbon stocks during the construction phase comprises between 0.001% and 0.004% of Scotland’s estimated blue carbon stocks (Smeaton et al., 2020; Cunningham et al., 2023), with loss arising from habitats of low relative importance to carbon storage as outlined in paragraph 22. Therefore, the effect will be of minor adverse effect, which is not significant in EIA terms.

                        Secondary mitigation and residual effect

90. No climatic effects mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.

                        Operation and maintenance phase

                        Magnitude of impact

91. Based on the MDS presented in Table 17.7   Open ▸ , the total area disturbed during the operation and maintenance phase is 1.22 km2 Using the same methodology as summarised in paragraph 86, total operation and maintenance emissions associated with disturbance to blue carbon stocks have been calculated to be between 447 tCO2 and 2,233 tCO2.
92. As set out in volume 3, appendix 17.1, blue carbon sequestration rates in offshore sediments in the North Sea are deemed to be negligible, and as such there is negligible loss of sequestration potential for the disturbed sediments over the Array’s 35 year operating lifetime.
93. The impact is predicted to be of international spatial extent, long term duration, intermittent and low reversibility. It is predicted that the impact will affect the receptor directly. The magnitude of impact is calculated to be between 447 tCO2 and 2,233 tCO2.

                        Sensitivity of the receptor

94. In accordance with paragraph 71, the receptor is deemed to be of high vulnerability, low recoverability and high value. The sensitivity of the receptor is therefore, considered to be high.

                        Significance of the effect

95. Overall, the magnitude of impact is deemed to be between 447 tCO2 and 2,233 tCO2, and the sensitivity of the receptor is considered to be high. The magnitude of emissions is unable to be contextualised within the UK Carbon Budgets given the operation and maintenance phase falls outside of such budgets. The magnitude of emissions arising from disturbance to blue carbon stocks during the operation and maintenance phase comprises less than 0.001% of Scotland’s estimated blue carbon stocks (Smeaton et al., 2020; Cunningham et al., 2023), with loss arising from habitats of low relative importance to carbon storage as outlined in paragraph 22. Therefore the effect will be of minor adverse effect, which is not significant in EIA terms.

                        Secondary mitigation and residual effect

96. No climatic effects mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.

                        Decommissioning phase

                        Magnitude of impact

97. As stated in the Project Description (volume 1, chapter 3), the sequence of activities in the decommissioning phase will generally be the reverse of the construction sequence and will involve similar equipment. It is anticipated that all floating structures, mooring lines, OSP topsides and foundations to the seabed level will be completely removed. Associated infrastructure, such as cables, scour protection and anchors and piles below the seabed may either be left in situ or removed, in accordance with the decommissioning plan. It may be decided, closer to the time of decommissioning, that removal will result in greater environmental impacts than leaving components in situ.
98. Given the negligible rates of sediment accumulation and associated carbon sequestration in the Array area, there is not anticipated to be any material change to the blue carbon stocks over the Array’s operational lifetime. As such, any disturbance to the seabed and blue carbon habitats that may result from infrastructure removal at the decommissioning phase is not likely to result in the release of additional emissions not captured by the range of likely emissions presented in the assessment of construction effects.
99. As such, there will not be substantial additional disturbance of the seabed, meaning that further blue carbon stores will not be disturbed and released. The magnitude of impact is therefore negligible.
100. The impact is predicted to be of international spatial extent, short term duration, intermittent and low reversibility. It is predicted that the impact will affect the receptor directly. The magnitude of impact is deemed to be negligible.

                        Sensitivity of the receptor

101. In accordance with paragraph 71, the receptor is deemed to be of high vulnerability, low recoverability and high value. The sensitivity of the receptor is therefore, considered to be high.

                        Significance of the effect

102. Overall, the magnitude of impact is deemed to be negligible, and the sensitivity of the receptor is considered to be high. Based on the definitions as set out in Table 17.9   Open ▸ , the effect will be of negligible effect, which is not significant in EIA terms.

                        Secondary mitigation and residual effect

103. No climatic effects mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.

GHG Emissions Arising from the Manufacturing and Installation of the Array

104. The below considers the embodied carbon emissions associated with materials and associated transportation emissions. This impact entails an assessment of the greatest number of wind turbines and floating foundations within the MDS in the Project Description ( Table 17.7   Open ▸ , volume 1, chapter 3), and maximum length of the inter-array and interconnector cables representing the greatest potential for GHG emissions from the construction and installation of the Array as a conservative estimate of impact.

