As the science magazine of "SRF" reports, the so-called "Terra preta" served as a model for the farmers of Zug around Fredy Abächerli. The Portuguese term translates as "black earth". For hundreds of years, the indigenous population in the Amazon region mixed wood and vegetable charcoal with the soil. This is how the extremely fertile black earth was created from originally barren land.

Carbonizing instead of burning

Farmers in Zug were looking for ways of recycling green waste with a high proportion of wood. These are not suitable for fermentation. In 2011, they finally began to produce plant coal from plant chips in a reactor produced with the help of a German university spin-off. They founded Verora AG and have constantly refined their method and production. The underlying process is called pyrolysis. The wood chips enter the reactor via a conveyor belt, where they are heated to 500-600 degrees Celsius. Because the reactor is airtight and contains no oxygen, the chips do not burn. They carbonize. The carbon remains in the coal. The resulting gases are burned by a second reactor. The waste heat is used to heat the adjacent house.

Extracting CO2 from the atmosphere

The production of plant coal is a so-called negative emission technology (NET). This means that it removes CO2 from the atmosphere. Plants absorb CO2 from the air during growth. Through carbonization, the CO2 remains in the charcoal and, when applied, in the soil. It is currently assumed that this carbon will remain in the soil for several millennia. In recent years, technology has therefore become a source of hope for the climate in specialist circles. But it's not that simple. In order to balance the earth's climate balance with plant coal, it would take 2500 times the volume of the Matterhorn every year. Nevertheless, the technology has the potential to help reduce greenhouse gases.

In addition to the positive effect on the climate, the plant coal also has other benefits: "We clearly see that the soil quality improves and that the soils function better again, they are more climate-resistant," said Abächerli. In addition, the plant coal can also be used as a feed additive. It binds toxins and causes cows to emit less methane when they digest.