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For a better concrete, mix sand with bacteria and urea

Posting in Environment
 
microbial manufacture sand.jpg
 
Concrete is the second most consumed substance on Earth, after water. It’s primary ingredient, cement, accounts for about 5 percent of the world’s carbon dioxide emissions. From bricks made with leftover brewery grains to concrete modeled after ancient Roman breakwaters, researchers have been looking hard for less energy-intensive alternatives. 

And now urea. For his thesis project at University of Edinburgh, Peter Trimble wanted to see if it was possible to grow our building material instead of using intensive heat, Wired reports. “I thought, Is there an equivalent material that’s more environmentally friendly but structurally comparable out there?” he says. Turns out, all you need is some sand, bacteria, calcium chloride and a decent amount of urea. 

Trimble’s design replaces the energy intensive methods with the low energy biological processes of “microbial manufacture.” He calls the method Dupe, and he's created a little stool capable of holding all his weight.

  1. Pack sand (right on the beach) into a cast of a stool. 
  2. Then, pump a liquid mixture of Bacillus pasteurii, calcium chloride, and urea into that sand-filled mold. 
  3. The bacteria cements the sand particles together. When urea and calcium chloride come into contact with the bacteria, they form a bond (a biological cementation), creating a sandstone-like biomaterial.

Watch a short film on the process here (and below). You can see, the portable setup is simple: a stainless steel container, a mixer from a food blender and a pump from a coffee machine, Wired explains
 
 
Greenhouse gases were not produced, and the process works at “biological temperatures,” according to Trimble, unlike the current “heat beat and treat” methods of production. Portland cement, for example, requires fossil fuels to burn calcium carbonate and clays at about 2,642 degrees Fahrenheit. Trimble’s not a scientist (a product designer, actually) -- and without reinforcement, the material is only around two-thirds as strong as cement -- but it’s a testament to the biomaterial’s potential uses, Wired reports. For starters, some smart street furniture.

And in case you’re curious, Trimble didn’t actually use urine. “I didn’t particularly fancy setting a bin in my bathroom and getting my flatmates to fill it up with urine, so we skipped that one,” he explains. “Technically it’s possible, but you would need like 100 liters or something, and that’s a lot of wee.”

[Via Wired]

Images/video: Peter Trimble 
 
microbial manufacture stool.jpg
 

— By on January 29, 2014, 11:55 PM PST

Janet Fang

Contributing Editor

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. Follow her on Twitter. Disclosure