Delivery systems of forest arisings for energy production in New Zealand

Abstract

The large area of planted production forest in New Zealand and the expected increase in area to be harvested in the next 10 years, offer good potential for the woody biomass residue to contribute to New Zealand complying with the goals set by the Kyoto protocol. The main focus is on forest arisings, which are residues produced during the harvesting of logs. The objective of this paper is to identify promising delivery systems (including harvesting, storage, transportation and processing) of forest arisings to an energy plant and the associated costs. Costs largely depended on the delivery system chosen, the site characteristics and the transport distance. The cheapest system identified ranged from 22 to 37 NZ$ per tonne dry matter (1.2–2.0 NZ$ per GJ) for residues accumulating at the landing and from 29 to 42 NZ$ per tonne dry matter (1.6–2.2 NZ$ per GJ) for residues collected from the cutover. The cheapest option tended to be the simplest system because each time the material was handled, extra costs were added. The simulation model developed to compare different delivery systems proved to be a useful tool. However, it was important that input parameters were estimated accurately, especially product characteristics (moisture content and material density) and machine data, because these were the most sensitive model parameters. The results indicate that the use of forest arisings for the generation of heat and/or electricity could be feasible in New Zealand. Note: All costs are expressed in NZ$, 1 NZ $=0.42 US$ (September 2000).