CPWM CPWM Composting and Organic Waste Management Questions and Answers 2 — Questions and Answers
Question 1: In-vessel composting differs from windrow composting primarily because it:
- Uses no oxygen
- Occurs inside an enclosed, controlled container (Correct answer)
- Requires a C:N ratio above 60:1
- Produces no finished compost
Correct answer: Occurs inside an enclosed, controlled container
In-vessel composting occurs in enclosed drums, tunnels, or reactors that allow precise control of temperature, moisture, and aeration.
Question 2: Which federal regulation governs land application of sewage sludge (biosolids) and sets limits for pathogens and heavy metals?
- RCRA Subtitle D
- 40 CFR Part 503 (Correct answer)
- TSCA Section 8
- CERCLA Section 107
Correct answer: 40 CFR Part 503
40 CFR Part 503 (EPA's 'biosolids rule') establishes standards for the use and disposal of sewage sludge, including pathogen reduction and pollutant limits.
Question 3: What does 'digestate' refer to in anaerobic digestion of organic waste?
- The biogas produced
- The solid/liquid residue remaining after digestion (Correct answer)
- The pre-sorted feedstock
- The enzyme used in the process
Correct answer: The solid/liquid residue remaining after digestion
Digestate is the nutrient-rich solid and liquid material left after anaerobic microorganisms have broken down organic feedstock and captured biogas.
Question 4: Which of the following is a contaminant commonly found in source-separated organics that reduces compost quality?
- Coffee grounds
- Fruit peels
- Plastic film bags (Correct answer)
- Grass clippings
Correct answer: Plastic film bags
Plastic film bags are a major contaminant in organics collection programs because they do not break down and leave microplastic residues in finished compost.
Question 5: What is the recommended moisture content range for an actively composting pile?
- 5–10%
- 20–30%
- 50–60% (Correct answer)
- 80–90%
Correct answer: 50–60%
Moisture content of 50–60% supports microbial activity without saturating the pile and causing anaerobic conditions.
Question 6: Anaerobic digestion of food waste primarily produces which two useful outputs?
- Compost and steam
- Biogas and digestate (Correct answer)
- Biochar and leachate
- Syngas and ash
Correct answer: Biogas and digestate
Anaerobic digestion generates biogas (mostly methane, used for energy) and digestate (a nutrient-rich residue used as fertilizer).
CPWM CPWM Composting and Organic Waste Management Questions and Answers 2
In-vessel composting differs from windrow composting primarily because it: