The plant processes approximately 80 per cent of the biosecurity waste entering the country, including that from airlines and the growing number of cruise ships.
A director, Lincoln Falconer, said as a waste treatment facility, the existing plant had the potential to generate odours but these were strictly managed and monitored under resource consents conditions with Auckland Council.
''Last Friday (December 6) we had an odour issue caused during cleaning out of our underground trade waste tanks, which was exacerbated by still weather conditions. We realise this caused concern for our neighbours and we have sincerely apologised,'' he said.
''The matter was dealt with as quickly as possible.''
Interwaste was working with Auckland Airport to design and build a new purpose-built facility to replace the site at Hape Dr with the latest generation sterilisation and air extraction technology.
Falconer said the design of this facility was advanced, and building was expected to start next year.
Air Chathams airline and charter manager Duane Emeny said he had noticed odour from Interwaste facility at times with certain wind conditions.
''However we had a very positive meeting with one of their senior managers this week and they are working on ways to mitigate that issue as much as possible while they transition to a new facility.''
An Auckland Airport spokeswoman said her company had been working closely with Interwaste to develop a new multi-million dollar warehouse facility.
Its location was still being confirmed, but the 3500sq m warehouse would be a standalone development in an industrial area.
New Zealand-owned Interwaste operates four specialist facilities in Auckland, Wellington, Christchurch and Dunedin.
Its Auckland plant can process more than 900 tonnes of quarantine and medical waste a month. The steam sterilisation plant replaced the last industrial incinerator, the company says.
