Sensitivity of the receptor

159. 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

160. Overall, the magnitude of the impact is deemed to be between 10,532,655 tCO2e and ‑131,667,016 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 is likely to represent an underestimate of the true value of avoided emissions from the Array. 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. Further, 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. Additionally, such emissions calculations do not account for the designed in measures adopted as part of the Array (detailed in Table 17.11   Open ▸ ), which are expected to reduce emissions associated with the manufacture and installation of the Array. As such, calculated emissions represent a conservative (reasonable adverse case) scenario. Operation and maintenance and decommissioning emissions have also not taken into account the designed in measures adopted as part of the Array, or the future decarbonisation of UK industry, as set out in paragraph 43, both of which are expected to reduce such emissions.
161. Consistent with paragraph 73, the magnitude of emissions comprise 0.31% of the Fifth and Sixth UK Carbon Budgets (set out in Table 17.1   Open ▸ ). 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 (in particular the respective net zero targets). In accordance with 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

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

17.12. Cumulative Effects Assessment

17.12.1. Methodology

163. The CEA assesses the impact associated with the Array together with other relevant plans, projects and activities. Cumulative effects are defined as the combined effect of the Array in combination with the effects from a number of different projects, on the same receptor or resource. Further details on CEA methodology are provided in volume 1, chapter 6.
164. With respect to the CEA assessment for climatic effects, all developments that emit, avoid or sequester GHGs have the potential to impact the atmospheric mass of GHGs as a receptor, and so may have a cumulative impact on climate change. Consequently, in line with IEMA guidance (2022), cumulative effects due to other specific local development projects are not individually considered but are taken into account when considering the impact of the Array by defining the atmospheric mass of GHGs as a high sensitivity receptor. The construction, operation and maintenance and decommissioning phase effects of the assessment of the Array takes account of cumulative changes in GHG emissions from other energy generation sources. As such, no specific study area beyond that of the Array area is relevant for the Cumulative Effects Assessment (CEA) for climate change. However, it is important to note that the Array cannot realise the avoided emissions and associated significant beneficial effect detailed in section 17.11.3 without transmission infrastructure to enable connection of the Array to the Grid. This transmission infrastructure has associated emissions for its construction, operation and maintenance and decommissioning phases that must be considered within the cumulative assessment for climate change.
165. Therefore, the CEA takes into account the impact associated with the Array together with the Proposed offshore export cable corridor(s) and Proposed onshore transmission infrastructure required to enable connection of the Array to the Grid. The Array, alongside the Proposed offshore export cable corridor(s) search area, is shown in Figure 17.2   Open ▸ .
166. A tiered approach has been adopted which provides a framework for placing relative weight upon the potential for each project/plan to be included in the CEA to ultimately be realised, based upon the project/plan’s current stage of maturity and certainty in the projects’ parameters. The tiered approach employs the following tiers:

• tier 1 assessment – Array and Proposed offshore export cables corridor(s) and Proposed onshore transmission infrastructure and all plans/projects which became operational since baseline characterisation, those under construction, and those with consent and submitted but not yet determined;
• tier 2 assessment – All plans/projects assessed under Tier 1, plus those projects with a Scoping Report; and
• tier 3 assessment – All plans/projects assessed under Tier 2, which are reasonably foreseeable, plus those projects likely to come forward where an AfL has been granted.

167. It should be noted that in line with paragraphs 164 and 165, projects and plans other than the Proposed offshore export cable corridor(s) and Proposed onshore transmission infrastructure are not applicable to climate change consideration of CEA and as such are not considered further.
168. The specific projects scoped into the CEA for climatic effects are outlined in Table 17.18   Open ▸ .
169. The range of potential cumulative impacts that are identified and included in Table 17.19   Open ▸ , is a subset of those considered for the Array alone CEA assessment. This is because some of the potential impacts identified and assessed for the Array alone, are localised and temporary in nature. It is considered therefore, that these potential impacts have limited or no potential to interact with similar impacts associated with other plans or projects. These have therefore not been taken forward for detailed assessment.
170. In order to aid proportionate EIA, impacts have been combined – lifetime emissions resultant from the Array together with (enabled by) the Proposed offshore export cable corridor(s) and Proposed onshore transmission infrastructure. This assesses the cumulative GHG emissions associated with the Array and associated transmission infrastructure across all project phases.

