Robust oxygen analyser helps composting process for organic fertiliser

An organic fertiliser manufacturer has selected Michell Instruments’ XZR500 to monitor oxygen levels in its composting process. The innovative process dramatically reduces the time taken to break down animal dung into a useable form and the XZR500 forms part of the control system. Traditionally, animal dung takes around 21 days to compost; however, the fertiliser manufacturer now achieves this in just 24 hours, with benefits to efficiency and costs.

The dung is fed into a rotating cylinder which agitates it for 24 hours, during which time the composting process is completed. Conditions in the composting chamber are very aggressive: the chicken and cow excrement used as a compost feedstock produce high levels of ammonia. The conditions in the chamber are also very humid, with temperatures ranging between 20 and 70°C. After the process is completed, the compost is dried and powdered.

The XZR500 - usually associated with applications measuring the combustion efficiency in boilers, incinerators and furnaces - helps to ensure the levels of oxygen in the composting chamber remain at the optimum level for maximum performance. The product’s probe is placed directly into the air outlet and an ejector is used to pull a sample out to the sensor housed in the ex-situ head. The MSRS zirconium oxide sensor is able to withstand the harsh atmosphere in the composting chamber without the need for a sampling system and does not require frequent replacement, ensuring low running costs.

The previous analyser used in the process had needed a sampling system with a more complex installation and routine maintenance. The sensor was an electrochemical cell which depleted over time, needed periodic replacing and added to the cost of ownership.