About This Report

Report Overview

Since 2016, SK ecoplant has been transparently disclosing its sustainable management strategy and key achievements in the economic, environmental, social, and governance areas to stakeholders through the annual publication of its Sustainability Report. Moving forward, SK ecoplant will continue to share its sustainable management strategies, goals, and performance results through the Sustainability Report. This will be used as a basis for communication with various stakeholders.

Reporting Principles

This report has been prepared in accordance with the GRI Standards (2021), the global framework for sustainability reporting. Material issues identified through a double materiality assessment are structured in accordance with the “IFRS S1 General Requirements for Disclosure of Sustainability-related Financial Information” and “IFRS S2 Climate-related Disclosures Standard” frameworks published by the International Sustainability Standards Board (ISSB). Furthermore, this report incorporates the business standards of the SASB (Sustainability Accounting Standards Board), disclosure recommendations of the TCFD (Task Force on Climate-Related Financial Disclosures), ISO 26000, and UN SDGs (United Nations Sustainable Development Goals). Financial information is presented in accordance with K-IFRS (Korean International Financial Reporting Standards) on a consolidated basis.

Reporting Period

This report is based on sustainable management activities and performance from January 1, 2025, to December 31, 2025. Quantitative performance data covers the most recent three years to illustrate annual trends; considering the timeliness and materiality of the information, some data and performance results from the first half of 2026 are also included (these sections are clearly marked with their respective reporting periods).

Reporting Scope

The scope of qualitative and quantitative data covers the activities and performance of SK ecoplant’s domestic sites (83 locations, including Seoul, Yongin, Icheon, and Cheongju), while the scope of quantitative data for subsidiaries includes SK ecoplant as well as its subsidiaries (SK ecoengineering, SK airplus, ESSENCORE, SK tes, and SK oceanplant). SK materials performance, SK trichem, SK resonac, and SK materials jnc were newly incorporated in December 2025; they were excluded from the quantitative data aggregation in this report, as there were limitations in applying the definitions and calculation standards of existing reporting indicators, verifying consistency, and ensuring comparability. In the quantitative data tables within this report, the names of each subsidiary are denoted as SKEE, SKAP, ESSENCORE, SK tes, and SKOP. Where additional explanation regarding the scope of reporting is necessary, separate notes have been provided in the footnotes of each table.

Report Assurance

The financial information contained in this report has been audited by an independent accounting firm. To ensure the objectivity, fairness, and reliability of the reported content, assurance was conducted by With Accounting Corporation—an independent third-party organization with no affiliation to SK ecoplant—in accordance with international assurance standards and procedures (ISAE 3000, AA1000AS v3 Type 2). Assurance results are included in the Third-Party Verification Statement.

Report Publication Date and Contact Information

Greenhouse Gas Verification Statement

The Korea Management Registrar Inc. (hereinafter “KMR”) has conducted the verification on the greenhouse gas(here in after “GHG”) emission(Scope 1,2,3) in 2025 of SK ecoplant CO.,LTD.

PURPOSE & SCOPE

The purpose of this verification is to present an independent verification opinion on the greenhouse gas emissions inventory and the scope of the verification is as follows.

• Verification of places of business and emissions facilities under the control of SK ecoplant CO.,LTD.

STANDARDS

• ISO 14064-3:2019, ISO 14064-1:2018

• WRI/WBCSD GHG Protocol(2004)

• IPCC Guidelines for National Greenhouse Gas Inventories (2006)

• Guidelines for Environmental Product Declarations (EPD) and EPD Characterization Factors

• For indirect emissions (electricity) in the UAE, the country-specific emission factors for combined heat and power (CHP) from the IEA are applied

• Technical Guidance for Calculating Scope 3 Emission(Greenhouse Gas Protocol)

• Guidelines on Emission Reporting and Certification under the Greenhouse Gas Emissions Trading Scheme (Ministry of Environment, 2025-64)

PROCEDURE

The assurance was conducted by the KMR based on a risk analysis approach and data evaluation.The data and factors applied to the calculation of GHG emissions were determined to be appropriate based on objective evidence.

INDEPENDENT

KMR does not have any stake in the verified entity and does not conduct verification with biased opinions/views. We have drawn an independent and objective verification conclusion based on the verification standards, and reviewed the every aspect of the verification we performed throughout the entire verification process through internal review.

