The UN’s Approach to Achieving its Environmental Sustainability Commitments

The UN’s approach to achieving our environmental sustainability commitments is broadly divided into four main areas:

  1. Measuring and Reporting Greenhouse Gas Emissions
  2. Measuring and Reporting Waste
  3. Reducing our Impacts
  4. Offsetting

Measuring and Reporting Greenhouse Gas Emissions

The UN greenhouse gas inventory follows the principles of the Greenhouse Gas Protocol developed by the World Resources Institute and the World Business Council for Sustainable Development and is compatible with ISO 14064. The Greenhouse Gas Protocol has been modified to suit the specific needs of participating UN entities

What does the UN Greenhouse Gas inventory cover?

The October 2007 decision of the Chief Executives Board (CEB) limits the boundary of the UN greenhouse gas inventory to emissions from facility operations and travel that can be influenced by management-level decisions. These include emission categories associated with the purchase or generation of electricity and heat (such as steam), use of refrigerants (for air-conditioning and refrigeration) and air, sea and ground transportation.

The inventory includes the six greenhouse gases (GHG) originally covered by the Kyoto Protocol: CO2, CH4, N2O, HFCs, PFCs and SF6. Additionally, the UN also logs the emissions of other GHGs not covered by the Kyoto Protocol, namely hydrochlorofluorocarbons (HCFCs) that are governed by the Montreal Protocol and are reported under the ‘Optional Emissions’ category. GHG emissions are reported separately for each greenhouse gas both in terms of their mass, and as an aggregate using the common comparable unit of carbon dioxide equivalents (CO2eq), using the global warming potential (GWP) of each substance.

The common minimum boundary excludes several sources of greenhouse gas emissions that could result from UN activities. Recommended best practice is to voluntarily document all sources of emissions not included in the minimum boundary under an additional category called Optional Emissions. These include:

  • Emissions associated with decisions for which individual staff members are responsible and that relate to their personal sphere (e.g. emissions from personnel commuting to and from the workplace),
  • Emissions from projects implemented by external entities,
  • Emissions due to couriers and postal mail,
  • Embodied carbon in products and equipment used by the UN, for instance food, beverages, paper and computers,
  • Emissions from the decomposition of organic waste and from wastewater treatment arising from UN premises.
  • Emissions of climate relevant gases not within the common minimum boundary, i.e. HCFCs

How are emissions calculated? 

Estimation and reporting of the emissions is done through the following tools:

  1. Formatted files for data collection, available in English, French and Spanish;
  2. A stand-alone air travel emissions calculator;
  3. An online emissions calculator for the remaining sources and
  4. A web-portal, where the data files can be uploaded to generate emission results.

The substantive inputs for developing the system were provided by the Sustainable United Nations (SUN) team, and software development was led by DFS. The air travel emissions calculator is a proprietary product of ICAO. 

How is the reporting process evolving? 

Over the past years improvements have been made to the data collection systems, for example:

  • A number of proxy methodologies were updated for reporting type and number of staff, and for several emission sources when the activity data was not available. The data collection files were updated with more concise guidance and tested extensively to avoid delays in emission calculations.
  • ICAO regularly updates the air travel emissions calculator with the latest industry data and statistics.

The changes made to data collection and reporting tools as well as the development and updating of proxy methodologies have made data reporting easier. It is expected that this will facilitate a larger coverage of offices and facilities in the future. The number of participating entities has grown over time and new organisations and Focal Points have joined the project. Future efforts will focus on replacing or upgrading the existing reporting system with a more versatile system and improving the reporting depth (i.e. inclusion of additional offices) among participating organisations and data quality.

Responding to the magnitude and significance of emissions from air travel and transportation used for official travel, a decision was taken by the EMG to make reporting mandatory, despite this being optional under the Greenhouse Gas Protocol. In accordance with international guidance of the protocol, emissions from the combustion of biomass or bio-fuels in equipment and vehicles are reported as an information item only. Similar guidance exists for Ozone Depleting Substances controlled by the Montreal Protocol such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), which are mostly used as refrigerants. However, due to their significant presence in UN facilities they have been included under the Optional Emissions category. It has also been decided to make the reporting of CFCs and HCFCs mandatory in the future. While recognising the significance of non-CO2 effects of aviation no provision was made for their estimation or incorporation - pending more clarity and internationally accepted guidance on this issue.

What are the issues with data quality?

Aspects of the methodologies used initially have been simplified over time in recognition of internal capacity and resource limitations. It is accepted that in some circumstances this affects the accuracy of the inventory. Such changes were made in Refrigerants, Purchased Steam and Vehicles (mobile sources). Where data was not readily available, estimates were based on clearly defined assumptions and proxies. A review of the methodologies, data and process is undertaken annually and the IMG is actively involved in this process. More rigorous methods and procedures will be introduced, based on feedback, as resources allow.

A few agencies have prepared Inventory Management Plans (IMPs) and others are expected to follow suit. An IMP is an internal document that records the details of each inventory and helps to institutionalize the process for preparing a high quality inventory. Efforts will also be made to develop a quality assurance and control (QA&QC) programme for the inventory, including external verification.

Why is it difficult to compare emissions between years and organizations?

The use of a common methodology and the development of proxy methodologies for issues identified as major data gaps have helped to improve the comparability of the inventory across agencies and between years. However, detailed analysis is needed to interpret the trends. The difference in the size, nature and operations of agencies, changes in coverage of offices across years, changes in methodologies, scope and underlying databases of the emissions calculator means that comparisons cannot be accurately made unless detailed analysis is done.

