Understanding Carbon Credits

What Are Carbon Crediting Programs

Carbon credits are issued by carbon crediting programs. Carbon crediting programs1 range from international or governmental regulatory bodies – such as the United Nations Framework Convention on Climate Change (UNFCCC) Secretariat, which oversees an international carbon crediting program under Article 6.4 of the Paris Agreement – to independent non-governmental organizations (NGOs). Historically, governmental bodies certified carbon credits for regulatory purposes (“compliance programs”), while independent NGOs primarily served voluntary buyers (“independent programs”). More recently, both types of programs have begun to serve both types of markets (see Table below). Each carbon crediting program issues its own labeled “brand” of credit.

Crediting programs perform three basic functions:

  1. Developing and approving standards that set criteria for the quality of carbon credits
  2. Reviewing crediting projects against these standards (generally with the help of third-party auditors)
  3. Operating registry systems that issue, transfer, and retire carbon credits
“Compliance” Carbon Credit Programs (run by governmental bodies)Geographic CoverageLabel Used for Carbon Credits
Article 6.4 of the Paris Agreement*GlobalArticle 6.4 Emission Reduction Units (A6.4ERs)
California Compliance Offset ProgramUnited StatesAir Resources Board Offset Credit (ARBOC)
Korean Offsetting Program**GlobalKorean Offset Credit (KOC)
Regional Greenhouse Gas Initiative (RGGI)Northeast United StatesRGGI CO2 Offset Allowance (ROA)
Australian Emission Reduction Fund (ERF)AustraliaAustralian Carbon Credit Unit (ACCU)

* Article 6.4 will allow projects to transition from the Clean Development Mechanism (CDM) if they meet all required conditions as set by Parties to the Paris Agreement. Read more.

** The Korean Offset Program allows the use of Certified Emission Reductions (CERs) generated from CDM projects.

“Independent” Carbon Crediting Programs (run by NGOs)Geographic CoverageLabel Used for Carbon Credits
ACRMultiple countriesEmission Reduction Tonne (ERT)
Climate Action Reserve (CAR)Multiple countriesClimate Reserve Tonne (CRT)
The Gold StandardInternationalVerified Emission Reduction (VER)
Plan VivoInternationalPlan Vivo Certificate (PVC)
Verra – Verified Carbon StandardInternationalVerified Carbon Unit (VCU)

Crediting Programs & Markets

Carbon markets can be used for regulatory compliance or for actors to make voluntary avoided emission or enhanced removal claims. Compliance markets are created and regulated by mandatory national, regional, or international carbon reduction regimes. Voluntary markets function outside of compliance markets and enable companies and individuals to purchase carbon credits on a voluntary basis with no intended use for compliance purposes. Compliance carbon market credits may in some instances be purchased voluntarily by non-regulated entities, but unless explicitly accepted into the compliance regime, voluntary carbon market credits are not allowed to fulfill compliance market demand.

The concept of carbon offsetting arose in the late 1980s, as policymakers first began to seriously grapple with how to mitigate climate change. Although the first demonstrations of carbon crediting projects involved voluntary arrangements, the idea evolved into a tool for controlling costs within broader “market mechanisms” for addressing greenhouse gas (GHG) emissions, including emissions trading systems. The first and largest carbon crediting program was the Clean Development Mechanism (CDM), established under the Kyoto Protocol as a mechanism to allow developed countries to cost-effectively meet emission reduction obligations by investing in mitigation in developing countries. Because demand for compliance carbon credits is driven by regulatory obligations, their prices tend to be higher than carbon credits issued solely for the voluntary market.

Independent, non-governmental carbon crediting programs serving the voluntary market started to develop after 2005, as the CDM became more established and the corporate social responsibility community began to recognize that there was a demand for these instruments beyond regulated companies and signatory countries to the Kyoto Protocol. There are now a variety of independent carbon crediting programs primarily serving the voluntary market, which is largely composed of corporations wishing to make avoided emissions or enhanced removal claims.

In some cases, non-compliance carbon credit programs have influenced and interacted with compliance markets. In California, for example, the Climate Action Reserve (CAR) developed a series of crediting project methodologies that were subsequently adopted (with some modification) by the California Compliance Carbon Offset Program. Carbon credits issued under these methodologies by CAR prior to the start of California’s cap-and-trade program were able to transition and become eligible for compliance. Countries like Mexico and South Africa have also recognized carbon credits issued by non-compliance crediting programs as a means of complying with carbon tax obligations.

