An environmental scientist investigates the rate of decomposition of organic food waste in three identical bioreactors under different ventilation conditions to optimize municipal composting:
- Bioreactor Alpha: active continuous aeration (forced airflow)
- Bioreactor Beta: passive ventilation (open vents)
- Bioreactor Gamma: completely sealed (no airflow)
The scientist wants to obtain valid results. Explain one factor (other than the ventilation method) that they should keep constant and suggest why.
The scientist monitors the temperature of the waste inside each bioreactor over a 6-week period. They know that heat is released by decomposing microbes during respiration.
The graph below shows the results of the investigation:
Write down two differences between the change in temperature in Bioreactor Alpha and the change in temperature in Bioreactor Gamma.
The scientist concludes that to decompose the food waste as rapidly as possible, active continuous aeration should be used. Explain how the data in the graph supports this decision.
The microbes responsible for decay require oxygen. Explain why aerobic conditions (such as those in Bioreactor Alpha) lead to a much faster rate of decomposition than anaerobic conditions (such as those in Bioreactor Gamma).