Environment: 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 i960 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 kerb-side 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 iom-i5m 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 Deutsch-land (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