It rises from the riverside like a cross between a gigantic ocean liner and some kind of space cruiser from a sci-fi film.

Its shiny, metallic black walls, crowned by three ship-inspired funnels, conceal a process of combustion capable of reducing 14.5 tons of domestic waste to a pile of ash every hour.

The Vesta energy-from-waste sorting centre at Rouen is the French answer to dealing with domestic waste. It is also the kind of operation Brighton and Hove City Council officers have in mind when they talk about waste burners.

At 113m by 178m and 40m high, the size of an identical operation would not be a feasible option for Sussex but councillors have been asked to consider what might be possible in terms of modern incinerators before consultations continue on the future of waste disposal in the county.

There is a long way to go before the people of Sussex are presented with a firm proposal on what type of incinerators, if any, are introduced on their doorstep.

No final decisions have been made on where any would be built or what form they would take.

Newhaven, in the west, and Mountfield Mine, near Robertsbridge in the east, remain the most likely locations in East Sussex while West Sussex has earmarked four potential sites at Chichester, Crawley, Shoreham and Horsham.

Council officers are keen to point out modern waste burners have changed dramatically from the ones which churned out toxic smog back in the Seventies.

This is why city councillors from Brighton and Hove took a trip to Rouen to take a look at the Vesta plant.

It is run by Smedar, the public corporation for waste disposal, which serves a 650,000-strong community in the area, a number close to the population of Sussex.

Nigel Green, the city council's principal planning policy manager, said this type of plant could be introduced in Sussex but the county could only cater for two separate sites of about half the size of the one at Rouen.

He said: "It is not a question of taking a carbon copy of this plant and transporting it back. We just thought it would be a good idea to take a look at what is possible in terms of a modern waste incinerator.

"I think when you talk about incinerators some people have this image of big chimneys belching out thick, black clouds of smoke into the air. But there is no doubt modern waste-to-energy burners have come a long way since the Seventies."

Whether or not they pose any threat to human health is a controversial issue. Simply pointing out that toxic emissions are so low as to be negligible, as recently revealed in a report by the National Society of Clean Air and Environmental Protection, is unlikely to appease protesters, who do not want to live near an incinerator.

Nor is it likely to comfort the people living near Byker in Newcastle who were told in the late Seventies the incinerator being built near their homes would be totally safe, only for tons of ash - allegedly including highly toxic dioxins - to fall on paths, parks and allotments across the city. The full extent of the problem was only revealed last year.

There is no doubt modern incinerators are cleaner and safer today, with toxic ash reduced to a minimum and smoke from stacks undergoing a treatment of neutralisation before it is pumped out into the air.

Up to 180 sealed lorries a day drive into the Rouen plant to unload 350,000 tons of domestic rubbish per year into a giant pit inside the building.

The waste is spread by two giant grabbers, operated by controllers who monitor the waste for batteries and other toxic objects. A conveyor belt then pushes the rubbish into three burners, heated to 850 degrees.

The burning waste heats up boilers, which consist of four flow-paths that direct the gases produced from the combustion.

This produces steam, which is transformed into electricity by means of a turbo-alternator producing 32 megawatts of power. It is enough to supply 100,000 people for a year.

Smedar president Claude Laine said his plant's gas emissions were lower than the legal limits in the Netherlands, some of the most stringent in the world, and lower than any other European country.

But low emissions do not equal no emissions and the plant still pumps out a quantity of hydrochloric acid, carbon monoxide, organic compounds, heavy metals, hydrofluoric acid, sulphur dioxide, nitrogen oxides and other dioxins and furans.

The majority of ash produced is inert and bagged up and sold to construction firms for use on building sites or roads. Toxic ash is sealed in containers and sent off to landfill sites.

Councillor Ann Norman, chairman of Brighton Pavilion Conservatives, said: "I was fairly satisfied with the safety of the site. There was little smell and emissions seemed well controlled.

"The main problem would be finding a suitable site to cope with such a large operation. It would have to be away from built-up areas and should fit into the landscape."

Labour councillor Pat Murphy said the visit did not change his mind about any incinerator plan.

He said: "The technology was impressive but my fundamental feeling is that incinerators must produce toxins into the atmosphere. Recycling should be the way forward."

Brighton and Hove's policy committee this week agreed to improve recycling targets for the authorities covered by the waste plan for the county.

Targets now range from 20 per cent of waste to be recycled by 2003 and 40 per cent by 2015. The current figure is about 11 per cent.