As the importance of recycling becomes more apparent, questions about it linger. Is it worth the effort? How does it work? Is recycling waste just going into a landfill in China? Here are some answers

IT IS an awful lot of rubbish. Since 1960 the amount of municipal waste being collected in America has nearly tripled, reaching 245m tonnes in 2005. According to European Union statistics, the amount of municipal waste produced in western Europe increased by 23% between 1995 and 2003, to reach 577kg per person. (So much for the plan to reduce waste per person to 300kg by 2000.) As the volume of waste has increased, so have recycling efforts. In 1980 America recycled only 9.6% of its municipal rubbish; today the rate stands at 32%. A similar trend can be seen in Europe, where some countries, such as Austria and the Netherlands, now recycle 60% or more of their municipal waste. Britain's recycling rate, at 27%, is low, but it is improving fast, having nearly doubled in the past three years.

Even so, when a city introduces a kerbside recycling programme, the sight of all those recycling lorries trundling around can raise doubts about whether the collection and transportation of waste materials requires more energy than it saves. “We are constantly being asked: Is recycling worth doing on environmental grounds?” says Julian Parfitt, principal analyst at Waste & Resources Action Programme (WRAP), a non-profit British company that encourages recycling and develops markets for recycled materials.

Studies that look at the entire life cycle of a particular material can shed light on this question in a particular case, but WRAP decided to take a broader look. It asked the Technical University of Denmark and the Danish Topic Centre on Waste to conduct a review of 55 life-cycle analyses, all of which were selected because of their rigorous methodology. The researchers then looked at more than 200 scenarios, comparing the impact of recycling with that of burying or burning particular types of waste material. They found that in 83% of all scenarios that included recycling, it was indeed better for the environment.

Based on this study, WRAP calculated that Britain's recycling efforts reduce its carbon-dioxide emissions by 10m-15m tonnes per year. That is equivalent to a 10% reduction in Britain's annual carbon-dioxide emissions from transport, or roughly equivalent to taking 3.5m cars off the roads. Similarly, America's Environmental Protection Agency estimates that recycling reduced the country's carbon emissions by 49m tonnes in 2005.

Recycling has many other benefits, too. It conserves natural resources. It also reduces the amount of waste that is buried or burnt, hardly ideal ways to get rid of the stuff. (Landfills take up valuable space and emit methane, a potent greenhouse gas; and although incinerators are not as polluting as they once were, they still produce noxious emissions, so people dislike having them around.) But perhaps the most valuable benefit of recycling is the saving in energy and the reduction in greenhouse gases and pollution that result when scrap materials are substituted for virgin feedstock. “If you can use recycled materials, you don't have to mine ores, cut trees and drill for oil as much,” says Jeffrey Morris of Sound Resource Management, a consulting firm based in Olympia, Washington.

Extracting metals from ore, in particular, is extremely energy-intensive. Recycling aluminium, for example, can reduce energy consumption by as much as 95%. Savings for other materials are lower but still substantial: about 70% for plastics, 60% for steel, 40% for paper and 30% for glass. Recycling also reduces emissions of pollutants that can cause smog, acid rain and the contamination of waterways.

A brief history of recycling

The virtue of recycling has been appreciated for centuries. For thousands of years metal items have been recycled by melting and reforming them into new weapons or tools. It is said that the broken pieces of the Colossus of Rhodes, a statue deemed one of the seven wonders of the ancient world, were recycled for scrap. During the industrial revolution, recyclers began to form businesses and later trade associations, dealing in the collection, trade and processing of metals and paper. America's Institute of Scrap Recycling Industries (ISRI), a trade association with more than 1,400 member companies, traces its roots back to one such organisation founded in 1913. In the 1930s many people survived the Great Depression by peddling scraps of metal, rags and other items. In those days reuse and recycling were often economic necessities. Recycling also played an important role during the second world war, when scrap metal was turned into weapons.

As industrial societies began to produce ever-growing quantities of garbage, recycling took on a new meaning. Rather than recycling materials for purely economic reasons, communities began to think about how to reduce the waste flow to landfills and incinerators. Around 1970 the environmental movement sparked the creation of America's first kerbside collection schemes, though it was another 20 years before such programmes really took off.

