Daimler Trucks, eBay and a US energy company were among the recent buyers of carbon offsets created by projects that involved injecting carbon dioxide underground in order to extract more oil.

Three US-based extraction projects were eligible to generate credits because their processes involved the capture of CO2. But this was used as a way to extract fresh oil that would otherwise have been inaccessible, a procedure known as “enhanced oil recovery” (EOR).

The offsetting rules that the credits were created under ignored the emissions associated with the extracted oil.