First tests of using an electronic nose to control biogas plant efficiency

The demand for online monitoring and control of biogas process is increasing, since better monitoring and control system can improve process plants stability and economy. A number of parameters in both the liquid and the gas phase have been suggested as process indicators (gas production, pH, alkalinity, VFA and H2). For different reasons these indicators do not offer sufficient information to build a consistent feedback control able to promptly forecast and solve plants functioning problems. The present study proposes the use of unconventional complex sensors as a possible solution to engineer a consistent control system. Tests were performed using an electronic nose Airsense PEN 2, AIRSENSE Analytics GmbH to analyze the biogas coming from a biogas plant in which conditions of pre-overloading and overloading were artificially inducted. In particular, a 108 olfactometric fingerprinting reference database obtained by different combination of VFA (acetic, propionic e butyric acids, pure or in solution with water) was initially determined. 476 biogas samples representing different inducted functioning conditions were fed into the analyser and compared with the fingerprinting database. The different inducted functioning conditions were recognised using a FOS/TAC tester. Statistic multivariate analysis confirm that the nose can distinguish different plant functioning conditions, demonstrating the possibility of using this technology as possible base for a biogas control system.