In 1991 Germany made history when it passed an ordinance shifting responsibility for the entire life cycle of packaging to producers. In response, the industry created Duales System Deutschland (DSD), a company that organises a separate waste-management system that exists alongside public rubbish-collection. By charging a licensing fee for its “green dot” trademark, DSD pays for the collection, sorting and recycling of packaging materials. Although the system turned out to be expensive, it has been highly influential. Many European countries later adopted their own recycling initiatives incorporating some degree of producer responsibility.

In 1987 a rubbish-laden barge cruised up and down America's East Coast looking for a place to unload, sparking a public discussion about waste management and serving as a catalyst for the country's growing recycling movement. By the early 1990s so many American cities had established recycling programmes that the resulting glut of materials caused the market price for kerbside recyclables to fall from around $50 per ton to about $30, says Dr Morris, who has been tracking prices for recyclables in the Pacific Northwest since the mid-1980s. As with all commodities, costs for recyclables fluctuate. But the average price for kerbside materials has since slowly increased to about $90 per ton.

Even so, most kerbside recycling programmes are not financially self-sustaining. The cost of collecting, transporting and sorting materials generally exceeds the revenues generated by selling the recyclables, and is also greater than the disposal costs. Exceptions do exist, says Dr Morris, largely near ports in dense urban areas that charge high fees for landfill disposal and enjoy good market conditions for the sale of recyclables.

Sorting things out

Originally kerbside programmes asked people to put paper, glass and cans into separate bins. But now the trend is toward co-mingled or “single stream” collection. About 700 of America's 10,000 kerbside programmes now use this approach, says Kate Krebs, executive director of America's National Recycling Coalition. But the switch can make people suspicious: if there is no longer any need to separate different materials, people may conclude that the waste is simply being buried or burned. In fact, the switch towards single-stream collection is being driven by new technologies that can identify and sort the various materials with little or no human intervention. Single-stream collection makes it more convenient for householders to recycle, and means that more materials are diverted from the waste stream.

San Francisco, which changed from multi to single-stream collection a few years ago, now boasts a recycling rate of 69%—one of the highest in America. With the exception of garden and food waste, all the city's kerbside recyclables are sorted in a 200,000-square-foot facility that combines machines with the manpower of 155 employees. The $38m plant, next to the San Francisco Bay, opened in 2003. Operated by Norcal Waste Systems, it processes an average of 750 tons of paper, plastic, glass and metals a day.

The process begins when a truck arrives and dumps its load of recyclables at one end of the building. The materials are then piled on to large conveyer belts that transport them to a manual sorting station. There, workers sift through everything, taking out plastic bags, large pieces of cardboard and other items that could damage or obstruct the sorting machines. Plastic bags are especially troublesome as they tend to get caught in the spinning-disk screens that send weightier materials, such as bottles and cans, down in one direction and the paper up in another.

Corrugated cardboard is separated from mixed paper, both of which are then baled and sold. Plastic bottles and cartons are plucked out by hand. The most common types, PET (type 1) and HDPE (type 2), are collected separately; the rest go into a mixed-plastics bin.

Next, a magnet pulls out any ferrous metals, typically tin-plated or steel cans, while the non-ferrous metals, mostly aluminium cans, are ejected by eddy current. Eddy-current separators, in use since the early 1990s, consist of a rapidly revolving magnetic rotor inside a long, cylindrical drum that rotates at a slower speed. As the aluminium cans are carried over this drum by a conveyer belt, the magnetic field from the rotor induces circulating electric currents, called eddy currents, within them. This creates a secondary magnetic field around the cans that is repelled by the magnetic field of the rotor, literally ejecting the aluminium cans from the other waste materials.

Finally, the glass is separated by hand into clear, brown, amber and green glass. For each load, the entire sorting process from start to finish takes about an hour, says Bob Besso, Norcal's recycling-programme manager for San Francisco.

Although all recycling facilities still employ people, investment is increasing in optical sorting technologies that can separate different types of paper and plastic. Development of the first near-infra-red-based waste-sorting systems began in the early 1990s. At the time Elopak, a Norwegian producer of drink cartons made of plastic-laminated cardboard, worried that it would have to pay a considerable fee to meet its producer responsibilities in Germany and other European countries. To reduce the overall life-cycle costs associated with its products, Elopak set out to find a way to automate the sorting of its cartons. The company teamed up with SINTEF, a Norwegian research centre, and in 1996 sold its first unit in Germany. The technology was later spun off into a company now called TiTech.

