Development of a Novel Multi-Parameter Monitoring Tool for Odour Management and Environmental Compliance of Anaerobic Digestion Technology

Anaerobic digestion technology has seen a significant deployment at full scale in the last decade, especially in Europe. The technology can treat organic wastes (i.e. municipal, industrial and agricultural wastes). Degradation of organic material has the potential to generate odour emissions, which can be mitigated by the use of sealed vessels, combustion of the biogas and an efficient organic degradation. Anaerobic digestion technology may be able to improve degradation efficiencies as well as regulatory compliance if a monitoring, diagnosis and management tool is developed to identify, quantify and control volatile compound emissions. Several monitoring approaches have been developed using sensory and biochemical analysis based on discrete parameters only. There is likely to be a benefit to be able to develop and apply an analytical based tool for measuring multiple parameters rapidly for wide-ranging chemical signatures. This research investigates the ability to use Gas Chromatography-Ion Mobility Spectrometry (GC-IMS) to enable the development of a novel multi-parameter monitoring tool for the optimisation of anaerobic digestion technology performance for improved energy production, odour management, and environmental compliance. Preliminary results have demonstrated that GC-IMS can be used to discriminate between feedstocks, intermediates and final products represented by their different chemical signatures. These signatures can be used for fingerprinting and identification of volatile compounds. A number of compounds have been identified and calibrated, such terpenes (limonene), alcohols (1-propanol), N-compounds (ammonia), ketones (2-butanone, 2-pentanone, 2-hexanone, 2-heptanone, 2-octanone, 2-nonanone), sulfur compounds (dimethyl sulfide). Analysis can be performed in less than 16 minutes for a broad range of samples (i.e. gas, fluid, and solid matrices). The instrument has shown a low limit of detection for compounds such as limonene and ketones (in the order of lower ppb) and in the order of ppm for compounds such as ammonia with up to 45oC of incubation temperature. The spectrum allows a clear separation of heavier and lighter compounds, however, dilution factors have a significant impact on the analysis as if a sample is too diluted, some of the heavy compounds are lost, and if the sample is too concentrated the system can be overloaded with a loss in the reaction ion peak. Ammonia present in the sample seems to impact on the measurement of other compounds and further evaluations are required in order to conclude the technique’s application within the AD field. If measurements could be performed improvements in plant design, operation and control could take place to optimise process efficiency and reduce environmental impacts including odours reducing the impact to plant surrounding neighbours and during digestate utilisation.