Green Ideas: Making Concrete from Rice

Jul 21, 2009 by Miranda Marquit weblog
Rice
Image source: Botanical.com

(PhysOrg.com) -- Concrete accounts for about 5% of all human-related CO2 emissions. The fact that we use so much cement in building could mean that the issue becomes even more pronounced in the future. But what if there was a way to make concrete that was more environmentally friendly? A team of researchers in Texas things there might be -- by adding rice to concrete.

One of the ingredients that can be used in is ash. By mixing husk ash into the cement, there is the possibility of greener concrete. Discovery News offers this on the process of creating carbon neutral rice ash:

Now, Rajan Vempati of ChK Group, Inc. in Plano, Texas, and a team of researchers have figured out a way to make nearly carbon-free rice husk ash. Heating husks to 800 degrees centigrade (1,472 degrees Fahrenheit) in a furnace drives off carbon, leaving fine particles of nearly pure behind.

"The process emits some CO2, but it's carbon neutral. Any that we emit goes back annually into the rice paddies," Vempati said.

Concrete is a favorite repository of unwanted waste materials, from steel slag to silica fume, since it can provide a useful way of recycling products that are hard to get rid of without filling landfills. Ash from rice husks, while not completely neutralizing the pollution that comes from making cement, could reduce it. On top of that, this ash provides protection against and strengthens the concrete.

The process has yet to be refined and tested in real-world conditions, so the idea is still mostly in its initial stages. However, when one considers that up and coming economic powers, such as India and (especially) China, will be likely ramping up production of concrete for use in buildings and roads, the prospect of reducing carbon emissions and pollution through the use of risk husk ash in becomes even more interesting.

© 2009 PhysOrg.com

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User comments : 7

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barakn
3 / 5 (6) Jul 21, 2009
Carbon neutral as long as you ignore the energy source of the furnace.
Velanarris
4.8 / 5 (5) Jul 21, 2009
This has zero to do with CO2 production relating to concrete.

90% of the CO2 generated in the production of concrete and other cements is due to the intense heating of Limestone and other Calcium Carbonates releasing the CO2 and CO. Creation of ash for subaggregate is almost of no consequence.

Hell you could replace it with Coal fly ash and it'd be about the same as this rice ash.
defunctdiety
4.7 / 5 (3) Jul 21, 2009
90% of the CO2 generated in the production of concrete and other cements is due to the intense heating of Limestone and other Calcium Carbonates releasing the CO2 and CO.

Hell you could replace it with Coal fly ash and it'd be about the same as this rice ash.


He's right.

And when you consider that fly ash is already almost universally controlled and collected in baghouses at the kinds of facilities that create it (power plants, boilers), it's a pretty good idea to sell it if it could be used, where as currently they probably just dump it...?
nkalanaga
5 / 5 (3) Jul 21, 2009
Both true, but the CO2 from the limestone is reabsorbed as the concrete cures, so that part is itself carbon neutral. The excess carbon comes from the fuel burned in the kilns, and the only way to reduce that is to find another way of baking the rocks.
TJ_alberta
5 / 5 (3) Jul 21, 2009
If the morphology of the silica from rice husk is suitable then it can strengthen the concrete. Fumed silica has been added to concrete before. I agree with Velanarris that this has nothing to do with CO2 or pollution - unless getting rid of unused rice husks is a big problem... if they succeed in making a good silica out of the rice husks & in an economical way then it could be a bonus for the rice farmers.
Velanarris
not rated yet Jul 22, 2009
Both true, but the CO2 from the limestone is reabsorbed as the concrete cures, so that part is itself carbon neutral. The excess carbon comes from the fuel burned in the kilns, and the only way to reduce that is to find another way of baking the rocks.

The limestones don't absorb 100% of the carbon they release, if anything it would have to be far less just due to exposed surface area.
3432682
4 / 5 (4) Jul 22, 2009
Is there no limit to the stretch toward "green" in the articles posted? It's beyond silly, it is destroying credibility. Please stop.

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