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Many mallee eucalyptus species have leaves that contain terpenoid oils commonly known as eucalyptus oil, of which 1,8-cineole is the major constituent. 1,8-Cineole is potentially a high-value product that might improve the economic viability of a mallee-based biomass industry. It can be extracted by hydrodistillation, but the extraction process may affect the fuel properties of spent biomass. It was found that extraction of 1,8-cineole from mallee biomass is fast initially and tapers off to completion after 30 min of hydrodistillation. The distillation process has little effect on the fuel chemistry or the mass energy density of the spent biomass. However, hydrodistillation can potentially extract a substantial proportion of the alkali and alkaline earth metallic species from the raw biomass, depending on the biomass component (leaf, wood, and bark). Typically, Na and K are easily extracted while Mg and Ca are hard to extract. After hydrodistillation, the spent leaf becomes more difficult to grind than the raw leaf, apparently because of the poorer grindiability of the oil gland enclosures and vascular bundles after hydrodistillation. However, hydrodistillation appears to have little effect on the grindability of spent wood and bark fractions.

The degree of clonality, interspecific hybridisation and inbreeding in rare species will have significant implications for maintenance of genetic diversity and resilience to environmental change, with related implications for immediate conservation management. Using microsatellites, we detected extensive clonality within the rare mallee, Eucalyptus absita, from a highly disturbed agricultural habitat in southwestern Australia. A total of just 16 unique genets, plus five putative hybrids with E. loxophleba, were detected across the known species range and these genets were estimated to be of considerable age. Each location possessed a unique genotype and overall diversity was moderate (H E = 0.547). The outcrossing rate in seedling progeny was low (t m = 0.281), reflecting a rarity of intraspecific sires and minimal inbreeding depression prior to seed dispersal. Of all seedling progeny, up to 19 % were putative hybrids. Our findings indicate that despite rarity and clonality, moderate levels of genetic diversity and the capacity to produce outcrossed seeds is maintained. However, the ongoing maintenance of E. absita genetic diversity is significantly compromised by a high rate of selfing and potential hybridisation in seedling progeny. Seeds collected for long-term storage or rehabilitation should be screened for inbreeding and hybridisation rates to improve conservation outcomes. All existing adults represent a unique portion of the genepool for conservation.

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