Recycling, reuse and disposal of materials

Is a long-life juice carton made of card? It looks like card, it feels like card, and most people drop it in with the paper. But bonded inside it are a thin layer of polythene and a layer of aluminium foil. Only specialist plants can pull those layers apart. The carton that looks so easy to recycle is far harder to recycle than it looks. The carton's trouble makes sense once you see what recycling does to a material.

Recycling means collecting a used product, breaking it down, and reprocessing its material into raw material for new products. Metal and glass are melted down. Paper is pulped with water. Some polymers can be melted and formed again. Follow one aluminium drinks can. It is collected, sorted from the other rubbish, and shredded into small pieces. The pieces are melted, and the liquid metal is cast into new sheet, ready to become new cans. Now a reason: why is the can sorted from everything else before it is melted? Because recycling reprocesses one material at a time. Steel, paper or plastic mixed into the melt would spoil the new aluminium. Metals like steel and aluminium can be recycled again and again without losing their properties. Two of recycling's benefits are plain to see. Fewer raw materials are dug up: every recycled can means less bauxite mined, and bauxite is finite. And less waste goes to landfill, because the can becomes a new can instead of lying buried in the ground for years. Recycling still has a cost. Collecting, sorting, transporting and reprocessing all use energy, which is why re-use and repair come before it.

A bike maker switches its frames from new aluminium to recycled aluminium, and two students explain one benefit. The first writes: it is better for the environment. The second writes: recycled aluminium only has to be remelted, which takes far less energy than extracting new aluminium from bauxite ore. So less fossil fuel is burnt, and less carbon dioxide is released. Which of the two answers scores, and what is the first one missing? The answer about remelting. It gives the benefit, the reason behind it, and what it does for the planet. The first is true, but it never says why. One examiner's report records this: The majority of candidates were able to provide a response related to being better for the environment however candidates often failed to provide a correct linked justification. The fix is never to stop at better for the environment: name what is saved, why it is saved, and what that does for the planet. Here is a second linked benefit for the same frames: no new bauxite has to be mined, so less land is dug up and fewer habitats are lost.

Recycling reprocesses one material at a time, and that is where the carton from the start runs into trouble. Its card, its polythene and its aluminium foil are each recyclable on their own. Bonded together in thin layers, they cannot go through any one process, so the carton needs a specialist plant to pull them apart. Dirt and food make it harder too: grease from a pizza box can spoil a batch of paper pulp. And some polymers set permanently when they are made, like the melamine of a picnic plate, so they can never be remelted. Now a crisp packet: polymer film, aluminium bonded inside. Why is it hard to recycle? The polymer and the aluminium are stuck together in very thin layers and cannot easily be separated. Recycling reprocesses one material at a time, so the packet fits neither process, and usually ends up in landfill or burned. Recyclable and biodegradable are two different words. Recyclable means people reprocess the material into new material, like a steel can. Biodegradable means nature breaks it down, like a paper-pulp plant pot that goes straight into the soil. Now another: a glass jam jar. Is it recyclable or biodegradable, and why? Recyclable. Glass does not rot away in the soil, but it can be crushed, melted and made into new jars many times over. One examiner's report, on a question about paper pulp, notes this: Other candidate responses stated the paper pulp could be recycled which did not achieve a mark. Paper pulp can be recycled, so that answer was true, but it missed the pulp's real advantage here: it breaks down naturally. The fix is to choose the word that fits the product. If nature breaks it down, say biodegradable, and say what that saves.

When a product is finished with, it leaves by one of four routes: re-used, recycled, sent to landfill, or burned. Re-use, including upcycling, keeps the whole product working, so nothing new is made. Recycling recovers the material, at an energy cost. Landfill takes up space for years, materials break down slowly, and harmful substances can leak into the ground and water. Burning shrinks the waste, but releases fumes and carbon dioxide. Now try this: put the four routes in order of preference, best first. Re-use comes first, then recycling, once re-use and repair are no longer possible. The two that lose the material come last. Recycling figures are compared as a percentage change. A percentage increase is the increase, divided by the original amount, times one hundred. The original is the earlier figure, the one you started from. A council records the tonnes of drinks cans it collects for recycling, in two thousand and nineteen and again five years later. The answer is wanted to one decimal place. Eighteen thousand tonnes rose to twenty-five thousand. What is the percentage increase? Step one, the increase. Twenty-five thousand tonnes take away eighteen thousand tonnes is seven thousand tonnes. Step two, divide by the original amount, the eighteen thousand from two thousand and nineteen. Seven thousand divided by eighteen thousand is nought point three eight eight eight, and the eights go on. The tonnes cancel. Step three, times one hundred. That gives thirty-eight point eight eight eight per cent, with the eights still going on. Step four, round once, at the end, to one decimal place. The answer is thirty-eight point nine per cent. Now a different check: what goes wrong if you divide by twenty-five thousand instead? You get twenty-eight per cent, which is wrong. A percentage change is measured against where you started, and that is the eighteen thousand. One examiner's report, on a question about composite food and drink containers whose second part asked for a percentage increase in recycling, records that both parts were answered very well. So the method is within reach. The habit that protects it is circling the original figure before you divide.

A short test now, from a single tin all the way back to the carton. Can you give one benefit of recycling a steel food tin, linked through to the planet? Less iron ore is mined, because the steel is remelted instead, so less land is dug up and less energy is used. Now another: a card tray with polythene film glued on. What stops it being recycled? The card and the film are bonded, so an ordinary plant cannot pull them apart, and recycling takes one material at a time. Here's a sum: two thousand tonnes rose to twenty-five hundred. The percentage increase? Twenty-five per cent. The increase is five hundred tonnes. Five hundred divided by the original two thousand is nought point two five, and times one hundred, that is twenty-five per cent. Now the last one: the long-life juice carton. Why is it so hard to recycle? Card, polythene and aluminium foil are bonded in thin layers. Recycling takes one material at a time, so only a specialist plant can pull them apart.

If you can walk a can through recycling and work the percentage, this one's done, and a thumbs up lets you pass it by next time. If not, keep the video saved: three practice questions in, it starts to feel normal.

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