Australia is beset by twin perils, the looming spectre of the Climate Crisis and the rising pressure of the housing market. While over the next 5 years the temperature is predicted to rise by up to 1.8°C on average1, Australia is planning to build 1 million homes 2 to tackle housing shortages.
While these issues might seem separate at first glance, which they did to us, they quickly become interlinked through one key point, Cement. This material is used constantly in the construction industry and is crucial in the production of concrete. Australia alone in 2021 consumed more than 9.60 million tonnes of cement3, and as demand rises with population, more and more will be needed4. This is a problem as cement production accounts for between 5% and 10%5,6 of all anthropogenic greenhouse gas emissions, primarily CO2, causing untold damage to the environment each year. As young Australians both of these issues affect us deeply, so after our initial brainstorming process, we narrowed down onto the MICP pathway and started research towards the improvement of the efficacy of this system.
However during our research we discovered the large quantities of ammonia that were produced and required by the MICP pathway to function7. Ammonia is also a potent pollutant, which has wreaked havoc on Australian waterways8. We did not wish to solve one issue at the cost of creating another, thus we included this into our context to act upon.
Australia needs a sustainable building material that can be produced at large scale and low cost. We must balance the societal necessity of keeping up with Australia’s rising population and demand for housing with the environmental imperative to rapidly reduce our carbon output. The most sustainable material wood cannot replace concrete’s production cost, tensile requirements and critically in Australia carries significant dangers around fires. Dangers that will only increase as climate change causes hotter and drier conditions. A sustainable equivalent material or augmentation to the current system is required.
To aid in solving these duel problems, UNSW 2023 has turned to the microbiome and specifically, Microbiologically Induced Calcite Precipitation (MICP).
Concrete requires cement to improve the tensile strength and binding ability of the aggregate and water. However as we mentioned above cements carbon emissions are extremely high, but the vast majority, around 90%, of emissions come from the burning of limestone to create clinker. Clinker acts as the material that binds cement together, like how cement acts with concrete.
So removal of burning Limestone would drastically reduce emissions, but mined CaCO3 is not fine, nor well shaped enough to act as a binding agent. This is where MICP comes in. The CaCO3 crystals that are produced by the microbes is small and pure enough to function as the binder, allowing cement produced to bypass the kiln stage, preventing the massive carbon releases.
However natural MICP has many flaws, the primary one for us at the start of this project was the inefficiency of the pathway in traditional bacteria and the difficulty cultivating microbes with the most powerful pathways. Thus after research and speaking with advisors we transplanted genes coding for the powerful H. pylori Carbonic anhydrase and urease metabolic pathways into a dependable and cultivatable E. coli chassis.
This transgenic arrangement allows the rapid and large-scale production of efficient, easily maintainable genetic machines.
Furthermore, during our research we highlighted the eutrophic dangers of the high levels of ammonia produced and required for this process, with runoff being an established environmental pollutant in Australia’s waterways. To counteract this issue and avoid the pattern of short-term thinking that has brought us to this situation, we added in the elements of nitrification pathway from Nitrosomonas Eutropha and Europaea along with a custom promoter to activate when the ammonia levels increase too much.
Concrete requires cement to improve the tensile strength and binding ability of the aggregate and water. However as we mentioned above cements carbon emissions are extremely high, but the vast majority, around 90%, of emissions come from the burning of limestone to create clinker. Clinker acts as the material that binds cement together, like how cement acts with concrete.