Giving a New Meaning to Head Space

Every so often a client hires me to work on what I call the “dark side” of olfaction, products like underarm deodorant, kitty litter, feminine hygiene products, and adult incontinence garments. To get anywhere on such projects, the first item of business is to identify the malodors involved, at both the descriptive and chemical level. You need a know what you are dealing with in order to design sensory tests to measure progress, much less assign perfumers and chemists to work on solutions.

This is precisely the tack researchers at Firmenich’s R&D division in Geneva, Switzerland, took when they turned their attention to an important public health issue: designing free-standing toilets (i.e., latrines) that are safe and attractive to use. Flushable toilets require infrastructure—water supply, plumbing, sewerage—that is not always available or affordable. Lacking even field latrines, “more than 2.5 billion people defecate in the open.” So there is a big need for well-designed models that minimize malodor. The Firmenich team tackled the essential first step, a “qualitative and quantitative analysis of volatile constituents from latrines.” They published the results last month.

The group examined traditional models (i.e., a toilet seat over a pit in an outhouse) and “next-generation” designs that separate urine and feces. They did field research in Africa (Kampala, Nairobi, Durban) and India (Pune) in order to capture variation in climate and culture. Deploying the full array of modern analytic chemistry (SPME, GC-MS), they produced a “top 10” list of the key latrine volatiles. It includes sulfur-containing compounds, carboxylic acids, phenol, p-cresol, and those shitty old favorites indole and skatole.

I particularly enjoyed their matter-of-fact field descriptions. Here’s one from Durban, South Africa:

The pit latrines sampled contained various garbage, and the sludge was greenish gray. The odor of the sludge was typical sewage, methyl mercaptan, and rotten egg. In the proximity of the Durban UD [urine diversion] latrines, there was a strong urine smell, slightly ammonia, and animalic, typical of urinals. Inside the UD latrines, the smell was weak, slightly urinal, and farmyard. The collected sample was quite solid and had a weak smell, most likely due to the sandy red soil added to cover newly added feces, and the odor was reminiscent of manure, styrax, and asphalt.

By identifying the malodor volatiles involved and how they vary with physical factors of latrine design and use, Firmenich has made a valuable contribution to improving the well-being of people everywhere. Well done.

The study discussed here is “Qualitative and quantitative analysis of volatile constituents from latrines,” by Jianming Lin, Jackline Aoll, Yvan Niclass, Maria Inés Velazco, Laurent Wünsche, Jana Pika, and Christian Starkenmann, which appeared in Environmental Science & Technology 47:7876-7882, 2013.