The biochar employed in this study was a commercially available product for use in gardening pyrolyzed at 680°C from landscape conservation and gardening wood waste from the region of Basel, Switzerland. The biochar contained pieces of the original branches/sticks with sizes of up to about 2 cm, see Fig. . Before pelletization, the biochar was dried at 40 °C for a minimum of 3 d. The water content in as-delivered biochar was relatively low (4% respect to the mass at 40 °C). In this study, pre-drying was used to enable better control of the composition of the pellets; in practical applications, the biochar could also be used wet, which could help reducing dust release from the charcoal in the process (biochar is often delivered containing around 25% of water). The organic carbon content (in the dry state) was declared as 74%. The specific surface (BET) was >220 m 2 /g and the bulk density was 221 kg/m 3 . In this study we used a sieved fraction of 8-20 mm. The fraction smaller than 8 mm and larger than 20 mm each constituted 4% by mass of the batch. Other sizes could be obtained depending on the sizes of the original biochar particles and pelletization parameters.