Processing of Lignocellulosic Materials from Agriculture to Pellets Sample Clauses

Processing of Lignocellulosic Materials from Agriculture to Pellets. 2.1 Process Chain Figure 3. Process chain of lignocellulosic materials from agriculture/ forest residues to fibres. [Source: ATB] Figure 3 shows how raw materials such as forest residues and agroforestry trees are processed into fibres. Trees from agroforestry are cut by a mower chipper or a modified forage harvester depending on the species and size. If the diameters are too large, they are cut down manually with chainsaws and are processed with a mobile chipper (Xxxxxxx and Xxxxxxxx 2015). Forest residues and horticultural prunings undergo the same process. After that process the wood chips are transported to a storage location where it is possible to dry them, reducing biomass degradation and potential contamination by mould. Once the moisture content of the wood chips is below 20 % they are shelf stable. Wood chips are usually stored within a short distance of the extruder to minimise transportation costs and carbon emissions due to transportation. Emissions can also be reduced if the short rotation coppice is close to the processing location. In this case, poplar is grown on ATB ground very close by. At ATB shortly before extrusion, dry wood chips are conditioned to a certain moisture content to achieve specific properties in the fibres and pellets produced. The wood chips are conditioned in a barrel by adding a specific amount of water. The barrel will tumble for 48 to 72 hours to let the wood absorb the water. In a commercial scale an exact calculated stream of water can be added continuously to the process so the wood chips need no pre-treatment. The amount of water added depends on the initial moisture content of the wood chips and the moisture content required for the particular fibre or pellet being produced. Moisture content also has an effect on the energy consumption of the extruder. Adding additives like biochar or lime is possible during extrusion or after, when the fibres are mixed. Ultimately the fibres are dried, packaged and stored or processed into pellets. At ATB the fibre produced is immediately dried at 150 °C in a flash dryer in preparation for storage. Fibre is sucked directly from the aperture of the extruder into the flash dryer. It stays in the flash dryer for approximately 2 seconds. The fibre is separated from the air by a cyclone separator and collected in a 1 m3 heavy-duty woven plastic bag. There is the potential to treat relatively moist material in an extruder, avoiding the high inputs of energy and effort required to dr...