Carbon Market Actors

Professional carbon credit traders purchase and sell avoided emissions or enhanced removals by taking advantage of market price distortions and arbitrage possibilities.

Credit providers act as aggregators and retailers between project developers and buyers. They provide a convenient way for consumers and businesses to access carbon credits from a portfolio of projects.

Individuals and organizations purchase carbon credits to counterbalance GHG emissions. Therefore, the final buyer has no interest in reselling the credit but will prompt the retirement of the carbon credit.

Compliance Crediting Programs

The Kyoto Protocol to the UNFCCC established a cap-and-trade system between countries that included negotiated national caps on the GHG emissions of high-income countries that ratified the Protocol (called Annex B countries). Each participating country was assigned an emissions target and the corresponding number of allowances – called Assigned Amount Units (AAUs).

Countries agreed to meet their targets within a designated period of time by:

  • Lowering their own emissions; and/or
  • Trading emissions allowances with countries that had a surplus of allowances; and/or
  • Meeting their targets by purchasing carbon credits.

JI was the instrument for crediting projects taking place within countries with binding emission commitments under the Kyoto Protocol (most high-income countries), while the CDM was for crediting projects in countries without such commitments (most low or middle-income countries). In addition to economic efficiency, the CDM had the objective of promoting sustainable development and technology transfer in host countries.

Clean Development Mechanism (CDM)

Part of the UNFCCC, the CDM was the largest project-based crediting program and offered the public and private sector in high-income nations the opportunity to purchase carbon credits from crediting projects in low or middle-income nations (non-Annex 1). CDM was involved in setting standards and overseeing auditing of projects. Crediting projects were audited by accredited third parties named Designated Operational Entities (DOEs).

Type of Standard and Context

Standard Authority and Administrative Bodies

The CDM Executive Board (EB) oversaw the functioning of the CDM. The EB was ultimately accountable to the governing body of the Kyoto Protocol, which included representatives of all the countries that ratified the treaty. The EB was supported by expert panels that focused on specific tasks.

The Accreditation Panel oversaw the accreditation of designated operational entities or auditors. The Methodologies Panel (Meth Panel) reviewed the methodologies for the 100+ approved project types and the methodologies for setting and monitoring baselines. The Registration and Issuance Team (RIT) was responsible for reviewing requests for project registration and issuance.

Each member country had a Designated National Authority (DNA), confirming projects’ voluntary participation in the CDM and facilitating host countries’ confirmation that the activity assisted national sustainable development.

DOEs were UNFCCC-approved auditors who validated and verified CDM projects.

Regional Scope

The scope of the CDM was international, involving all countries that ratified the Kyoto Protocol.

Recognition of Other Standards/ Linkage with Other Trading Systems

Join Implementation (JI)

Type of Standard and Context

Joint Implementation (JI), like the CDM, was a project-based mechanism under the Kyoto Protocol. It is limited to transactions between countries that have commitments to limit or reduce their national inventory GHG emissions under the Kyoto Protocol. The goal of the program was to increase market efficiency by allowing industrialized countries to invest in GHG abatement projects in another industrialized or EIT country.

Standard Authority and Administrative Bodies

JI distinguished between Track 1 and Track 2 projects. Track 1 projects were approved by their respective host countries. Projects that follow the Track 1 auditing procedure established by their respective host country governments were located in countries that meet all the eligibility requirements for participating in the JI program and were thus authorized. Track 2 projects must be approved by the Joint Implementation Supervisory Committee (JISC). Track 2 projects are located in countries that either do not fully comply with the eligibility requirements for participating in the JI program or meet the eligibility requirements, but have voluntarily chosen to use the Track 2 verification procedure under the JISC. ERUs were issued and transferred by the host country under both the Track 1 and Track 2 auditing procedures.

The JI track 2 program was supervised by the Joint Implementation Supervisory Committee (JISC). The JISC was supported by an expert panel for the accreditation of independent auditors (JI Accreditation Panel) and was ultimately accountable to the governing body of the Kyoto Protocol, which included representatives of all countries that ratified the treaty.

Within each industrialized and EIT country, there was a Designated Focal Point (DFP) that served as the nodal agency responsible for administering JI activities within its jurisdiction.

Regional Scope

The JI scheme was international in its scope, but only industrialized and EIT countries that ratified the Kyoto Protocol could host JI projects and issue the carbon credits (ERUs) generated from the projects.

