Veolia is seeking to source non-recyclable commercial and industrial waste for its Newhaven Incinerator from areas neighbouring East Sussex and Brighton and Hove.
It argues this will allow the incinerator to produce enough energy to power 25,000 homes continuously.
But cllr Rod Main from Newhaven said this would lead to more trucks and pollution.
Veolia applied for planning permission to East Sussex County Council to lift a planning condition to enable the scheme to go ahead.
General manager for Veolia in South Downs Allan Key said the company wanted to extend the catchment area outside East Sussex and Brighton and Hove.
He said it would not lead to physical changes at the incinerator or increase to the 242,000tpa capacity.
Mr Key said: “Energy demands are going to increase year on year. Facilities such as the one we have here in Newhaven recovers energy from waste that would otherwise be lost by going to out of county landfill.”
Cllr Main said: “They need more waste to help ESCC’s carbon footprint by pumping more carbon dioxide into the atmosphere (and it’s around 100,000 tonnes pa now) not to mention how many more trucks will be coming right across Sussex from who knows where adding to the pollution.
“It’s helping to power 25,000 homes. There’s a proposed wind farm just off the coast which might power 20 times that and it won’t be pumping 100,000 tonnes of CO2 into the atmosphere every year for the next 20 or more years.”