Green bonds are debt instruments whose proceeds are earmarked for environmental projects — renewable energy, clean transport, green buildings. They are the largest corner of the sustainable bond market, governed by the ICMA Green Bond Principles and, in Europe, the EU Green Bond Standard. This guide covers how they work, what the standards require, and how they differ from their cousins.
What green bonds are
A green bond is a standard bond with one defining feature: the issuer commits to using the proceeds exclusively for eligible green projects. The credit profile is the same as the issuer’s conventional bonds — investors are not taking project risk. What differs is transparency: allocation reporting, project selection criteria, and external review.
Eligible project categories under market standards include renewable energy, energy efficiency, pollution prevention, sustainable water management, clean transportation, green buildings, and biodiversity conservation. Refinancing existing green assets is allowed, with look-back periods typically disclosed.
The ICMA Green Bond Principles
The Green Bond Principles (GBP), administered by ICMA, are the voluntary market standard most issuers follow. They rest on four pillars:
- Use of proceeds — clear designation of eligible green project categories, with environmental objectives described.
- Process for project evaluation and selection — how the issuer decides what counts as green, and who decides.
- Management of proceeds — proceeds tracked in a sub-account or portfolio, with unallocated balances disclosed.
- Reporting — annual allocation reporting (where the money went) and impact reporting (what it achieved) until full allocation.
ICMA also publishes guidelines for external review: second-party opinions (pre-issuance), verification, certification, and scoring. A second-party opinion from a recognized provider remains the market norm for benchmark-sized deals.
The EU Green Bond Standard (EuGB)
The European Green Bond Standard (Regulation 2023/2631), applying since December 2024, is the regulatory gold standard — voluntary to use, but binding once chosen. Key requirements:
- Proceeds must fund activities aligned with the EU Taxonomy’s technical screening criteria (with limited flexibility).
- Issuers need an EU Green Bond factsheet, annual allocation reports, and impact reports.
- External reviewers must be ESMA-registered — a regulated reviewer market, unlike the voluntary second-party opinion market.
- Grandfathering provisions protect taxonomy-alignment if criteria change within a set window.
The EuGB sits above the ICMA GBP in stringency. Issuers targeting EU institutional demand increasingly weigh the two labels side by side.
Sustainability-linked bonds: the cousin
Sustainability-linked bonds (SLBs) differ fundamentally: proceeds are for general corporate purposes, but the bond’s financial terms change based on whether the issuer hits predefined sustainability performance targets (SPTs) tied to key performance indicators (KPIs). Miss the target, pay a higher coupon (the “step-up”).
SLBs suit issuers without large green asset pipelines — but they demand credible, ambitious, externally verifiable targets. Weak SPTs (targets the issuer would hit anyway) are the SLB market’s chronic greenwashing risk, and investors have grown markedly more skeptical of unambitious structures.
Greenium: does green pricing exist?
The “greenium” — a pricing advantage for green-labeled bonds versus conventional equivalents — exists but is inconsistent. It tends to appear in oversubscribed benchmark deals and in currencies with deep ESG-mandated investor bases (notably EUR), and to vanish in volatile markets. Treat any greenium as a sometimes-bonus, never as the investment thesis.
Assurance and second-party opinions
Market practice layers multiple checks:
- Pre-issuance — second-party opinion on framework alignment with GBP (voluntary market) or ESMA-registered review (EuGB).
- Post-issuance — annual allocation assurance; impact reporting assurance is less universal but growing.
- Certification — the Climate Bonds Standard offers pre- and post-issuance certification against sector criteria, a step beyond opinion-based review.
Greenwashing risks
- Weak eligibility criteria — frameworks that stretch “green” to cover business-as-usual capex.
- Allocation opacity — proceeds commingled without credible tracking.
- Impact inflation — claimed emissions savings without baselines or methodology.
- SLB target softness — SPTs set below business-as-usual trajectories.
Regulators are watching: the EU’s greenwashing directives, the FCA’s UK regime, and the SEC’s climate disclosure framework all raise the cost of loose labeling.
What issuers should do in 2026
- Decide the label deliberately: ICMA-aligned, EuGB, or both — and say why.
- Build the allocation tracking before the deal, not after.
- Get the external review early — reviewer timelines are the most common cause of delayed launches.
- Write the impact methodology into the framework; investors discount impact claims without it.