No coal company would comment on the record and the NSW Minerals Council said its members had not raised any concerns, but many diesel-engined machines built after 2016 are fitted with the equipment - which sprays a one-to-three mixture of purified urea and demineralised water into diesel exhausts to turn noxious nitrous oxide (NOx) gases into nitrogen and water.

The Adblue shortage arose after China moved in October to put export restrictions on urea, preserving stocks for domestic use as fertiliser and generating warnings of global consequences.

In other news:

Although road transport has been the main concern - diesel vehicles meeting "Euro 5" and the higher "Euro 6" standards have Adblue tanks - there are concerns the shortage will also hit off-road users led by mines and farms.

On Monday, federal Industry Minister Angus Taylor announced a $29.4-million grant to Incitec-Pivot in Brisbane to "design, trial and manufacture" at least 5000 tonnes - or a month's national supply - of the "technical grade" urea needed, starting in February.

At the same time, Trade Minister Dan Tehan confirmed we would buy 5000 tonnes from Indonesia for another month's supply.

A government spokesperson said the coal industry was one of the sectors of concern.

He confirmed the government had been asked to allow users to turn off the Adblue if supplies ran out.

This is presently illegal, with a substantial fine as penalty and the spokesperson said it would only be considered "as a last resort".

Manufacturers say disabling Adblue would void warranty.

On Wednesday, the Australian Competition and Consumer Commission gave Australian Adblue makers an "interim authorisation" allowing them to work together to secure supplies without breaching competition laws.

Queensland federal MP Bob Katter thanked the government for stepping in after previously slamming a "lack of response". Federal Labor said it was too little too late, and criticised a reliance on imports.

Like "Hoover" was for vacuum cleaner, "Adblue" has become a generic term for various competing brands of "diesel exhaust fluid" that is typically consumed at about one litre for every 20 of fuel.

Simon O'Hara, chief executive of the industry body Road Freight NSW, said Adblue had gone from 80 cents a litre to between about $2.80 and $6 a litre.

The Herald was quoted $10 for a litre at one Newcastle service station, while others said they were "almost out" of supplies.

ACCC material on Adblue here

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