Scope 2 マーケット基準 vs 立地基準 実践ガイド

Scope 2 refers to indirect emissions associated with the "purchase of electricity, heat, steam, or cooling from third parties." The GHG Protocol Scope 2 Guidance (2015) requires dual reporting, where emissions from purchased electricity are calculated using both location-based and market-based methods. Japan's Ministry of the Environment's Green Value Chain Platform also describes the location-based method as using grid average emission factors and the market-based method as using emission factors corresponding to the actual electricity menus contracted.

The location-based method uses the average emission factor of the country, region, or power grid to which factories and offices are connected. It is independent of procurement contracts, making it easier to compare the reality of regional grids. The market-based method is based on the contractual attributes held by a company, such as electricity menus, renewable energy certificates, and PPAs. While it allows for the reflection of renewable energy procurement effects in Scope 2, errors regarding certificate quality, retirement, target periods, or geographical boundaries can lead to exaggerated reduction claims.

Renewable energy certificate systems vary by region. Common examples include European Guarantees of Origin (GOs), North American RECs, international I-REC(E)s, and Japan's non-fossil certificates or J-Credits. The I-TRACK Foundation describes attribute tracking standards, including I-REC, as auditable mechanisms to avoid double counting and double claiming. Under the RE100 Technical Criteria 2023, claims for renewable electricity require exclusive ownership of generation attributes, separation of attribute information, retirement records, geographical market boundaries, and vintage matching. Simply buying a certificate labeled "renewable energy" will not withstand scrutiny from RE100 or CDP.

To include PPAs (Power Purchase Agreements) in the market-based method, it must be verified that both the electricity volume and environmental attributes belong to the same consumer, and that the corresponding certificates have not been sold to third parties. For on-site PPAs, distinguish between self-consumption and surplus power sales. For off-site PPAs, maintain a registry of generation and consumption within the same market, certificate retirement, contract periods, and the additionality of power plants. In months where generated electricity is less than demand, residual electricity must be accounted for using the residual mix or an appropriate electricity menu emission factor.

The reason for significant numerical differences is the disparity in referenced emission factors. In grids with a high coal ratio, the location-based method will result in higher figures, while companies with renewable PPAs or non-fossil certificates will have lower figures under the market-based method. Conversely, even if located in a low-carbon grid, the market-based figure may exceed the location-based figure if the contracted electricity menu factor is high. Therefore, when using Scope 2 reduction as a management goal, explicitly state in board materials which method is used for the KPI.

A practical challenge is obtaining market-based factors. Using grid average emission factors directly for the market-based method may deviate from the strict definition of the GHG Protocol. More accurately, it is necessary to obtain electricity menu-specific factors from retail electricity providers or use the actual emission attributes of the certificates or PPAs held. When responding to CDP or investors, it is required to be able to explain Scope 2 emission factor rationale, certificate IDs, retirement dates, and subject electricity volumes annually.

The practical checklist consists of six points: 1) Fixing electricity volume by site monthly, 2) Selecting location-based country/regional factors, 3) Obtaining contract menu factors from retailers, 4) Saving retirement records for GOs, I-RECs, RECs, non-fossil certificates, and J-Credits, 5) Verifying environmental attribute ownership clauses in PPAs, and 6) Using the same calculation sheet for CDP/RE100 guidelines. Scope 2 is more difficult to manage via evidence than calculation. Anticipating audits, the shortest path is to manage the certificate registry and electricity volume registry with the same granularity.