BHP and Rio Tinto’s proposals to earn a windfall from environmental projects has been rejected by federal officials who have knocked back the commodity giants’ hopes of earning valuable credits by storing carbon in mine waste and producing carbon-neutral diesel from trees.

The country’s two biggest mining companies have been urging the government to use Australian Carbon Credit Units to encourage a wider range of projects as part of Labor’s push to give industry a bigger say in what should be eligible under the lucrative emissions permits scheme.