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As PAS:100 regulations and the Quality Protocol for Compost come into force, Nigel Palmer from Gemini Data Loggers discusses the potential challenges for temperature monitoring of composting units.

In systems that don’t depend on stirring or turning (static systems), the compost can be easily monitored using loggers with probes.

These loggers can either be cabled or wireless.

Effective monitoring of processes where the compost is stirred or turned (dynamic systems), such as aerated in-vessel, rotating drums or agitated bins, is harder to achieve.

Their flexibility and cost-effectiveness mean that they are well-known methods of producing high-quality compost quicker, as the matter breaks down faster.

However, in order to comply with PAS:100, temperature monitoring is required and data loggers with probes are not well suited for this job.

A logger that could travel with the matter and monitor temperature during the process would give a much better indication of what is happening throughout.

Producing this kind of logger has proved a challenge for this industry.

Gemini’s data loggers, though water-proof and extremely rugged, found it very difficult to withstand the harsh conditions generated by compost-turning equipment such as screw augers.

Something even more rugged was required to protect the circuit board that forms the core of the logger, while also producing accurate data.

Some composters have already tried to monitor these dynamic systems by attaching probed loggers to the side of the vessel.

The problem discovered with this approach was that although they monitor fixed points in the process, they still don’t provide random data for the whole process.

The solution Gemini Data Loggers has come up with is a conventional logger contained in a very robust nylon egg-shaped case.

The logger is bright yellow, to ensure it is spotted when the compost is passed through a grid at the end of the process.

Because of its shape this logger is colloquially referred to as the ‘egg logger’.

One example of successful use of our egg logger is The Eden Project in Cornwall.

They have recently installed a 30m in-vessel composter that can hold up to 10 tonnes of waste and makes easy work of the 2.5 tonnes/week of catering waste disposed of at the Project during peak season.

The Eden Project needs to prove compliance with PAS:100 and animal by-product regulations, therefore 20 in-built loggers record data for this reason alone.

As the composting system is also a research project, it is important that additional data is collected to provide in-depth information on the process; Tinytag egg loggers can provide this.

‘Whatever we chose for this job had to be rugged’ commented Maureen Newton, laboratory manager at the Eden Project.

‘The only way out of the machine is through a screw auger, so we wanted a logger that would stay intact throughout the whole process.

‘The loggers could withstand the hostile environment in the vessel and their brightness means they are easy to spot.’

Gemini Data Loggers

Gemini Data Loggers designs and manufactures Tinytag, self contained and battery operated data loggers for monitoring temperature, humidity, shock, vibration and other environmental parameters in a variety of locations.

Tinytag loggers are suitable for indoor, outdoor and underwater applications, including ATEX hazardous areas, in many industries such as environment, food, logistics, health & laboratories, agriculture, museums, compost, etc.

All Tinytags use the same Tinytag Explorer data logging software for simple configuration of the logger and later compilation and display of results for analysis. It is Window based and data can easily be exported into programs e.g. Excel and Word.

While Tinytag extensive range of off-the-shelf data loggers and probes suit most needs, Gemini Data Loggers can produce custom solutions where required. Tinytag hardware and software are designed and manufactured in house allowing us to be adaptable to the requirements of your application.

Gemini has an in-house calibration laboratory providing UKAS traceable certification.

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