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Pile Temperature Analysis
Time estimates are ranges — actual results vary by climate, material mix, and management. See methodology.
Compost Pile Temperature Tracker
Track your pile's decomposition phase, estimate time to finished compost, and get a recommended action plan. Pathogen kill zone indicator per EPA 40 CFR Part 503 Appendix B.
Understanding Compost Pile Temperature
Compost pile temperature is the most visible indicator of decomposition activity. A healthy active pile passes through three distinct phases: a brief mesophilic warm-up, a sustained thermophilic hot phase, and a cooling curing phase as easily decomposable materials are exhausted.
Temperature Phases
Mesophilic (50–105°F / 10–40°C): The initial phase, dominated by mesophilic bacteria and fungi. Typically lasts 1–3 days in a new pile. Also the state of a pile that has finished or gone cold from lack of moisture or nitrogen.
Thermophilic (105–160°F / 40–71°C): The active hot phase. Thermophilic bacteria dominate, decomposition is rapid, and temperatures above 131°F (55°C) begin killing pathogens and weed seeds. Target temperature for most active composting is 130–150°F (55–65°C).
Cooling/Curing (<105°F / <40°C after hot phase): The pile has consumed its active materials. Mesophilic organisms return to finish stabilization. Allow 4–6 weeks of curing before use.
Pathogen Kill Requirements
The EPA 40 CFR Part 503 Appendix B standard for Process to Further Reduce Pathogens (PFRP) requires: 131°F (55°C) for at least 3 consecutive days for a static pile, or 131°F for 15 days with a minimum of 5 turnings for a windrow.[12] This standard also satisfies USDA NOP compost requirements for organic production.
Use the Moisture Calculator and C:N Ratio Calculator to diagnose why a pile is not heating up.
Frequently Asked Questions
What temperature should a compost pile be?
An active hot pile should reach 131–160°F (55–71°C) during the thermophilic phase. This range kills most weed seeds and pathogens. Below 90°F (32°C), the pile has either finished or is not actively decomposing. Above 160°F (71°C), beneficial microorganisms may be killed — turn the pile to cool it down.
How long does composting take?
Berkeley Hot method (turn every 2 days): 14–21 days. Active hot composting (weekly turning): 4–8 weeks. Passive cold composting (no turning): 6–18 months. These are estimates — actual times vary by climate, pile size, and material mix.
At what temperature are pathogens and weed seeds killed?
EPA 40 CFR Part 503 Appendix B requires 131°F (55°C) for at least 3 days for a static pile, or 15 days with 5 turnings for a windrow. Most weed seeds are killed between 120–145°F (49–63°C). E. coli and Salmonella are killed within minutes at 145°F (63°C).
Why is my compost pile not heating up?
Common causes: pile too small (minimum ~1 cubic yard), C:N ratio too high or too low (target 25–35:1), pile too dry (below 40% moisture), or the pile has already finished. Check the C:N Ratio Calculator and Moisture Calculator.
Should I turn my compost pile?
Turning reintroduces oxygen. For hot composting, turn when the core drops below 110°F (43°C) or after 3–5 days. Berkeley method: every 2 days. For passive cold composting, turning is optional but accelerates the process significantly.
What is the difference between hot and cold composting?
Hot composting requires a minimum pile size of 1 cubic yard, a balanced C:N ratio of 25–35:1, and active management. It completes in weeks and kills pathogens. Cold composting requires no management — pile and wait. It takes 6–18 months and may not kill all weed seeds or pathogens.