Scientists in Valencia have developed a new use for leftover olive
stones – in sound barriers such as those used to reduce rail and road
noise.
They found the porosity of olive stones – charred ones in particular – gives them high absorption ability.
The
Panolston project researchers, from the Polytechnic University of
Valencia’s (UPV) Institute of Transport and Territory, together with the
prefabrication company Precon, claim porous concrete acoustic screens
made with carbonized olive stones are a viable alternative to current
options.
Civil engineer and UPV researcher Julia Real said they
not only mitigate rail and road noise, “they provide a new outlet and
value-adding for an agricultural by-product, olive stones.”
“We
have compared their acoustic performance to screens made with
conventional porous concrete, and also with wood or mineral wool with
perforated sheet metal, and their absorption capacity is highly
competitive, ” she said.
Screens made with mineral wool are one of
the best options currently on the market but they are expensive,
costing €90-120/m2, and work more by reflecting than absorbing noise.
Wood screens are now largely obsolete, she said.
“Our screens of
porous concrete and charred olive stones not only reflect noise, they
absorb it, and with very high levels of absorption. Furthermore, they
don’t burn because the stones have already been burned, and they’re 18
percent cheaper.”
Depending on the proportion of olive stone char
used and a screen’s surface finish, different frequencies can be
absorbed. This allows adaptability to different kinds of noise, such as
from a highway or high-speed railway, she said.
Fellow UPV researcher Laura Montalban Domingo told Olive Oil Times
that charred olive stones have a high level of porosity. “The open
porosity allows a sound wave to penetrate the material and dissipate as
it ‘crashes’ into the interior walls of a pore, while the closed
porosity modifies the density and rigidity of the material, modifying
the screen’s vibrational response,” she said.
According to a
ScienceDaily report on making bioethanol from olive stones, Spain’s
olive oil and table olive sectors together generate about 4 million tons
of olive stone waste a year. Its main use has so far been for energy
generation in biomass boilers.
Meanwhile, according to the Tea
Obsession blog, olive stone charcoal is part of the ancient tea culture
of Chao Zhou, China, where it is used to both boil and flavor the water.
Source
by Julie Butler, Olive Oil Times