Figure 17.2: Other Projects/Plans Screened into the Cumulative Effects Assessment for Climatic Effects

Table 17.18: List of Other Projects and Plans Considered within the CEA for Climatic Effects

17.12.2. Maximum Design Scenario

171. The maximum design scenarios identified in Table 17.19   Open ▸ have been selected as those having the potential to result in the greatest LSE1 on an identified receptor or receptor group. The cumulative effects presented and assessed in this section have been selected from the details provided in volume 1, chapter 3 of the Array EIA Report as well as the information available on other projects and plans (see volume 3, appendix 6.4), to inform a ‘maximum design scenario’. Effects of greater adverse significance are not predicted to arise should any other development scenario within the Project Description (volume 1, chapter 3), to that assessed here, be taken forward in the final design scheme.

Table 17.19: Maximum Design Scenario Considered for Each Impact as part of the Assessment of Likely Significant Cumulative Effects for Climatic Effects

17.12.3. Cumulative Effects Assessment

172. An assessment of the likely significance of the cumulative effects of the Array on and from climate change is given below.

Emissions resultant from the Array together with (enabled by) the Proposed offshore export cable corridor(s) and Proposed onshore transmission infrastructure, resulting in lifetime emissions for Ossian

                        Tier 1

173. This section presents an assessment of the GHG impacts during the construction, operation and maintenance and decommissioning phases from the Array, together with (enabled by) the Proposed offshore export cable corridor(s) and Proposed onshore transmission infrastructure.
174. However, detailed design parameters for the Proposed offshore export cable corridor(s) and Proposed onshore transmission infrastructure are not available at the time of writing. As such, the magnitude of impact presented below for the construction, operation and maintenance, and decommissioning phases represent a high level estimate of total emissions with a high degree of uncertainty. This is reflective in a precautionary and conservative MDS (see paragraphs 43 and 50). Such estimates have been informed by indicative maximum design scenarios based on the information currently available for the transmission infrastructure, as set out in Table 17.19   Open ▸ , alongside assumptions based on the available Array design information. Furthermore, the MDS used to assess the GHG impacts associated with the Array are also precautionary and likely to be reduced following final Array design. These assumptions are set out in volume 3, appendix 17.1.
175. As the future transmission projects and applications are brought forward in relation to the transmission infrastructure, the assessment presented below will be enhanced and refined in the future consent applications for those elements of infrastructure.
176. Table 17.20   Open ▸ sets out a summary of the cumulative GHG impacts, which are assessed in the sections below 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. As mentioned in paragraph 151, although a range of net GHG effects is provided for the Array and Ossian as a whole, the operation of Ossian would avoid the need for fossil fuel generators through the provision of renewable electricity. As such 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 below.

Table 17.20:  Summary of Cumulative GHG Impacts

* The range presented in this table reflects displacement of alternative energy generation sources from a range of future baseline scenarios.

                        Construction phase

177. The below considers the embodied carbon emissions associated with materials, associated transportation emissions and disturbance of blue carbon habitats for the cumulative assessment.
178. Construction GHG emissions from the Array are set out in Table 17.20   Open ▸ .
179. Major components of the Proposed offshore export cable corridor(s) and Proposed onshore transmission infrastructure are likely to be:

• offshore export cables and cable protection;
• scour protection;
• onshore export cables;
• onshore converter stations; and
• cables from the converter stations to National Grid substations.

