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  • Writer's pictureJenna Granger

How Long Until it’s Gone?

Updated: Feb 17, 2021

An exploration into decomposition rates

Grade Level:



Life Science

  • Cycles of Matter & Energy Transfer in Ecosystems

Earth Science

  • Human Impacts on Earth’s Systems

Tools & Materials

  • Scientific notebook or paper

  • Computer with internet access

To Do & Notice

1. Question: How long does it take for our waste to decompose (or break down)? Do all waste items break down or do some just break up into smaller particles?

2. Make a claim:

  • Note: Decomposition rates do vary depending on where the item is decomposing. The answers in this quiz are specifically for items breaking down in the ocean. The answers were taken from NOAA and Woods Hole Sea Grant.

  • Take the quiz:

3. Analyze and Interpret Data

Answer the following questions in your notebook:

  • Did you get all the answers to the quiz right?

  • Did any answers surprise you? Which ones? Why?

  • Can you see a pattern? What kind of items break down faster (under 100 years or so)? Which items tend to take longer than 100 years?

  • What do you think causes some items to break down faster than others?

  • Does plastic actually break down or does it just break up into smaller pieces?

  • How can you reduce plastic pollution? See “What can you do?” section below for some ideas.

4. Communicate Your Findings:

  • Tell us what you learned. Post photos or video on social media and tag us @sweptahoe on Instagram and/or to @swep4 on Facebook. Be sure to hashtag and follow #SWEPsnippets. If you cannot post directly yourself, send SWEP your photos (

What’s Going On

What does decompose mean?

  • Decompose means to break down or separate something into its components.

How does matter decompose?

  • Microbes (or microorganisms) + sunlight + water + oxygen = decomposition.

  • Microbes (such as fungi and bacteria) are microscopic living organisms that decompose organic matter into carbon dioxide and nutrients. The nutrients feed the microorganisms and support them in reproducing.

  • Light, water and oxygen help microorganisms break down all of the natural items on the planet.

  • All natural items decompose in nature. However, not all items can decompose in the landfill because they may not have the key ingredients mentioned above (microbes, light, water & oxygen). Food waste, for example, will not decompose in a landfill and instead puts off the potent greenhouse gas: methane.

  • Many scientists think that plastic and styrofoam never break down, as microbes do not recognize these items as food (they are man-made polymers, see image to the right). Instead they break up into smaller and smaller microplastics which are then passed through the biosphere via wind, water, animals, snow, etc. creating plastic pollution.

What can you do?

  • Start a compost at your house to reduce the amount of food that will end up in the landfill. Check out the "Compost at Home" SWEP Snippet to learn 2 simple ways to start composting your food waste.

  • Use less plastic by making mindful choices in purchasing. Buy in bulk and make more from scratch.

  • Recycle your clean plastics #1 and #2, aluminum, cardboard, clean paper, clean tin foil, and glass. Visit Keep Truckee Green to learn more about what is recyclable in our region.

  • Pick up any trash you see to avoid more microplastics being passed around the planet.


Going Further

How do plastics and trash end up in our lakes, rivers and oceans? Create a simple watershed model to find out:

  • Get paper, pens, food coloring and a spray bottle of water

  • Scrunch up paper into a ball then unfold, but don't flatten

  • Trace the ridges with a green pen this represents the mountain tops, trace the lower parts with blue pen and color in any flat spots, this represents streams, rivers and lakes

  • Put the paper on a large plate or tray to catch water runoff

  • Spray the paper with water, does the water follow your rivers and streams to end up in your lakes?

  • Now, add a drop of food coloring here and there in your watershed and spray with water again. These colors represent plastic in the environment like a balloon from a birthday party, a plastic water bottle, etc…

  • Where do the colors end up? Can you see the pollution travel through the watershed?

  • What can you do to reduce the amount of trash and plastic pollution ending up in your watershed?

What is your watershed? Refer to the Build your Watershed SWEP Snippet to learn where the water and snow from around your house ends up. To learn more about stormwater watch this Freddy the Fish video.

Thank you to our many partners for supporting student's science, sustainability and outdoor learning experiences.

Please review SWEP's Terms of Use prior to using this resource.

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