Electronic Noses and Their Applications for Sensory and Analytical Measurements in the Waste Management Plants—A Review

Abstract

Waste management plants are one of the most important sources of odorants that may cause odor nuisance. The monitoring of processes involved in the waste treatment and disposal as well as the assessment of odor impact in the vicinity of this type of facilities require two different but complementary approaches: analytical and sensory. The purpose of this work is to present these two approaches. Among sensory techniques dynamic and field olfactometry are considered, whereas analytical methodologies are represented by gas chromatography–mass spectrometry (GC-MS), single gas sensors and electronic noses (EN). The latter are the core of this paper and are discussed in details. Since the design of multi-sensor arrays and the development of machine learning algorithms are the most challenging parts of the EN construction a special attention is given to the recent advancements in the sensitive layers development and current challenges in data processing. The review takes also into account relatively new EN systems based on mass spectrometry and flash gas chromatography technologies. Numerous examples of applications of the EN devices to the sensory and analytical measurements in the waste management plants are given in order to summarize efforts of scientists on development of these instruments for constant monitoring of chosen waste treatment processes (composting, anaerobic digestion, biofiltration) and assessment of odor nuisance associated with these facilities.

Odors Emitted from Biological Waste and Wastewater Treatment Plants: A Mini-Review

“…In this sense, Burgués et al (2021) developed an e-nose mounted on a small drone which was capable of generating realtime aerial maps of the odor emissions in WWTPs, using a set of 21 gas sensors together with four environmental parameters sensors to highly correlate the concentrations of H 2 S, NH 3 , mercaptans, amines, and different VOCs with odor concentrations measured by the dynamic olfactometry of field samples [71,72]. As stated before, the conclusion is that electronic noses are helpful tools for odor impact assessment; however, it is also clear that maximizing the odor information in terms of olfactometric analysis together with powerful analysis by GC-MS and electronic noses is the way to follow for a proper odor emission characterization [26].…”

“…In fact, the combination of the two approaches is claimed to have advantages for the measurable and objective evaluation of the odor nuisance [25]. Specifically, Jonca et al ( 2022) present a recent review on the use of electronic noses in waste treatment plants, focusing on the development of these apparatuses for the constant monitoring of waste treatment processes (composting, anaerobic digestion, and biofiltration, among others) [26]. The conclusion is that electronic noses are promising tools for the control of the waste treatment process and odor impact assessment; however, "current trends clearly stand that maximum information on the odorous samples investigations is achieved when olfactometry, gas chromatography coupled to mass spectrometry (GC-MS) and e-noses are used as complementary approaches to a given problem" [22].…”

Recent Progress in Electronic Noses for Fermented Foods and Beverages Applications

“…A photograph and schematic diagram of a prototype portable E-nose system are displayed in Figure 3. Nowadays, E-nose systems based on a diversity of gas sensor arrays are applied in all major sectors, such as agriculture and forestry [64][65][66], industrial processes [67], environmental toxin/pollutant analysis [68][69][70], space stations [71,72], medical/healthcare [73][74][75][76], authentication of a person [77], medicine/pharmaceuticals [78], forensic science [79], military [80], toxicology/security [81,82] and the food and beverage industry [83][84][85]. Another emerging direction in the field could be to develop mobile and affordably priced devices for people who suffer from anosmia (loss of smell) [86,87].…”

“…In terms of food business competition, they have been used to analyze aromas and compare them with competitor products [103,104], evaluate the impact of changes in the production process and components that affect organoleptic characteristics [105,106] and compare different food formulations [84,107]. Moreover, E-nose systems have showed high performance in identifying the quality of many products, including wine [108], beer [109], coffee [110], carbonated drinks [111], dairy products Nowadays, E-nose systems based on a diversity of gas sensor arrays are applied in all major sectors, such as agriculture and forestry [64][65][66], industrial processes [67], environmental toxin/pollutant analysis [68][69][70], space stations [71,72], medical/healthcare [73][74][75][76], authentication of a person [77], medicine/pharmaceuticals [78], forensic science [79], military [80], toxicology/security [81,82] and the food and beverage industry [83][84][85]. Another emerging direction in the field could be to develop mobile and affordably priced devices for people who suffer from anosmia (loss of smell) [86,87].…”

Characterization and Discrimination of Apples by Flash GC E-Nose: Geographical Regions and Botanical Origins Studies in China

“…The gas chromatography type E-nose (GC E-nose) is also named ultra-fast or flash gas chromatography, which is usually coupled with gas chromatography. Unlike sensor-based ones, flash GC (FGC) E-nose is possible to identify the volatile compounds [ 10 , 11 ].…”