麻豆传媒

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 鈥� notably aluminium 鈥� 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鈥檛 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 鈥� 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 of methane emissions, making it the after the fossil-fuel industry and livestock.

鈥淚n the US, landfill accounts for 18 per cent of methane emissions, making it the third largest source鈥�

What鈥檚 more, most of the methane produced in landfill sites comes from organic waste, which can be disposed of in greener ways. The simplest is composting, but the carbon in organic waste can also be converted to carbon dioxide and carbon monoxide by high-temperature, high-pressure processes. This can then be reconstituted into liquid fuels such as ethanol or methanol, or used as feedstock in other industrial processes. In Edmonton, Canada, for example, one trash-to-methanol process is making headway. According to one calculation, the product has the smallest carbon footprint of any liquid fuel, when methane emissions avoided by not landfilling the waste are included.

Why do I have to separate my recyclables?

Keeping recyclables separate from the rest of your rubbish reduces contamination and makes recycling more effective. Recycling companies like it if we also segregate different types of recyclables because then they don鈥檛 have to incur the extra expense of doing this.

Separate collections of organic waste, recycling and other rubbish can make waste-handling more efficient. Kitchen waste is dense and self-compacting, so organics can be collected frequently with simple vehicles. With the stinky organics gone, recycling and other rubbish can be collected less often 鈥� even once a month or two 鈥� which makes more efficient use of expensive compactor trucks.

But the more complex the household sorting task becomes, the more likely householders are to give up and simply pitch something into the rubbish. As a result of this trade-off, local authorities often lump all recycling into a single bin, or just separate paper and cardboard from plastic, metal and glass.

What if my carefully segregated load is contaminated?

Everyone makes mistakes, and recyclers accept a certain amount of contamination. But too much of it can downgrade the quality of the batch and reduce the price reprocessors will pay. In practical terms, that means you should take reasonable steps to rinse and sort your recyclables according to your waste-management system鈥檚 protocol, but don鈥檛 obsess over every last decision.

Pay particular attention, however, to instructions on how to handle plastic wraps and plastic bags, because these can clog up the shredding and sorting machinery in some systems. If your local authority asks you not to put them in the recycling bin, don鈥檛.

Does recycling keep plastic from polluting the ocean?

Most of the plastic that ends up in the oceans is 鈥渓eakage鈥� 鈥� the stuff that gets tossed out of car windows, dropped on the street or otherwise escapes the waste management system. That accounts for 32 per cent of global plastic packaging. So, if plastic is recycled 鈥� or even sent to landfill or burned 鈥� it should stay out of the ocean.

Is burning rubbish in incinerators better than dumping it?

Incinerators reduce the volume of waste that might otherwise be dumped into landfill sites, and most also generate heat for electricity or heating homes. Modern waste-to-energy incinerators are very clean, so toxic emissions aren鈥檛 generally an issue. But then modern landfill sites generally don鈥檛 leach toxins into their environment either. Incinerators do, however, release a lot of carbon dioxide for every kilowatt-hour of electricity produced 鈥� more than many coal-fired power plants, in fact. And as the electricity grid shifts more towards renewables, burning trash to generate electricity is likely to look increasingly less attractive.

Another consideration is that burning waste may reduce levels of recycling. Cities that rely too heavily on incineration can find themselves trapped by the system鈥檚 demands. 鈥淭hese things are hungry,鈥� says Thomas Kinnaman, an environmental economist at Bucknell University in Pennsylvania. 鈥淭hey need lots and lots of fuel to stay efficient, and they鈥檙e increasingly looking at that recycling pile.鈥�

Is there any point to composting?

Composting is one of the most useful things you can do. Compacted, airless landfill sites are the perfect breeding ground for anaerobic bacteria called methanogens that feed on organic waste. For every kilogram they digest, they produce methane with a climate change impact equivalent to about 2 kilograms of carbon dioxide. That doesn鈥檛 happen in a compost bin. , two-thirds of which could have been composted. Separating kitchen scraps, garden waste and other organic waste from the rest of the rubbish stream means they can be used to generate high-quality compost to increase soil fertility for crops and gardens. Organic waste contaminated by household chemicals, glass, metal fragments and the like may only produce compost fit for restoring industrial sites and roadsides.

Isn鈥檛 鈥渞ecycling鈥� a misnomer?

Some materials, such as glass and aluminium, can be melted and recast into new products that are just as good as those from virgin material. But others can only be 鈥渄owncycled鈥� into products of lower quality than the original. Each time paper is recycled, for example, its fibres break into shorter lengths so it can be used only for increasingly low-quality papers such as newspaper and toilet paper. Most plastics are downcycled into products that cannot themselves be recycled. In fact, only about 15 per cent of recycled plastics end up in products of similar quality. Researchers are working on finding new ways to chemically break down plastics into their component molecules so that they can be rebuilt into high-quality material.

There is a move to redesign products and packaging to minimise waste. In the meantime, environmentally aware consumers can reduce, reuse, avoid disposable items and repair broken ones instead of throwing them away.

This article appeared in print under the headline 鈥淲aste not 鈥�?鈥