Among renewable energy sources, the use of bioenergy is projected to enjoy the highest growth rate. Socio-economic concerns have prompted the wide utilisation of agricultural wastes and non-food biomass (second generation of biomass) and algae (third generation of biomass) as alternative energy sources.
Sustainable production of bioenergy in areas with scarce fresh water supply and limited agricultural land must rely on special types of biomass and plants that are native to arid regions or can flourish in their environments. In this regard, there have been very promising attempts in the United Arab Emirates and in several coastal regions worldwide to grow and cultivate halophytes for edible and non-edible purposes.
Halophytes are plants that can thrive in extreme conditions of high salinity (ie, several times higher than that of seawater) and excessive heat (ie, conditions that are intolerable to most other plants). Salicornia bigelovii is arguably the most investigated halophyte species.
This is primarily ascribed to the high oil content of their seeds, which typically exceeds 35% (on a dry basis), an aspect that makes Salicornia bigelovii a potentially important feedstock in the production of bio-oil as well as vegetable oil.
In this work, researchers at the United Arab Emirates University have investigated the possibility of extracting biofuel from catalytic upgrading of bio-oil extracted from seeds of Salicornia bigelovii.
Through a combined experimental modelling approach, the objective of this study was twofold: to evaluate the potential catalytic upgrading of raw Salicornia bigelovii seeds’ pyrolysates via HDO reactions over mono Ni-CeO2 catalysts and to underpin the involved surface-assisted reaction mechanism through detailed density functional theory calculations.
A two-stage catalytic reactor was deployed in the experiments. Optimum operational conditions for the effective removal of O- and N-containing compounds were highlighted. The nature of the active sites and their connections with the observed catalytic reactivity were thoroughly discussed.
The outcomes from this study shall find direct applications toward sustainable and effective exploitation of halophytes in the production of biofuel.
For instance, the research found that the yield of the BXT (benzene-xylene-toluene) valuable compounds accounted for approximately 22% of the bio-oil’s makeup at 500°C. Likewise, the load of jet fuel compounds resided within the narrow range of 42%-45% between 400°C and 500°C. The content of the aromatic compound (ie, approximately 26% at 400°C) satisfactorily reflected the required range in real jet fuels.
Demonstrated findings herein provide a practical procedure to increase the share of bioenergy without competing for the scare land and freshwater resources in coastal areas.
The research was funded by the National Water and Energy Center at the United Arab Emirates University (UAEU). This work was inspired by the increasing demand to explore new and alternative venues in the production of biofuel from sustainable resources that could be cultivated on a wider scale in coastal areas.
Through the Sustainable Bioenergy Research Consortium, airlines and research centres in the UAE are collaborating in the development of a clean, alternative aviation fuel to reduce carbon emissions. Clearly, this research taps into this important milestone.
In an extension to this work, the researchers are planning to study catalytic upgrading of bio-oil produced from other types of halophytes and from their co-pyrolysis with other categories of biomass local to the environment. Likewise, they also aim to investigate in detail combustion properties of the produced jet fuel.
The research is conducted by Labeeb Ali and Mohamed Shafi, PhD research scholars, and Professor Mohammednoor Altarawneh, in addition to other collaborators from various departments at the United Arab Emirates University.
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