Pig data: Odour analysis

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  • Published: Jul 15, 2016
  • Author: David Bradley
  • Channels: Chemometrics & Informatics
thumbnail image: Pig data: Odour analysis

Porcine perfume

Pig ignorant: Chemical informatics can be used to let you know just how smelly is that pig farm, without having to muddy your boots. (Photo credit: David Bradley)

Chemical informatics can be used to let you know just how smelly is that pig farm, without having to muddy your boots. Usually, it takes a nose to know a smell, but processing analytical data can now be used to define odour levels, according to researchers in Denmark.

Engineers at Aarhus University have developed the first multivariate model that is not to be sniffed at, which can give an objective idea of odour from pig farms by means of precise measurements of the content of odorants in the atmosphere. The approach might, of course, be extended to other sites that produce strong and unpleasant smells, such as biomass and composting sites, sewage plants. It could then be used to provide an objective measure of how effective is any odour abatement process or system that has been put in place to protection the olfactory senses of workers and local people.

The Aarhus model developed in cooperation with SEGES, the recently established Knowledge Centre for Agriculture and the Danish Pig Research Centre in Aarhus. The data processed by the model comes from measurements of odorants taken by means of proton-transfer-reaction mass spectrometry (PTR-MS).

This place is like a pig sty!

Any rambler who has encountered the pungent and less than delicate scent of a pig sties will not forget the stench in a hurry. Of course, those working in this malodorous environment may well become immune, but a rose by any other name would be preferable for them and the people who live nearby, one must assume. It also might stymie expansion plans for pig farmers if the locals catch a whiff of their aspirations. As such, odour abatement is an important area of research that could equally applied to other sites with a low olfactory aesthetic too.

Air filters and alternative porcine housing design are possible technical solutions to the odour issue, but assessing their effectiveness currently relies on the rather subjective human nose. Stakeholders may not agree on what constitutes an acceptable smell level and so a more objective approach is needed that could be used in a regulatory setting to establish a legal or moral baseline acceptable to all parties. The residents of the pig sty itself generally being indifferent, if not happy, regardless of the human debate.

The optimum method will be to quantify the connection between the smell that the human nose experiences and the actual, measured amount of specific odorants in the air considered noxious to the sensibilities of any sensible person. Analysis on the pig farm itself, rather than with limited atmospheric samples in the laboratory would be the best approach given the inconvenience of transporting "bags of air" and the problem of running out of sample or losing specific volatiles from the bag. The research thus aimed to develop a model to measure the concentration of odorants using on-site measurements as well as identifying the most significant odorants.

Olfactory aesthetics

The researchers measured the odours on different pig farms - some with odour abatement solutions in place and others without, respectively. Their new mobile odour laboratory equipped with a PTR-MS for measuring odorants was used as well as an olfactometer, simply a device that allows a human panellist to assess the odour.

There were 115 simultaneous sensory and analytical chemical odour measurements taken down on the farm with the mobile laboratory. The team, Michael Hansen, Kristoffer Jonassen, Mette Marie Løkke, Anders Adamsen, and Anders Feilberg, suggests that the results are very promising. The researchers, scientists found that phenols and indoles are perhaps the most significant unpleasant odorants. They also demonstrated that their partial-least-squares regression model showed a high correlation between predicted and measured odour concentrations. This was in contrast to previous studies and shows for the first time that direct measurement of atmospheric odorants on-site can be used as an alternative to dynamic olfactometry.

Related Links

Atmos. Environ., 2016, 135, 50-58: "Multivariate prediction of odor from pig production based on in-situ measurement of odorants"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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