Note: This advice is given by the CAP Executive about non-broadcast advertising. It does not constitute legal advice. It does not bind CAP, CAP advisory panels or the Advertising Standards Authority.


Carbon offsetting is the process of reducing the net carbon emissions of an individual or organisation, either by their actions or through arrangements with a carbon-offset provider. Carbon-offset providers are companies that either prevent the emission of gases that would otherwise find their way into the atmosphere or companies that absorb carbon dioxide (or other greenhouse gases) that have already been emitted into the atmosphere. They then “sell” that reduction in carbon dioxide (CO2) or other greenhouse gases to companies that produce greenhouse gases.

Although no universally accepted definition of the concept exists, all definitions follow the same general lines: carbon neutrality involves achieving zero net emissions associated with an organisational unit, product, service or process. The zero net emissions target is generally achieved through a combination of internal emission reduction and external carbon offsetting. The established process to achieve best-practice carbon neutrality is:

Calculating Emissions – This stage requires a clear decision of what emissions will be calculated, and the setting of a clear boundary for which emissions will be covered.

Reducing Emissions – Each business should assess on an individual basis its potential for reducing emissions, for example energy efficiency measures.

Offsetting Residual Emissions – Carbon credits should then be purchased to offset residual emissions, after the initial emissions have been calculated, and internal emission reduction has been taken into account.

CAP recommends that advertisers wanting to estimate the amount of CO2 to claim carbon neutrality should use sound calculation methodologies such as The Greenhouse Gas Protocol (GHG Protocol) developed by the World Resources Institute and the World Business Council for Sustainable Development. To ensure that their data assurance strategies are sound, they should have received advice from reputable experts.

We recommend marketers to make clear in their advertisements the elements they have included in their calculations. For example, the ASA considered that most people would expect a claim of "carbon neutral journeys" to refer to those aspects of the journey for which the advertiser was responsible: the traction energy used by a train, the auxiliary energy used to power lights and heating and the global warming potential of the chemicals that leaked from the on-board refrigerants and air conditioning units but not the energy used in the manufacture of the rolling stock or the track, stations and tunnels (Eurostar Group Ltd, 4 June 2008). If the ad had included an unqualified claim such as “Carbon Neutral” and had not made clear that the claim referred only to journeys, the ASA might have decided that the quantity of emissions that had to be offset was larger than for the claim “carbon neutral journeys”.

Similarly the ASA investigated complaints made about emissions produced by an electric car. As the advertiser’s website contained the claim "The all-electric Nissan LEAF doesn't produce one gram of CO2 whilst driving" the ASA considered that the basis of the emissions claim was clear and that the claim was therefore unlikely to mislead. (Nissan Motor GB Ltd. 22 February 2012).

A solar panel advertiser claimed that their products provided “zero carbon solar power & water heating”. The Code requires that ads featuring environmental claims take into account the full life cycle of the product unless they state otherwise. As this ad did not, and a zero carbon claim for the entire lifecycle of the product was not justified, the ad was found to be misleading (Solar Twin Ltd, 14 December 2011).

An ad for houses stated “zero carbon homes” and “zero carbon sustainable town houses”. Although the ASA noted that the development had some energy reducing features, and that it would be supplied by a renewable electricity supplier, they considered that the use of a 100% renewable energy tariff was insufficient to demonstrate that the homes were guaranteed to produce zero carbon in use. They therefore concluded that the claim "zero carbon homes" was likely to mislead (Roy Williamson Properties Ltd, 30 April 2008).

The ASA expects companies that claim carbon neutrality to offset their carbon emissions in a robust and verifiable manner. Generally that can be achieved by buying offsets from companies that run emissions-reduction or emission-capture projects that comply with a generally recognised standard.

To date, the ASA has commissioned expert advice on the robustness of three international offsetting standards. The ASA understands that the key factors that need to be taken into account when considering whether an offsetting standard is robust are additionality, validation, verification, project type, timing of credits, leakage and prevention of double counting. It would use the same criteria to consider the robustness of other offsetting standards. For example the ASA considered a complaint that an advertiser could not substantiate their claim that you could "offset 100% of your car's carbon emissions with ibuyeco car insurance". Despite the fact that the ASA noted the calculation methodologies used by ibuyeco were sound and in general followed best practice they were found not to have a concrete policy regarding the creditability of their offset scheme and therefore the claim was found to be problematic on the basis of a lack of third party verification, additionality and the avoidance of double counting (BISL Ltd ibuyeco, 22 July 2009).

The ASA considered that projects that conformed to the standards of the three schemes listed below had been evaluated and validated to a high enough level to be compatible with a robust and verifiable offsetting system. Marketers who had accurately estimated the amount of carbon that had to be offset and who bought offsets that were certified by any of the three schemes could substantiate that their activities were carbon neutral.

Name of Scheme: Name of carbon credit per tonne of CO2 equivalent offset:

Clean Development Mechanism (CDM) Certified Emissions Reduction (CER)

Voluntary Carbon Standard (VCS) Voluntary Carbon Unit (VCU)

Voluntary Gold Standard (GS VER) Gold Standard Verified Emission Reduction (GS VER)

See also: Motoring: Fuel consumption and emission figures, Environmental claims: Aviation and Environmental claims: Motoring


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