Metrics
What is a Metric?
A metric, in the context of measurement and data analysis, is a quantifiable and standardized measure used to assess, evaluate, or track the performance, status, or characteristics of a system process. Metrics provide a way to express specific aspects of production in numerical terms, making it easier to compare, analyze, and make decisions.
AEYD utilizes metric rules as set by a processing method in combination with log data for teams to assess progress and quality.
Which Metrics are analyzed?
"Temperature is the chief measured indicator. Moisture is the next priority. Additonal information can be gained from monitoring oxygen... in some instances, oxygen monitoring is mandated by protocols or by regulations." The Compost Handbook, page 501
Temperature
Mesophilic
"Mesophilic" refers to organisms, processes, or environments that are adapted to or thrive at moderate temperatures. The term "mesophilic" is derived from the Greek words "meso," meaning middle or intermediate, and "philo," meaning to love or have an affinity for. In general, mesophiles thrive in temperature ranges that are neither extremely hot nor extremely cold, typically between 68 to 113°F (20 to 45°C). However, the specific temperature range for mesophilic organisms and processes may vary depending on the context.
Thermaphilic
"Thermophilic" is a term used to describe organisms, processes, or environments that thrive at relatively high temperatures. It comes from the Greek words "thermo," meaning heat, and "philo," meaning to love or have an affinity for. Thermophilic conditions are typically characterized by temperatures in the range of 113 to 158°F (45 to 70°C) or even higher, although specific temperature ranges may vary depending on the context.
PFRP (Process to Further Reduce Pathogens)
The process to further reduce pathogens (PFRP) in composting is often referred to as "post-pasteurization" or "post-treatment." Composting itself can contribute to reducing pathogens through natural microbial activity, but additional steps may be taken to enhance pathogen reduction.
The US EPA's PFRP criteria depend on the method of composting:
For Aerated Static Pile or In-Vessel methods, the temperature must be maintained at or above 131ºF (55ºC) for three days.
For Turned Windrow, the temperature must be maintained at or above 131ºF (55ºC) for at least 15 days and the windrow must be turned a minimum of five times during the period that the temperature remains at 131ºF (55ºC) or higher.
The specific criteria for PFRP designation and the regulatory bodies overseeing compost safety can vary by region and country, so it's essential for compost operations to be aware of and comply with the relevant safety regulations and guidelines in their specific jurisdiction.
Further Seed Destruction
Temperatures at or above 145°F (62.78ºC) have the ability to destroy more heat resistant seeds compared to temperatures below 145°F (62.78ºC).
Danger Zone
Hyperthermophilic Phase (Very High Temperature Range):
Temperature Range: Above 160°F (71°C)
In this phase, temperatures can become extremely high.
Hyperthermophilic microorganisms are at work, and decomposition continues.
Sustained temperatures above 160°F (71°C) for extended periods can be detrimental to microbial activity and may lead to a loss of beneficial microorganisms.
Extreme Temperatures (Destructive Range):
Temperature Range: Above 160-170°F (71-77°C) or below freezing (32°F or 0°C)
Extremely high temperatures (above 160-170°F or 71-77°C) can kill or denature many beneficial microorganisms in the compost, reducing their activity.
Freezing temperatures (below 32°F or 0°C) can also halt microbial activity, effectively putting composting on hold until conditions become more favorable.
Moisture
In the context of composting, moisture refers to the amount of water present in the compost pile, windrow or bin. Maintaining the right level of moisture is crucial for the success of the composting process, it affects microbial activity, decomposition rates, and the overall quality of the finished compost.
Target
The optimal moisture content for a compost pile typically ranges from 40% to 60%.
Oxygen
Oxygen is essential for aerobic (oxygen-dependent) decomposition, which is the preferred method for composting because it is efficient, produces less odor, and results in high-quality compost.
Preferred Range
The preferred range for oxygen 10-25%.
Reasonable Range
The reasonable range for oxygen is 5-10%
Turn
In the context of composting, a "turn" refers to the act of mixing or aerating the compost pile or bin by either physically turning over the materials or using a tool or equipment to agitate and redistribute them. Turning is an important practice in composting because it helps provide oxygen to the microorganisms responsible for decomposition and ensures even decomposition throughout the pile.
Turn criteria depends on the method of composting:
A Turned Windrow must be turned a minimum of five times times during the period that the temperature remains at 131ºF (55ºC) or higher.
How are metrics applied?
Learn about methods!
Last updated