Yucca plants, strategically deployed, might one day take the pong out
of public toilets, according to recent research at Galway in Ireland. The
plants have already proved their worth in offal-rendering plants and factory
Neighbours stopped complaining of the smell when essence of yucca was
sprayed over existing biofilters made of heather and moss. In later tests,
yucca extracts fed to factory-farmed pigs cleared the choking atmosphere
inside the piggeries – to the benefit of both pigs and farm workers. Denis
Headon, professor of biochemistry at the National University of Ireland,
Galway, finds that yucca sweetens the air by binding the ammonia given off
by animal excretions, especially the urea in urine.
Yucca plants (Yucca schidigera) have their own reasons for soaking up
ammonia. They live in the southwestern deserts of the US where nitrogen,
as well as water, is in short supply. The plants have solved one of their
problems by evolving a way to make a meal out of the ammonia emanating from
the waste products of desert animals.
In the raw, ammonia is highly volatile and toxic to animals and plants
alike. But yucca can apparently bind ammonia in such a way as to make it
nonvolatile and nontoxic. The plants then exploit the nitrogen in the ammonia
to manufacture the proteins vital for their rapid growth.
Agriculturalists have long known that livestock fed with yucca extracts
produce less ammonia, but thought that the plant’s saponins deserved the
credit. The idea was that saponins inhibit the enzyme urease, which releases
ammonia from urea.
Headon and his colleagues have now found that yucca preparations still
bind ammonia even after the saponins have been removed. Headon’s experiments
strongly suggest that yucca’s odour-eating properties come from its ability
to bind ammonia, rather than from any blocking of the enzyme. This explains
why yucca in chicken feed also reduces ammonia emissions from battery hen
houses, even though chickens excrete uric acid, which is not directly attacked
by urease. But, as yet, the identity of yucca’s ammonia-binding molecules
Headon is now studying the Quillaia plant which dominates the Chilean
deserts. It too binds ammonia.