ou know, I produce a lot of garbage (and no, I’m not talking about this column). I’m not alone, either: Canadians produce more garbage per capita than any other nation in the world. Regina alone produces, on average, 600 tons of residential waste a day. That garbage has to go somewhere, and in most communities, that “somewhere” is a landfill.
In the most common kind of landfill, trash is dumped in a hole in the ground, spread out in layers, compacted as tightly as possible, and then covered with soil. Each completely covered, compacted unit of waste is called a cell; in Regina’s landfill, by way of example, each cell consist of three metres of garbage covered with a metre of dirt. Adjoining cells, all the same height, make up a “lift”; lifts are built on top of each other until the landfill is complete.
As soon as the garbage is in the landfill, it begins to change.
The first change is compaction. Not only is it compacted as it’s deposited, but as more and more garbage is piled on top of it, it compacts further. Even a well-compacted landfill may settle 15 percent; a poorly compacted one may settle 25 percent.
Next, some of the garbage begins to decompose, passing through three different stages, each involving different bacteria. At first, it’s aerobic bacteria (which means they use oxygen, not that they wear spandex and sweat a lot) who eat away at the waste, producing carbon dioxide, water and nitrate. As the oxygen is used up, anaerobic (non-oxygen-using) microbes get into the act, producing acids (which begin to dissolve some of the inorganic material) and more carbon dioxide. Finally, methane-producing anaerobic bacteria take over, turning the acids into methane and carbon dioxide.
This produces a lot of gas: roughly 4,000 cubic feet per ton of waste. Some escapes at once into the atmosphere; some is trapped in the landfill, which is why modern landfills have gas wells drilled into them. In fact, in some locations, plans are afoot to use garbage-produced methane to generate electricity.
A landfill enters the final stage of decomposition when all the readily degradable organic material has been broken down–a process that can take years, or even decades. Methane production decreases, and the landfill is said to have stabilized.
But the garbage still hasn’t gone away. Because landfills are so tightly sealed away–especially modern landfills, which use extensive synthetic lining materials to prevent leakage–a lot of our trash ends up mummified.
The University of Arizona’s Project Garbage analyzed city landfill sites. Even after two decades, up to half of the organic material had not decayed. Bananas, carrot tops, onion parings and hot dogs were still recognizable 20 years after they were dumped. Newspapers clearly proclaimed the latest news from the war in Europe. Apparently only about 10 percent of landfill material biodegrades quickly; the rest changes at a snail’s pace.
Project Garbage turned up some other interesting facts. For example, most people think fast-food packaging, polystyrene foam and disposable diapers are major constituents of garbage. In fact, less than one-third of one percent of the total volume of landfill garbage is fast-food packaging; expanded polystyrene foam accounts for no more than one percent, and disposable diapers approximately 1.4 percent. Plastics in general account for only 16 percent of landfill volume: paper, on the other hand, accounts for a whopping 40 percent.
It’s also not true that we’re producing garbage at an ever-rising rate. In fact, we’re still generating roughly the same amount of waste per person as we did 100 years ago–it’s just changed. A century ago, the average North American generated 1,200 pounds of coal ash per year from home stoves and furnaces, and a lot more food had to be thrown away because of the lack of packaging and refrigeration.
Nor are we in danger of being buried in garbage. At the current rate, all of America’s garbage for the next 1,000 years would fit into a single landfill only 120 feet deep and 44 miles square. Landfills’ two big problems are that they’re expensive, and they’re subject to NIMBY (Not In My Back Yard–understandable, because a poorly constructed landfill eventually becomes a major environmental problem). This has led to a shortage of landfills in some areas.
So recycling this newspaper is still a good idea. If you throw it out, future archaeologists might thank you; future generations might not.