180. Construction phase emissions from the cables, cable protection, offshore booster station(s)/OSP(s) and scour protection have been estimated using appropriate material emission intensities, as in paragraph 108 above, using MDS parameters as stated in Table 17.19   Open ▸ . Construction phase emissions from the converter stations have been estimated using the same methodology as in paragraph 109 above.
181. Emissions resulting from disturbance to blue carbon habitats have been calculated based on the total length of offshore export cable required for the Array. In the absence of detailed information regarding the extent of disturbance during construction of the Proposed offshore export cable corridor(s), it is assumed that the offshore export cable(s) will have the same area of disturbance per kilometre as the inter-array and interconnector cables of the Array. This area of disturbance was then scaled by the Array blue carbon emissions factor of 5.00 tC/ha (see paragraph 86).
182. In the absence of indicative vessel and traffic information, emissions from transportation have been estimated by applying an uplift to the total construction emissions, based on the relative contribution of construction transport emissions for the Array.
183. Table 17.20   Open ▸ presents the total construction phase emissions for the cumulative assessment. More details on the calculation methodology can be found in volume 3, appendix 17.1.

Magnitude of impact

184. 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. In order to assess the most adverse scenario, albeit likely to constitute a significant overestimate, the magnitude has been considered to be 10,764,230 tCO2e for the construction phase.

Sensitivity of receptor

185. 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 effect

186. Overall, the magnitude of the cumulative impact is deemed to be a precautionary 10,764,230 tCO2e and the sensitivity of the receptor is considered to be high. Consistent with paragraph 73, the magnitude of emissions comprise 0.35% of the Fifth and Sixth UK Carbon Budgets (set out in Table 17.1   Open ▸ ). It should be noted however that construction phase emissions have been calculated based on precautionary calculations of material quantities as set out in paragraphs 43 and 50, 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.
187. 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 cumulative effect will, therefore be of minor adverse effect, which is not significant in EIA terms.

Secondary mitigation and residual effect

188. 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

189. Operation and maintenance GHG emissions from the Array, are set out in Table 17.20   Open ▸ . The range reflects displacement of alternative energy generation sources from a range of future baseline scenarios, in order to provide additional context to the assessment.
190. Operation and maintenance GHG emissions from the Proposed offshore export cable corridor(s) and Proposed onshore transmission infrastructure will arise from the consumption of materials and activities required to facilitate operation and maintenance. These emissions are presented in Table 17.20   Open ▸ , and further details are included in volume 3, appendix 17.1. The majority of emissions result from the vessel, traffic and helicopter movements required to undertake maintenance activities. Remaining emissions are associated with the replacement of cables and electrical equipment. Emissions from the vessel and helicopter movements and cable and electrical equipment replacement have been calculated following the methodology outlined in paragraphs 108 to 110, 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.
191. As stated in paragraph 92, there is not anticipated to be any material change in the blue carbon stocks over the operational lifetime of the Array. This is also assumed for the Proposed offshore export cable corridor(s) in the absence of further detailed information. As such, it is not anticipated that there will be additional disturbance (and associated emissions) to blue carbon habitats for the Proposed offshore export cable corridor(s) during the operation and maintenance and decommissioning phases, as activities are not likely to disturb blue carbon habitats additional to those accounted for during the construction phase.

Magnitude of impact

192. 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 2,409,282 tCO2e and -139,790,388 tCO2e.

Sensitivity of receptor

193. 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 effect

194. Overall, the magnitude of the cumulative impact is deemed to be between 2,409,282 tCO2e and ‑139,790,388 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 (and hence Ossian). 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 continued decarbonisation of UK industry, as set out in paragraphs 43 and 50. 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.
195. The Array, in combination with the Proposed offshore export cable corridor(s) and Proposed onshore transmission infrastructure, will produce electricity at an emissions intensity of 9.8 gCO2e/kWh, based on the lifetime generation output presented in Table 17.14   Open ▸ and the cumulative operation and maintenance emissions set out in Table 17.20   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).
196. Within the context of national policy, the purpose of Ossian 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 cumulative effect will, therefore be of beneficial effect, which is significant in EIA terms.

