International - Bug-laden foam destroys stink of manure
Published:May 31, 2004
Source :NewScientist.com
A bacteria-laden foam could destroy the foul-smelling pongs from animal waste on intensive farms. The waste from intensive pig and chicken farms produces smells that can destroy the quality of life for nearby communities.
People who are only familiar with ordinary farmyard smells find it hard to believe how bad it is, says Amy Chapin, who studies the health effects of intensive farming at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland. "It's an incredibly strong and pungent odour," she says.
US federal regulations mandate farmers to deal with odorous compounds such as hydrogen sulphide - the "bad egg" smell.
At present, this usually means passing the air through a filter, but this is not always feasible with outside odour sources such as lagoons of swine faeces. Also, filters have to be maintained at the correct temperature and humidity to be effective.
To deal with localised sources of smell, a Korean team led by Kyoungphile Ham at Seoul National University in Korea have developed a bacteria-containing foam that is capable of removing whiffy compounds such as ammonia and hydrogen sulphide.
The foam would be sprayed directly onto dung heaps or lagoons. The base of the foam is the protein keratin, which is the key compound in hair and nails. It is "fluffed up" by passing compressed air through it. "It is like whipping cream," says Nam.
The foam also contains non-toxic stabilising chemicals to increase its volume and stop it from going flat too quickly. These chemicals extend the lifespan of its foaminess from just a few hours to three days. The keratin itself is already available as a waste product from feathers on chicken farms.
Bacteria such as Pseudomonas are well known for their ability to extract smelly compounds from air and metabolise them into neutral compounds. But by adding them to the foam mixture before it is "fluffed up" they are able to occupy a large surface area within the foam. This improves their ability to catch the bad smells.
In the lab, Nam found that his foam was able to remove around two-thirds of the ammonia and three-quarters of hydrogen sulphide given off by samples.