Recognition of Other Standards/ Linkage with Other Trading Systems

Independent Crediting Programs

Voluntary carbon markets enable businesses, governments, nonprofit organizations, universities, municipalities, and individuals to offset their emissions outside a regulatory regime. These entities can purchase credits that were created either through the voluntary or compliance markets. Trading and demand in the voluntary market are created only by voluntary buyers (corporations, institutions, and individuals) whereas, in a compliance market, demand is created by a regulatory mandate.

Because voluntary carbon credits cannot be used in compliance markets, they tend to be cheaper. Because voluntary credits are typically purchased in coordination with public relations efforts to present a company or organization as a climate actor, many factors can influence a buyer’s interest in a project to best present this image. Pricing in voluntary carbon credit markets reflects this reality, in which buyers have varied objectives in purchasing carbon credits. Voluntary market carbon credits differ in price based on project charisma and potential for marketing, project type, location, and co-benefits beyond climate impact that match with buyers’ preferences.

The voluntary carbon credit market includes a wide range of programs, entities, standards, and methodologies. Carbon credits generated for voluntary markets have been promoted as an opportunity for experimentation and innovation. They have the general advantage of lower transaction costs than carbon credits generated for use in compliance programs.

Voluntary markets also serve as a niche for micro-scale projects that are too small to warrant the administrative burden of compliance crediting programs or for projects currently not covered under compliance schemes. However, the lack of standardized quality criteria, in the early stages of the voluntary market, generated concern from the wider carbon credit market.

In response, carbon market actors launched several efforts to create standards and methodologies to improve the quality and credibility of carbon credits for voluntary use. These standards and independent programs differ significantly in their goals and the services provided.

At one end are complete crediting programs that have developed standards, including rules, requirements, and administrative systems for accounting, quantifying, monitoring, reporting, verifying, certifying, and registering crediting projects and tracking credits. The standards developed by these full-fledged programs tend to build on existing rules and procedures from compliance markets, most notably the CDM. These programs are designed to furnish carbon credit sellers with quality assurance certification and carbon credit consumers with greater transparency and confidence in the credibility and integrity of certified credits.

The proliferation of standards, methodologies, and other programs reflects the significant flux and experimentation in the voluntary carbon credit market.

Ambitious Climate Results (ACR)

Type of Standard and Context

ACR, which stands for Ambitious Climate Results, was founded in the USA in 1996, was the first independent GHG crediting registry in the world. ACR was founded by the environmental non-profit organization Environmental Resources Trust (ERT).

In 2007, ERT and its registry became part of Winrock International, a non-profit based in the USA. The registry was re-branded as American Carbon Registry (ACR) in 2008.

In 2012, ACR was accepted as an approved Offset Project Registry by the California Air Resources Board within the California cap-and-trade compliance carbon credit market. Then in 2023 the crediting program rebranded once again to ACR “Ambitious Climate Results” reflecting that its program reaches beyond the Americas.

Standard Authority and Administrative Bodies

Direct oversight of ACR is provided by the Winrock International Management and Executive Teams, as well as the Winrock International Board of Directors. Technical decisions are made by sector-specific Technical Committees (e.g., Agriculture, Forestry and Other Land Use – AFOLU) who review new methodologies and tools, advise the selection of scientific peer reviewers, and advise ACR on the need to update standards and commission new methodologies or tools.

Methodologies are developed internally by Winrock staff or can be developed by third parties and brought to ACR for approval. All approved methodologies have undergone public comment and blind scientific peer review.

Regional Scope

ACR registers crediting projects around the globe, although some sectors and methodologies within the ACR Program prescribe regional applicability limitations.

Recognition of Other Standards / Linkage with Other Trading Systems

Climate Action Reserve

Type of Standard and Context

CAR establishes standards for quantifying and verifying GHG emissions reduction projects, provides oversight to independent third-party verification bodies, and issues and tracks carbon credits, called Climate Reserve Tonnes (CRTs).

Standard Authority and Administrative Bodies

CAR is administered by employed staff with overall direction from a Board of Directors. The Board of Directors is comprised of representatives from the state government, business, environmental organizations, academia, and others.

CAR’s operations are funded by account holder fees, CRT issuance and transfer fees, grants, contract work, and sponsorships.

Regional Scope

The Reserve provides services to companies and project developers in North America.

Recognition of Other Standards/ Linkage with Other Trading Systems

Verra’s Verified Carbon Standard (VCS)

Type of Standard and Context

The Verified Carbon Standard is a full-fledged carbon offset program developed and run by the non-profit Verra. It focuses on GHG reduction attributes only and does not require projects to have additional environmental or social benefits. The VCS is broadly utilized by the carbon credit industry (project developers, large credit buyers, verifiers, and project consultants) as the largest independent program by credit volume (as of 2024) and is active globally.

