Questions 57 to 61 are based on the following passage.
Within fif years Britain and other nations should be well on with the building of huge industrial architectures for the recycling of waste. The word rubbish could lose its meaning because everything which goes into the dumps would be made into something useful. Even the most erous and unpleasant wastes would provide energy if nothing else.
The latest project is to take a city of around half a million residents and discover exactly what raw materials go into it and what go out. The aim is to find out how much of these raw materials could be provided if a plant for recycling waste were built just outside the city. This plant would recycle not only metal such as steel, lead and copper, but also paper and rubber as well.
Another new project is being set up to discover the best ways of sorting and separating the rubbish. When this project is completed, the rubbish will be processed like this: first, it will pass through a powerful fan to separate the lightest elements from the heavy solids; after that grounders and rollers break up everything that can be broken. Finally, the rubbish will pass under magnets (磁铁), which will remove the bits of iron and steel ; the rubber and plastic will then be sorted out in the final stage.
The first full-scale giant recycling plants are, perhaps, fif years away. Indeed, with the growing cost of transporting rubbish to more distant dumps, some big cities will be forced to build their own recycling plants before long.
Questions 57 to 61 are based on the following passage.The passage is mainly about ______.