Development of time-temperature probes for tracking pathogen inactivation during composting

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Courtesy of BioCycle Magazine

Pathogen inactivation is expected to occur in compost if temperatures over 55°C (131°F) are maintained for at least 3 days, or 15 days in windrows. However, a literature review revealed pathogen survival in a significant number of processes appearing to meet the prescribed time-temperature criteria. It was hypothesized that pathogen survival may be due to the existence of undetected temperature variations within the compost mass. In order to investigate this possibility, it is necessary to monitor the conditions that a random particle of compost would experience as it passes through the composting process.

As no adequate methods currently exist to monitor the temperatures of random particles, it was deemed necessary to develop a method to monitor temperature conditions that random particles of compost material encounter during the high-temperature phase of composting. A self-contained, battery powered temperature probe was designed for this purpose, with properties of size and density similar to those of compost particles, in order to allow it to move freely as it undergoes the composting process (in a manner similar to that of a random particle of material). Preliminary tests were done to ensure adequate device operation prior to manufacturing. Though the results were promising, improvements and further testing were recommended to ensure that the probe could withstand the harsh conditions encountered during composting, and to ensure that it would move randomly during compost agitation.

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