Agriculture and horticulture contribute significantly to increasing the climate-damaging content of carbon dioxide (CO₂) in our atmosphere. Carbon-rich peat deposits in wetlands play a key role in this context. Their extraction and horticultural use leads to the unavoidable release of CO₂.

Alternative materials such as composts, wood fibres or biochar could replace peat in substrates for cultivated plants in the future. Biochars offer great potential for this, partly because they have similar low pH and conductivity values as peat. Peat substitutes should feature the lowest possible nutrient and lime content, low N immobilisation, loose storage and high structural stability, as well as a high air capacity and sufficient water storage capacity.

With our research work in ATB's biochar lab we are currently investigating to what extent chars from pyrolysis and hydrothermal carbonisation (HTC) can be used as alternative substrates to supplement or even replace the peat used in growing media.

In the case of HTC carbons, furfurals and phenols, which may be generated depending on the process conditions, must be removed. In order to meet the quality criteria for peat replacement in growing media, we develop further post-treatments of the chars and evaluate their effectiveness by means of germination tests.