Standard Authority and Administrative Bodies

The VCS is managed and overseen by the VCS Program Advisory Group and the Verra Board. The VCS Program Advisory Group provides strategic guidance to Verra staff on the evolution of the VCS Program, Rules, and insight to support the range of user groups.

The Verra Board has a number of responsibilities. It is responsible for approving any substantial changes to the VCS. It also makes a final determination regarding the approval of other GHG programs under the VCS and has the authority to suspend an approved program temporarily or indefinitely if changes are made to it that affect its compatibility with the VCS Program. The Verra Board has the authority to approve accreditation bodies that will accredit auditors. Finally, the Verra Board makes final decisions on any appeals brought forward to the VCS.

The Technical Advisory Groups (TAGs) support Verra by providing detailed technical recommendations on issues related to the program and its requirements (e.g., the AFOLU TAG for bio-sequestration projects).

Regional Scope

The VCS is an international independent crediting program.

Recognition of Other Standards / Linkage with Other Trading Systems

A process exists for approving GHG programs that meet VCS Program criteria. The program in question must demonstrate compliance with the VCS Program, hire an external qualified consultant team to complete a detailed gap analysis of the two programs to evaluate the proposed program, and then the Board decides to either fully adopt or adopt elements of the other crediting program based upon the consultant’s analysis report. The approval process is based on the principle of full compatibility with the VCS program, with acceptance required by the Verra Board.

If an entire crediting program is fully adopted by the VCS, all their auditors and methodologies are automatically accepted by the VCS, and credits certified by that standard can be fungible with VCUs. Verra periodically reviews approved programs to ensure continued compliance with the VCS Program.

Gold Standard

Type of Standard and Context

Standard Authority and Administrative Bodies

Regional Scope

The GS is an international independent carbon crediting program. The large majority of projects are in developing, low, and middle-income countries.

Recognition of Other Standards/ Linkage with Other Trading Systems

The GS can be applied to CDM projects and many other project types, but GS does not recognize any other independent crediting programs for generating GS-carbon credits.

Plan Vivo System

Type of Standard and Context

Plan Vivo is an independent crediting program for Agriculture, Forestry, and Other Land Use (AFOLU) with a focus on promoting sustainable development and improving rural livelihoods and ecosystem services.

Plan Vivo projects work closely with rural smallholders and communities and the standard emphasizes participatory design, ongoing stakeholder consultation, the use of native species, and biodiversity enhancement within a variety of payment for ecosystem service schemes – including avoided emissions and enhanced removals. The Plan Vivo Foundation certifies and issues forward crediting (‘ex-ante’) and post-sequestration (‘ex-post’) carbon credits called ‘Plan Vivo Certificates’. Ex-post credits can be issued before third-party verification through the submission of an annual report.

Standard Authority and Administrative Bodies

Recognition of Other Standards/ Linkage with Other Trading Systems

Plan Vivo allows projects that may fit within other standards although projects must inform the Plan Vivo Foundation to ensure double-counting or duplicate claims of the ecosystem services generated by the project does not occur.

Add-on Standards

Climate, Community & Biodiversity Standards

The Climate, Community & Biodiversity Standards (CCB Standards) is a project design standard that offers rules and guidance for project design and development. It is intended to be applied early on during a project’s design phase to ensure local community and biodiversity benefits. It does not quantify or verify carbon credits nor does it provide a registry. The CCB Standards focuses exclusively on land management projects, and requires demonstration of net-positive social and environmental benefits in addition to robust stakeholder participation.

The CCB Standards is a program of Verra, and was developed by the Climate, Community and Biodiversity Alliance (CCBA) with feedback and suggestions from independent experts. CCBA is a partnership of non-governmental organizations, corporations, and research institutes.

The first edition CCB Standards was released in May 2005, the Second Edition in December 2008, and the Third Edition in 2013. In addition to these milestones, the Rules for the Use of the CCB Standards were added to guide the evaluation of projects using CCB Version 2 in 2010 and became required for use with projects implemented after July 20, 2014.

Standard Authority and Administrative Bodies

Working groups are comprised of alliance members and external advisors, and are appointed when needed to address specific issues. Working group proposals for changes must be approved by the Steering Committee.

CCB validations and verifications must be performed by an environmental auditing company with one of the following qualifications:

Regional Scope

Projects using CCB Standards are worldwide.

Recognition of Other Standards/ Linkage with Other Trading Systems

SocialCarbon Standard

Standard Authority and Administrative Bodies

The Ecológica Institute is in charge of accrediting other organizations who wish to use the SocialCarbon Standard.

