In-vessel composting monitoring

The Eltek in-vessel compost monitoring system is designed for batch tunnel in-vessel composting systems which can process various materials such as kitchen waste, green waste and organic fines. It is field proven within demanding, corrosive and moist environments.

Eltek data loggers with Eltek GenII transmitters are used to monitor temperature in a large scale composting operation, which enables foodstuffs to be safely composted in compliance with DEFRA (Department of Environment Food and Rural Affairs) Animal By-Products Regulations (ABPR) and matching EU regulation (EU) 142/2011. The customer needed to be able to compost both vegetable matter and animal by-products in this large-scale composting facility and approached Eltek for a solution that would meet regulatory standards and provide records for an audit trail. The solution provided is suitable for use in composting facilities anywhere. A wireless probe version is also available for the "wind rows" method of composting.

Meeting customer expectation

Our most recent facility processes food waste, green waste and organic fines, which consist of residue from black bin waste that can pass through a 12mm screen. Aerobic sanitisation is used to produce a compost for brown field site restoration.

The Eltek compost system is designed for (but not limited to) batch tunnel-in-vessel composting systems. The system is approved for use in both PAS100 and Non PAS100 facilities. Typically the vessel is 3m x 3m x 10m long with a retractable roof. Such a vessel can take 100 to 200 tons of feed stock. The batch tunnel-in-vessel composting process can comprise of a two stage pasteurisation process of at least 60°C for a minimum of 48 hours as required under ABPR 2005 / National Standards, or 70°C for 1 hour under the European Standard. Our system works for both standards.

The temperature is monitored using specialist designed stainless steel temperature ('lance') probes inserted into the material at predetermined positions and depths. The probes are connected by long runs of robust cable to the transmitter located outside the vessel. The feed stock is referred to as the batch.

The process is policed by AHVLA veterinarians who will require evidence that the two heat cycles detailed above have been correctly implemented. A total of 8 probes is considered ideal to provide a mean batch temperature of greater than 60°C for 48 hours, However, a mean temperature calculated from 6 probes worth of data is considered sufficient by the vets, providing redundancy in the system should a probe fail.

Regulatory Compliance

The process is policed by AHVLA veterinarians who will require evidence that the two heat cycles detailed above have been correctly implemented. A total of 8 probes is considered ideal to provide a mean batch temperature of greater than 60°C for 48 hours, However, a mean temperature calculated from 6 probes worth of data is considered sufficient by the vets, providing redundancy in the system should a probe fail.

Rugged and reliable

This type of system needs to be extremely rugged and reliable, the environment is harsh and with heavy machinery moving large quantities of material around there is no room for delicate equipment. The Eltek system uses heavy duty stainless steel probes, connected to a ruggedized transmitter which sends its data to the more benign office environment where it can be analysed and processed on a desktop computer.

The Eltek system comprises:

Lance Probe

  • Heavy duty stainless steel
  • Detachable probe tip to facilitate easy on-site sensor renewal
  • Low cost sensor
  • Standard low cost connecting cable allows easy on-site maintenance
  • High accuracy (± 0.1°C at 0 to 70°C)

RX250SH Receiver / Logger

  • Compact size - 180 x 120 x 60mm
  • Includes full battery backup in the event of AC mains or PC failure
  • Memory for 245,000 readings ensures continuous system reliability if power to site fails
  • Quick setup using front panel buttons

TR38 Transmitter

  • Heavy duty robust weatherproof enclosure
  • Up to 8 probe inputs
  • Screw down terminals for easy probe connection
  • Front panel controls can set temporary fast transmission interval - ideal for detailed analysis
  • LCD display shows current measured temperature(s) and battery condition
  • License exempt UHF radio transmitter with outstanding range and reliability
  • Field-exchangeable, off the shelf batteries provide greater than 1 year of operation
  • Range of transmission can be significantly extended using Eltek Repeater unit(s)

Darca Compost Software

Darca Compost has been designed specifically for compost recycling applications. It allows the user to keep track of each batch of compost as it moves between physical storage containers ("Bays"). Batches are grouped either as "Current" (typically less than 6 months old) or as "Historical" for ease of access in the software. The software calculates the results from the two tests each batch must undergo, informing the user whether a batch has passed or failed.

Key Features

Batch process example

The batch in this example will be referred to as Batch 1.

  1. Batch 1 is subjected to the first phase of the composting process in the first vessel (‘Bay 1' or ‘Clamp 1'). The temperature profile for Batch 1 is logged.
  2. The material is moved (and in doing so turned) and put in a second bay, Bay 2.
  3. The probes in Bay 2 are now inserted into Batch 1 and the batch movement event is entered into the Darca software. Temperature data is logged in order to provide evidence that a temperature of >60°C is held for 48 hours.
  4. If all tests are passed, the material at the end of Bay 2's composting process is deemed ready for use.

Download

In-vessel compost monitoring case datasheet (PDF)

Windrow compost monitoring datasheet (PDF)