Firms looking to offsets their carbon emissions have today been advised to steer clear of three high profile emissions reduction schemes after a study claimed that while they are delivering environmental benefits they should not be treated as a source of offset credits.

The study from environmental publisher Environmental Data Services (ENDS) claims that offset buyers should avoid credits emanating from the Chicago Climate Exchange (CCX), the New South Wales Greenhouse Gas Abatement Scheme (NGACs) and Renewable Energy Credit projects, on the grounds that they were not developed specifically as offset schemes and as such do not adhere to the most robust offset criteria.

Tejas Ewing, author of The ENDS Guide to Carbon Offsets, said that while each of these initiatives were created for "worthy purposes" and are delivering environmental benefits the credits they offer should not be mistaken for offsets.

The Chicago Climate Exchange (CCX) works as a cap-and-trade scheme whereby firms sign up to the initiative and agree to meet emission reduction targets and those that cut emissions below their targets can then sell credits through the scheme. "It's a well intentioned scheme, but the criteria for the issuing of credits aren’t as tough as the CDM [UN Clean Development Mechanism] or VER [Verified Emission Reduction] schemes with third party standards," said Ewing. "For example, you can back date emissions reduction projects undertaken before your company signs up to the scheme."

Ewing raises similar concerns with the NGACs scheme, which was also developed as a cap-and-trade scheme and has repeated the error of the European emissions trading scheme by setting emission caps too high and undermining of the price of credits.

He also advises firms to distinguish between offset credits and Renewable Energy Credits (RECs), both of which serve a different purpose and are issued using different criteria. "RECs were developed to allow firms to show they have bought renewable energy to meet renewable energy targets and provide an extra incentive to drive development," he said. "But despite the fact many offset providers are selling them they are not the same as offset credits.

For one, RECS are often not a major revenue stream for renewable energy developers and these projects would go ahead anyway regardless of whether or not you buy the credit – that means they fail the additionality test from the off."

The new guide also warns firms to avoid carbon offset credits based on forestry projects, where it is impossible to verify whether or not advertised emission reductions will be achieved, and offsets that are not verified by an independent third party.

The guide assesses 170 offset providers globally and points buyers to 30 operators that adhere to the highest standards when sourcing offset credits. The top three providers with the strictest criteria are identified as MyClimate based in Switzerland, Atmosfair in Germany and Offset the Rest in New Zealand.