Willow supply strategies to energy plants

The main objective of this study was to develop minimum cost supply strateg ies for willow to energy plants (two plant sizes: 0.5 and 30 MWe, two energ y conversion technologies: combustion and gasification). Time span between harvest and energy conversion varied from 1 to 12 months. For a realistic c omparison, different supply chains were based on the same initial character istics (i.e., moisture content 50% wb at harvest) and final fuel specificat ions at the energy plant (moisture content 20% wb, particle size chips or c hunks). Cost calculations were based on the integral cost calculation metho d and were presented for all process steps, The main conclusion was that th e time span between harvest and energy conversion and the size and conversi on technology of the energy plant largely influence the design of the suppl y chain and consequently the supply costs. The fuel supply costs ranged fro m 17.6 to 26.1 ECU/t DM (where DM stands for oven dry matter) or 0.010 to 0 .023 ECU/kWh, The cost reduction which could be achieved by choosing the mi nimum cost chain design could be as high as 45% or 14.4 ECU/t DM. Generally , the strategy of minimum costs for supply of fuel to an energy plant runni ng all year round on willow was as follows: for farmers who should supply their willow within 6 months after harvest: h arvest as chips, forced drying at the farm and transport (if necessary); for farmers who should supply their willow beyond 6 months after harvest: h arvest as chunks or stems, natural drying near the willow field, transport (if necessary) and central chipping (if applicable). (C) 1999 Elsevier Scie nce Ltd. All rights reserved.