                        Construction phase

105. This section considers the GHG emissions arising from the consumption of materials and activities required to construct the Array. Calculations to reach such emissions consider the maximum amount of materials required to construct the wind turbines and OSPs, maximum lengths of all cables, with associated scour protection and cable protection, representing the greatest potential for GHG emissions from the construction and installation of the Array as a conservative estimate of impact. Further, the designed in measures adopted as part of the Array (detailed in Table 17.11   Open ▸ ) have not been able to be quantitatively assessed given the early stage in the Array’s design. As such, it can be expected that their implementation will result in a reduced magnitude of emissions than that presented within this assessment. Their impact on the significance of effect assessed has been considered qualitatively.
106. The following items are considered within this assessment:

• wind turbines (including floating foundations, mooring cables and anchors);
• OSP topside structures and foundations;
• interconnector and inter-array cables (including cable protection);
• inter-array cable junction boxes;
• scour protection; and
• vessel and helicopter movements.

107. Detailed and current Life Cycle Assessment (LCA) are not available for all items specific to the Array infrastructure due to the early stage of the Array design. As such, a combined approach has been taken to calculate embodied carbon, informed largely by conservative estimates of construction materials or fuels scaled by relevant emissions factors, and also in part by LCA data.
108. The potential impact of the wind turbines and foundations, mooring cables, anchors, OSP topsides and foundations, junction boxes, cabling (including inter-array and interconnector), cable protection and scour protection has been estimated using appropriate material emission intensities ICE database (Jones and Hammond, 2019), scaled by material estimates for each element. Material types and the emissions factors by which they have been scaled are listed within volume 3, appendix 17.1.
109. Construction phase emissions associated with the proposed electrical plant included on the OSPs has been captured using an intensity for the manufacturing GWP of 2,190 kgCO2e per MW (ABB, 2003). This was scaled by the Array output capacity of 3,600 MW to give an estimated embodied emission value of 7,884 tCO2e.
110. Emissions associated with fuel combustion from vessel and helicopter movements have been calculated based on the maximum number of movements proposed during the construction phase, likely base port and fuel consumption rates per vessel type where available, in order to reach a conservative estimate. Anticipated fuel consumption for each movement was scaled by an appropriate emissions factor to give total estimated emissions of 385,615 tCO2e during the construction phase.
111. Table 17.12   Open ▸ summarises the calculated construction phase emissions based on conservative estimates and a MDS (section 17.8.1) associated with the Array, which totals 9,479,984 tCO2e. It is anticipated that the actual construction phase emissions would be lower than those detailed in Table 17.12   Open ▸ as this is a conservative maximum design scenario which will be further refined to reflect final detailed design for the Array.

Table 17.12:  Construction Phase GHG Emissions

                        Magnitude of impact

112. The impact is predicted to be of international spatial extent, short term duration, intermittent and low reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be 9,479,984 tCO2e for the construction phase.
113. As detailed within paragraph 105, the magnitude of emissions presented above does not account for the designed in measures adopted as part of the Array, which are not able to be quantified at this stage in the Array’s design. It is likely that the magnitude of such emissions will be reduced when accounting for the impact of these measures.

                        Sensitivity of the receptor

114. In accordance with paragraph 71, the receptor is deemed to be of high vulnerability, low recoverability and high value. The sensitivity of the receptor is therefore, considered to be high.

                        Significance of the effect

115. Overall, the magnitude of the impact is deemed to be 9,479,984 tCO2e and the sensitivity of the receptor is considered to be high. Consistent with paragraph 73, the magnitude of emissions comprise 0.3% of the Fifth and Sixth UK Carbon Budgets (set out in Table 17.1   Open ▸ ). Note that construction phase emissions have been calculated based on precautionary calculations of material quantities as set out in paragraph 43, which will be refined throughout the design stage. Further, as detailed within paragraph 105 and 113, the magnitude of such emissions do not account for designed in measures adopted to reduce emissions associated with the construction phase. As such, calculated emissions represent a conservative (reasonable adverse case) scenario.
116. Owing to the designed in measures adopted as part of the Array (comprising adherence to a NZTAP, alignment with the principles of PAS 2080, and incorporation of sustainable procurement practices), it can be concluded that the Array’s impacts are consistent with good practice design aligned with a 1.5°C compatible trajectory towards net zero. Based on the definitions as set out in Table 17.9   Open ▸ , the effect will be of minor adverse effect, which is not significant in EIA terms.
117. It is important to note that this assessment is based on a precautionary MDS and the magnitude of impact is likely to be lower after final design of the Array. In addition, the purpose of the Array is to provide a source of renewable energy, and as such, the effects due to GHG emissions from the manufacture and installation of the Array must be considered together with the effect of avoided GHG emissions arising from the operation of the Array (see paragraphs 119 to 131 below), so as to determine the net effects of GHG emissions resulting from the Array (see section 17.11.3 below), in line with IEMA (2022) guidance.