Read about the UN GHG Inventory Boundaries

Measuring and Reporting Waste

The methodology for measuring and reporting waste management practices was developed and implemented during the 2016 waste inventory. It was improved in 2018 by incorporating lessons learnt and feedback from UN focal points. The methodology requires the collection of data on waste quantities by:

  1. type of waste (e.g. paper, plastics, metal, e-waste, etc.).
  2. method of collection (e.g. municipality, private contractor, take-back scheme, etc.); and,
  3. type of treatment and disposal (e.g. landfill, recycling, reuse, etc.);

The approach follows the recommendations of the Framework for the Development of Environment Statistics developed by the Statistics Division at the UN Department of Economic and Social Affairs and is in line with Global Reporting Initiative indicators.

In addition, qualitative information on activities such as implementation of policy and waste management plans is collected to enable the sharing of best practices between UN entities.

Reducing our Impacts

As well as the work that’s going on within individual UN organizations, there’s also a considerable amount of activity at the UN System level to reduce the UN’s environmental impacts, including:

  • Work by inter-agency groups to embed sustainability into policies and practices
  • The development of tools and guidance for specialists across the UN
  • The development of UN organization Emissions Reductions Plans and Environmental Management Systems.

The UN’s main areas of focus are:

Environmental Management Systems

Work is underway to introduce Environmental Management Systems (EMS) across UN entities. An EMS should include an organizational structure, planning activities, well-defined responsibilities, practices, procedures, processes and resources. It must be based on the specific operations of each organization as it is designed to help streamline and organize the organization’s environmental deliberations and activities. Read more about Environmental Management Systems in the UN.

Emission Reduction Strategies

Emission Reduction Strategies detail each organizations commitments and plans for reducing their greenhouse gas emissions. In 2018, 67 UN entities participated in the annual greenhouse gas emissions inventory. Among these, 55 entities - representing 95% of reported greenhouse gas emissions - were climate neutral for their 2018 greenhouse gas emissions.


Travel is the UN’s largest single source of greenhouse gas emissions, accounting for around 54% of the total reported footprint in 2018. Work is underway with the inter-agency travel teams to identify ways of reducing the impacts of our travel, without jeopardizing the work that we do. Read more on travel


Facilities account for about 46% of the UN’s 2018 greenhouse gas emissions. With offices around the world, this presents plenty of opportunities. Work is ongoing to integrate environmental considerations into procurement and decision-making processes for new buildings, leases and retro-fits and to engage staff in using buildings more efficiently. Read more on facilities


The UN is a big spender. In 2016 alone the UN purchased goods and services worth USD 17.7 billion. The UN is therefore able to directly influence the market place by increasing demand for more sustainable goods and services. Read more on procurement

Staff engagement

With over 290,000 staff (including peacekeepers) the UN is one of the largest employers in the world. Staff have a critical role to play in enhancing the sustainability of the organization. Find staff engagement resources and ideas in the Tools section of the website here.


The UN, like many large international organizations, convenes a huge number of meetings each year, from small workshops to high-profile international summits. Making our meetings more sustainable is not just critical for reducing our impact - it's also an effective way of communicating our values. Find meeting resources here.


The UN Climate Neutral Strategy commits all UN agencies to minimise their impact on climate change by following a three-part strategy to achieve climate neutrality. Organisations must first measure their emissions according to the UN agreed boundary, then take steps to reduce them. The final stage is to offset any unavoidable emissions. Only when an organisation has successfully offset all of its reported greenhouse gas emissions can it be declared 'climate neutral'.

At the September 2014 Climate Summit, Secretary General Ban Ki Moon issued a call for the UN system to be climate neutral by 2020. Measuring, reducing and offsetting greenhouse gas emissions will all be required to achieve this goal.

In 2019 the UN offset 95% of its total reported 2018 greenhouse gas emissions. You can see more about each UN entity's progress on offsetting here Greening the Blue Report.

What is offsetting?

Whilst the UN is working hard to reduce its emissions, some are unavoidable. Offsetting is the process whereby organizations take responsibility for their remaining emissions by purchasing carbon credits from projects that are achieving reductions in greenhouse gas emissions of an equivalent amount. Example projects include installing new renewable energy facilities, restoring forests, delivering clean cook-stoves or improving energy efficiency in homes.  

Carbon credits and Certified Emission Reductions

Carbon credits are created and issued to projects that can prove their activities are reducing levels of carbon dioxide in the atmosphere, either today (through capturing carbon dioxide) or in the future (through reducing or replacing the use of fossil fuels). A reduction of one tonne of carbon dioxide equals one credit. The project must demonstrate that the financing gained from the sale of the credits is a vital income stream, without which the emission reduction would not happen. This is known as 'additionality' and makes sure that offsetting schemes have a tangible impact on atmospheric levels of greenhouse gases.

Certified Emission Reductions (CERs) are carbon credits issued by projects that are part of the UN’s Clean Development Mechanism. There is a 2% levy on CDM projects which goes into the UNFCCC’s Adaptation Fund to finance projects that help developing countries build resilience and adapt to climate change.

How does the UN buy its offsets?

The carbon credits purchased by the UN are secured either via UNFCCC’s Adaptation Fund, via UNOPS or using external brokers.

Offsets are purchased using core funds or extra-budgetary resources. In some cases, such as for offsetting specific events, funding is provided by external sponsors - for example, individual governments or private foundations. In these cases, the UN is not always the direct buyer.  A more systematic approach is to finance offsets at the point where the greenhouse gas emissions are generated, charging to the travel budget, without compensation, the costs of offsetting emissions from official travel.  In this way, the budget available for travel is effectively reduced, as are travel-related emissions, and the overall cost is budget-neutral. At the same time, staff are sensitized to the climate impact of travel. Find answers to some common questions about offsetting in the offsetting FAQs.