The photo shows a compilation of straw, digestate from biogas production, and so-called biochar. The fascination is given by the growth of mushrooms through the charred layer. The hydrothermal production of biochar is a process that takes place at 180-250 °C and 20-50 atmospheres using biomass as a feedstock. Biochar can be beneficial for poor soils such as the Amazonian “Terra Preta”. Our idea is to use the biochar for soil amendment and as an additional long-term carbon sink.