                        Secondary mitigation and residual effect

118. No climatic effects mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.

GHG emissions arising from the consumption of materials and activities required to facilitate the operation and maintenance of the Array and estimated abatement of UK Grid emissions

                        Operation and maintenance phase

119. The primary purpose of the operational phase of a wind farm is to generate electricity which avoids the need for fossil fuel generated electricity and reduces the UK Grid carbon intensity. The avoided emissions associated with the displacement of projected marginal generation of the UK Grid should be considered in combination with the impact of GHG emissions arising from the consumption of materials and activities required to facilitate the operations and maintenance of the Array.
120. The GHG emissions arising from the consumption of materials and activities required to facilitate the operation and maintenance of the Array are presented in Table 17.13   Open ▸ , and further details are presented in volume 3, appendix 17.1. The majority of emissions result from the vessel and helicopter movements required to undertake maintenance activities over the Array’s lifetime. Remaining emissions are associated with the replacement of cables, electrical equipment and scour protection, informed by conservative assumptions for material replacement rates. Emissions from the vessel and helicopter movements and cable, scour protection and electrical equipment replacement have been calculated following the methodology outlined in paragraphs 108 to 110 above, representing the greatest potential for GHG emissions from the operation and maintenance of the Array as a conservative estimate of impact. Further, the designed in measures adopted as part of the Array (detailed in Table 17.11   Open ▸ ) have not been able to be quantitatively assessed given the early stage in the Array’s design. As such, it can be expected that their implementation will result in a reduced magnitude of emissions than that presented within this assessment. Their impact on the significance of effect assessed has been considered qualitatively.

Table 17.13:  Operation and Maintenance Phase GHG Emissions

121. It should be noted that when considering the Array’s impact on climate change, the emissions as a result of operation and maintenance activities must be considered alongside the displacement of marginal alternative sources of electricity generation. This element is further considered in the assessment below.
122. Table 17.14   Open ▸ sets out the parameters for the Array and associated annual energy output.

Table 17.14:  Energy Flows for the Array

123. The input and output figures for the operation and maintenance phase of the Array have been scaled against the assumptions stated within the DESNZ long-run marginal (DESNZ, 2023a). This allows for a direct presentation of the cumulative GHG emissions avoided throughout the operation and maintenance lifetime of the Array and therefore, how the Array contributes towards reaching net zero targets.
124. The resulting estimated avoided emissions associated with the operation and maintenance phase of the Array would be 882,416 tCO2e avoided emissions associated with the abatement of the UK Grid.

                        Sensitivity analysis

125. It should be noted that as the UK and Scotland move towards the 2050 and 2045 net zero carbon targets respectively, the marginal source of electricity generation will likely become a combination of renewables (predominately solar and wind) and energy storage. By the time the Array is anticipated to be fully operational, the UK and Scotland are expected to have made significant progress towards a low-carbon electricity grid, with the current UK Government policy target year of 2035 (BEIS, 2021). It is important to note therefore that from circa 2035 onwards, long-run marginal projections assume that there is no unabated fossil fuel generation, in line with UK Government policy.
126. However, the UK Government has highlighted that some ‘transition’ fossil fuels will continue to play a part in the UK’s energy supply (DESNZ, 2023c). Further, the use of the long-run marginal projections may not present a true ‘without development’ future baseline and does not account for uncertainty in the UK grid carbon intensity as a result of annual fluctuation due to changes in the energy market (as detailed in paragraph 41). Therefore, it is likely that the true value of the avoided emissions displaced as a result of the Array’s contribution to the UK electricity grid would be higher than that of avoided emissions detailed above.
127. As such, a sensitivity analysis has been carried out using the current UK electricity grid carbon intensity and current estimated intensity from electricity supplied for ‘all non-renewable fuels’, as detailed in volume 3, appendix 17.1. This is shown in Table 17.15   Open ▸ .

