Article 6.4

The Article 6.4 mechanism, often referred to as the Sustainable Development Mechanism (SDM), is a pivotal part of the Paris Agreement's rulebook for international climate cooperation. It creates a centralized global market, governed by a UN Supervisory Body, to succeed the Kyoto Protocol's Clean Development Mechanism (CDM). The mechanism is designed for both public and private entities to develop projects that reduce or remove greenhouse gas emissions, generating credible carbon credits (known as A6.4ERs) that can be traded internationally and used for a variety of climate goals.

The core purpose of Article 6.4 is to enhance climate ambition by making it more cost-effective for countries to meet their Nationally Determined Contributions (NDCs). By creating a robust and transparent market, it encourages investment in sustainable activities, particularly in developing nations.

The mechanism operates through a rigorous lifecycle designed to ensure environmental integrity and prevent the issues that affected older systems:

• Project Development and Approval: A project developer (e.g., a company or a public body) designs a project—like a large-scale solar farm or a carbon capture facility—and submits it for approval under specific, UN-agreed methodologies.
• Validation and Verification: An independent third-party auditor validates the project's design, and later verifies that the claimed emission reductions have actually occurred. The UN Supervisory Body oversees this entire process.
• Credit Issuance: Once verified, the project is issued tradable carbon credits, called Article 6.4 Emission Reductions (A6.4ERs). A portion of these credits is automatically cancelled to ensure an "overall mitigation in global emissions" (OMGE), meaning the mechanism contributes a net reduction to the atmosphere.
• Avoiding Double Counting: When a credit is sold to another country for use towards its NDC, the host country must make a "corresponding adjustment" to its own emissions inventory. This prevents both countries from claiming the same emission reduction.

Concrete Use Cases

• Use Case 1: Renewable Energy in a Developing Nation. A European energy company finances the construction of a major geothermal power plant in Kenya, replacing planned fossil fuel capacity. The project is registered under the Article 6.4 mechanism. The resulting A6.4ERs are purchased by the government of Japan to help meet its NDC target, providing a crucial revenue stream that made the project financially viable.
• Use Case 2: Industrial Decarbonization. A cement manufacturer in India invests in innovative Carbon Capture, Utilization, and Storage (CCUS) technology. The captured CO₂ generates A6.4ERs. These credits are then bought by a multinational corporation for its voluntary "net-zero" commitment, allowing it to compensate for emissions it cannot yet eliminate from its value chain.

The Article 6.4 mechanism is a key pillar of the international carbon market architecture, distinct from compliance markets like the EU ETS. While it primarily serves country-level goals, it also provides a new source of high-quality credits for the corporate voluntary market.

For more information on the different market types, read our guide on compliance vs. voluntary carbon markets. For official documentation, refer to the official UNFCCC page on Article 6.