Ontario Operator-in-Training (OIT) Practice Exam

How does aerobic digestion differ from anaerobic digestion?

1. Aerobic digestion produces fertilizers, anaerobic does not

2. Aerobic uses microorganisms, anaerobic produces methane gas

3. Aerobic is faster, anaerobic is more efficient

4. Aerobic requires higher temperatures than anaerobic

The correct answer is: Aerobic uses microorganisms, anaerobic produces methane gas

Aerobic digestion involves the breakdown of organic material by microorganisms in the presence of oxygen. This process primarily uses aerobic bacteria, which thrive in an oxygen-rich environment, to decompose the waste, resulting in carbon dioxide, water, and other byproducts. One of the key characteristics is that it can effectively reduce the volume of organic waste while converting it into compost or fertilizers, although the focus here is on the microbial action during digestion rather than the end products. On the other hand, anaerobic digestion occurs in environments devoid of oxygen, utilizing anaerobic microorganisms that break down organic matter and produce biogas, primarily composed of methane. This methane can be harnessed as a renewable energy source, and the process is often slower than aerobic digestion due to the reliance on different, sometimes less active, microorganisms. The distinction highlighted in the chosen answer emphasizes both the presence of microorganisms in aerobic digestion and the production of methane gas during anaerobic digestion, showcasing a fundamental difference between these two biological processes. This understanding is key to recognizing their applications in waste management and energy production.