A characterisation of eucalyptus short rotation forestry plantations in Ireland.

Abstract

This paper details the characterisation of the biomass for use as a wood fuel of fifteen eucalyptus plantations (including twelve Eucalyptus nitens stands, two with E. gunnii and one with E. delegatensis) being grown on a short rotation in Ireland. Two of the plantations were mature (22 and 23 years old), while 13 of the plantations were more recently established (5 to 7 years old). Mortality rates were high, ranging from 11% to 62%. Trees were sampled and analysed for moisture content, ash content, calorific value, chemical composition (C, H, N, Cl, S) and ash melting behaviour. A biomass expansion factor was developed from the sample tree data to estimate total aboveground biomass from merchantable biomass and total height. Productivity on the measured sites ranged from 0.4 – 12.6 odt (oven dry tonnes) of whole tree biomass ha-1 yr-1. The chemical composition analysis indicated that the eucalyptus trees tested had higher than typical, as quoted in EN14961-1, values for chlorine content for bark, branch, tops, and foliage partitions, which may be problematic for some biomass boilers. Tests carried out on ash melting behaviour indicated that the wood and branch partitions have a low ash melting point. The results are limited, as the eucalyptus plantations in Ireland currently are either less than 10 years of age, or are over 20.