Waste Disposal Methods
Open dumps release hazardous substances into the air and water
Often people dispose of waste by simply dropping it someplace. Open, unregulated dumps are still the predominant method of waste disposal in most developing countries, where government infrastructure, including waste collection, has difficulty serving growing populations. Giant megacities in the developing world have enormous garbage problems. Mexico City, one of the largest cities in the world, generates some 10,000 tons of trash each day. Until recently, most of this torrent of waste was left in giant piles, exposed to the wind and rain, as well as rats, flies, and other vermin. Manila, in the Philippines, has at least ten huge open dumps. The most notorious is called “Smoky Mountain” because of its constant smoldering fires. Thousands of people live and work on this 30 m high heap of refuse. They spend their days sorting through the garbage for edible or recyclable materials. Health conditions are abysmal, but these people have nowhere else to go, and the city has no current alternatives for waste disposal. Most developed countries forbid open dumping, at least in urban areas, but illegal dumping is still a problem. You have undoubtedly seen trash accumulating along roadsides and in vacant,
weedy lots. Is this just an aesthetic problem? No. Much of this trash washes into sewers and then into the ocean (see next section). Often illegally dumped garbage includes waste oil and solvents. An estimated 200 million liters of waste motor oil are poured into the sewers or allowed to soak into the ground every year in the United States. This is about five times as much as was spilled by the Exxon Valdez in Alaska in 1989! No one knows the volume of solvents and other chemicals disposed of by similar methods. Increasingly, these toxic chemicals are showing up in groundwater, on which nearly half of Americans depend for drinking. An alarmingly small amount of oil or other solvents can pollute large quantities of drinking or irrigation water. One liter of gasoline, for instance, can make a million liters of water undrinkable.
Ocean dumping is mostly uncontrolled
The oceans are vast, but they’re not large enough to absorb our waste without harm. Every year some 25,000 metric tons (55 million lbs) of packaging, including millions of bottles, cans, and plastic containers, are dumped at sea. Even in remote regions, beaches are littered with the nondegradable flotsam and jetsam. About 150,000 tons (330 million lbs) of fishing gear—including more than 1,000 km (660 mi) of nets—are lost or discarded at sea each year. An estimated 50,000 northern fur seals are entangled in this refuse and drown or starve to death every year in the North Pacific alone. Until recently, many cities in the United States dumped municipal refuse, industrial waste, sewage, and sewage sludge into the ocean. Federal legislation now prohibits this dumping. New York City, the last to stop offshore sewage sludge disposal, finally ended this practice in 1992. Plastic debris is a growing problem in all the world’s oceans. Millions of tons of plastic drink bottles, bottle caps, plastic shopping bags, and other debris end up at sea. Most is probably carelessly disarded litter and uncontained garbage, but there is also deliberate disposal at sea, especially from cruise ships and container ships. All this debris, floating just below the surface, accumulates in vast regions of slowly swirling ocean currents.
The Great Parcific Garbage Patch, discovered in 1997 by sailing captain Charles Moore, is the best known of these plastic debris fields. In all the world’s oceans, vast circulating currents known as gyres are driven by the earth’s rotation. These currents collect floating plastic debris, much of it tiny fragments, in regions thousands of km wide. The North Pacific gyre has captured at least 100 million tons of plastic. An estimated 80 percent of this debris originates from improper or accidental disposal of plastics on land. The remaining 20 percent is dumped or lost by ships at sea. All this plastic flotsam outweighs the living biomass in large parts of the Pacific and Atlantic oceans. Fish have been found with stomachs full of plastic fragments. Seabirds gulp down plastic debris, then regurgitate it for their chicks. With stomachs blocked by undigestible bottle caps, disposable lighters, and other fragments, chicks slowly starve to death. In one study of Laysan albatrosses, 90 percent of the carcasses of dead albatross chicks contained plastic. Oceanographers are trying to find ways of collecting or controlling this debris that is slowly starving ocean ecosystems. In 2010 the Plastiki, a catamaran built from discarded plastic drink bottles, did a worldwide tour to promote ocean conservation and publicize the problem of uncontrolled plastic waste. Most material is too fine-grained to capture easily in nets, and it is distributed widely around the world’s oceans. Growing awareness, however, is a first step toward resolving the problem. You can learn more by searching online for information on Plastiki or on the Pacific garbage gyre.
Landfills receive most of our waste
Currently, landfills receive 54 percent of all municipal solid waste in the United States, 33 percent is recycled, and 13 percent is incinerated. While we have a long way to go in controlling waste, this is a dramatic change from 1960, when 94 percent was land filled and only 6 percent was recycled.
A modern sanitary landfill is designed to contain waste. Operators are required to compact the refuse and cover it every day with a layer of dirt, to decrease smells and litter and to discourage insects and rats. This method helps control pollution, but the dirt fill also takes up as much as 20 percent of landfill space. Since 1994, all operating landfills in the United States have been required to control such hazardous substances as oil, chemical compounds, and toxic metals, that seep through piles of waste along with rain water. To prevent leakage to groundwater and streams, landfills require an impermeable clay and/or plastic lining. Drain- age systems are installed in and around the liner to catch drainage and to help monitor chemicals that leak out. Modern municipal solid waste landfills now have many of the safeguards of hazardous waste repositories.
