What happens to the banana peel, empty cereal box, and milk carton you threw away after breakfast this morning? In many communities, garbage eventually ends up in a landfill (see "What a Dump!"). And when trash hits the dirt, it's chow time for billions of invisible organisms called microbes.
These tiny creatures abound in garbage mounds, with thousands of species in residence. Scientists think microbes may be the oldest life forms on Each. They devour just about anything that's biodegradable (materials that can be broken down by living things), from discarded food and paper to certain chemicals like toluene, a component of gasoline.
Most microbes found in trash are bacteria, single-celled organisms that are round, rod-shaped, or spiral. Other trash-eaters: fungi, organisms like fuzzy molds and mushrooms that absorb food from living or dead matter around them, and yeasts, single-celled organisms that break down sugars into carbon dioxide.
THE BIG CHEW
Microbes fall into two distinct types: aerobic and anaerobic. Aerobic microbes need oxygen to survive; anaerobic microbes can live without oxygen. When it comes to chewing garbage, aerobic microbes gorge first. They quickly decompose organic matter (decaying organisms, including plants and animals).
Anaerobic microbes take over when no more oxygen is available--they tend to thrive deep within densely-packed trash heads. Anaerobic microbes work slowly and sometimes make the pile stink.
If you've seen a rotting apple, you've witnessed microbes in action. As microbes break down decaying food or plants, the process creates gas byproducts--and some of these reek. Two gases, methane and carbon dioxide, also contribute to global warming: they're greenhouse gases that trap heat in the atmosphere.
A host of other garbage-eaters, or decomposers, join in, including hundreds of species of insects and worms. Under proper conditions, decomposers can reduce a pile of trash to almost nothing and transform some of it into fertile soil. Red worms; for example, digest shredded newspaper and food scraps, then excrete their meal as rich dirt.
Microbes, insects, and worms even take on big jobs. When scientists at the Paleontological Research Institution (PRE) in Ithaca, N.Y., wanted to clean the bones of a dead 40-foot-long Northern right whale, they buried the skeleton--still encrusted with flesh--in horse manure for a whole year. When they dug it up, they discovered that, "bacteria and insects cleaned the bones very nicely," says Warren Allmon, PRE's director. Some recently discovered microbes even dine on gasoline, and researchers are studying these anaerobic microbes as a strategy to help clean up lakes and rivers.
But microbes can't consume everything you throw away, especially trash from synthetic (man-made) materials. Plastic, for example, takes decades to disintegrate in a landfill. And glass, made from melted rock, can last for eons! Microbes can't devour many toxic chemicals, and many types of new synthetic materials like rayon aren't biodegradable at all. How to safely dispose of trash is an ever-growing challenge for all inhabitants on Earth. We can't depend merely on hungry microbes to clean up after us.
WHICH MATERIALS GET RECYCLED MOST? (percent of total waste recovered, averages) This graph shows the percentage of common trash items recycled in 1996. Recycling and composting kept 57 million tons of trash out of landfills and incinerators. Why do you think more metal was recycled than plastic? Metals 41.5% Paper 34% Glass 22% Textiles 11.7% Wood 9.6% Rubber and leather 5.9% Plastics 3.5% SOURCE: U.S. Environmental Protection Agency, 1996 Note: Table made from a bar graph.
Take a closer look at your trash.
They say a diamond is forever--and so is most trash! This bar graph shows the average number of years it takes for common litter items to biodegrade, or rot after disposal. Why does it take a glass bottle longer to decompose than a banana peel?
HOW LONG WILL LITTER LAST? NUMBER OF YEARS Orange and banana peels 1-2 weeks Cigarette butts 1-5 years Wool socks 1-5 years Plastic-coated paper 5 years Plastic bag 10-20 years Plastic film containers 20-30 years Nylon fabric 30-40 years Leather up to 50 years Rubber boot sole 50-80 years Aluminum cans and tabs 80-100 years Glass bottles 1,000,000 years SOURCE: National Park Service Note: Table made from bar graph. TOTAL TRASH GENERATION (209.7 mil. tons) Paper 38.1% Yard Waste 13.4% Food Waste 10.4% Other 9.9% Plastics 9.4% Metals 7.7% Glass 5.9% Wood 5.2% What types of garbage do Americans generate the most? This pie chart shows the percentages of different materials trashed in 1996. How can you help reduce, reuse, and recycle your trash? SOURCE: U.S. Environmental Protection Agency, 1996 Note: Table made from a pie chart
The U.S. produced 390 million tons of garbage last year. That's 8 pounds per person each day!
In 1997, 28% of all U.S. solid trash--bottles, food, newspapers--was recycled or composted.
In 1996, recycling of trash prevented the release of 33 million tons of carbon into the air--about the same amount emitted by 25 million cars!
Did You Know?
* Microbes break down garbage by releasing enzymes and digestive proteins that help break down food into chemicals such as nitrates, phosphorus, and potassium--nutrients that are essential to plant life.
* Composting organic materials keeps trash out of landfills--and transforms garbage into rich soil.
* In a compost pile, mesophilic (moderate-temperature-loving) microorganisms break down organic matter for the first few days. Then temperatures rise for days--or months--and thermophilic, or heat-loving microorganisms take over.
English: Write a story about a microbe's creepy-crawly life.
National Science Education Standards Grades 5-8: structure and function in living systems * properties and changes of properties in mater * populations, resources, and environments
Grades 9-12: interdependence of organisms * matter, energy, and organization in living systems * environmental quality
For information on garbage-eating microorganisms:
For more Oil toxin-eating microbes, log on to:
Directions: Read "Eating Trash" and then fill in the blanks.
1. Millions of tiny organisms called -- inhabit garbage dumps and break down trash.
2. These creatures eat anything that is --.
3. Most of these organisms are --.
4. Other garbage eaters include --, organisms like fuzzy molds and mushrooms.
5. There are two distinct types of trash eating organisms: -- organisms need oxygen, while -- organisms do not.
CHECK FOR UNDERSTANDING
5. aerobic, anaerobic
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|Title Annotation:||bugs that eat garbage could help clean up the environment|
|Date:||Apr 9, 2001|
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