From sand to rock—quickly!
As this picture of a toy car encased in stone shows (see
Toy car rocks million-year belief), you don’t need millions of years
for sediment to harden into rock. Now researchers have identified that the process
can be helped along by microbes secreting cementing agents (as a by-product of their
normal metabolic processes).
by David Catchpoole
Published: 3 November 2009(GMT+10)
If anyone thinks that rocks need millions of years to form, then experiments carried
out by Murdoch University (Perth, Western Australia) researchers would surely overturn
that idea.
That’s because the researchers have been able, with the help of added microorganisms,
to turn sand into stone rapidly.1
The researchers investigated microbes for their ability to produce a cementing agent
(dubbed “biocement”) that would bind sand particles together, forming
rock. The bacterium Sporosarcina pasteurii (formerly known as Bacillus
pasteurii) has an enzyme that enables it, in the right circumstances, to
do just that. Its urease enzyme hydrolyses urea, and when this hydrolysis occurs
in a calcium-rich environment, it generates binding calcite cement (calcium carbonate)
as a by-product.2
In a series of trials, the bacterium treatment altered the consistency of sand,
making soft sand harder, even “changing it into a substance as hard as marble”.
According to Dr Ralf Cord-Ruwisch, “The biggest block we have made so far
was in a shipping container, just to prove that it can not only work in the laboratory.”1
With repeated treatment, “we found that it turns harder each time”,
said Dr Cord-Ruwisch. “At the very end, it turned into something resembling
marble more than sandstone.”
The bacterium treatment altered the consistency of sand, making soft sand harder,
even changing it into a substance as hard as marble
The results of the research have excited many people who can see that such “biocement
technology” will be a great boon to construction and mining industries—not
just to someone wanting “to take their sandcastle home from the beach in the
form of a solid rock sculpture”.
A Dutch company sent sand samples from Holland to Murdoch University for testing.
Dr Cord-Ruwisch explained that the Netherlands has a keen interest in solidifying
the dikes that prevent the sea from flooding that country’s vast areas of
reclaimed low-lying land.
“Dikes would normally be made of rocks, solid stuff, but Holland is a bit
like Perth in that they only have sand,” he said. “While dikes made
from sand are long lasting, there are certain risks if water intrudes into the dike
sand and lubricates the sand particles so they start shifting against each other.
Then you can have some instability of the dikes.”1 The Dutch have
been impressed by the capability of the bacteria to cement the sand samples—hard.3
Another potential application will be in the restoration of historical buildings.
As Vicky Whiffin, whose PhD thesis investigated the ability of bacteria to convert
sand into stone, explained, “Cement is currently used for a lot of restoration
work, but water can build up behind it and cause it to crumble away. This new biological
system allows the water to leach out, which makes it a more secure option than concrete
for mending heritage structures.”3
However, probably the major practical application for the biocementation technique
will be in mining. “It doesn’t need oxygenation,” Cord-Ruwisch
explained. “In theory we could solidify the sea bed before drilling for oil.
We could also drill tunnels in the sand, we could make the sand harder so it doesn’t
cave in.”1
The take-home message from all this? In the global Flood of Noah’s day (about
4,500 years ago), there would have been lots of microbes “floating around”
and buried in sand in low-oxygen conditions, just right for them to release cementing
agents into the surrounding sediment. Little wonder then we see as a legacy of that
watery event, lots of beautifully preserved creatures (fossils) in layers upon layers
of rock-hard sediment!
Readers’ comments:
Tinus de B. , South Africa, 4 November 2009
Let’s go build some pyramids..!
Michael C., United States, 18 November 2009
Oh man! That is so cool. God is great! His creations are so creative and unique.
And in the beginning, he had given us the mandate to dominate it all and work in
it. We can still do that, of course. ;)
I’m going to go share this article with my friends and family. I love the
fact that you really don’t need MILLIONS of fairytale years to preserve something.
|
Related articles
Related resources
References
- Calvo, S., Scientists turn sand to stone, Science Alert,
www.sciencealert.com.au/content/view/19095, 7 May 2009. Return
to text.
- Whiffin, V., Microbial CaCO3precipitation for the
production of biocement, PhD thesis, 2004—Abstract viewed via Murdoch University
Digital Theses Program, <https://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20041101.142604>,
last accessed 22 October 2009. Return to text.
- Murdoch University Synergy 6(2): Winter 2002,
Biocement for Sandcastles, <http://about.murdoch.edu.au/synergy/0602/biocement.html>,
last accessed 22 October 2009. Return to text.
|
