Bacteria and the Fight against Coastal Erosion
Posted by Science Oxford on November 3, 2009 | comments
Wow, it would be amazing if in the future we could simply seed an area of eroding coast with bacteria designed to slow down or even prevent the erosion.
This is what a PHD student is proposing. The below article contains a summary of the ideas in his work:
Visit this page »Sand can be hardened into sandstone in just a few days through the addition of bacteria. This could help to combat subsidence in houses, for example. Leon van Paassen has succeeded in scaling up the technique. He will defend his PhD thesis on Tuesday 20 October at TU Delft.
Chalk
Van Paassen’s PhD research focused on BioGrout, a new biological technique for reinforcing sandy soils. Within a few days, the sand hardens into sandstone. Specially cultivated bacteria cause calcium-carbonate precipitation in the sand.
Possible applications include railway stabilisation, stabilising pillars in the Limburg marl mines, and combating coastal erosion and housing subsidence.Wedges
In his research, Van Paassen used Sporosarcina pasteurii, a bacterium that contains the enzyme urease. The bacteria are cultivated, injected into the ground and supplied with a solution of urea and calcium chloride. The enzyme urease catalyses the conversion from urea into ammonium and carbonate, whereby the carbonate precipitates as calcium carbonate crystals (chalk). These crystals form wedges between the grains of sand, increasing the strength and stiffness of the sand. The remaining ammonium chloride is then pumped out of the ground and disposed of.Scaling up
Van Paassen, who is working in cooperation with the Deltares knowledge institute and contractor Volker Wessels, succeeded in scaling up the BioGrout process to an experiment of 100 cubic metres (a sand pit measuring 8 x 5 x 2.5 metres), in which the sand is hardened over a distance of five metres within 12 days.
However, there were a number of disadvantages to this method. Removing the ammonium chloride and using specific bacteria make the process relatively costly and therefore less interesting in terms of practical applications.Alternatives
Van Paassen therefore researched possible alternatives to the original process. He discovered an interesting variant whereby calcium acetate (or other salts of fatty acids) and calcium nitrate are injected and converted by bacteria into chalk and nitrogen gas.
A main advantage of this new variant is that the work is done by naturally occurring bacteria and there is no ammonium chloride to be removed. Furthermore, in principle the initial substances calcium acetate and calcium nitrate can be extracted from waste.
Van Paassen demonstrated in experiments that the process actually occurs, but the technique has not been scaled up yet. The coming years will reveal how much potential the technique has.Note for editors
For more information
Leon van Paassen; e-mail: L.A.vanPaassen@tudelft.nl
Research information officer TU Delft Roy Meijer, e-mail r.e.t.meijer@tudelft.nl
For more background information check: www.smartsoils.nl
20
Nov
With Global Warming and the predicted rise in sea levels this must have collosal commercial potential. I know of areas in East Anglia which would benefit immensely.