TiTech's systems—more than 1,000 of which are now installed worldwide—rely on spectroscopy to identify different materials. Paper and plastic items are spread out on a conveyor belt in a single layer. When illuminated by a halogen lamp, each type of material reflects a unique combination of wavelengths in the infra-red spectrum that can be identified, much like a fingerprint. By analysing data from a sensor that detects light in both the visible and the near-infra-red spectrum, a computer is able to determine the colour, type, shape and position of each item. Air jets are then activated to push particular items from one conveyor belt to another, or into a bin. Numerous types of paper, plastic or combinations thereof can thus be sorted with up to 98% accuracy.

For many materials the process of turning them back into useful raw materials is straightforward: metals are shredded into pieces, paper is reduced to pulp and glass is crushed into cullet. Metals and glass can be remelted almost indefinitely without any loss in quality, while paper can be recycled up to six times. (As it goes through the process, its fibres get shorter and the quality deteriorates.)

Plastics, which are made from fossil fuels, are somewhat different. Although they have many useful properties—they are flexible, lightweight and can be shaped into any form—there are many different types, most of which need to be processed separately. In 2005 less than 6% of the plastic from America's municipal waste stream was recovered. And of that small fraction, the only two types recycled in significant quantities were PET and HDPE. For PET, food-grade bottle-to-bottle recycling exists. But plastic is often “down-cycled” into other products such as plastic lumber (used in place of wood), drain pipes and carpet fibres, which tend to end up in landfills or incinerators at the end of their useful lives.

Even so, plastics are being used more and more, not just for packaging, but also in consumer goods such as cars, televisions and personal computers. Because such products are made of a variety of materials and can contain multiple types of plastic, metals (some of them toxic), and glass, they are especially difficult and expensive to dismantle and recycle.

Europe and Japan have initiated “take back” laws that require electronics manufacturers to recycle their products. But in America only a handful of states have passed such legislation. That has caused problems for companies that specialise in recycling plastics from complex waste streams and depend on take-back laws for getting the necessary feedstock. Michael Biddle, the boss of MBA Polymers, says the lack of such laws is one of the reasons why his company operates only a pilot plant in America and has its main facilities in China and Austria.

Much recyclable material can be processed locally, but ever more is being shipped to developing nations, especially China. The country has a large appetite for raw materials and that includes scrap metals, waste paper and plastics, all of which can be cheaper than virgin materials. In most cases, these waste materials are recycled into consumer goods or packaging and returned to Europe and America via container ships. With its hunger for resources and the availability of cheap labour, China has become the largest importer of recyclable materials in the world.

The China question

But the practice of shipping recyclables to China is controversial. Especially in Britain, politicians have voiced the concern that some of those exports may end up in landfills. Many experts disagree. According to Pieter van Beukering, an economist who has studied the trade of waste paper to India and waste plastics to China: “as soon as somebody is paying for the material, you bet it will be recycled.”

In fact, Dr van Beukering argues that by importing waste materials, recycling firms in developing countries are able to build larger factories and achieve economies of scale, recycling materials more efficiently and at lower environmental cost. He has witnessed as much in India, he says, where dozens of inefficient, polluting paper mills near Mumbai were transformed into a smaller number of far more productive and environmentally friendly factories within a few years.

Still, compared with Western countries, factories in developing nations may be less tightly regulated, and the recycling industry is no exception. China especially has been plagued by countless illegal-waste imports, many of which are processed by poor migrants in China's coastal regions. They dismantle and recycle anything from plastic to electronic waste without any protection for themselves or the environment.

The Chinese government has banned such practices, but migrant workers have spawned a mobile cottage industry that is difficult to wipe out, says Aya Yoshida, a researcher at Japan's National Institute for Environmental Studies who has studied Chinese waste imports and recycling practices. Because this type of industry operates largely under the radar, it is difficult to assess its overall impact. But it is clear that processing plastic and electronic waste in a crude manner releases toxic chemicals, harming people and the environment—the opposite of what recycling is supposed to achieve.

Under pressure from environmental groups, such as the Silicon Valley Toxics Coalition, some computer-makers have established rules to ensure that their products are recycled in a responsible way. Hewlett-Packard has been a leader in this and even operates its own recycling factories in California and Tennessee. Dell, which was once criticised for using prison labour to recycle its machines, now takes back its old computers for no charge. And last month Steve Jobs detailed Apple's plans to eliminate the use of toxic substances in its products.

