A study has finally revealed what has been causing a stink up in eastern Christchurch.
Residents in the suburb of Bromley have long been complaining about strong odours in the area - likened to rotting fish - which prompted a pilot study by the Canterbury Regional Council.
It says the findings clearly identified that two waste plants - EcoDrop and Living Earth are responsible for the odours.
The study was carried out in March by using the "Smelt It" odour reporting app, with reports cross referenced with weather conditions and onsite observations.
The Christchurch City Council - which runs the facilities - said it welcomes the findings and is working on what actions might be needed.
Christchurch City Council head of three waters Helen Beaumont said identifying the sources was a major step towards resolving the issue for residents in the area.
"We have always recognised that odour has been a problem for residents in the Bromley area, but now that we have better data to understand causes, we can remedy the situation," she said.
"We fully appreciate our community will want action and we are using the findings to work immediately with Environment Canterbury [regional council] on the actions which might be needed."
Beaumont said Living Earth had already invested heavily into odour management initiatives, such as bio-filters and misting systems to minimise any compost smell.
"We'll be working with Living Earth to see how these can be further optimised. EcoCentral has identified potential techniques for minimising rubbish smell that it will now urgently begin exploring," she said.
Regional council operations director Nadeine Dommisse said the Bromley community should continue report odours to monitor progress in reducing the stench.
"A collaborative approach will produce faster results for affected residents. We can now better identify where problems can occur in certain conditions, potential emitters, and address them," she said.
"While we have identified the Christchurch City Council-run facilities as being significant emitters, we will also be working with other odour-emitting businesses in Bromley to ensure they are managing odour appropriately."