What are green bonds and how do they work?
Green bonds are fixed-income instruments where the proceeds are specifically earmarked to finance or refinance eligible environmental projects. They are one of the most established instruments in sustainable finance — and one of the fastest-growing. Here is how they work and what to know before eval
Financial information only
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Green bonds are fixed-income instruments where the proceeds are specifically earmarked to finance or refinance eligible environmental projects. They are one of the most established instruments in sustainable finance — and one of the fastest-growing. Here is how they work and what to know before evaluating them.
What makes a bond "green"?
A conventional bond raises debt capital for general corporate purposes. A green bond raises debt capital specifically to fund projects with environmental benefits — renewable energy installations, energy-efficient buildings, clean transportation, water management, sustainable agriculture, or similar categories.
The "green" label does not change the financial structure of the bond. The coupon, maturity, credit rating, and payment obligations are identical to a conventional bond from the same issuer. What changes is the use of proceeds: the issuer commits to allocating the funds raised to specific eligible projects, and to reporting on how that money has been used.
How are green bonds verified?
The Green Bond Principles (GBP), published by the International Capital Market Association (ICMA), are the most widely used voluntary framework for green bond issuance. They cover four components: use of proceeds, process for project evaluation and selection, management of proceeds, and reporting.
Most green bond issuers also obtain an external review — typically a second-party opinion (SPO) from a specialist firm such as Sustainalytics, ISS ESG, or Vigeo Eiris — confirming that the bond's framework aligns with the Green Bond Principles.
The EU Green Bond Standard (EU GBS), finalised in 2023, goes further: it requires that all proceeds be allocated to taxonomy-aligned activities (projects that meet the EU Taxonomy's technical screening criteria), and that issuers obtain verification from an accredited external verifier. EU GBS bonds are expected to carry higher credibility than standard GBP-aligned bonds.
Who issues green bonds?
| Issuer type | Examples | Typical use of proceeds |
|---|---|---|
| Supranational | European Investment Bank, World Bank, KfW | Climate projects in developing countries, renewables, efficiency |
| Sovereigns | UK, Germany, France, Netherlands | Green infrastructure, sustainable transport, nature |
| Financial institutions | Lloyds, NatWest, Barclays, BNP Paribas | Green mortgages, renewable energy lending, ESG loans |
| Corporates | Orsted, Enel, Iberdrola, Tesla | Renewable energy projects, fleet electrification, efficiency |
| Municipalities | City of London, Stockholm, New York | Public transport, sustainable buildings, urban green space |
Do green bonds offer a yield premium or discount?
Green bonds often trade at a small yield discount (known as the "greenium") relative to conventional bonds from the same issuer — meaning investors accept slightly lower returns in exchange for the green label. The greenium has been consistently observed in EU sovereign green bonds, where it has ranged from 2 to 8 basis points.
For investors, this means green bonds are often marginally more expensive to buy (lower yield for the same credit risk) than conventional bonds. The trade-off is access to an instrument with clear environmental impact reporting and, for institutional investors, alignment with sustainability mandates.
Greenwashing risk in green bonds
Not all green bonds are created equal. "Greenwashing" in bond markets includes: use of proceeds allocated to projects with marginal environmental benefit, frameworks without credible external verification, or issuers with overall business models incompatible with their green bond claims.
The highest-risk category is bonds from issuers in carbon-intensive industries who use green bond proceeds to fund isolated green projects while their core business continues expanding. A fossil fuel company issuing a green bond to fund one solar installation while continuing to develop new oil fields is a contested use of the label.
Green bonds and net zero portfolios
For investors building a sustainable fixed-income portfolio, green bonds provide a way to direct capital toward specific environmental outcomes with documented impact reporting. EU GBS bonds, once the market develops further, will provide the highest-certainty alignment with the EU Taxonomy.
Understanding the carbon market context — including where renewable energy projects and carbon offset projects sit in the credit market — helps evaluate the quality of use-of-proceeds claims in green bonds. The Carbon Workbench provides reference data on voluntary carbon market pricing and project verification standards that is relevant background when reviewing green bond frameworks.
Key takeaway
Green bonds are conventional bonds with a specific environmental use-of-proceeds commitment. The Green Bond Principles and EU Green Bond Standard are the main quality frameworks. A small yield premium (the "greenium") means slightly lower returns versus comparable conventional bonds. Quality varies significantly — check external verification, project eligibility, and the issuer's overall sustainability credentials. This article is informational only and not financial advice.