The electronic nose : a tool for controlling the industrial odour emission. Application to the compost processing

Different laboratory-made electronic noses, based on commercial tin oxide gas sensors were used to identify typical sources of odour nuisance : printing houses, paint shop in a coachbuilding, wastewater treatment plant, urban waste composting facilities or rendering plant. All the samples were collected in the field from real malodours in uncontrollable conditions. In spite of the influence of environmental parameters, results demonstrated the ability of such simple systems to detect and identify typical odour nuisances.
Those findings encouraged us to develop portable instruments able to monitor continuously the odours emerging from factories or from landfills sites.
The paper analyses the type of output signal most adapted both to detect the rise of a particular odour in the background and to monitor it continuously, in order to allow a decision making in real time.
The method is illustrated on a particular application : the monitoring of the odour generated by a municipal waste composting process. The paper discusses the ability of a technique based on an electronic nose to control the odour abatement device, which is the atomisation of a neutralising agent.

To reach such final goal, the main difficulties to overcome are :
- to cope with the sensor drift
- to lower the limit of detection and the limit of recognition of the sensor array
- to improve the reproducibility of the sensors.

However, comparing the sensor array signals with analytical and olfactometric results leads to promising conclusions regarding two main possible applications :
- using the odour, as detected by the electronic nose, as a process variable for the compost formation;
- predicting the raise of malodour in the background before it becomes an annoyance for the surrounding.