Introduction

In this experiment you will learn that it is possible to recycle some organic waste, such as grass, leaves and table scraps into fertilizer, water and fuel by composting. Composting is a biological process during which organic materials are broken down into a soil like product, water and various gases.

The soil like product is an excellent fertilizer that is filled with nutrients that help plants grow. This soil like product is also very porous and can hold moisture which is very useful for gardens and farmers fields during dry spells.

Water is another product of composting. The water created by composting is not clean enough to drink but with a little filtering it has other uses, like irrigating crops.

Various gases are also products of composting. This is because composting involves bringing together organic matter and leaving it sit until it decomposes (rots). When something decomposes it is actually being broken down by small microbes that live off of the organic material. When microbes break down organic material they leave behind nutrients and various gases. One of the most abundant of these gases, methane, is very flammable and can be used as fuel. As a matter of fact natural gas that we use to heat our homes and cook with is mostly methane.

Objective

You will experiment to find out what conditions affect the rate at which organic matter decays. You will also learn that composting is a great way to recycle organic material to be reused as fertilizer, water, and possibly fuel.

Materials Needed

Safety Note: Do not use dairy products or meat/animal products in your compost, because harmful bacteria may develop. Never eat any of the material in your compost. Always wash your hands after handling the compost jars or bottles. Also check your students to make sure nobody is allergic to mold. Some allergic reactions can be life-threatening. Four clear jars or bottles to collect your compost. 16 ounce plastic soda bottles, and baby food jars work well. The lids or bottle caps are not needed. Organic material (table scraps) such as corn husks, potato pealings, apple cores, and other left over parts of food that you don't eat. Make sure you have enough food bits to fill all your bottles or glass jars at least 1/2 full. Balloons, all the same size, that are large enough to stretch over the top of your bottle or jar. A kitchen scale, or balance Scissors Rubber gloves

Procedure:

1. Mark each bottle 1,2,3, and 4. Mark four balloons 1,2,3,and 4. Weigh each of your four bottles separately with their corresponding balloon. Record the total weight for each bottle and ballon on your data sheet.
2. Look carefully at your food scraps. Make a list of what you have and record it on your data sheet.
3. Using scissors, carefully cut your food scraps and other organic material into small enough bits to fit through the openings of your jars or bottles.
4. Separate the cut food scraps into four equal piles. As best as you can put equal amounts of food bits and organic scraps into each pile. For example if you have eight pieces of apple core each pile will get two pieces. Fill each bottle or jar at least 1/2 way up with the food scraps.
5. Stretch your balloons over the lids of all four bottles or jars as shown.
6. Weigh each 1/2 filled bottle and record it on your data sheet. Subtract the weight of the empty bottle and ballon from the total. This is the weight of the organic material inside your bottle.
7. Place one of the prepared bottles or jars on a shelf that is away from windows and receives constant temperature between 64 and 72 degrees Fahrenheit. Label this jar or bottle "control". (See What is a control?)

What is a Control?
	A control in an experiment is the test group in which the variable is not altered. The control is used as a benchmark to measure the variable's effect. Question: A scientist, Dr. Nepf, wants to know if certain fertilizers work better than others. She marks off four rows of sunflower seeds. She adds different fertilizers (the variables) to row B,C and D. Her control row is row A. She gives the same water and care to all four rows. At the end of the experiment she concludes that fertilizer C and D causes the sunflower to bloom quicker. What is wrong with Dr. Nepf's experiment?
Answer: Dr. Nepf starts out with good intentions since she uses the same seed and applies equal amounts of water and care to all four rows. However, she did make one mistake, she forgot to check the soil. In this case the soil was not the same for all four rows and therefore a hidden variable altered her experiment. Since the soil was not consistent, her control had a different variable and Dr. Nepf's conclusion is incorrect.



8. You already have a bottle or jar labeled control. The food scraps in that jar will undergo decomposition in the next few days. What can you do to another bottle or jar that might speed up decomposition? What can you do to another jar or bottle that might give a better yield of useful recycled materials?
9. Using the hypothesis worksheet page, write up a hypothesis for each jar or bottle.
10. Go ahead and start experimenting!

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