Seven months after a $1.4 million blowout in costs for the project was revealed, the council again needed approval for more money - this time to purchase a slow speed shredder for the facility.

The council had budgeted $550,000 for the shredder, based on five years of research, but machines have since been improved and the only viable option was the $751,000 cost from Brisbane-based company Finlay Waste and Recycling.

Extra money will be transferred from the council's waste reserve, after councillors voted unanimously to grant the request.

The machine is expected to last for 10 to 20 years.

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Speaking at Tuesday night's council meeting, deputy mayor Mark Currie said he understood the budgeted amount was a "best guess", but asked infrastructure services director Alan Clark if officers would be coming back a third time to ask councillors for an increase in the project's budget.

"No, this is the last item to be purchased as part of this plan," Mr Clark said.

"Down the track we will be coming to council and asking for things such as a weighbridge if we go regional."

The organics processing plant will cost more than $4.5 million in total and will compost 3500 tonnes of organic waste from homes and business, plus another 500 to 1000 tonnes of garden waste from council tips.

"The shredder is integral to the organics processing plant, which we've nearly finished constructing ... We have to keep using this shredder everyday so it's vital that it's reliable and can do the job," Mr Clark said.

"Although it's a lot of money, it's small in the overall scheme of things with the cash flow that will be going through the organics processing plant."

Cr Harry Bussell said the organics plant was "a classic case of us helping the environment", using the shredder to compost waste instead of sending it to landfill.