Table 17.15:  Array Avoided Emissions Sensitivity Test

128. Although the use of the current UK electricity Grid average and DESNZ ‘non-renewable fuels’ carbon intensities would conclude greater avoided emissions and an ultimate reduction in carbon payback period, these are static baselines and do not account for future UK electricity grid decarbonisation. Further, as the Array’s generation output would be dictated by day-to-day demand alongside commercial factors and the National Grid’s needs, the benefit of provision of additional low carbon electricity capacity cannot be used to quantify avoided emissions. As such, the long-run marginal provides a conservative quantification of avoided emissions for the purpose of this assessment. The true avoided emissions value for the Array is likely to lie between the upper and lower limits shown in Table 17.15   Open ▸ (i.e. between 882,416 tCO2e and 143,082,086 tCO2e) and has been used to provide additional context to the assessment of significance.

                        Magnitude of impact

129. The impact is predicted to be of international spatial extent, long term duration, continuous and low reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is considered to be an emissions impact of between 605,756 tCO2e (long-run marginal) and -141,593,914 tCO2e (DESNZ ‘non-renewable fuels mix’)[5], when considering the emissions associated with operations and maintenance ( Table 17.13   Open ▸ ) alongside the avoided emissions of the Array ( Table 17.15   Open ▸ ). This range reflects displacement of alternative energy generation sources from a range of future baseline scenarios (note that negative values represent avoided emissions, i.e. emissions that would have occurred without the Array), in order to provide additional context to the assessment.

                        Sensitivity of receptor

130. In accordance with paragraph 71, the receptor is deemed to be of high vulnerability, low recoverability and high value. The sensitivity of the receptor is therefore, considered to be high.

                        Significance of the effect

131. Overall, the magnitude of the impact is deemed to be between 605,756 tCO2e and ‑141,593,914 tCO2e and the sensitivity of the receptor is considered to be high. As discussed in paragraph 126, it is likely that the use of the long-run marginal projections represents an underestimate of the true value of avoided emissions from the Array. Additionally, emissions associated with operations and maintenance have been calculated based on precautionary calculations of material quantities and do not account for the designed in measures adopted as part of the Array, which are not able to be quantified at this stage in the Array’s design, or for the continued decarbonisation of UK industry, as set out in paragraph 43. Both of which are anticipated to reduce emissions associated with the operation and maintenance phase. The magnitude of emissions is unable to be contextualised within the UK Carbon Budgets given the operation and maintenance phase falls outside of such budgets.
132. The Array will produce electricity at an emissions intensity of 4.4 gCO2e/kWh (see Table 17.14   Open ▸ ). This is lower than the current grid average (207 gCO2e/kWh), fossil fuel generation (424 gCO2e/kWh) and the Climate Change Committee’s electricity emissions intensity target for 2035 (10 gCO2e/kWh) (Climate Change Committee, 2020).
133. Within the context of national policy, the purpose of the Array is to provide a source of renewable energy, thereby contributing towards UK and Scottish climate change policy goals and associated renewable energy targets. Based on the definitions set out in Table 17.9   Open ▸ , the effect will be of beneficial effect, which is significant in EIA terms.

                        Secondary mitigation and residual effect

134. No climatic effects mitigation is considered necessary because the likely effect in the absence of mitigation is beneficial.