Secondary mitigation and residual effect

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

                        Decommissioning phase

198. Decommissioning emissions from the Array are set out in Table 17.20   Open ▸ .
199. Although the approach to decommissioning of the Proposed offshore export corridor(s) and Proposed onshore transmission infrastructure is yet to be determined, the required infrastructure will either be left in situ or removed from site. The components of the Proposed offshore export corridor(s) and Proposed onshore transmission infrastructure are considered to be highly recyclable. As discussed in paragraph 138, 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. As such emissions associated with either leaving components in situ or removal and disposal are likely to be limited to the vessel and vehicle movements during decommissioning activities.
200. In alignment with the approach to decommissioning phase transport emissions for the Array (set out in paragraph 139), it has been assumed that cumulative transport emissions equal those associated with the construction phase. These emissions are presented in Table 17.20   Open ▸ .

Magnitude of impact

201. 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 435,142 tCO2e. As mentioned in paragraph 139, this value is precautionary and likely to be reduced after final design of the Array.

Sensitivity of receptor

202. 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 effect

203. Overall, the magnitude of the cumulative impact is deemed to be 435,142 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. Based on the definitions set out in Table 17.9   Open ▸ , the cumulative effect will, therefore be of minor adverse effect, which is not significant in EIA terms.

Secondary mitigation and residual effect

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

                        Net Whole Life GHG Emissions

Magnitude of impact

205. The below considers the lifetime cumulative net GHG emissions, including the net emissions from the Array and the Proposed offshore export cable corridor(s) and Proposed onshore transmission infrastructure. This has been summarised within Table 17.20   Open ▸ .
206. Although the whole lifecycle and combined emission totals likely overstate the predicted GHG impact due to conservative assumptions, as set out in paragraphs 43 and 50, avoided emissions during the operation and maintenance of the Array through the displacement of alternative electricity generation sources result in a beneficial contribution to the UK and Scotland meeting its emission reduction targets.
207. Ossian would likely have a carbon payback period of 3 years (at the earliest) when accounting for construction, operation and maintenance and decommissioning phase emissions from both the Array and associated transmission infrastructure.
208. The cumulative 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 is therefore considered to be between 13,608,654 tCO2e and -128,591,016 tCO2e.
209. In accordance with IEMA (2022) guidance, the magnitude of impact has also been contextualised against the UK carbon budgets. Note that these carbon budgets do not cover the whole lifetime of Ossian, as discussed in paragraph 153. Cumulative net emissions have been contextualised within the UK Fifth and Sixth Carbon Budgets ( Table 17.21   Open ▸ ).

Table 17.21: Cumulative GHG Impacts in the Context of the UK’s Fifth and Sixth Carbon Budgets

210. Ossian’s cumulative net emission intensity, when accounting for cumulative construction, operation and maintenance and decommissioning emissions alongside total generation output is 42.9 gCO2e/kWh. There are no established net emission intensity benchmarks available for the industry that Ossian’s net emission intensity can be compared against.

Sensitivity of receptor

211. 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 effect

212. Overall, the magnitude of the cumulative effect is deemed to be between 13,608,654 tCO2e and ‑128,591,016 tCO2e. 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. Further, the construction and operational phase emissions are likely to provide an overestimate of emissions due to the use of a conservative MDS. Such emissions will likely reduce as the design of the Array and transmission elements are refined, and designed in measures adopted as part of the Array are able to be accounted for quantitatively. Operation and maintenance and decommissioning emissions have also not taken into account future decarbonisation of UK industry, as set out in paragraph 43.
213. Consistent with paragraph 73, cumulative emissions up to 2037 represent 0.35% of the UK’s carbon budget over this period.
214. The sensitivity of the receptor is considered to be high.
215. In addition, 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 (in particular the respective net zero targets). Based on the definitions set out in Table 17.9   Open ▸ , the cumulative effect will, therefore, be beneficial, which is significant in EIA terms.

Secondary mitigation and residual effect

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