Regional Scope

The SocialCarbon Standard is internationally applicable.

Recognition of Other Standards/ Linkage with Other Trading Systems

Program Administration & Authority

All crediting programs include some form of administrative body to oversee the project approval process to ensure that the crediting projects developed meet established program requirements. Although there are common components of the project approval process, programs have developed varied approaches to key quality assurance concerns.

  • Validation requirements provide ex-ante assessment and confirmation of crediting project eligibility as defined by the rules of the program.
  • Verification requirements provide ex-post assessments and confirmation of quantification of the volume of avoided emissions or enhanced removals that have been produced from a crediting project across a certain period of time.
  • Registries are used to reduce concerns regarding double counting by tracking information regarding ownership of the crediting projects and the credits generated.
  • Third-party auditors are required by most programs to help limit any potential conflict of interest between crediting project developers and buyers, which both have financial incentives for inflating the volume of carbon credits generated.

The structure of program administrators varies by program type and design. Compliance programs are generally administered by either an existing regulatory agency or an administrative body established exclusively for the crediting program. Independent crediting programs are managed by a mix of Boards of Trustees, advisory committees, and paid program staff.

Nearly all crediting programs require some form of project validation and verification. Programs require verification to be conducted by an approved third-party auditor independent of the project developer. Some programs give their auditors the decision-making power to approve or reject a project. Others have a separate body to evaluate and approve projects based upon the verification report results. Such a program or standard-based decision-making body adds another layer of quality assurance, as well as administrative burden and cost.

Methodologies & Standards

Project Methodologies

Project methodologies cover GHG accounting rules and program requirements for monitoring, reporting, verification, and certification. In other words, they outline the rules and procedures to determine project eligibility, additionality, and baseline and project emissions for a particular project type. The terms “methodology” and “protocol” are often used interchangeably. Crediting Programs either have their own methodologies for a set of project types or approve the use of methodologies developed by another crediting program.

Crediting Programs

There are three core components of a carbon crediting program:

  1. Eligibility definitions and rules for the design and early implementation phase of a project. They can include additionality and baseline methodologies, definitions of accepted project types, and procedures for validating project activities.
  2. Monitoring, reporting, verification, and certification rules ensure that crediting projects perform as they were predicted to during project design. Certification rules are used to confirm the actual avoided GHG emissions or enhanced removals that can enter the market, as carbon credits, once the project is implemented.
  3. Registration and enforcement systems clarify ownership, enable trading of credits, track credit retirement, and ensure that credits are not double counted through sale to multiple buyers. These systems must include a registry with publicly available information to uniquely identify crediting projects and a system to transparently track ownership and ownership transfers of credits.

Registries

A carbon credit registry is a system for reporting and tracking crediting project information including project status, project documents, credits generated, ownership, sale, and retirement. Crediting Programs must utilize a registry.

Standards

Registries & Enforcement

Enforcement

Enforcement systems assure that contracts clearly identify ownership of carbon credit and define who bears the risk in case of project failure. Carbon credit registries track crediting projects and issue carbon credits for each unit of avoided emission or enhanced removal that is verified and certified. Registries are vital in creating a credible, fungible carbon credit commodity. Registries record the ownership of credits. A serial number is assigned to each verified carbon credit. When a credit is sold, the serial number for the credit is transferred from the account of the seller to an account for the buyer. If the buyer “uses” the credit by claiming the avoided emissions or enhanced removals against their own emissions, the registry retires the serial number so that the credit cannot be resold. In this manner, registries reduce the risk of double counting. Registration and enforcement systems must include:

  • A registry with publicly available information to uniquely identify crediting projects.
  • Serial numbers for each carbon credit generated by each project.
  • A system to transparently track ownership of carbon credits which makes it possible to trace each credit back to the project from which it originated.
  • A system to easily check on the status of a carbon credit (i.e., whether a credit has been retired).
  • Contractual or legal standards that clearly identify the original “owner” of carbon credits.
  • Contractual or legal standards that spell out who bears the risk in case of project failure or partial project failure (e.g., who is responsible for replacing the credits that should have been produced by the failed project).

Voluntary Market Registries

There are several registries in the voluntary carbon credit market, which have been developed by governments, independent non-profits, and the private sector. The following voluntary registries are currently operating:

  1. The terms “standard” or “registry” are sometimes used when referring to crediting programs. However, a comprehensive carbon crediting program will consist of more than just a standard and a registry. ↩︎