Trash: What a Waste
When items that are no longer needed aren't reused or recycled, chances are they will end up in the trash. Just a generation ago, it was common to toss trash into sinkholes or spent mining pits or quarries, but now garbage is disposed of in highly engineered landfills or burned in incinerators.
The EPA reports that over the past thirty-five years the amount of waste generated for each person has increased from 2.7 to 4.4 pounds per day. This adds up to over 236 million tons of municipal solid waste annually in the United States, double what was thrown away in 1980.
Federal legislation involving solid waste or garbage was initially enacted in 1966 and was born out of a need to protect human health more than the environment. Garbage was put in open dumps where pigs were allowed to scavenge and flies continued to breed. Much of the garbage was then burned with no real controls in place.
The Resource Conservation and Recovery Act was passed in 1976 and amended in 1984. States are now obligated to enforce either federal regulations or more stringent local laws for managing garbage. All solid waste facilities, both landfills and incinerators, are permitted by state or federal agencies and are required to be operated according to the applicable laws.
The Life of a Landfill
Most discarded waste is disposed of in landfills with strict guidelines for construction, operation, and closure when the landfill has reached its allowable height. The groundwater, surface water, and air around the facility must be monitored, even if it is no longer operating.
As waste decomposes in a landfill, it produces a liquid called leachate. The leachate drains through the waste and collects on a liner of plastic sheeting in the bottom of the landfill. Leachate is usually pumped to storage tanks at the landfill facility and is later either pumped or trucked to a wastewater treatment plant. Because little was known about what happened when waste degraded, older landfills were not required to have bottom liners, and the leachate was able to migrate into the ground where it contaminated groundwater or surface water.
Decomposition also produces methane, a dangerous greenhouse gas. Methane can be collected through piping and used to generate electricity; however, there is a limited time in landfill life when this is economically feasible as methane generation peaks and then decreases. Vents are constructed on top of landfills that go into the waste and allow the gas to either disperse into the air or be collected and burned. The size of the landfill and the volume of gas produced dictate how methane is handled.
Bioreactor landfills, a recent advance in solid waste, have piping and pumps that recirculate the leachate from the bottom of the landfill back to the top so it can again drain through the waste. This practice provides liquid that microorganisms need to degrade the waste, speeding up the process of decay and allowing the waste to settle or become more compact in less time. Because landfill height is one of the limiting factors for operation, compacting the waste allows for more garbage to be buried within the landfill.
The number of landfills has decreased over time, but their size has increased. Finding a place to construct a landfill is difficult because it doesn't make a pleasant neighbor. So rather than try to locate new landfills, municipalities are choosing to expand the landfills they already have. Instead of operating a landfill, many municipalities would rather send their waste to other counties or even to other states.
The Burning Issue of Incinerators
About 14 percent of collected solid waste goes to incinerators where it's burned at very high temperatures, which destroys bacteria and certain chemicals. However, incineration also produces air contaminants like nitrogen oxides, sulfur dioxides, mercury compounds, dioxins, and carbon dioxide. The composition of the waste incinerated affects the types and quantities of compounds emitted. Pollution equipment is required at all incinerators, but strict adherence to operations must be maintained for the incinerator and pollution equipment to work properly.
Backyard burning isn't such a great idea either. Depending on where you live, you may be able to burn waste in your own backyard in a barrel or a pit. Unless the waste is burned in an incinerator, the high temperatures needed to safely break down dangerous chemicals won't be reached, which could cause the release of chemicals like dioxin. For a safer alternative, try composting.
Ash is produced as part of the incineration process. Bottom ash, the remnants of the burned material, remains in the incinerator. Fly ash is lighter particulate matter that floats up the stack of the incinerator. Stacks are required to capture the fly ash before it escapes. Both types of ash are usually disposed of in landfills; this is a concern for workers and nearby residents because it can be difficult to manage the light material. Contamination — namely, from metals and organics such as dioxins and furans — is also a concern because it can trickle from the ash into the leachate and potentially into the groundwater and surface water.
Waste-to-energy plants generate power from garbage that is incinerated and use the heat to generate steam and produce electricity. Construction of these plants is very expensive, but as the cost of energy continues to rise and the space for new landfills becomes harder to find, these facilities may become a more popular disposal approach.
