Hydrothermal Carbonization is a process first noted by Friedrich Bergius at the beginning of the 20th century, as means of producing biochar. During production the natural coalification process is emulated. Combining air exclusion with temperatures over 180C and a pressure level above 10bar, biomass will form into biochar within a short period of time. Whilst Bergius first mentioned hydrothermal carbonization over 100 years ago, it was only “rediscovered” at the beginning of the 21st century, where a more detailed comprehension of the process and its by-products was pursued. This paper focuses on building and further developing a reactor capable of HTC, researching the exothermic of the process. To examine the influence of the process-parameters an experimental series was commenced and continued by Mrs Stutzenstein. Feed-material for these experimental series was biogas slurry. Experiments commenced showed, that a combination of high carbonization levels paired with a high concentration of nutrients is not possible in hydrochar, as the high temperature requirements have a negative impact on the rate of yield as well as nutrients reclaimed. Further result of the research conducted was, that a controlled hydrothermal carbonization is possible with the reactor built by the department. Additionally, varying process parameters resulted in different elemental compositions. It was further demonstrated, that reactions of hydrothermal carbonization are overall exothermic, since energy required for heating and temperature preservation, was lower using biomass instead of water.