Harvest, storage and drying of hemp for energy

In 1996 and 1997 harvesting experiments with hemp for energy were carried out at the experimental farm of IMAG-DLO in the North West of the Netherlands. The aim was to investigate the process and costs of field drying and drying at storage. Field drying of unconditioned cut hemp was compared to that of conditioned cut hemp. The studied alternatives of drying at storage on a practical scale were: mechanical drying by means of a fan inside a building and in the open air in a pile both with ambient air, and natural drying in the open air without a fan. About sixty big square and big round bales with a weight of 200 to over 400 kg with a moisture content (wet base) of about 30% were dried in these piles. In a building, also chips were dried mechanically with ambient air. The results showed that field drying depended on the swath structure and the weather conditions. Conditioning only increased field drying rate in the swath which was made of whole stalks, The piles of natural dried square bales (density: 132 kg/m(3)) and round bales (density: 90-112 kg/m(3)) dried in seven weeks from 30-35 to 20% moisture content just like the pile of square bales (density: 100 kg/m(3)) with mechanical ventilation. The costs of mechanical ventilation were calculated for 5 ECU/t DM.