Decomposition of bio-degradable plastic spoonsFeatured science projectScience project video

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Complexity level:
8
Project cost ($):
0
Time required:
1 hour to prepare, 31 days for the science project experiment
Material availability:
Easily found
Safety concerns:

Basic safety requirements

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Abstract

This science fair project was done to evaluate the rate of decomposition of bio-degradable plastic in the natural environment. Biodegradable spoons are supposed to decompose with time, but exactly how soon does this process take place? The experiment involved using disposable spoons made from corn starch, wheat and plastic. These spoons were planted in soil.

Hypothesis

Bio-degradable spoons lose some of their weight as quickly as within 30 days after being kept in soil

Background

Biodegradable plastic

Bio-degradable plastic materials are able to degrade and decompose over time under natural environmental conditions. The degradation of these bio-degradable plastics is achieved by allowing micro-organisms to metabolize on their surface and decompose the plastic into smaller parts and less harmful materials.

The decomposing of bio-degradable plastic can be done by natural composting or in a landfill. Moisture and oxygen are normally required for the decomposition process to take place and these conditions are readily available in most composting facilities.

Some of the concerns over the use of bio-degradable plastics are the release of carbon dioxide during the decomposition process. The release of carbon dioxide into the environment contributes to the release of greenhouse gases, which cause global warming. However most bio-degradable plastics are made from natural plant material ? and these plants hav consume and reduce carbon dioxide gas in our atmosphere.

Scientific Terms

Biodegradable, decomposition, microorganisms, metabolize, composting, greenhouse gas

Materials

The materials required for this science fair project:

- 10 pieces corn starch based bio-degradable spoons

- 10 pieces wheat-based bio-degradable spoons

- 10 pieces plastic spoons

- 1 digital weighing scale

- Soil, or a garden plot

- Water

- A black marker pen
 

Procedure

1.  For this science fair project, the independent variable is the type of spoon used ? corn starch based, wheat based and plastic. The dependent variable is the amount of decomposition observed after 30 days. This is determined by using the digital weighing scale to measure the weight of the spoons before and after the 30 days. The constants (control variables) are the type of soil used, the length of time allowed for decomposition, the temperature and humidity.

2.  10 pieces of each of the corn starch-based bio-degradable spoons, wheat-based biodegradable spoons and plastic spoons are marked accordingly, as ?corn?, ?wheat? and ?plastic?.

3.  The total weight of each type of spoon is checked using the digital weight scale. The total weight for the 10 spoons is divided by 10 to obtain the average spoon weight. The values are recorded in the table given below.

4.  The spoons are then planted inside a pile of garden soil and left there for 30 days to decompose. Ensure that each spoon is surrounded entirely by soil, and ensure that soil from the same bag/garden plot is thoroughly mixed, and used to cover all of the spoons. The soil is watered daily to keep it moist. After the 30 days, the spoons are removed from the soil and cleaned under tap water. The spoons are then allowed to dry in the sun for a day.

5.  The average weight of the spoons is again calculated as described in procedure 3 and the results are recorded in the table below.

Observation

The results showed that the weight of the corn starch based spoon and wheat based spoon had reduced after 30 days in the soil but the weight of the plastic spoon  remained the same.

Spoon material

Spoon decomposition after 30 days

Start weight (g)

Finish weight (g)

% decomposition

Corn starch

4.1

3.2

21.95%

Wheat

5.6

4.9

12.50%

Plastic

3.1

3.1

0%

The chart below represents the results of our science project experiment.

biodegrable plastic decomposition science project

Conclusion

The hypothesis that  biodegradable spoons  lose some of  their weight after as little 4 weeks in the soil, is proven to be correct. At 30 days, it was evident that the corn starch-based spoons and the wheat-based spoons  had begun to decompose, but this was not the case for the plastic spoons.

More than 20 million tons of plastic materials are produced around the globe every year. Out of these, only a small percentage are recycled. The difficulty faced in the recycling of  plastic material is that  most plastic waste matter comes mixed together with other types organic wastes. The process of separating the plastic from organic waste is time consuming and costly. However, in the case of bio-degradable plastics, the presence of organic waste actually aids the process of decomposition! Bio-degradable plastics may be a good alternative to regular plastic, in order to prevent the pollution of our environment.

Also consider

Try to repeat this science fair project, this time, evaluating different environments for decomposition, such as by immersing the plastic in lake water or vegetable oil.

You could also try repeating the science project with other types or brands of biodegradable spoons, or by introducing specific species of bacteria into the soil.

References

Biodegradable plastic - http://en.wikipedia.org/wiki/Biodegradable_plastic

Biodegradable, compostable spoons - http://www.ecowise.com/product_info.php?products_id=536

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