Abstract
The production of concrete for construction purposes is a major source of anthropogenic CO2 emissions. One promising avenue towards a more sustainable construction industry is to make use of naturally occurring mineral-microbe interactions, such as microbial-induced carbonate precipitation (MICP), to produce solid materials. In this paper, we present a new process where calcium carbonate in the form of powdered limestone is transformed to a binder material (termed BioZEment) through microbial dissolution and recrystallization. For the dissolution step, a suitable bacterial strain, closely related to Bacillus pumilus, was isolated from soil near a limestone quarry. We show that this strain produces organic acids from glucose, inducing the dissolution of calcium carbonate in an aqueous slurry of powdered limestone. In the second step, the dissolved limestone solution is used as the calcium source for MICP in sand packed syringe moulds. The amounts of acid produced and calcium carbonate dissolved are shown to depend on the amount of available oxygen as well as the degree of mixing. Precipitation is induced through the pH increase caused by the hydrolysis of urea, mediated by the enzyme urease, which is produced in situ by the bacterium Sporosarcina pasteurii DSM33. The degree of successful consolidation of sand by BioZEment was found to depend on both the amount of urea and the amount of glucose available in the dissolution reaction.
Highlights
More than 10 km3 of concrete is produced every year [1], making it by far the most used construction material
The fossil CO2 released from limestone during calcination, and from burning of fossil fuels to drive this process, currently accounts for more than 5% of global anthropogenic CO2 emissions [2]
Uniaxial strengths as high as 40 MPa have been reported for microbial-induced carbonate precipitation (MICP) applications [25], showing that the method we present here is by no means optimised in terms of injection strategy, aggregate composition, and other processing parameters
Summary
More than 10 km of concrete is produced every year [1], making it by far the most used construction material. Biocementation through bacterial dissolution and recrystallization of limestone our adherence to PLOS ONE policies on sharing data and materials. The fossil CO2 released from limestone during calcination, and from burning of fossil fuels to drive this process, currently accounts for more than 5% of global anthropogenic CO2 emissions [2]. One possible avenue to significantly reduce the environmental footprint of the concrete industry is to employ naturally occurring mineral-microbe interactions in the production of construction materials [3,4,5] thereby replacing extensive heating requirements
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