Thymelaea hirsuta and Echinops spinosus: Xerophytic Plants with High Potential for First-Generation Biodiesel Production

Abstract

The negative impacts of fossil fuel on the environment should be replaced by clean and sustainable energy sources worldwide. Therefore, the use of biodiesel as a clean energy source is crucial. Biodiesel is produced from various natural resources through a transesterification process. Considering the importance of this topic, this study focuses on the assessment of oil properties of Thymelaea hirsuta and Echinops spinosus as primary sources for biodiesel production. The two investigated plants were collected from the Western Desert of Egypt. The results showed that the lignocellulosic content was about 57.3 and 79.8 g/100 g in E. spinosus and 59.1 and 82.8 g/100 g in T. hirsuta, respectively. The two investigated samples showed variable lipid contents (30.2–76.1%). The GC-MS fatty acid profile characterized seven FAs in E. spinosus and twelf FAs in T. hirsuta. The greatest CN was calculated in T. hirsuta (379.2) compared to the lowest in E. spinosus (229.9). Furthermore, the values of saponification number (SN) were 27.9 in E. spinosus and 16.07 in T. hirsuta. The value of higher heating value (HHV) was about 47.5 MJ/kg in E. spinosus and 48.3 MJ/kg in T. hirsuta. Meanwhile, T. hirsuta exhibited a higher induction period (IP) value (19.3 h) comparable to that of E. spinosus (4.3 h). The results revealed that both plants are potential sources for biodiesel production according to various international standards for biodiesel production, and this work appears to be one of the first reports regarding such wild xerophytic plants as promising new primary sources for biodiesel production in Egypt.