Sounding out stinks

High-frequency sound will clear the smell of pig manure from the air if a
pork producer’s $87 000 gamble pays off. Heartland Pork Enterprises of
Iowa Falls is paying the University of Iowa to find out if the stink can be
cleared from pig farms using ultrasound, which is known to catalyse some
chemical reactions. David Soll, the biologist who received the grant, hopes that
blasting manure with ultrasound will speed up the oxidation of hydrogen sulphide
into less smelly sulphur, and of ammonia into nitrogen.