An army of road sweepers and refuse collectors keep the streets clean in the heart of Hong Kong — but on the outskirts, growing mountains of waste are testament to what campaigners say is an environmental crisis.

While the city may look well-kept, its three huge outdoor landfill sites are piled high with rubbish and are set to reach capacity by 2020, according to the government’s Environmental Protection Department (EPD).

Some predictions say the first will be full in a year or two.

“We need to have a clear roadmap for waste reduction, otherwise our rubbish will be on the streets in seven years’ time,” environmental scientist Professor Jonathan Wong, of the Hong Kong Baptist University , told AFP.

The majority of the 13,000 tonnes of rubbish dumped at landfills in Hong Kong each day is termed ‘municipal solid waste’ (MSW), generated by households, business and industry.