REPURPOSING EUCALYPTUS TREES IN CALIFORNIA

A California icon, fire hazard, and invasive tree can be harvested for mass timber products

FIG. 1. Conceptual collage. Images from Miller Wood Trade Publications, GIS Geography, California Department of Fish and Wildlife, Cutout Trees.

Abstract

The state of California currently has an estimated 40,000 eucalyptus trees (Fig.2). An invasive species that was introduced in the mid-19th century by Australian settlers at a time when wood was the main source of energy and construction. Eucalyptus plantations boomed in the early 20th century and spread throughout the state, quickly losing their charm due to the harvested soft wood being unsuitable for building, and the introduction of concrete and steel. Currently there are eucalyptus trees over 100 years old throughout the state. These trees pose a constant threat in fire season since the predominant species is the blue gum eucalyptus, which due to its properties is highly combustible. Considering that young trees absorb more carbon than old ones, it is proposed to study the feasibility of harvesting old eucalyptus trees that exist in the state, replacing them with young native trees, and using the harvested wood to produce hardwood Cross Laminated Timber panels. The idea proposed in this essay has been tested by the CLTP Tasmania company in Australia, which already has in its catalogue the first hardwood Cross Laminated Timber panel made of eucalyptus. In the same way, different investigations have been carried out on the properties of this type of eucalyptus and its viability to be transformed into mass timber. One prominent example is the first permanent elastic timber gridshell built in Spain, which is also the first made with Eucalyptus worldwide.

FIG. 2. Habitat map for Eucalyptus Trees in the State of California, California Department of Fish and Wildlife, accessed July 2022

At a time when carbon absorption is so important due to the global warming crisis, building with Mass Timber ensures carbon is stored for a long time. If we add to this that the raw material can be trees that are an invasive species and that pose a threat in times of fire, a tree specimen that arrived with the intention of building the emerging cities of the 19th century, and that was discarded at the time , today it can be used to continue building those cities as the most sustainable building material available.

Repurposing eucalyptus trees in California is a project of IaaC, Institute for Advanced Architecture of Catalonia developed at MMTD, Master in Mass Timber Design in 2021/2022 by Student: Juan Bugarin. Faculty: Daniel Ibanez. Course: Narative 3