Cambridge Environmental Research Consultants (CERC)

- Comprehensive Emissions Inventory Toolkit


EMIT is a comprehensive tool for compiling and editing emissions inventories, which allows simple, fast calculation and analysis of emissions.


Typical applications include:

  • Emissions calculations across large urban areas for dispersion modelling with ADMS-Urban
  • Predicting the impact of Clean Air Zones and Low Emission Zones on emissions of toxic pollutants and greenhouse gases
  • Source apportionment: quantifying the contributions from particular road vehicles such as diesel cars to emissions and concentrations (when using EMIT with ADMS-Urban)
  • Producing greenhouse gas emissions inventories

Current users of EMIT include government bodies and local authorities across the United Kingdom and elsewhere, as well as environmental consultancies and research institutions. All users of ADMS-Urban and ADMS-Airport are highly recommended to use EMIT to store and manipulate the typically large quantities of data involved in these types of modelling. ADMS-Roads users will also find that EMIT can speed up the input and manipulation of emissions data for dispersion modelling.

Traditionally emissions inventories are developed with laborious and error-prone methods such as complex spreadsheet manipulations or GIS calculations. EMIT can substantially simplify the process. For example:

  • Comprehensive Datasets : EMIT contains over fifty emissions calculation datasets for sources such as road and rail traffic, airports and aircraft.
  • Visualisation : The EMIT Mapper can be used to visualise and edit input and output data.
  • Editing : Emissions and activity data can be edited individually on a source-by-source basis or by applying changes in bulk to multiple sources. Source geometry can be edited in the EMIT Mapper.
  • Speed : EMIT’s simple, fast features for emissions calculation and manipulation will save time and increase productivity.
  • Import : Data can be imported in the following formats: comma-separated text file (CSV), ArcGIS shape file or MapInfo MIF.
  • Export : EMIT output can be exported in the following formats: CSV and ArcGIS shape file. The CSV format can be imported directly into ADMS-Urban and ADMS-Roads for dispersion modelling, including ADMS-Urban grid sources which are automatically calculated by EMIT.
  • Consistency : EMIT’s automatic calculations ensure a consistent, verified and traceable methodology for emissions assessment.
  • Auditing : EMIT gathers together the input and output data for emissions calculations into a single file, which inherently provides an audit trail for the assessment procedure.

Scenario Assessment

When local authorities develop Air Quality Action Plans for an urban area, an important aspect is estimating the emissions consequences of traffic management schemes such as Local Emission Zones. EMIT has been specifically designed to help with this task. EMIT allows you to consider the effect on emissions of the following aspects, both individually and in combination:

  • Projected changes in traffic flows due to national trends
  • Projected changes in national fleet composition through the introduction of cleaner technology with time in response to national and international emissions legislation
  • Changes in local fleet composition, traffic flows, and speeds through local interventions

The effect on emissions can be quantified for individual toxic pollutants and greenhouse gases, in total and as contributions from specific road vehicles such as diesel cars.

The figure below shows an approach for investigating the effectiveness of traffic management schemes. Four different scenarios are considered:

  • Base case: The current situation without traffic management.
  • Future year: Predicting changes in future emissions due to national trends in traffic flows and fleet composition in a 'business as usual' scenario without traffic management.
  • Impact in base year: Predicting changes in emissions due to the impact of a proposed local intervention on traffic flows, fleet composition, and traffic speed.
  • Impact in future year: Predicting future emissions in the future year under the local intervention and national expected trends.

Comparing the different emissions from these scenarios allows a clear assessment of the impact and effectiveness of the proposed scheme. EMIT enables the user to assess multiple scenarios in a fraction of the time required by traditional methods.

Emissions Sources

EMIT can store emissions data from a variety of sources. These broadly fall into two categories.

Firstly there are the explicit sources such as:

  • major roads,
  • rail and
  • industrial sources (point and area).

UK inland energy consumption for 2012

Secondly, EMIT can hold data from sources that may be too small to be considered explicitly, and instead are treated as average emissions on a 1 km2 grid, such as:

  • minor road,
  • commercial, and
  • domestic sources.

Emissions Calculations

Sources with known emission rates can be imported directly, for example, the emissions from Part A industrial sources can be downloaded from the UK Pollutant Release and Transfer Register (UK PRTR).

However, explicit emissions from most sources are not known. This means that emissions have to be estimated. This can be done in one of two ways.

Firstly, emissions can be calculated from activity data, such as traffic flows for road and rail traffic, and fuel consumption for industrial sources. Below are examples of activity data for various sources whose emissions can be estimated in EMIT (some or all of the activity data listed may be required to estimate emissions).

  • Agriculture, e.g. number of animals, land area, fuel used.
  • Industrial plants, e.g. amount of raw materials consumed, amount of product, fuel consumption.
  • Road and rail traffic, e.g. traffic flows, fleet compositions, number of vehicle kilometres, number of trips.
  • Air traffic, e.g. number of landing/take off cycles, fuel consumption.
  • Electricity, e.g. number of kWh, fuel consumption used.
  • Landfill, e.g. volume of landfill.
  • Commercial and domestic heating, e.g. house type, fuel type, insulation, heating efficiency.

In order to calculate emissions from activity data, associated emission factor datasets are required. Over fifty datasets are held in EMIT. The table below gives some examples.

  • Road Traffic : EMIT includes DfT's latest road traffic factors (2014) to calculate accurate estimates of moving vehicle emissions, alongside the factors from Defra's latest Emission Factor Toolkit (v 6.0), and datasets to estimate emissions from resuspension, brake wear, tyre wear and road wear.
  • Rail Traffic : Relevant data from the UK Emission factor Database (UK EFD) have been collated and included in the database.
  • Aircraft : Emission factors are included for jet aircraft engines (from the ICAO databank), turboprop and piston engines, auxiliary power units, and ground support equipment. The ICAO databank factors include PM10 emissions calculated by the First Order Approximation method version 3.
  • Industry : Hundreds of emissions factors for industrial sources have been included using data from the UK Emission factor Database (UK EFD).
  • Electricity : Datasets have been included in EMIT to estimate emissions from electricity, both in terms of the fuel used for power generation, and also using end-use values of electricity consumption in terms of the number of kWh used.

Emission factors are included for the following pollutants:

  • 9 local Air Quality Strategy pollutants: oxides of nitrogen (NOx and nitrogen dioxide), particulate matter (PM2.5, PM10), sulphur dioxide, carbon monoxide, lead, benzene and 1,3-butadiene
  • Many other pollutants including carbon dioxide, methane, volatile organic compounds (VOC), mercury and benzo[a]pyrene

Full details and references for all the datasets in EMIT are contained in the User Guide.

Secondly, emissions can be estimated as a scaling of a national emissions figure by a local statistic. For example, the local population is often a good indicator of emissions—if you were to scale the total emissions from landfill sites in theUK by the ratio of the local to national population, this would give an estimate of the emissions from landfill that could be attributed to the local population.

Emissions Inventory

CERC provides training on compiling an emissions inventory. The course focuses on collating data for use in air dispersion modelling and covers the type of sources to include in an inventory, the data format, calculating emissions, locating emission factors, and aggregating sources into grids.

Tool Output Data

Import and export

Emissions data in the following formats can be imported directly into EMIT:

  • ArcView shape files,
  • MapInfo Professional MIF files, and
  • Comma Separated Variable (.csv) files.

Once data manipulations and calculations within EMIT have been performed as required, emissions data can be exported from EMIT as ArcView shape files. For major roads data, these files can be imported directly into noise mapping software that implements the UK noise standard Calculation of Road Traffic Noise (CRTN).

Alternatively, the data can be exported to a format that can be imported directly into CERC's air quality management tool, ADMS-Urban/ADMS-Roads for use in local air quality assessments of Air Quality Strategy pollutants, or to the industrial assessment model, ADMS 5.

Emissions totals are displayed in the EMIT interface, and can be copied and pasted into other packages for editing, use in reports and so forth.

Viewing and Manipulating Data

EMIT contains an integrated visualisation and manipulation utility called the EMIT Mapper. It allows source data not only to be displayed graphically but also manipulated. New sources may be added and existing sources may be moved between groups. The geometry of a source may be changed directly, perhaps by using background map data as a guide. Additionally, sources may be edited via their EMIT source data screens. The map created in the EMIT Mapper can be copied and pasted into other packages such as Microsoft Word.

The Mapper allows the user to choose which source types to show or hide. Sources can then be selected and are highlighted in red in the above image and also listed in the Selections window.

The Mapper has various GIS tools and options are available for filtering and shading the sources. The Database Explorer displays all the inventories within the database and the source groups within each inventory.

The tool interface is designed so that the user can enter the data required for the modelling in as straightforward a way as possible.

The interface consists of several main screens. To set up a model run, the user simply works through the screens entering the relevant data or referencing external data files.

EMIT is supplied with an in-depth user guide (see the User guides page) that details how to set up an emissions inventory, traffic management and greenhouse gas inventories, as well as appendices giving full details of all the emission factors datasets included within the database.

An annual maintenance contract provides support for users; this includes:

  • maintenance upgrades,
  • use of the helpdesk by e-mail, phone, fax or post,
  • access to the password-protected user area.

CERC also offer basic and advanced training.

Current versions and system requirements

  • Current software versions and release dates are listed here.
  • System requirements and compatibility with third-party software are described on the System requirements page.