This is the VOA Special English Agriculture Report.
hulls, or husks, are the protective coverings on grains of rice. Rice with just
its hull removed is brown rice. Rice without its hull or bran is white rice.
Once rice is harvested, the hulls are out of a job.
They may be taken to landfills or burned. Sometimes they are used to absorb
waste in chicken houses. Other times they are used to amend soil.
But a chemist in Texas has another idea.
Rajan Vempati led a group that developed a new process to make rice hulls into ash.
The idea is to replace some of the portland cement traditionally used in making
concrete. Portland cement is a material that holds together the sand and
crushed stone in concrete.
Rajan Vempati thinks rice hull ash could
help the concrete industry produce less carbon dioxide. Carbon dioxide is
released in cement manufacturing when fuel is burned and limestone is heated. The
Portland Cement Association says the gas from the limestone is reabsorbed as
cement manufacturing produces around five percent of the carbon dioxide
released by human activity worldwide. Carbon dioxide is one of the gases that
may affect the climate by trapping heat.
process for making rice hull ash heats the hulls to eight hundred degrees centigrade.
Carbon is driven out, and fine particles of almost pure silica remain. The
process releases some carbon dioxide, but Rajan Vempati says it would be reabsorbed
into the soil naturally.
Another inventor, Prasad Rangaraju, is
an engineer at Clemson University in South Carolina. He tested the cement, and says
less could be used because the rice hull ash makes it a stronger building
material. Also, the inventors say the light-colored material better reflects
sunlight, so buildings would cost less to cool.
National Ready Mixed Concrete Association points out that using ash in cement
is not a new idea. The ancient Romans discovered that volcanic ash made better
But the modern inventors say rice hull
ash works better than other materials. They developed the process with money
from the National Science Foundation. They have not yet brought it to market.
hull ash is already available, but the product is relatively costly.
Cost, including transportation, may
decide the success of the new technology. Using it could make the most sense in
areas where farmers grow lots of rice and the hulls might just go to waste.
that's the VOA Special English Agriculture Report, written by Jerilyn Watson
with Steve Baragona. I'm Bob Doughty.