The new service is due to be launched on February 28 next year, but members of the public have only until October 31 to tell the council if they want a smaller recycling wheelie bin as part of the new service.
Each household was to be provided with a 240-litre wheelie bin early next year, but hard-to-reach homes could have a smaller, 80-litre, bin instead on request.
However, council city environment general manager Tony Avery said about 2000 people had already requested the smaller bins, and it appeared many were doing so based on confusion about the wheelie bins' purpose.
Many were asking for smaller bins in the mistaken belief they were for rubbish, when in fact both the 240-litre and 80-litre bins were for plastics, cardboard, paper and other non-glass recycling, he said.
Existing black bags would continue to be used for rubbish, and existing blue bins for glass.
The influx of requests for smaller bins meant council staff were worried the overall amount of recycling generated would be reduced, and could drive up the cost of the service, he said.
The cost of the service had been calculated at $63 per household per year, based on a rebate expected from selling the recyclables, he said.
If the volume of recycling produced dropped because people were confused, so, too, would the rebate - meaning the cost per household would have to rise.
"It would put the $63 per household potentially at risk. It might need to increase," Mr Avery said.
The worst-case scenario was a complete loss of the rebate, adding at least $5 per household, or $225,000, to the cost of the service, although Mr Avery considered that "unlikely".
The rebate was calculated to be about $5 or $6 per household, based on a "conservative" assessment of expected market conditions, out of a total possible rebate of about $15 per household, he said.
The maximum rebate could be achieved only if all variables worked in the council's favour - from the cleanliness of glass collected for recycling, to currency exchange rates and market conditions at the time of sale.
The council's aim was to keep the cost of the scheme at $63 per household for the duration of the seven-year contract, but the cost could reduce if the recycling market performed better than expected, he said.
The council has invested heavily in the new scheme, awarding a $24.8 million contract to a group of four companies - headed by EnviroWay, a division of EnviroWaste - earlier this year.
A new resource recovery park was being built, as part of the contract price, near the Green Island landfill to handle the recycled materials.
Details of the new service had been highlighted recently in the council's City Talk magazine, as well as in radio adverts and a mail drop, but it appeared not all households had received copies of the pamphlet, he said.
The need to confirm preferences months ahead of the service's launch had added to confusion but the October 31 deadline was necessary to allow wheelie bins to be ordered in time, he said.
Anyone changing their mind after October 31 could be accommodated, but it was possible they might be charged for changes, he said.
"It hasn't been determined yet."
Experience from other councils was that larger bins encouraged greater levels of recycling, and it was hoped the number of people requesting smaller bins could be kept to a minimum, he said.
"Once you start getting two weeks of newspapers, cardboard, plastics, cans, that sort of stuff, it will fill up ... The 80-litre one, which is quite a bit smaller, may not give sufficient capacity."
DCC's new refuse service
- Due to launch on February 28.
- Cost $63 per household, paid by uniform annual charge (UAC).
- 240-litre wheelie bin, or 80-litre wheelie bin substitute, for non-glass recyclables.
- Existing black bags for rubbish.
- Existing blue crates for glass.
- October 31 deadline to request smaller 80-litre wheelie bin, if required.
