The effect of temperature on dairy waste decomposition and the production of methane gas
The materials required for the experiment:
- 3 Erlenmeyer flasks
- 3 corks to stopper the flasks
- 1 nail
- 3 tubes
- Cow manure
- Tap water
- 3 measuring cylinders
- 3 basins
- 1 refrigerator
- 1 hot plate
- 1 ruler
1. For this experiment, the independent variable is the temperature at which the manure in the flasks is kept – at 14 °C, 24 °C and 34 °C. The dependent variable is the amount of methane gas collected in the measuring cylinder. This is determined by observing and taking the measurement of the gas level from the cylinder every day. The constants (control variables) are the amount of cow manure and the size of the Erlenmeyer flask used.
2. Using the nail, make a hole in the middle of each of the 3 corks. The hole should be just big enough for the tube to be inserted into the cork.
3. Scoop an equal amount of cow manure into each Erlenmeyer flask. You can ascertain this by the weight of the flasks. Then, fill each flask with water. Insert a tube into each cork, then seal each Erlenmeyer flask tightly with the corks.
4. Fill each of the 3 basins with tap water. Fill each measuring cylinder with water and invert it inside the basin, as per Figure 1. Place the loose end of each tube inside a measuring cylinder.
5. Place one set-up inside a refrigerator, with the temperature set to 14 °C. Leave the second set at room temperature, or 24 °C, and place the third set on a hot plate, with the temperature maintained at 34 °C.
6. Observe the amount of methane gas released into each measuring cylinder every day for 5 days. Record the measurements in a table, as shown below.