Students feel uneasy looking at the life-size "waste wall".

Apart from reducing waste volume, Prof Lo said waste-to-energy facilities have other benefits. The planned incineration facility is expected to treat 3,000 tonnes of solid waste a day. Based on this, the government estimates that it would produce about 480 million Kwh a year -- enough to supply electricity for about 100,000 homes, she said. This can reduce coal-fired electricity generation and cut greenhouse gases, she said.

Some critics have suggested the use of plasma gasification technology for the incinerator, Prof Lo said. While the technology is clean in theory, its reliability and safety are still unproven.

"Currently there are only 15 plasma gasification plants in the world. And out of these 15 plants, only four plants are used for municipal solid waste treatment," she said.

The four plants' capacity ranges from 15 to 220 tonnes a day. The largest of the four is in Japan, and it was shut down in December 2012.

"There is limited reliable information for us to judge whether this technology is proven technology," said Prof Lo, adding Hong Kong cannot afford to pick the wrong technology due to our imminent waste crisis.

To avert the crisis, Prof Lo also believes it is necessary to expand the city's landfills. "Some people think that the Hong Kong Government should pay more attention to waste reduction, recycling and reuse. This is the first priority. However, it won't be the one and only solution to the solid waste management problem," she said.

"No matter how much people do to reduce waste, there are some things not worth recycling. And even if there is an incinerator, it will eventually produce ash. Landfills are needed as the final step for solid waste disposal."

The bureau has proposed to expand all three landfills, which will be full from next year if things remain unchanged. A series of improvement measures are or will be in place to reduce nuisance around the landfills, including subsidising the retrofitting of all private refuse trucks with equipment that prevents liquid leakage and alleviates odours.

It is also stepping up enforcement against refuse trucks that cause hygiene and overloading problems, and is boosting air quality monitoring at Wan Po Road.

Mrs Li offers practical advice.

"Hong Kong has a growing population. More people create more rubbish. If we oppose the incinerator's construction, there is no way to dispose of rubbish. The landfills will be exhausted one day. The Government and Hong Kong people must work together to solve this problem."