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Which materials are worth recycling?

From the most basic environmental point of view, all materials are worth recycling, because this reduces the need for energy-intensive mining and smelting of virgin materials. That makes a huge difference for some things – notably aluminium – but even recycling glass leads to a small energy saving and consequent reduction in greenhouse gas emissions. Recycling can also provide a reliable, non-imported source of scarce resources such as the rare earth metals that are crucial parts of touchscreens and other high-tech devices.

However, the answer gets muddier when we consider economics. The price of recycled material fluctuates wildly, and some often aren’t profitable to recycle, especially if the recovered material has to be shipped long distances to a reprocessing plant. Waste managers often have to pay recyclers to take glass off their hands, for example. That can make virgin glass look like a better deal – but only because we often fail to include the environmental costs of mining sand and the carbon emissions from glassmaking furnaces. Similarly, plastics are often reprocessed in China, so proximity to a seaport may dictate whether it is profitable to recycle them.

Other low-value materials such as wood and textiles need to be clean to be recyclable. The extra effort and expense required to separate them from general waste means they often end up in landfill.

Can we make landfill greener?

Landfill sites emit methane, a potent greenhouse gas. A growing number capture this and convert it to energy but even in the most efficient systems up to 10 per cent escapes. In the US landfill accounts for 18 per cent…