The ISEP Greenhouse Gas Management Hierarchy (GHG Hierarchy) is a structured framework designed to guide organisations in systematically reducing their greenhouse gas emissions.
Recognised as the global best-practice approach for tackling the emissions that cause climate change by the UNFCCC and ISO, the GHG Hierarchy has always been an open-source resource.
First created in 2009 by the Institute of Sustainability and Environmental Professionals (ISEP) – when known as IEMA – it has since been through several updates to align with evolving mitigation and net-zero targets.
Since 2015 it has been recognised and referenced by the UNFCCC as the globally applicable model for organisations planning their pathways and transitions to net-zero.
From 2020 it has been referenced by International Organization for Standardization (ISO) in their Guidelines for addressing climate change in standards.
Over the years, many businesses have used this resource to support transition planning, while organisations, researchers and students all around the world have referenced the GHG Hierarchy in their reports. The resource remains freely downloadable for public use and re-publication (subject to attribution).
The purpose of the GHG Hierarchy has remained consistent:
• Prioritising meaningful action: The hierarchy emphasises tackling emissions at their source rather than relying solely on offsets.
• Supporting net-zero transitions: It provides a roadmap for organisations aiming to achieve net-zero emissions, in line with global climate agreements like the UNFCCC Paris Agreement.
• Standardising best practices: By offering a clear structure, it helps unify approaches across industries and sectors.
Organisations use the hierarchy to plan and implement sustainability strategies. It consists of four levels:
| LEVEL | ACTION | GOAL | ||
| 1. | ELIMINATE | Prevent GHG emissions entirely by changing business models or operations. | Avoid emissions-generating activities from the outset. | |
| 2. | REDUCE | Improve efficiency in processes, energy use, and operations. | Achieve real reductions in emissions. | |
| 3. | SUBSTITUTE | Switch to renewable or low-carbon technologies. | Lower the carbon intensity of energy sources. | |
| 4. | REMOVE | Balance residual emissions through removals or carbon credits. | Prioritise removal emissions via projects within organisational control and with a low risk of reversal. |
• Encourages proactive planning rather than reactive offsetting.
• Helps businesses align with science-based targets, transition planning, and climate-related financial disclosures.
• Easy to understand - promotes engagement across the workforce, making sustainability a shared responsibility.
The terminology of ‘emissions hierarchies’ has been picked up by international standards, with complementary meanings and usage.
For instance, BS ISO 14068-1:2023 Climate change management – 'Transition to net zero Part 1: Carbon neutrality' describes the hierarchy approach to carbon neutrality as being ‘primarily achieved through GHG emission reductions, then GHG removal enhancements within the boundary of the subject, before offsetting’. This builds on the ISEP Greenhouse Gas Management Hierarchy, in which the stages eliminate, reduce, substitute guide organisations in systematically reducing the greenhouse gas emissions within their boundaries, before the stage 'remove' which is addressed in the standard.
The ISEP GHG Management Hierarchy has been designed by ISEP to support sustainability professionals to guide their organisations’ strategic decision making process by setting out a series of best practice steps.
However, while the hierarchy provides a framing and scoping approach, supporting efforts to seek out significant carbon savings within the organisation, it is recognised that context will vary and in all cases, transition actions themselves should not be restricted by a fixed sequential approach. Actions that can be taken in the three stages of eliminate, reduce and substitute should not be held up or delayed because previous steps cannot be taken immediately.
Avoided emissions, and mass-balancing of emissions outside the value chain, are not part of the GHG Hierarchy and should only be used for calculations when all previous options have been exhausted.
First version of the GHG Hierarchy developed.
GHG Hierarchy updated.
ISEP (formerly IEMA) worked with the UNFCCC, which used the Hierarchy in its Climate Neutral Now initiative as the model for reducing greenhouse gas emissions: Recommendations for Reducing Greenhouse Gas Emissions.
GHG Hierarchy updated.
ISEP (formerly IEMA) worked with the International Organization for Standardization and a copy of the GHG Hierarchy is included in ISO Guide 84 2020e Guidelines for addressing climate change in standards.
GHG Hierarchy updated.
UNFCCC-aligned Pledge to Net Zero utilises the model for reducing greenhouse gas emissions.
KAEFER UK & Ireland, a leading provider of technical services across the energy,
industrial, nuclear, and construction sectors. Kaefer adopted the ISEP GHG Hierarchy to manage the reduction of greenhouse gas in a structured way, prioritising actions to
Eliminate → Reduce → Substitute → Remove.
Download the full case study here: ISEP GHG Management Hierarchy | Kaefer Case Study
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