GHG emissions arising from decommissioning works of the Array

                        Decommissioning phase

135. The majority of emissions during decommissioning of the Array relate to the use of plant/equipment for Array decommissioning, disassembly, transportation to a waste site, and ultimate disposal and/or recycling of the equipment and other site materials.
136. At this stage, the approach to decommissioning the Array is still to be determined. However, it is anticipated that all floating structures, mooring lines, OSP topsides and foundations to the seabed level will be completely removed. Associated infrastructure, such as cables, scour protection and anchors and piles below the seabed may either be left in situ or removed, in accordance with the decommissioning plan. It may be decided, closer to the time of decommissioning, that removal will result in greater environmental impacts than leaving components in situ.
137. The components of the wind turbines are considered to be highly recyclable. When disposing of wind turbines, recycling is the preferred solution. This not only prevents the materials from being sent to landfills, but also reduces the need for the extraction of primary materials. Material which cannot be recycled might be used for incineration or energy from waste. It is considered the same approach can be applied to all mooring lines, OSP topsides and foundations and cables retrieved during decommissioning.
138. Cables and other infrastructure, such as anchoring systems, may be left in situ during decommissioning or removed. If removed, this infrastructure would be recycled or reused where possible, or used for incineration or energy from waste as per paragraph 137. If left in situ, this will not result in additional emissions during this phase. As such, emissions associated with the disposal of materials at the end of their lifetime is considered to be immaterial and may even result in future avoided emissions. This impact is not assessed further.
139. In the absence of detailed information regarding offshore transport movements during the decommissioning phase, it has been assumed that such emissions equal those associated with the construction phase, totalling 385,615 tCO2e. It is worth noting that this value is precautionary and likely to be reduced after final design of the Array. Given carbon emissions associated with use of plant and fuel is expected to have achieved good levels of decarbonisation at the decommissioning phase of the Array, this is likely to present a conservative maximum design scenario.

                        Magnitude of Impact

140. The impact is predicted to be of international spatial extent, short term duration, intermittent and low reversibility. It is predicted that the impact will affect the receptor directly. The magnitude of impact is determined to be 385,615 tCO2e.

                        Sensitivity of the receptor

141. In accordance with paragraph 71, the receptor is deemed to be of high vulnerability, low recoverability and high value. The sensitivity of the receptor is therefore, considered to be high.

                        Significance of the effect

142. Overall, the magnitude of the impact is deemed to be 385,615 tCO2e and the sensitivity of the receptor is considered to be high. The magnitude of emissions is unable to be contextualised within the UK Carbon Budgets, as required by paragraph 73, given the decommissioning phase falls outside of such budgets when the UK will have achieved net zero. It is expected that the decommissioning activities will have achieved good levels of decarbonisation in line with applicable policy requirements at that time. The effect will, therefore, be of minor adverse effect, which is not significant in EIA terms.

                        Secondary mitigation and residual effect

143. No climatic effects mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.

17.11.2. Climate Change Risk

Effects of Climate Change on the Array

                        Operation and maintenance phase

144. The CCRA (see volume 3, appendix 17.2), identifies the following risks:

• increases in average and extreme air temperatures, both in winter and summer;
• increases in sea surface temperatures and ocean acidification;
• changes to rainfall patterns, leading to increased annual precipitation;
• increased frequency and intensity of extreme weather i.e. storms;
• increased wind speeds and changes to wind patterns;
• increase in mean sea level;
• increased wave height; and
• changes in the tidal range.

145. These risks could lead to:

• efficiency losses and more frequent turbine shut-downs, reducing output of the Array;
• the failure of electrical equipment, increasing operation and maintenance activities;
• damage to infrastructure, increasing operation and maintenance activities; and
• reduced accessibility for maintenance and inspection.

146. The impact is predicted to be of local spatial extent, long term duration, continuous and low reversibility. It is predicted that the impact will affect the receptor directly. Volume 3, appendix 17.2 summarises the potential climatic changes in the coming decades and considers the potential consequences for the Array in a risk assessment format, including scoring for each risk.
147. The risk assessment presented in volume 3, appendix 17.2 considers in its scoring the level of influence the design of the construction and operations and maintenance of the Array can have upon the remaining risks, in addition to its severity and probability. Those risks over which the Applicant has little or no influence are therefore typically not considered significant effects of the Array, save where the severity and/or probability are highest.
148. The assessment of effects has considered the measures adopted as part of the array ( Table 17.11   Open ▸ ) in determining the combined risk score. As detailed in paragraph 80 a score of 5 or more is assessed as a significant effect which is presented in the ‘significant effect’ column. Should an effect be significant, secondary mitigation is presented where relevant to reduce the residual effect to negligible and not significant in EIA terms.
149. No risks to the Array due to climate change have been identified as significant before mitigation (see volume 3, appendix 17.2). As such, the effect on the Array has been determined to be negligible which is not significant in EIA terms.

