Science Project:

Algae Fuel

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The goal is to have the student test a hypothesis about optimal conditions for producing algal oil.

  • What conditions cause algae to produce the most oil?
  • Is it possible to use calorimetry to differentiate between algae samples?

Algae are organisms commonly found in aquatic environments. The large multicellular macroalgae show up in ponds and in the ocean. They tend to be measurable in inches, although macroalgae in the ocean (giant kelp) can grow to more than 100 feet in lenght. Microalgae are tiny unicellular organisms that grow as suspensions in water; they are measurable in micrometers. They are frequently found in bogs, marshes, and swamps.

All algae require sunlight, water, nutrients, and carbon dioxide to grow. Through the process of photosynthesis, algae convert the carbon dioxide into glucose (a sugar). The glucose is then broken down into fatty acids, which under normal conditions, are used to produce membranes for new algal cells. If, however, the algae are starved of nutrients, the fatty acids produce fat molecules (oil). Most algae do not produce much oil unless they are physiologically stressed, which is to say deprived of one or more of their basic requirements for growth. Unfortunately for algal oil producers, algae produce much less mass when grown under starvation conditions.

Evaluating the oil content of algae usually requires expensive equipment not readily available outside chemistry laboratories. However it is possible to compare the relative contents oil in different types of algae using a calorimeter. In this method, the energy produced when an algae sample is burned is compared for different samples. (A calorimeter identifies the amount of heat produced when a sample burns by measuring the associated rise in temperature of a specific amount of water.) Because oil has a higher energy density than non-lipid tissue, the sample that contains the most oil will have the highest energy output.

  • Food calorimeter; algae; collection jars; notebook; filter paper; microwave oven; thermometer. Plans for (or commercial sources of) simple food calorimeters may be found on:

http://www.carolina.com/product/food+calorimeter.do?keyword=food+claorimeter&

http://www.amazon.com/Economy-Calorimeter-Chamber-Flask-Instructions/dp/B0017Y9FKY/ref=sr_1_6?s=industrial&ie=UTF8&qid=1296106316&sr=1-6

  • Materials can be found at a scientific supply house on the Internet.
  • Materials are readily available.

  1. Build (or purchase) a food calorimeter.
  2. Collect samples of algae (macroalgae and microalgae) from various sources such as the ocean, ponds, marshes, or swamps. Store each algae specimen in a jar filled with water.
  3. Record the conditions under which you found each specimen in your notebook. Note whether the conditions placed growth stress on the algae.
  4. Formulate a hypothesis that predicts which algae samples will contain the most oil.
  5. Remove the water from each of the algae specimens by heating in a microwave oven. Take care not to burn the algae. (Strain any microalgae first with filter paper.)
  6. Weigh out equal amounts of each type of dried algae.)
  7. Fill the calorimeter’s water chamber to the calibration point and measure the temperature of the water.
  8. Ignite one of the algae samples in the calorimeter, allowing the heat produced from the combustion to heat the water.
  9. Continue burning the algae sample until it has been completely reduced to carbon.
  10. Measure the temperature of the water after the algae has finished burning.
  11. Calculate the number of calories produced by burning the algae. TIP: One calorie is the amount of energy required to raise the temperature of one gram of water by 1 deg C.
  12. Repeat these steps for each of the algae samples.
  13. Compare the number of calories produced by burning each of the algae samples.
  14. Evaluate your hypothesis in light of you experiment, and revise it if necessary. Propose and conduct additional experiments as necessary.
Environment

Initial temperature

Final temperature

Temperature difference

Calories

Sample 1

Pond, Very stressed

Sample 2

Creek, Not stressed

Sample 3

Bird bath, Mildly stressed

Terms: Algae; Macroalgae; Microalgae; Photosynthesis; Algal oil;Calorimetry

References:

Author: Randall Frost, Ph.D.
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