Sanitary landfills also must manage methane, a greenhouse gas produced when organic material decomposes in the anerobic conditions deep inside a landfill. Landfills are the single largest anthropogenic source of methane in the United States. Globally, landfills are estimated to produce more than 700 million metric tons of methane annually. Because methane is 20 times as potent at absorbing heat as CO2, this represents about 12 percent of all greenhouse gas emissions. Until recently, almost all this landfill methane was simply vented into the air. Now about half of all landfill gas in the United States is either flared (burned) on site or is collected and used as fuel for electrical generation. Methane recovery in the United States produces 440 trillion Btu per year, and is equivalent.
We often export waste to countries ill-equipped to handle it
Most industrialized nations agreed to stop shipping hazardous and toxic waste to less-developed countries in 1989, but the practice still continues. In 2006, for example, 400 tons of toxic waste were illegally dumped at 14 open dumps in Abidjan, the capital of the Ivory Coast. The black sludge—petroleum wastes containing hydrogen sulfide and volatile hydrocarbons—killed ten people and injured many others. At least 100,000 city residents sought medical treatment for vomiting, stomach pains, nausea, breathing difficulties, nosebleeds, and headaches. The sludge—which had been refused entry at European ports—was transported by an Amsterdam based multinational company on a Panamanian-registered ship and handed over to an Ivorian firm (thought to be connected to corrupt government officials) to be dumped in the Ivory Coast. The Dutch company agreed to clean up the waste and pay the equivalent of (U.S.)$198 million to settle claims. Most of the world’s obsolete ships are now dismantled and recycled in poor countries. The work is dangerous, and old shipsoften are full of toxic and hazardous materials, such as oil, diesel fuel, asbestos, and heavy metals. On India’s Alang Beach, for example, more than 40,000 workers tear apart outdated vessels using crowbars, cutting torches, and even their bare hands. Metal is dragged away and sold for recycling. Organic waste is often simply burned on the beach, where ashes and oily residue wash back into the water. Discarded electronics, or e-waste, is one of the greatest sources of toxic material currently going to developing countries. There are at least 2 billion television sets and personal computers in use globally. Televisions often are discarded after only about five years, while computers, play-stations, cellular telephones, and other electronics become obsolete even faster. It’s estimated that 50 million tons of e-waste are discarded every year worldwide. Only about 20 percent of the components are currently recycled. The rest generally goes to open dumps or landfills. This waste stream contains at least 2.5 billion kg of lead, as well as mercury, gallium, germanium, nickel, palladium, beryllium, selenium, arsenic, and valuable metals, such as gold, silver, copper, and steel.
Until recently, most of this e-waste went to China, where villagers, including young children, would break it apart to retrieve valuable metals. Often, this scrap recovery was done under primitive conditions where workers had little or no protective gear.Health risks in this work are severe, especially for growing children. Soil, groundwater, and surface-water contamination at these sites is extremely high. Food grown in contaminated soils often contains toxic levels of lead and other metals.
Shipping e-waste to China is now officially banned, but illegal smuggling continues. With tighter regulation in China, informal e-waste recycling has shifted to India, Congo, and other areas with weak environmental regulation. Adding to the difficulty of this problem, these developing areas will soon be producing more e-waste than wealthier countries with better regulation. Will those developing areas be able to defend public health with this increase in waste production?
The Basel Action Network is an international network of activists seeking better controls on global trade in toxic materials. This group, named after the city where an international agreement was made banning the practice, tracks international e-waste shipments and working conditions. Exporting waste to poor communities also occurs within countries.
Incineration produces energy from trash
Faced with growing piles of garbage and a lack of available landfills at any price, many cities have built waste incinerators to burn municipal waste. Another term commonly used for this technology is energy recovery, or waste-to-energy, because the heat derived from incinerated refuse is a useful resource. Burning garbage can produce steam used directly for heating buildings or generating electricity. Internationally, well over 1,000 waste-to-energy plants in Brazil, Japan, and Western Europe generate much-needed energy while reducing the amount that needs to be landfilled. In the United States more than 110 waste incinerators burn 45,000 metric tons of garbage daily. Some of these are simple incinerators; others produce steam and/or electricity. Municipal incinerators are specially designed burning plants capable of burning thousands of tons of waste per day. In some plants, refuse is sorted as it comes in to remove unburnable or recyclable materials before combustion. This is called refuse derived fuel because the enriched burnable fraction has a higher energy content than the raw trash. Another approach, called mass burn, is to dump everything smaller than sofas and refrigerators into a giant furnace and burn as much as possible. This technique avoids the expensive and unpleasant job of sorting, but it produces more unburned ash and often produces more air pollution as plastics, batteries, and other mixed substances are burned. The cost-effectiveness of garbage incinerators is the subject of heated debates. Initial construction costs are high—usually.