17.11.3. Net Effects

Net GHG impacts of the Array

150. As detailed in section 17.9, consideration of the Array’s whole life impact is an important consideration when assessing the Array’s impacts and subsequent effects on climate change. As such, the consideration of the Array’s net emissions in the context of existing and emerging policy commitments and UK and Scottish carbon budgets is necessary.
151. Over its lifetime, the net impact of the Array would result in between 10,532,655 tCO2e and ‑131,667,016 tCO2e, based upon a precautionary range derived from the calculations in volume 3, appendix 17.1 (as detailed in paragraphs 41, 125 and 126). This net impact considers the GHG emissions associated with disturbance to blue carbon habitats, materials and vessel movements during the construction, operation and maintenance and decommissioning phases, alongside the avoided emissions from the operation of the Array. Negative emissions represent net avoided emissions. The Array would have a carbon payback period of 2 years (at the earliest) when accounting for construction, operation and maintenance and decommissioning phase emissions (see Table 17.16   Open ▸ below). As discussed in paragraph 128, the true avoided emissions value is likely to lie between these values. Given the operation of the Array would avoid the need for fossil fuel generators through the provision of renewable electricity, the associated avoided emissions would likely be greater than those presented in the conservative case (i.e. when using the long-run marginal projections) resulting in a reduction to the conservative net effect scenario presented above.

Table 17.16:  Summary of Array Net GHG Emissions

*Including emissions associated with blue carbon. The greatest magnitude of emissions released have been reported within this table, to provide a conservative estimate of net GHG emissions from the Array.

152. Consideration of the Array’s net emissions performance can be considered with the following contextualisation:

• it provides additional low carbon electricity generation capacity; and
• it is in keeping with Scottish and UK energy and climate policy.

153. The Array’s net emissions accounting for the construction phase up to the end of the UK Sixth Carbon Budget are detailed in Table 17.17   Open ▸ below. As the Array is anticipated to become fully operational by 2038, the avoided emissions resulting from the operation and maintenance phase of the Array and the final year of construction lie outside the scope of the currently quantified UK carbon budgets, which end in 2037 (HM Government, 2008). GHG emissions associated with the construction phase have been scaled annually, and applied to the relevant carbon budget periods. When accounting for the first seven years of the Array’s construction phase GHG emissions (8,346,669 tCO2e) to the end of the Sixth Carbon Budget (2037), this corresponds to approximately 0.31% of the UK Carbon Budget for the same period. Note that construction phase emissions have been calculated based on precautionary calculations of material quantities as set out in paragraph 43, which will be refined throughout the design stage, and do not account for the designed in measured adopted as part of the Array (detailed in Table 17.11   Open ▸ ). As such, calculated emissions represent a conservative (reasonable adverse case) scenario.

Table 17.17:  GHG Impacts in the Context of the UK’s Carbon Budgets

154. The Array’s net emission intensity, when accounting for construction, operation and maintenance and decommissioning emissions alongside total generation output, is 33.8 gCO2e/kWh. There are no established net emission intensity benchmarks available for the industry that the Array’s net emission intensity can be compared against.
155. The Array is in line with the Scottish NMP’s principle of supporting new offshore wind and marine renewable energy, in addition to their associated infrastructure, in order to contribute to reductions in GHG emissions. In addition, the up to 3.6 GW capacity from the Array, based on current understanding, would contribute towards the UK Government’s ambitions to increase low carbon electricity generation, with an anticipated doubling in electricity demand by 2050.
156. Further, the Array is supported by national energy and climate change policy (including the National Infrastructure Strategy, Net Zero Strategy, Energy and Just Transition Plan and Scotland’s Climate Change Plan) which highlight the need for an end to the use of unabated fossil fuel generation, whilst also significantly ramping up electricity generation capacity to meet the demands of increased electrification of transport, heat and industry. As such, UK and Scottish government policy dictates that large-scale deployment of renewable energy generators such as the Array are necessary in order to meet GHG reduction targets.
157. In addition, National Grid modelling anticipates an increase in annual electricity demand across the UK to between 570 TWh and 726 TWh per year by 2050, compared to 286 TWh per year in 2022 (National Grid ESO, 2023). By facilitating the expansion of renewable energy supply, the Array would assist the UK Government target of achieving a fully decarbonised power system by 2035, and the UK and Scottish Government’s aim to become net zero by 2050 and 2045 respectively.

                        Magnitude of impact

158. The impact is predicted to be of international spatial extent, long term duration, continuous and low reversibility. It is predicted that the impact will affect the receptor directly. Between 10,532,655 tCO2e and ‑131,667,016 tCO2e. This range reflects displacement of alternative energy generation sources from a range of future baseline scenarios, in order to provide additional context to the assessment.