Climate and Environmental Solutions

Given the current environmental and climate crisis, we have started to look into ways in which our research in microbial systems ecology can contribute to better understand, mitigate and adapt to climate change. We are now using molecular and microbiological analyses and tools to address environmental challenges through a number of projects:

• Microbial processes are widely used to remove nutrients and pollutants such as ammonia and phosphate from wastewater. Among the available technologies, aerobic granular sludge (AGS) represents a promising alternative to conventional activated sludge systems due to its improved biomass settleability and separation. AGS consists of dense, free-floating biofilms formed by multispecies bacterial communities and generally achieves better treatment performance than conventional systems. However, AGS processes still face challenges related to long-term stability and greenhouse gas emissions, motivating our use of sequencing and modeling approaches to investigate how factors such as biomass exchange, granule breakage, and within-granule evolution shape microbial community composition and stability over time. (Guilhem, in collaboration with Simon van Vliet and Nicolas Derlon)

• Seasonal underground heat storage is emerging as an important strategy to balance fluctuations in renewable energy supply and demand. One important approach is High-Temperature Borehole Thermal Energy Storage (HT-BTES), which stores excess heat underground during summer and recovers it during winter using closed-loop borehole systems. A large HT-BTES facility was recently constructed at the Empa–Eawag campus in Dübendorf, where injected temperatures may raise local groundwater temperatures by up to 50 °C. The ARTS collaboration investigates how such temperature changes affect groundwater flow, hydrogeochemistry, microbial activity, and subsurface ecosystems through field monitoring, sampling campaigns, and modeling. The resulting hydro-bio-geochemical “digital twin” model will support long-term predictions and help optimize the sustainability of underground thermal energy storage systems. (Kim and Megan, ARTS Collaboration)

• Limiting global warming will require not only major reductions in greenhouse gas emissions, but also safe long-term strategies for CO2 removal and storage. Geological CO2 sequestration is a promising approach in which CO2 is stored underground and converted into carbonate rock through mineralization, although this process is often slow and strongly dependent on site-specific geochemical and physical conditions. To accelerate mineralization, we are investigating the potential of bacteria to promote CO2 biomineralization under geological storage conditions. We established a high-pressure, temperature-controlled microfluidic system using micromodels fabricated from Swiss rock samples to study bacterial behavior under relevant storage conditions. This project aims to identify bacterial strains and metabolic processes best suited to enhance biomineralization and support safe long-term underground CO2 storage in Switzerland. (in collaboration with Oliver Brandenberg and Joaquin Jimenez-Martinez)