LIMITATION

The verification team verified the related reports, information and data presented by the audited institution by sampling or enumeration methods. As a result, there are many inherent limitations, and there may be disagreements in the interpretation of appropriateness. Although we have tried to faithfully perform verification that meets the verification standards, we suggest that errors, omissions, and false statements that could not be found may be latent as the limitations to the verification.

OPINION

• The assurance engagement was performed to satisfy a limited assurance level, and no significant distortions were found in the verification results.

• According to KMR's approach, nothing was found that would lead to a finding that SK ecoplant CO.,LTD. failed to disclose data and information that was accurate and reliable in all material respects.

• Criticality: meets the criterion, which is less than 5%

GHG Emissions & Energy Consumption

Scope 3 Emissions

RESULTS

Based on the above assurance criteria, we did not identify any inappropriate calculations or errors for the emissions of major emitting facilities.
As a result, we express “unmodified” opinion.

May, 18, 2026

KMR CEO

Korea Management Register T: 02)6309-9001 / F: 02)6309-9004

Third-Party Verification Statement

Independent Assurance Report on the 2025 Sustainability Report of SK ecoplant Co., Ltd.

To the Management of SK ecoplant Co., Ltd.

With Accounting Corp. (hereinafter referred to as the “Assurer”) was engaged to provide third-party assurance on the 2025 Sustainability Report of SK ecoplant Co., Ltd. (hereinafter the “Company”) for the fiscal year from January 1, 2025 to December 31, 2025. We conducted a limited assurance engagement in accordance with ISAE 3000 (Revised), issued by the International Auditing and Assurance Standards Board (IAASB), and performed a Type 2 assurance engagement with Moderate level assurance in accordance with AA1000AS v3.

Identified Sustainability Information

The Identified Sustainability information covered in the assurance engagement includes the following:

• Pages of the report related to the GRI Standards 2021 Index

• Pages of the report related to the SASB Index

• Pages of the report related to the Task Force on Climate-related Financial Disclosures (TCFD) online disclosures

The scope of our assurance engagement is limited to the fiscal year ending December 31, 2025. While some key performance indicators may reference data from periods prior to 2025 and the first half of 2026, no assurance was provided over any other content outside the defined subject matter.

Applicable Criteria

The criteria used by the Company to prepare the Identified Sustainability information include:

• GRI Standards 2021

• SASB Industry Standards

• IFRS (International Financial Reporting Standards) Sustainability Disclosure Standards

• TCFD (Task Force on Climate-related Financial Disclosures) Recommendations

Responsibilities of the Company

The Company is responsible for preparing the Identified Sustainability information in accordance with the applicable criteria, and for designing, implementing, and maintaining internal controls to ensure the information is free from material misstatement, whether due to fraud or error.

Inherent Limitations

The absence of a significant body of established practice on which to draw to evaluate and measure non-financial information allows for different, but acceptable, measures and measurement techniques and can affect comparability.

Our Independence and Quality Control

We complied with the ethical requirements of the International Ethics Standards Board for Accountants (IESBA), including principles of integrity, objectivity, professional competence and due care, confidentiality, and professional behavior. We applied ISQM 1 (International Standard on Quality Control 1) to maintain a system of quality control including policies and procedures to ensure compliance with ethical and professional standards and applicable legal and regulatory requirements.

Assurer’s Responsibility

Our responsibility is to express a limited assurance conclusion based on the procedures we performed. We conducted the engagement in accordance with ISAE 3000 (Revised), which requires us to plan and perform procedures to obtain limited assurance about whether the Identified Sustainability information is free from material misstatement.

A limited assurance engagement involves assessing the suitability in the circumstances of SK ecoplant use of the Criteria as the basis for the preparation of the Identified Sustainability Information, assessing the risks of material misstatement of the Identified Sustainability Information whether due to fraud or error, responding to the assessed risks as necessary in the circumstances, and evaluating the overall presentation of the Identified Sustainability Information. A limited assurance engagement is substantially less in scope than a reasonable assurance engagement in relation to both the risk assessment procedures, including an understanding of internal control, and the procedures performed in response to the assessed risks. The procedures we performed were based on our professional judgment and included questions, observations of processes performed, document reviews, analytical procedures, suitability assessments of quantification methods and reporting policies, comparisons between basic information, and lines.

