Emissions Inventory

01 Make a plan for Stage 1

Review the steps below and make sure you/your department have adequate staffing, resources and authority to carry through with what is required. Stage 1 may require approximately three full-time-equivalent staff, including collaborators or contractors, with secure access to the laptops and basic computing resources needed for inventory compilation and archiving. Ensure that your management is committed to sustaining your efforts into the future. This guidance recommends you start the process of integrated emission inventory development using GHG inventory guidance for collecting activity data; however, we recommend integration of air pollutants in the emissions inventory system from the outset by collecting additional emission factors, as this will allow for substantial efficiency gains and policy-making benefits in later stages. In order to prepare the development of a fully integrated emissions inventory (see Emissions Inventory Guidance Stage 2), we recommend that you start collecting relevant emission factors and activity data. ​At Stage 1, however, the inventory itself should remain focused on greenhouse gases from the major activity sectors. Collection of air-pollutant information at this stage is preparatory and is intended to facilitate integration during Stage 2. You can have a good overview by reading the resources below.

02 Check the guidelines and Tiers to use

Different guidelines exist to build an emission inventory, like the EMEP/European Environment Agency (EMEP/EEA) Guidebook, the Intergovernmental Panel on Climate Change (IPCC) Guidelines, the US Environment Protection Agency (US EPA) AP42, etc. They are all based on the same overarching principles. They all present 3 levels of accuracy called Tiers: the higher the Tier the higher the accuracy of the emission estimates and the higher the requirements in terms of data parameters and models used. The IPCC method is the required methodology to use for the reporting of GHG emissions for the UNFCCC. Tier 1 from the IPCC is the simplest in terms of data requirements. A better overview can be found in the resources below.

03 Choose the base year of the inventory

Emissions vary in time seasonally, weekdays vs. weekends, but also yearly. To follow any policy measure implemented, the yearly trend is observed. Therefore, an emission inventory is established for a specific year. All the data collected for the calculation of the emissions will target the chosen year of the inventory, the inventory base year. The base year is chosen before beginning the collection of data, e.g. the year can be based on the requirements of the UNFCCC reporting for National communications or Biennial Transparency Report. An example on how to choose a base year can be linked to the UNFCCC reporting.

04 Establish institutional arrangements

To prepare the data collection process, you should establish official communication and data sharing channels/processes with the different stakeholders, mainly the ministries, agencies, and most importantly the national statistics agency. This process is formalized by signing a Memorandum of Understanding (MoU) with each stakeholder. The MoU presents the objectives of the cooperation, the scope, the responsibilities and duties of each party, timelines, etc. A high-level inter-ministerial committee is usually required to facilitate the contributions across different Ministries. It may take a long time to establish this but is likely to be fundamentally important in ensuring effective dataflows and the longevity of the emissions inventory team. You will find below some resources that explain the establishment of the institutional arrangements.

05 Collect activity data

Once the methodology is chosen along with the different reporting Tiers, collect the required activity data from the literature, reports, the national statistics agency, line ministries, agencies, customs, etc. Some of the data might not be available, so assumptions are generally used. More information on data collection can be found in the resources below.

06 Conduct quality checks on the input data

All data, whether collected from ministries, surveys, reports, etc. should be checked for quality at the different stages of the process. You will find examples of quality checks in the resources below.

07 Compile the inventory

Emissions are then estimated either manually over a spreadsheet or using a dedicated software from the IPCC or commercially available. You might need to mix both spreadsheets and other sector specific software/programs. You will be using emission factors from the literature that will be multiplied by the activity data to get an estimation of the emissions. Some activity data require assumptions since it is unavailable for this inventory. The following resources provide more information on emission factors and calculation methodologies.

08 Conduct uncertainty analysis and determine key categories

To determine which categories/sources are the most important in terms of emissions but also uncertainty and accuracy, you need to conduct the uncertainty analysis using Approach 1, which is simpler than Approach 2 (note: these approaches differ from Tiers mentioned above). You can then determine the most important sources for each pollutant. Combining the two, namely the emission intensities and the uncertainty associated for the different years, you will be able to determine the key categories which have the most impact in the inventory. You will find more information in the resources below.

09 Prepare the report and conduct quality checks

Once the calculations are completed, you will need to write the report that presents the methodology used for every sector and sub-sector, the activity data used, its origin, the emission factor, etc. After the report writing, quality checks should be conducted again on the entire system, calculations, assumptions, etc. You will integrate the comments, rerun the concerned calculations, etc. and prepare the final report. The quality checks are explicated in the links of Step 6 but concern this time the entire system, external reviews, etc. See the IPCC guidance below for an explanation of the content of the report.

10 Submit and archive

The final report needs to be submitted to the concerned party or authority, e.g. UNFCCC. Once the concerned party has reviewed the report and amendments have been brought, the final report along with all the data, calculation sheets, etc. will be archived. Consider and document the priority improvements that could be made in the compilation of the next version of the emissions inventory. At this stage, updates may be undertaken when required by reporting obligations, donor commitments, or identified improvement needs; a fixed recurring update cycle is not yet expected. Some guidance on the archiving system is presented in the resources below.