Optimising bacteria production and storage for field-scale application of a new biomineralization technology in ground engineering

Challenge

The construction industry accounts for ~39% of global carbon emissions. Cement production alone accounts for 5% of global emissions. Finding low carbon alternatives to traditional cement-based construction methods is therefore a priority.

BAM Ritchies would like to reduce their emissions by finding lower carbon footprint alternatives. The best way to reduce the carbon footprint embodied in construction materials, such as cement, is not to construct! The vast majority of UK infrastructure in degraded and has passed its original design life. We therefore need new innovative technologies that can repair and restore our infrastructure; sealing fractures in concrete; strengthening foundations; and restoring/reinforcing our coastal and flood protection schemes.

Solution

IBioIC awarded £100,000 from our Innovation Fund to BAM Ritchies and Professor Lunn at University of Strathclyde to work together to advance the development of a biomineral technology using bacteria. The team used IBioIC’s FlexBio labs to optimise the growth conditions of the bacteria, ensuring a balance between cell number and activity. IBioIC also provided a connection to a spray drying facility to help develop a process for stabilising and storing the bacteria.

Prof Lunn’s group use a natural, harmless, soil bacteria to solidify sands using a calcium rich solution. The concept had been proven at lab scale, but there was work to do to optimise the growing conditions of the bacteria, to improve the fluid dynamics of injecting the bacteria solutions to granular soil substrates, and to test the process at demonstrator scale. The technology uses bacteria injected into a porous or cracked material to precipitate calcium carbonate, increasing the material strength and reducing its permeability.

BAM were involved in the engineering of facilities to conduct demonstrator scale trials, which were carried out at their facilities in Kilsyth.

The project aimed to reduce or eliminate the requirement to use high carbon techniques or materials to stabilise or strengthen ground works. This technique will help reduce our reliance on traditional construction methods and materials to reduce BAM’s carbon footprint and provide a USP for the company.

Core and demonstrator-scale trials were performed to turn loose sand into rock. Bacteria, followed by urea and calcium chloride, are injected into the sand. Calcium carbonate then precipitates at the sand grain contacts, turning a loose sand into a rock. Biocemented cores drilled after treatment from the demonstrator scale trials achieved strengths ranging from 3.6MPa to 7.6MPa which was similar to those produced during the lab scale experiments. Visual inspection of the biocemented block suggested that in areas the strength could be significantly higher as deviation of the core holes was observed after drilling, and hammers and chisels were required to extract block samples.

Outcome

The project expanded BAM Ritchies’ understanding of the IB landscape and enabled them to see and develop new opportunities in the area outside their normal sphere. The project also enabled Prof Lunn and her group to optimise the bacterial growth and provided testing of the strength of the biocemented sand cores, and this collaboration is set to continue beyond this project.