Our procedures included:

• Interviews with personnel responsible for internal sustainability reporting and data aggregation.

• Understand the systems and processes in place for managing and reporting the Identified Sustainability Information of SK ecoplant. Review of documentation regarding policies, risk assessments, materiality analysis, and stakeholder engagement.

• Assessment the adequacy of the design and operation of processes and control activities for the measurement of GHG emissions and sustainability information management and reporting during the reporting period

• Conduct limited assurance on the subject data primarily through inquiries and analytical procedures

The nature, timing, and extent of the assurance procedures performed in a limited assurance engagement are designed to obtain a lower level of assurance than a reasonable assurance engagement. Accordingly, we do not express a reasonable assurance conclusion on whether the subject information has been prepared, in all material respects, in accordance with the applicable criteria.

AA1000AS v3 Assurance

In addition, to enhance the interoperability of third-party assurance, we conducted our assurance in accordance with a Moderate level of the international assurance standard AA1000AS v3. Our engagement was performed as a Type 2 assurance, which evaluates both the organization’s adherence to the AA1000AP (2018) principles—Inclusivity, Materiality, Responsiveness, and Impact—and the reliability and quality of selected sustainability information. Our conclusions on each principle are presented as follows:

Inclusivity: The Company has identified its primary stakeholders as shareholders and investors, employees, customers, business partners, and local communities, and operates tailored communication channels accordingly. The Company has demonstrated a strong understanding of its accountability regarding stakeholder engagement, incorporating diverse stakeholder needs into its sustainability activities. Since 2023, the company has published its sustainability report via a dedicated website, improving accessibility and transparency for stakeholders. We confirmed that, throughout this process, the company makes efforts to ensure that the views and expectations of stakeholders are reflected in the reporting organization's strategy.

Materiality: The Company conducted a Double Materiality assessment in accordance with the topic selection principles and evaluation methodology of the GRI Standards. The Company identified environmental, social, and financial impact levels based on media research analysis, benchmarking analysis of peer industries and key customers, analysis of major global sustainability-related initiatives, and the analytical judgments of expert groups. Based on the double materiality assessment and analysis, a total of three issues were identified as topics of high materiality from environmental, social, and financial impact perspectives: ① Climate Change Response, ② Occupational Safety and Health, and ③ Sustainable Supply Chain. We confirmed that the company discloses its management approach, strategies, targets, and performance through this report, and provides detailed information on each material topic throughout the report.

Responsiveness: The Company has established ① Climate Change Response, ② Occupational Safety and Health, and ③ Sustainable Supply Chain as its key sustainability material topics, and is strategically responding to these issues in a timely and appropriate manner while publicly disclosing such responses. In addition, we confirmed that the company is advancing its environmental management, sustainable products and services, quality management, customer satisfaction, talent acquisition and diversity, and human rights, social contribution. Furthermore, the company is strengthening sound governance operations, integrated risk management, and ethical management, and is responding to related impacts in a timely manner from the perspective of sustainability materiality and disclosing them accordingly.

Impact: The Company identifies and discloses how its activities, operations, and performance affect ecosystems, the economy, the environment, and society at large.

We found no material non-compliance with the AA1000AP (2018) principles.

Reliability and Quality of Specified Sustainability Performance Information

We additionally assessed the reliability and quality of the specified performance data, excluding forward-looking statements. The evaluation covered the Company’s GHG emissions, energy usage, waste generation, and water consumption. Interviews were held with personnel responsible for data processes and controls. We reviewed data flows, source documentation, and internal records. Based on our findings, we found no evidence of intentional error or material misstatement in the performance information disclosed.

Conclusion

Based on the procedures we have performed and the evidence we have obtained, nothing has come to our attention that causes us to believe that SK ecoplant’s Identified Sustainability Information the year ended 31 December 2025 and the first half of 2026 is not prepared, in all material respects, in accordance with the Criteria. And, we have not found any inadequacies in respect of the principles presented by AA1000AP (2018)

Restriction of Use

This assurance report is intended solely for the management of SK ecoplant Co., Ltd. to support their understanding of the Company’s sustainability performance. We accept no responsibility to third parties.

June 26, 2026

	711 Eonju-ro, Gangnam-gu, Seoul With Accounting Corp.
	Yeong-Seok Lee, CEO