The purpose of this experiment is to determine what happens to common household items that are discarded and placed in a landfill. In nature, physical, chemical, and biological factors act upon our waste and work together in the process of decomposition. This experiment will determine what action organisms in the soil have on garbage. Before you begin, make an educated guess about the outcome of this experiment based on your knowledge of composting and decomposition. This educated guess, or prediction, is your hypothesis. A hypothesis should explain these things:
A hypothesis should be brief, specific, and measurable. It must be something you can test through observation. Your experiment will prove or disprove whether your hypothesis is correct. Here is one possible hypothesis for this experiment: "Household garbage covered with soil will decay faster than garbage not covered with soil."
In this case, the variable you will change is the presence or absence of soil, and the variable you will measure is the differences in condition between the garbage in the two bags after two to three months. If the garbage in the bag with soil has decayed more than the garbage in the bag without soil, you will know your hypothesis is correct.
Easy/Moderate, because of the time involved.
$5 for the materials that cannot be found in your household or at school.
Three to four months for decomposition to take place.
When analyzing the contents of each bag, sketch the objects and write a brief description of their conditions (use a chart like this one). Look for any activity of organisms like worms or insects. If anything is smelly, slimy, or has a black stain due to bacterial action, record it in the result chart (see sample chart). Note the difference in decay between the organic waste (food) and the inorganic waste (containers).
You can vary this experiment by changing the variables. For example, you can place one bag in a chilly basement or the freezer and the other bag in a warm spot outside to determine the effect of temperature. You could also add water to one bag, but not to the other, to determine the effect of water. To determine the effect of pH on decomposition, you could add an acidic material like vinegar to one bag, and add water to the other bag.
Source: Experiment Central. U·X·L, 2000.