All-year-round harvesting of short rotation coppice eucalyptus compared with the delivered costs of biomass from more conventional short season, harvesting systems

This study attempted to define the optimum harvesting, processing and transport system in terms of the cost per tonne of delivering biomass produced from a commercial short rotation coppice crop to a 10 MW e bioenergy conversion plant 25 km away. Harvesting the crop during one short seasonal period of the year results in the need to store most of the material for between one to 12 months in order to provide a continual supply of feedstock. Storage of large volumes of biomass is costly and also results in dry matter losses over time. An alternative system would be to harvest small areas as required every few weeks throughout the year. This would enable cheaper, lower performance equipment to be used and hence provide a continual supply of biomass feedstock for delivery to the plant. Four systems of conventionally harvesting the biomass during one short seasonal period of 8–10 weeks were compared with two systems of harvesting it continually throughout the year. Whether the biomass is stored on the farms after harvest to allow for transpirational drying or at the plant was also compared. All-year-round harvesting using a simple tractor-mounted circular saw showed cost benefits in terms of $/GJ of energy delivered to the bioenergy plant but the performance assumptions made will require confirmation by field monitoring. A sensitivity analysis was conducted on several key parameters.