Potential applications of biochar and terpene-enriched bio-oil produced from a semi-arid native Asteraceae

Abstract

Biomass of Flourensia oolepis, a native shrub of the semi-arid central region of Argentina, was treated by vacuum pyrolysis to investigate the potential of this species to be used as a source of energy and chemicals. In this study we determined the influence of temperature on the product yields in different plant organs (leaves and stems), characterized the bio-oil, and assessed the bioactivity of biochar aqueous extracts through germination and growth bioassays with Lactuca sativa. The pyrolysis oils showed a predominance of long chain, cyclic and aromatic hydrocarbons in the leaves pyrolysate. The sesquiterpene spathulenol was the major compound in these reactions. Pyrolysis of stems produced mainly phenolic compounds. The effect of phosphoric acid pretreatment on leaves and stems was also evaluated in order to improve bio-oil yield and selectivity to any interesting compound. The results showed that acid treatment enhanced the liquid formation in pyrolysis of leaves giving a high amount of long chain hydrocarbons compared with the untreated organ. The biochar water extracts from leaves exhibited a hormetic type of response, with a promoting growth effect on roots and shoots up to 225%, and only a transient inhibition of germination at higher doses (≥7.5% w/v). Biochar water extracts from stems did not affect seed germination and showed a remarkable promoting effect, stimulating growth at all concentrations tested up to 330%. Although additional testing is required, overall results show F. oolepis as a promissory species for the production of bio-oil and biochar with a wide range of applications, including the potential use as growth regulator.