Science Interviews


Sun, 12th Feb 2006

Taking The Stench Out of Malodorous Manure

Dr Charles Wysocki, Monell Chemical Senses Centre, Philadelphia

Part of the show Science of Seduction, Pheromones and the Food of Love

Chris - Tell us about your work.

Charles - Over the past few years we've been focussing on agricultural practices in the state of Pennsylvania, and focussing on ways to reduce the impact of odours that are associated with agricultural practices. Notable among them is pig farming, mushroom composting, dairy cattle and chickens. What we've found is that by using a combination of techniques, such as using crushed up charcoal and the introduction of pleasant smelling odours, we are able to reduce the impact of these nasty smelling odours for people who live down wind.

Chris - How do you actually get the reduction in the experience of the smell? I understand that the charcoal will mop up some of the nasty smell molecules, but how does the pleasant odour manage to down tune the nose so it starts to ignore the smell of the manure?

Charles - We use specially built molecules that competes for the receptor sites that Peter spoke about. These specially built molecules are pleasant smelling and they activate some of those receptor proteins that provide a pleasant smelling experience for the people. They also compete for the receptor sites that would be occupied by the nasty smelling odour.

Chris - So you're switching off the nasty smell on the one hand, but switching on a nice smell on the other hand with the same molecule.

Charles - Yes.

Chris - That's very clever. Do you think you could take that into the home or to the nearest sewage works, for example, and mask all kinds of nasty odours?

Charles - We actually started this many years ago looking at underarm odour. That proved to be successful. We have attempted it with home air fresheners and it appears to be working well there as well. Unfortunately we need to know exactly what the nasty smelling odours are, so it takes a lot of analytical chemistry.

Chris - Yes, how do you home in on what they are?

Charles - By combining expertise in chemistry with expertise in sensory perception. We have to make use of the human nose as well as the information that comes out of all these analytical instruments.

Chris - So you make up a molecule, try it, see what it smells like and whether it's close to the smell of manure, and tweak it until it smells better.

Charles - In part. What we do is identify the nasty smelling odours that are in the manures or the slurries and that's where the chemistry comes in. We then make a molecule based on that identification. The molecule that we make is pleasant smelling.

Chris - And from there it's just a case of trial and error to see if it's able to compete on equal terms with the manure. How much of this stuff do you have to add to a big bucket of pig swill to knock out the effect? Is it actually effective? Can you actually achieve what you set out to do?

Charles - We don't have a product yet that we can market, but that's not our goal. We do the basic research and leave it to others to develop. What we have found is that anywhere from zero point one to one per cent of the total is sufficient.

Chris - So it could actually be realistic and cost effective for farmers to do this?

Charles - That's what we're thinking, yes.

Chris - And I bet their neighbours are rubbing their hands together and thinking, yes please!

Charles - Yes. The only problem is that it still smells, but it will be a pleasant odour in the air.


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