Far less controversial is the recycling of glass—except, that is, in places where there is no market for it. Britain, for example, is struggling with a mountain of green glass. It is the largest importer of wine in the world, bringing in more than 1 billion litres every year, much of it in green glass bottles. But with only a tiny wine industry of its own, there is little demand for the resulting glass. Instead what is needed is clear glass, which is turned into bottles for spirits, and often exported to other countries. As a result, says Andy Dawe, WRAP's glass-technology manager, Britain is in the “peculiar situation” of having more green glass than it has production capacity for.

Britain's bottle-makers already use as much recycled green glass as they can in their furnaces to produce new bottles. So some of the surplus glass is down-cycled into construction aggregates or sand for filtration systems. But WRAP's own analysis reveals that the energy savings for both appear to be “marginal or even disadvantageous”. Working with industry, WRAP has started a new programme called GlassRite Wine, in an effort to right the imbalance. Instead of being bottled at source, some wine is now imported in 24,000-litre containers and then bottled in Britain. This may dismay some wine connoisseurs, but it solves two problems, says Mr Dawe: it reduces the amount of green glass that is imported and puts what is imported to good use. It can also cut shipping costs by up to 40%.

The future of recycling

This is an unusual case, however. More generally, one of the biggest barriers to more efficient recycling is that most products were not designed with recycling in mind. Remedying this problem may require a complete rethinking of industrial processes, says William McDonough, an architect and the co-author of a book published in 2002 called “Cradle to Cradle: Remaking the Way We Make Things”. Along with Michael Braungart, his fellow author and a chemist, he lays out a vision for establishing “closed-loop” cycles where there is no waste. Recycling should be taken into account at the design stage, they argue, and all materials should either be able to return to the soil safely or be recycled indefinitely. This may sound like wishful thinking, but Mr McDonough has a good pedigree. Over the years he has worked with companies including Ford and Google.

An outgrowth of “Cradle to Cradle” is the Sustainable Packaging Coalition, a non-profit working group that has developed guidelines that look beyond the traditional benchmarks of packaging design to emphasise the use of renewable, recycled and non-toxic source materials, among other things. Founded in 2003 with just nine members, the group now boasts nearly 100 members, including Target, Starbucks and Estée Lauder, some of which have already begun to change the design of their packaging.

Sustainable packaging not only benefits the environment but can also cut costs. Last year Wal-Mart, the world's biggest retailer, announced that it wanted to reduce the amount of packaging it uses by 5% by 2013, which could save the company as much as $3.4 billion and reduce carbon-dioxide emissions by 667,000 tonnes. As well as trying to reduce the amount of packaging, Wal-Mart also wants to recycle more of it. Two years ago the company began to use an unusual process, called the “sandwich bale”, to collect waste material at its stores and distribution centres for recycling. It involves putting a layer of cardboard at the bottom of a rubbish compactor before filling it with waste material, and then putting another layer of cardboard on top. The compactor then produces a “sandwich” which is easier to handle and transport, says Jeff Ashby of Rocky Mountain Recycling, who invented the process for Wal-Mart. As well as avoiding disposal costs for materials it previously sent to landfill, the company now makes money by selling waste at market prices.

EPA

It does get recycled, honest

Evidently there is plenty of scope for further innovation in recycling. New ideas and approaches will be needed, since many communities and organisations have set high targets for recycling. Europe's packaging directive requires member states to recycle 60% of their glass and paper, 50% of metals and 22.5% of plastic packaging by the end of 2008. Earlier this year the European Parliament voted to increase recycling rates by 2020 to 50% of municipal waste and 70% of industrial waste. Recycling rates can be boosted by charging households and businesses more if they produce more rubbish, and by reducing the frequency of rubbish collections while increasing that of recycling collections.

Meanwhile a number of cities and firms (including Wal-Mart, Toyota and Nike) have adopted zero-waste targets. This may be unrealistic but Matt Hale, director of the office of solid waste at America's Environmental Protection Agency, says it is a worthy goal and can help companies think about better ways to manage materials. It forces people to look at the entire life-cycle of a product, says Dr Hale, and ask questions: Can you reduce the amount of material to begin with? Can you design the product to make recycling easier?

If done right, there is no doubt that recycling saves energy and raw materials, and reduces pollution. But as well as trying to recycle more, it is also important to try to recycle better. As technologies and materials evolve, there is room for improvement and cause for optimism. In the end, says Ms Krebs, “waste is really a design flaw.”