CRP Composting & Organics Recycling 1 — Questions and Answers
Question 1: What temperature range must be maintained during the active composting phase to ensure pathogen destruction according to EPA standards?
- 55–65°C (131–149°F) (Correct answer)
- 35–45°C (95–113°F)
- 70–80°C (158–176°F)
- 20–30°C (68–86°F)
Correct answer: 55–65°C (131–149°F)
EPA requires temperatures of 55–65°C (131–149°F) to be maintained for a specified duration to kill pathogens and weed seeds in compost.
Question 2: What is the recommended carbon-to-nitrogen (C:N) ratio for optimal composting?
- 5:1 to 10:1
- 25:1 to 30:1 (Correct answer)
- 50:1 to 60:1
- 100:1 to 150:1
Correct answer: 25:1 to 30:1
A C:N ratio of 25:1 to 30:1 provides the optimal balance of carbon for microbial energy and nitrogen for microbial protein synthesis during active decomposition.
Question 3: Which composting technology uses enclosed, mechanically aerated vessels to control temperature, moisture, and odors?
- Windrow composting
- Aerated static pile composting
- In-vessel composting (Correct answer)
- Vermicomposting
Correct answer: In-vessel composting
In-vessel composting uses enclosed containers or tunnels with mechanical aeration controls, offering the greatest environmental control and odor management of all composting methods.
Question 4: What is the primary distinction between aerobic and anaerobic composting processes?
- Aerobic composting produces methane; anaerobic does not
- Aerobic composting requires oxygen; anaerobic does not (Correct answer)
- Aerobic composting is always slower than anaerobic
- Anaerobic composting consistently produces higher quality compost
Correct answer: Aerobic composting requires oxygen; anaerobic does not
Aerobic composting requires oxygen for microbial decomposition, while anaerobic composting occurs without oxygen and produces different byproducts, including methane and hydrogen sulfide.
Question 5: Which of the following is classified as a 'brown' or carbon-rich feedstock in composting?
- Grass clippings
- Fresh food scraps
- Coffee grounds
- Dry leaves and wood chips (Correct answer)
Correct answer: Dry leaves and wood chips
Dry leaves and wood chips are carbon-rich 'brown' materials that provide structure and balance the nitrogen found in 'green' feedstocks such as food scraps and fresh grass clippings.
Question 6: What characteristic best indicates that compost has reached maturity and is considered 'finished'?
- It reaches its maximum internal temperature
- It has a uniformly dark color with no recognizable feedstocks
- It is biologically stable with no further significant decomposition and has a soil-like odor (Correct answer)
- It has been processed for a minimum of 90 days
Correct answer: It is biologically stable with no further significant decomposition and has a soil-like odor
Finished or mature compost is characterized by biological stability (no further significant decomposition), a pleasant earthy odor, and absence of recognizable original feedstock materials.
Question 7: Which EPA regulation under the Clean Water Act establishes standards governing the land application of biosolids used in composting programs?
- EPA 40 CFR Part 257
- EPA 40 CFR Part 503 (Correct answer)
- RCRA Subtitle D
- EPA 40 CFR Part 261
Correct answer: EPA 40 CFR Part 503
EPA 40 CFR Part 503 establishes standards for the beneficial use and disposal of sewage sludge, including composted biosolids, covering pathogen reduction requirements and land application limits.
CRP Composting & Organics Recycling 1
What temperature range must be maintained during the active composting phase to ensure pathogen destruction according to EPA standards?