Beginners Guide to Carbon Footprinting with the PAS 2050

27/12/2008 § Leave a Comment

The Carbon Trust has been working hard developing a methodology for calculating the GHG emissions or the carbon footprint due to a particular product or service. Known as PAS 2050, it is currently going through a consultation exercise before being finalised. 383ppm has prepared a primer on completing a carbon footprint using the PAS 2050 explaining briefly what it means.

Purpose of the PAS 2050

Provide a consistent method for assessing life cycle GHG emissions for goods and services


Covers both goods and services e.g. a computer or an internet banking service

Emissions of the following Green House Gases (GHGs)

  • Carbon Dioxide (CO2)
  • Methane (CH4)
  • Nitrogen Oxide (N2O)
  • HFC
  • PFC
  • Sulphur HexaFlouride (Sf6)

Applicable to organisations assessing the lifecycle GHG emissions of goods and services across their lifecyle. Does not cover any other environmental, social or economic impacts e.g. acidification, eutrophication, or biodiversity



  • All relevant GHG emissions to be included
  • All relevant information to support these claims should be documented and available for inspection


  • Data should be used and collected in a way which facilitates meaningful comparison between GHG information


  • Spatially, temporally and technologically specific
  • Information should be provided on the reliability and completeness of the data used

System Boundary

The boundary conditions for a product are taken from the Product Category Rule developed with ISO14025:2006, if one exists. Where one doesn’t exist, use the guidelines on systems boundary – inclusion types.

Threshold for inclusion

  1. GHG emissions from a source should be included in the analysis if it is likely to contribute more than 1% of the lifecycle emissions of the functional unit
  2. the final analysis should have a coverage of at least 95% of the anticipated lifecycle emissions for the functional unit
  3. where a single source contributes more than 50% of the total anticipated emissions, the 95% threshold applies to the remaining sources of emissions

For the Use Phase of a product points 1 and 2 apply.

When less than 100% of the anticipated emissions have been determined, the assessed emissions are to be scaled up to represent 100%



GHG emissions due to the use and provision of energy during a process are included. Upstream emissions are to be included for example the drilling of oil and its transport to a power station.

Raw Materials

GHG emissions arising from obtaining and transporting the raw materials, from it’s natural state, to the process that requires it are included.

Capital Goods

Emissions arising from production and transport of capital goods are included. As the contribution of these is expected to be less than 1%, PAS 2050 suggests excluding these from detailed calculations.

Manufacture or Service Delivery

The GHG emissions arising from actually producing the product or delivering the service are to be included. For most organisations this will require the collection of primary data on what they actually do.

Lighting, Heating, Cooling and Ventilation

Any GHG emissions arising from operating any buildings required are included


Emissions for the transport of:

  • inputs forming part of the product lifecycle
  • waste products or material from the point they become waste to the point of disposal or reprocessing


Emissions arising from storage are included, including

  • storage of any inputs to the product lifecycle
  • cooling or heating of a product at any point in the lifecycle
  • storage prior to re-use or recycling activities

Use Phase

Emissions due the use phase are included, remember these should be temporally and spatially specific e.g. you should identify in which country a product is being used. The Use Profile of a Use Phase is determined using a hierarchy of definitions:

  1. Product Category Rules (PCRs) that specify a use phase for the product being assessed
  2. published international standards
  3. published industry guidelines
  4. published national guidelines

Where none of the above is available, a description of the use profile for the use phase is recorded.

Recycling & Reuse

The GHG emissions arising from the recycling of a product will be attributed to the life cycle of the product to which the recycled product forms an input

Final Disposal

GHG emissions arising from products disposed of permanently are attributed to the lifecycle from which it arose. GHG emissions may arise over time, in this case projected emissions over 100 years from the date of disposal are included.


  • Human energy inputs
  • Transport of consumers to and from the point of sale
  • Animals providing transport services (does this mean LowHub should get itself a fleet of horse and cart?)


The general aim is to be as accurate and reliable as possible, using data which is place, time (and possibly technology) specific. The GHG emission of an emissions source is calculated by multiplying activity data by an emission factor.

Primary data is used for processes owned or operated by the organisation undertaking the analysis. For each of these processes, 60% of the GHG emissions will be calculated from emission factors which have been derived from primary data for previous processes in the supply chain. This process continues until the input to a process step becomes a commonly available commodity such as cooking oil or diesel (which have published emission factors e.g. in the ELCD)

When collecting primary data care should be taken to ensure it is representative.

Where primary data is unavailable, secondary sources for emission factors can be used, in the following order of preference:

  1. those calculated in accordance with PAS2050
  2. reported in the ELCD
  3. reported in ELCD compliant databases
  4. reported in national (government) produced publication
  5. published national and industry guidelines
  6. reported in peer review research

Emissions Data for Fuel, Electricity and Heat

The GHG emissions will be calculated using the amount of energy used and the average emission factor for the energy source.

Emission factors for onsite generation are calculated using the method described in PAS2050 for offsite generation use the emission factor provided by the supplier or another reliable secondary data source e.g. tables published by DEFRA.

The emission factor for biofuels will be based upon GHG emissions due to the production of the fuel and excludes CO2 emissions from the biogenic carbon component of the fuel. When associating renewable energy to a process it must be clearly demonstrated the process consumed the energy generated or it consumed the same amount and type produced renewably and no other process consumed the energy and claimed it as renewable.

Allocation Guidelines

Between Co Products

When a process results in a co-product, the GHG emissions up to that point in the lifecycle are allocated according to their relative economic value (economic allocation)

Waste Emissions

CO2 emissions
No GHG emissions are attributed if the CO2 arises from the biogenic carbon fraction of the waste but they are attributed if they arise from the fossil carbon fraction.

Methane emissions
All methane emissions are attributed to the lifecycle unless the methane is combusted (producing carbon dioxide and water). If the methane results from a fossil component of waste, the GHG emissions are attributed, if it is from a biogenic component then none is attributable.

Where more than one product is being transported, emissions arising from transport are allocated on the basis of mass or volume, whichever is the limiting factor.


An organisation can claim three levels of conformity PAS 2050

  1. Results certified by an independent third party certification body who is able to demonstrate compliance to ISO 17021 with PAS in it’s scope
  2. Results validated by an independent third party
  3. Self Validation



Emission Factor The average emission rate per unit used / employed for a particular input to a process
Acidification The decrease in pH of a substance (e.g. fresh water, oceans or air) due to the action of pollutants
Eutrophication Excess nutrients in a body of water causing a dense growth of plant life leading to death of animal life due to a lack of oxygen. Can be due to run off of agrichemicals from cultivated land.
Product Category Rule Standardised and published rules for completing the GHG lifecycle assessment for a particular product type
Global Warming Potential (GWP) An estimate of how much a particular mass of atmospheric gas contributes to global warming. Measured using a relative scale with the GWP of CO2 taken to 1. The GWP of the six GHGs are shown below:
Carbon Dioxide – 1 Methane (CH4) – 25
Nitrous Oxide (N2O) – 298
Sulfur Hexaflouride (SF6) – 22,800
Hydroflourocarbons – specific to gas Perfluorocarobons – specific to gas
CO2 equivalent. See GWP, for example Methane has a CO2e of 25.
ELCD European Reference Life Cycle Data System (ELCD)
life cycle assessment dataset compiled by the European Platform on Life Cycle Assessment containing secondary emission factors for selected materials and processes
DEFRA Department for Environment Food and Rural Affairs
Co Product Two or more products of the same process which cannot be produced independently of each other
Biogenic Produced or brought about by a living organism

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