Biochar is obtained by pyrolysis of biomass, such as straw, green waste or manure. During this process, biomass is charred in the absence of air. When incorporated into soils, it permanently stores carbon. It can be used in a variety of ways in agriculture – as water retaining substance, a carrier for nutrients, and a habitat for microorganisms.
In enhanced weathering of rocks its natural properties are used: CO2 is dissolved in rainwater and corrodes the rock. This produces dissolved carbonate compounds in the water. This process can be deliberately enhanced – for example, by grinding the rock to very small grain sizes and exposing it to humid climate on agricultural land. The dust can also improve soil fertility and thus crop yields – because it supplies important nutrients such as potassium. The resulting carbonate compounds are transported by rivers to the sea, where they counteract ocean acidification.
The PyMiCCS project (Pyrogenic carbon and carbonating minerals for enhanced plant growth and carbon capture and storage) now wants to find out whether the joint application of biochar and enhanced weathering has positive synergistic effects – for example, an improvement of soil properties.
But what is smartest way to combine the two methods? Which type of rock or biochar is best suited? The researchers will investigate these questions in detail – first in the laboratory, later in the field and ultimately with the help of ecosystem models to calculate global potentials for CO2 sequestration and soil improvement.