Researchers from Aarhus University have reviewed natural power banks known as geobatteries existing in our soil and water systems. These natural substances, acting like tiny rechargeable batteries, could help understand how soil deals with environmental challenges.
Within soils, geobatteries can power their surroundings by giving away electrons, recharge themselves by taking in electrons, and store electrons for later use.
In their July 2024 review, PhD scholar Shihao Cui and colleagues explored the mechanisms and significance of geobatteries, highlighting their role in electron transfer within environmental soil cycles and their potential applications in addressing climate change, treating pollution, and other environmental challenges.
These “redox” reactions also happen when we charge phones, laptops, or car batteries. Charging these batteries means one point of the battery is oxidised (meaning it loses electrons) to power the device. Electrons then reach the second point of the battery, which gets reduced (gains electrons). Charging batteries reverses this process, bringing the electrons back to their starting point.
Unlike the batteries in our phones, these natural geobattery power banks are constantly recharging thanks to the ever-changing environmental conditions, such as water table fluctuations.
Geobatteries contain special chemical groups that can grab and release electrons when needed. This ability allows them to bridge the gap between different parts of the soil ecosystem, helping transfer energy where it is needed the most.
The research team identified several types of geobatteries. The first type is the natural organic matter – the decaying leaves and plant materials accumulating over the soil, for example in peatlands. The second type is pyrogenic carbon, charcoal-like substances that form due to even slightly or partially charring or burning of organic material after wildfires, for example biochar, soot, or wood ash. Another type of geobatteries is mixed-valent mineral phases – minerals present in the soil, for example iron and manganese. Interestingly, the study team also highlighted that even tiny plastic particles – better known as microplastics – can act as geobatteries.
Benefits
These tiny powerhouses can boost anaerobic digestion, a process that breaks down waste to produce energy. They also help clean up pollutants by speeding up the breakdown of harmful substances like pesticides in soil and water. Perhaps most excitingly, geobatteries might play a role in fighting climate change. They can influence how carbon moves through soil, potentially trapping more of it underground. Some geobatteries may even help reduce emissions of methane, a potent greenhouse gas.
Geobatteries are significantly influenced by water table fluctuations, and understanding their responses to these changes can help us better predict how ecosystems will react to floods, droughts, and other hydrological events, thus improving our ability to predict environmental changes after such disturbances.
Cui told Earth.Org that “by understanding how geobatteries function under fluctuating water conditions, we can develop targeted strategies to reduce methane emissions from rewetted peatlands, where methane increases after rewetting can undermine the climate benefits of restoration.”
The discovery of geobatteries could have far-reaching potential applications.
“Understanding geobatteries’ electron transfer abilities will help regulate processes like recycling nutrients, breakdown of pollutants, and reduce greenhouse gas emissions such as methane,”explained Cui.
Field Work
Some substances in the soil work better as geobatteries than others. For example, biochar can stay in the soil longer than natural organic matter and have more surface area and pores than mineral-based geobatteries. Farmers can add biochar to soil to boost soil fertility, hold more water and prevent erosion.
However, one main challenge is the complexity of natural environments, which makes it harder to accurately measure electron transfer processes. Therefore, researchers are carrying out fieldwork for monitoring water levels in peatlands or rewetting areas.
“These field studies bridge the gap between controlled lab experiments and the unpredictable, variable conditions found in nature, helping us understand how geobatteries contribute to greenhouse gas regulation,”said Cui.
These field studies can better show how the elements get recycled and how greenhouse gases are emitted. The field research studies in wetlands are part of the EU-funded WET HORIZONS project, which is developing tools to enhance the protection and restoration of Europe’s wetlands.
“Understanding geobatteries helps us gain deeper insights into wetland ecosystems and discover new ways to fight climate change,” said Cui.
This article was published at Earth.org on 19. November 2024
Author: Dhanashree Alshi for ESCI