Description: This is
a VOA Special English Agriculture Report.
See text below
Text:
Rice 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 concrete ages.
But 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.
The 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.
The 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 cement.
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.
Rice 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.
And that's the VOA Special English Agricultur
Report.
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Hi. I
personally reviewed this video and found it appropriate for
the news section of English Global Group. This
is a Voice of America video which covers an interesting
topic in Special English. I would appreciate some feedback from both
students and teachers about this video. You can comment in
the window below using any of a number of different services
including Facebook, Yahoo, AOL, and Hotmail.
