People tossed all sorts of waste into these dumps. The dumps were breeding grounds for disease-carrying pests such as flies, mosquitoes, and rats. Rainwater flushed filthy, and sometimes poisonous, liquids from the dump into nearby streams and groundwater supplies that people used for drinking, bathing, and clothes washing.

Later, some towns spread dirt to contain the dumped waste and to discourage vermin. This helped, but it was little more than a cover-up for unsanitary dumping.

Today, we still bury our garbage, although not in the open dumps of yesterday. About 55 percent of our garbage is hauled off in garbage trucks and packed into sanitary landfills-making landfilling America's number one way of getting rid of its trash. (The other 45 percent is either recycled or burned.)

Although the nation as a whole has plenty of space to build landfills, some areas in the Northeast may be running out of room for new landfills. Obtaining permits to build new landfills has become increasingly difficult because of public opposition-people don't want landfills built in their backyards. And besides, a new landfill costs up to $10 million to build.

That's why some communities are looking for new ways to deal with solid waste-recycling and burning, for instance. But there will always be a need for landfills. Why? Because not all waste can be recycled or burned. How do you recycle a broken light bulb, and why burn it if it doesn't provide any heat energy?

Landfill burial is the only feasible way to dispose of some types of waste, and sometimes it's the safest way, too. Generally, the best disposal method for hazardous wastes-batteries, paints, pesticides, and the like-are state-of-the-art landfills. These landfills are designed to prevent hazardous wastes from seeping into underground water supplies.

Now that open dumping is illegal, deciding where to put a landfill requires careful planning. Skilled engineers inspect potential landfill sites. They look at a number of things including:

• the geology of the area
• the nature of the local environment
• how easy the site is to reach
• how far the site is from the area that generates the waste.

Work on a landfill site begins only after the site passes strict legal, environmental, and engineering tests. It is not a quick procedure; landfills can take five years to complete.

Modern Landfill

Today's landfills are very different from the open dumps of the past. For one thing, new landfills are situated where clay deposits and other land features act as natural buffers between the landfills and the surrounding environment.

Second, the bottom and sides of modern landfills are lined with layers of clay or plastic to keep the liquid waste, called leachate, from escaping into the soil.

A network of drains collects the leachate and pumps it to the surface where it can be treated. Ground wells are also drilled into and around the landfill to monitor groundwater quality and to detect any contamination. These safety measures keep ground water, which is the main source of drinking water in many communities, clean and pure.

To protect the environment even more, the landfill is divided into a series of individual cells. Only a few cells of the site (called the working face) are filled with trash at any one time, minimizing exposure to wind and rain.

At the end of each day's activities, workers spread a layer of earth--called the daily cover--over the waste to reduce odor and control vermin. The workers fill and cap each cell with a layer of clay and earth, and then seed the area with native grasses.

A Full Landfill

When a landfill is full, workers seal and cover the landfill with a final cap of clay and dirt. Workers continue to monitor the ground wells for years after a landfill is closed to keep tabs on the quality of groundwater on and around the site.

Old landfill sites can be landscaped to blend in with their surroundings, or specially developed to provide an asset to a community. Closed landfills can be turned into anything from parks to parking lots, from golf courses to ski slopes. Building homes and businesses on these sites is generally not permitted, though, since it can take many years for the ground to settle.

Biodegradation 

You have probably seen all sorts of consumer products, from paper bags to egg cartons, claim that they are biodegradable. What does biodegradable mean and are the claims true?

Biodegradation is a natural process. It happens when microorganisms, such as fungi or bacteria, secrete enzymes that chemically break down or degrade dead plants and animals. In other words, biodegradation is when waste decays or rots.

Most organic wastes are biodegradable under normal environmental conditions. Given enough time, the waste will disintegrate into harmless substances, enriching the soil with nutrients.

A landfill is not a normal environmental condition, though, nor is it intended to be. Instead, a landfill is more like a tightly sealed storage container. A landfill is designed to inhibit degradation to protect the environment from harmful contamination. Deprived of air and water, even organic wastes-like paper and grass clippings-degrade very slowly in a landfill.

Bioreactor Landfills 

A new approach to landfills is designing them so that organic waste is allowed to biodegrade. These landfills, called bioreactors, are different than most landfills used today.

One type of bioreactor is aerobic (with air). Leachate is removed from the bottom layer of the landfill and put into storage tanks. The leachate is then pumped back into the landfill, allowing it to flow over the waste repeatedly. Air is then added to the landfill. This type of bioreactor models normal air and moisture environmental conditions better than other landfills and encourages the natural process of biodegrading.

Another type of bioreactor is anaerobic (without air). In this type of landfill, air is not added, but the leachate is collected and pumped back into the landfill. Additional liquids may also be added to the leachate to help the waste biodegrade. Because the waste is broken down without oxygen, anaerobic bioreactors produce landfill gas, or methane, which can be used as an energy source.

Bioreactor landfills have advantages over traditional landfills. They reduce the cost of removing and disposing of leachated, which is used on site. Anaerobic bioreactors begin producing methane much more quickly than landfills designed to inhibit degradation. bioreactors also gain space as the waste degrades, meaning more waste can be added.

Landfill Energy 

Did you know that landfills can be sources of energy? Organic waste produces a gas called methane as it decomposes, or rots. Methane is the same energy-rich gas that is in natural gas, the fuel sold by natural gas utility companies. Methane gas is colorless and odorless. Natural gas utilities add an odorant so people can detect seeping gas, but it can be dangerous to people or the environment. New rules require landfills to collect methane gas as a pollution and safety measure.

Some landfills simply burn the methane gas in a controlled fashion to get rid of it. But the methane can be used as an energy source. Landfills can collect the methane gas, treat it, and then sell it as a commercial fuel; or they can burn it to generate steam and electricity. In 2003, East Kentucky Power Cooperative began recovering methane gas from three landfills. The utility uses the landfill gas to generate 8.8 megawatts of electricity, enough power 7,500-8,000 homes.

Today, there are almost 400 operating landfill gas energy projects in the United States. California has the most projects in operation with 73, followed by Illinois with 36 and Michigan with 27. The United States Environmental Protection Agency examined landfill conditions throughout the nation and almost every state has at least one landfill that would likely produce methane gas for energy use.