The Norwegian Environment Agency said ExxonMobil's Esso subsidiary misclassified biofuels made from animal fat from the US as "advanced" and failed to provide adequate sustainability documentation.
The government body suspects "the error is industry-wide" and said other companies will be audited.
There are different categories of animal fat — categories 1 and 2 can be double counted towards national targets in Norway, while category 3 animal fats can only be single counted.
The agency's audit found that Esso did not have the relevant documents to show how the manufacturer and raw materials suppliers differentiate between types of animal fats. ExxonMobil has not yet responded to a request for comment.
In 2017-22, half of all advanced biofuels in Norway were made from animal fat from the US, the Norwegian Environment Agency said. It is common that companies importing the biofuels "have not used certification schemes approved by the European Commission to document that they meet the requirements of the Product Regulation", it added.
The agency said it is considering amendments to the current regulation to reduce the risk of violations in the future. A proposal has already been put forward to only allow EU-approved certification systems.
