Portuguese researchers have found a way to incorporate leftover brewery grains into a paste used to make bricks.
In particular, the high-fiber waste containing spent grains -- barley malt and maize grits -- an easily available, pulpy cake that can be used as animal feed or in a landfill.
Conventional red clay bricks contain polystyrene (a synthetic polymer), which helps enhance their heat-trapping abilities. This is appealing, because the bricks remain strong, and they can be built into energy-efficient buildings, Eduardo Ferraz of the Polytechnic Institute of Tomartold New Scientist. But EU restrictions on carbon emissions have made it expensive to incorporate these sorts of synthetic materials into bricks.
After experimenting with various ratios of grain to brick raw material, the team found the best compromise between “highest mechanical bending strength” and “lowest thermal conductivity.” That is, bricks that provide insulation without sacrificing strength, New Scientist explains:
With a clay paste containing 5 percent spent grains, the team was able to create bricks just as strong as the conventional type, while reducing the amount of heat they lost by 28 percent.
Turns out, the grains make the bricks more porous, so they trap more air, which increases heat retention, according to the team. (These experimental bricks were slow fired at 900, 950, and 1,000 degrees Celsius.)
But then there’s the smell. U.S. brick manufacturer Acme Brick Company had previously given up on experimenting with this material because of the overpowering stench of moist grains, New Scientist reports. Although according to Ferraz, the problem vanishes once the bricks are fired.
The work was published in Journal of Materials in Civil Engineering last month.
Janet Fang has written for Nature, Discover and the Point Reyes Light. She is currently a lab technician at Lamont-Doherty Earth Observatory. She holds degrees from the University of California, Berkeley and Columbia University. She is based in New York.
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