The microbial fuel cell consists of an anode and a cathode, which correspond to the positive and negative poles of a battery. Electroactive microorganisms release electrons to the anode when they break down organic waste products such as plant residues, thus preventing the development of algae blooms. In addition, the filtering of the pond water is coupled with energy generation in the form of electricity. Electroactive microorganisms can be used for a wide range of innovative technologies, opening up new prospects for a bio-based circular economy.

Storing thermal energy in aquifers using ATES systems (Aquifer Thermal Energy Storage) offers potential for CO2-free heat management in urban areas. In the warm season, the aquifer is “charged” with hot water, which is pumped up in winter. In winter, the process is reversed. However, near-surface aquifers are often contaminated by industrial pollutants, which limits their function as seasonal heat reservoirs. The KONATES project is investigating how the cyclical operation of a thermal management system can be combined with simultaneous groundwater remediation.

The droughts of recent years have highlighted how quickly groundwater levels can fall and water can become a scarce resource – even in our geographical latitudes. The decentralised and local reuse of water is an important measure to conserve drinking water reserves. A marsh plant roof can fulfil several functions here. It purifies grey water (fecal-free household wastewater), cools the environment on hot days and provides food for insects – in other words, it strengthens urban biodiversity.

Climate change leads to a shift in precipitation patterns: droughts on the one hand and heavy rainfall on the other are on the increase. Innovative methods of rainwater management are being developed to better cope with periods of drought and, in the event of heavy rainfall, to relieve the burden on the sewage system and prevent localised flooding. A retention green roof increases the capacity of a green roof structure to absorb rainwater many times over and serves to regulate the irrigation of the green roof vegetation.

Tree trenches – underground water reservoirs planted with trees – are part of bluegreen infrastructures. With their help, urban runoff can be controlled in cities during heavy rainfall, reducing the risk of flooding. Rainwater carries organic pollutants such as tire wear or fuel spillage into the root zone, where these pollutants can partially be degraded by the microbial community. UFZ researcher test how this pollutant degradation can be optimised by adding biochar and organic degradation stimulants.

In combination with other blue-green infrastructures, green roofs have a variety of positive effects on the urban and building climate, on biodiversity, on rainwater management and also on the preservation of buildings, in addition to their visual appeal. On the UFZ research green roof, extensive sensor technology enables the creation of energy balances and long-term measurements of the effects that different roof coverings have on the microclimate and biodiversity and how they function as rainwater reservoirs and pollutant sinks.

In the field, pollutants often affect aquatic communities at much lower concentrations than in laboratory systems. The reason for this is the combined effect of multiple stressors. The UFZ river experiment consists of 47 flow channels, each 14 metres long, and simulates a natural stream system in which individual parameters can be specifically controlled and monitored. The results – coupled with laboratory tests – are processed using mathematical models and lead to more realistic predictions of chemical effects in ecosystems.

UFZ scientists are developing and validating application-oriented measurement methods to investigate natural and anthropogenic processes and their effects. One such method is direct push-based sensing, which allows to describe various properties of the subsoil at depths of up to 30 meters. The UFZ is trialling such probing methods and other sensor technology at this test site. These include sensors that use cosmic radiation to record soil moisture in the root zone within a radius of up to 150 meters and thus improve drought forecasts. In addition, particulate matter and nitrogen oxide sensors are being tested in order to steer traffic flows in Leipzig and other cities in an environmentally sensitive manner – coupled with artificial intelligence.

Urban trees provide multiple functions that help to make cities more resilient to climate change and attractive. Amongst those are cooling effects through shade and evaporation, increased biodiversity, or attractive recreational spaces. To optimally fulfil those functions, trees require resources such as soil, water, and enough space. Jointly, colleagues from Helmholtz centers KIT, Hereon and UFZ investigate how different irrigation in summer affects sap flow, trunk and root growth as well as air temperature and humidity in the canopy. The results contribute to sustainable urban planning and adaptable tree management strategies.