Pattle Delamore Partners air quality technical director Andrew Curtis said he was confident there was "a low potential" for there to be off-site odour nuisance when the Dunedin landfill site was redeveloped.
While there would be a higher chance of "odour events" at the site when landfill operations continued alongside composting, the events would decrease when the landfill closed.
Proposed management and mitigation measures, including best practice composting operations, would ensure that the effects of odour would be less than minor, Mr Curtis said.
The Dunedin City Council’s application for a proposed "resource recovery park precinct" at the Green Island site will go to a hearing next week.
Odour and issues with vermin were the subjects most frequently raised in the six public submissions.
The council proposal relies on the present municipal landfill closing at the site by the end of the decade and a suite of other waste management operations taking its place.
A facility for sorting kerbside mixed recycling bins, a waste transfer station, an organics storage building and a "forced air static composting" facility presented the greatest risk of producing odour, Mr Curtis said in his brief of evidence for the council.
He said prevailing lighter winds came from the northeast and would carry any odour away from nearby residential areas.
All incoming loads at the site would be inspected and, if any were too odorous, they would not be be accepted.
All food scraps and other decomposing waste to be composted would be stored inside the organics receiving building.
"This building has no ventilation to reduce odour to be discharged," he said.
A "misting system" would be installed to suppress dust and odour elsewhere.
Emptying of compost bunkers would not be done when wind speeds were low and blowing towards sensitive "receptors".
And there were contingency measures as well, such as immediately burying odorous loads, applying deodorant chemicals and removing the offending waste from the site as soon as possible.
"Of the 166 complaints relating to odour from Green Island landfill between July 2017 and June 2023, only six appear to relate to the existing static pile composting operation and none to the transfer station," Mr Curtis said.
"As the proposed aerated static pile (ASP) system is quite different to the existing composting operation, the complaints related to it are not relevant."
There could be short intermittent "odour events", but he said these were more likely when the landfill remained in operation at the site.
"Potentially the longest duration will be when composting material is moved from the bunkers to the curing area.
"While this could result in a longer duration of odour, odours are unlikely to be observable at off-site receptors.
"In addition, it is not intended, as far as reasonably practicable, to undertake this activity when the wind is blowing less than 3m per second and towards sensitive receptors."
Otago Regional Council consents manager Alexandra King said yesterday the city council’s application to extend the life of Green Island landfill and then close it before the end of the decade would be publicly notified on Saturday.
