Green bins in Kambah and Weston Creek had an average of 30 grams of contamination each during a trial of a new garden waste service, ACT government officials have said.
More than 8000 homes are part of the green bin pilot, which gives Canberrans a government-coordinated kerbside pick-up service for garden waste.
Tuggeranong residents can opt to receive a green waste bin later this month, Belconnen residents from next year and the rest of the ACT in 2019.
During annual reports hearings, Transport Canberra and City Services deputy director-general Jim Corrigan and ACT NoWaste director Michael Trushell said they'd been "very surprised" at how low the contamination rate was - 0.05 per cent overall.
"On average I think per household it's maybe about 30 grams of contamination over about a four or five month period so it's been exceptional," Mr Trushell said.
Contaminants can include food scraps, paper and cardboard and plastic bags.
Liberal politician Mark Parton said the low rate "blew" him away, as contamination was one of the reasons why a 2002 green bin trial in Chifley was abandoned after 10 months.
"People's habits for taking things out to the bins ... must have changed dramatically in 10 years," Mr Parton said.
City services minister Meegan Fitzharris put the low contamination rate down to education and the information inside the bin lid.
Mr Trushell said their education officer had been going around checking green bins and giving households feedback.
"She goes around, audits bins, provides positive feedback when she checks a bin if there's no contamination and provides information where there is and I think that aspect of it has been really important, the whole education aspect of it has demonstrated its worth," Mr Trushell said.
But the contamination rate is likely to rise as green bins are rolled out to higher density areas.
Mr Trushell said multi-unit developments with gardens could apply for a green bin, which would present "unique challenges".
The committee heard anecdotal evidence that people living in large complexes were less waste conscious.
"Obviously Weston Creek and Kambah don't have the same density of these as other parts of Canberra and as we work though that we'll engage more intensively with strata managers and body corporates and translate our education program from a single unit development into those [multi-unit developments]," Mr Trushell said.
Mr Trushell said the pilot had been largely a success and the take-up rate across Canberra was likely to settle at 50 per cent.
However the rollout has been marred after the ACT government inadvertently breached the privacy of about 3000 people who'd signed up to get a green bin.
People who'd subscribed to updates about the service were mistakenly sent an email with thousands of strangers' email addresses copied in.
An ACT government spokeswoman said the email addresses had been accidentally copied from a spreadsheet into the "To" field instead of the "BCC" field.
"The staff member became aware of the mistake immediately after transmitting the email and recalled the email straight away. The incident was reported immediately within Transport Canberra and City Services," she said.
The spokeswoman said the directorate had sent a follow-up email to all those affected.
"This email was an apology for the human error made and providing details of the Office of the Australian Information Commissioner if they wish to lodge a complaint. Transport Canberra and City Services has notified the Office of Australian Information Commissioner," she said.