This week's question: If Hong Kong ran out of places to put its rubbish in a few months, how would you solve the city's waste woes?

Benjamin Allan, 16, La Salle College

One of the major causes of waste is the murky definition of rubbish. Rubbish exists only if we label it as rubbish. Half the battle is to not let things become trash - find different uses for it!

We also need to rethink how we dump waste. It's left to rot in giant heaps. If we compacted and stacked it, we would save space and need smaller landfills. Or we could build rubbish skyscrapers - remember Disney's Wall-E?

Arthur Chan, 17, Li Po Chun United World College

I guess the problem with the average household's waste is that it all adds up. When we throw a tissue away, it is just a small, crumpled feather-weight piece of garbage. We never foresee the packed rubbish bag it will become a part of. My solution is to put the problem right in front of the troublemaker's eyes. Each rubbish bag would have to stay in a bedroom for five days before it can be disposed of. When we see the problem, we'll realise the importance of throwing away less and conserving more.

Caleb Lin, 17, United Christian College, Kowloon East

Waste and space are two of Hong Kong's biggest problems. My suggestion is to use waste as landfill or reclamation material. We have lost so much land, with melting glaciers and so on. I'm not saying we should ignore the causes of rising sea levels, but we could at least get back the land. Using waste also fulfills the '3R's