Imagine cooling buildings with a material used in fossil infrastructure, currently heating the planet. This might not be such a bold claim after all. Millions of tons of drilling fluid are landfilled or discharged into the ocean from oil and gas wells each year. What is interesting, is that drilling fluids contain a mineral that is the main ingredient for the world’s most promising cooling paints: barite. Can we recover this mineral from soon-to-be-obsolete fossil wells to cool our houses in a heated world?

Drilling for oil and gas has to penetrate hard rock and bring it to the surface. For that, extremely heavy fluids are needed to generate enough buoyancy for rock to float. A barite solution is the right candidate for the job, reaching 4.2 times the density of water. According to our estimates, a stock of 173 million tons are currently in use in fossil infrastructure, potentially a valuable resource.

One fascinating approach to cool down buildings with minimal energy is the application of cooling paints, which – when applied to a surface facing the sky – radiates heat right into outer space without active energy. One of these paints – “Ultrawhite” – achieves sub-ambient temperature surfaces even under daylight conditions. Its main component is barium sulfate – alias barite! Can we access waste barite from decommissioned gas and oil wells, refine it, and produce cooling paints?

In a first step, we want to assess whether cooling paint application makes ecological sense, considering that painted building surfaces will compete with photovoltaics. For this, we currently investigate how cooling paints can be optimally combined with solar energy harvest on building envelopes and evaluate the environmental benefits of repurposing drilling fluids into radiative cooling paints. This analysis combines building physics, energy system modelling, and environmental assessments. And it is an interesting case for how circular thinking can help to achieve the energy transition.

By Hauke Schlesier and Harald Desing – Empa