| Summary: | Peat is a highly contentious input in agriculture. Replacing or reducing peat by substitution with lignocellulosic biomass processed into fibre by twin-screw-extrusion could contribute to more sustainable agriculture with regard to horticultural production. Therefore, plant wastes including pruning from <i>Olea europaea</i> L. and <i>Vitis</i> spp. L., residues from perennial herbs like <i>Salvia</i> spp. L., <i>Populus</i> spp. L. and forest biomass were processed to fibre for peat replacement with a biomass extruder. The water-holding-capacity (WHC), particle-size-distribution and other physical fibre characteristics were determined and compared to peat. The specific energy demand during extrusion was measured for aperture settings from 6–40 mm. No fibre reached the 82% WHC of peat. At the setting of 20 mm of all materials investigated, <i>Salvia</i> performed best with a WHC of 53% and moderate specific energy demand (167 kWh t<sub>DM</sub><sup>−1</sup>) followed by <i>Olea europaea</i> with a WHC of 43% and a low energy demand (93 kWh t<sub>DM</sub><sup>−1</sup>). For <i>Populus</i>, opening the aperture from 20–40 mm decreased energy demand by 41% and WHC by 27%. The drying of biomass for storage and remoistening during extrusion increased the specific energy demand. Despite a lower WHC than peat, all investigated materials are suitable to replace peat in growing media regarding their physical properties.
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