The compost is produced from garden waste collected in more than 15,000 brown bins located all over the city. It was being sold at garden centres and has an excellent reputation, topping a test of compost by a national consumer gardening magazine.

A council spokesman said, “Compost now has to be accredited PAS100 and samples are currently in the laboratory for testing. We are confident the standard will be met and Discovery Compost will be available again in the near future.”

The new standard was devised by the Business Resource Efficiency and Waste programme, the Waste and Resources Action Programme, and the Environment Agency, and is a guarantee of quality.

The Scottish Environment Protection Agency, which regulates the disposal of waste, said compost-producing councils were keen to achieve accreditation, otherwise their compost would lose the status of a “product” and instead would have to be monitored under waste guidelines.

SEPA’s Colin Anderson said, “It’s a very positive thing to be aiming for. If it doesn’t meet PAS100, it means there may be some elements in it that would make it unsuitable for general use by the public.

“For instance, one of the tests is in relation to germinating seeds. It may be there are still some seeds capable of germinating in the compost and that could lead to weeds growing from it.”

Thousands of tons of garden and kitchen waste finds its way into the council’s composting process at the Riverside civic amenity site every year. Bacteria, fungi and worms are all involved in the job of converting a pungent and wet substance into an odourless, humus-like material smelling of soil and freshly-turned earth.

Discovery Compost came top of the heap when Gardening Which reviewed composts in 1998.